1.21.11 Mounts of Mayhem Release

Lots of rendering related changes, specifically for BackedQuad and IQuadTransformers.
Removed our deprecated model generators, modders should have been using vanilla's for a while.

.gitattributes

@@ -3,6 +3,7 @@
 *.patch text eol=lf
 *.java text eol=lf
 *.gradle text eol=crlf
+**/MANIFEST.MF text eol=crlf
 *.png binary
 *.gif binary
 *.exe binary

.github/workflows/publish.yml

@@ -0,0 +1,28 @@
+name: Publish
+
+on:
+  push:
+    branches: [ '1.21.11' ]
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    uses: MinecraftForge/SharedActions/.github/workflows/gradle.yml@main
+    with:
+      java: 21
+      gradle_setup: './gradlew setup'
+      gradle_tasks: 'build publish'
+      artifact_name: 'forge'
+    secrets:
+      DISCORD_WEBHOOK: ${{ secrets.DISCORD_WEBHOOK }}
+      PROMOTE_ARTIFACT_WEBHOOK: ${{ secrets.PROMOTE_ARTIFACT_WEBHOOK }}
+      PROMOTE_ARTIFACT_USERNAME: ${{ secrets.PROMOTE_ARTIFACT_USERNAME }}
+      PROMOTE_ARTIFACT_PASSWORD: ${{ secrets.PROMOTE_ARTIFACT_PASSWORD }}
+      MAVEN_USER: ${{ secrets.MAVEN_USER }}
+      MAVEN_PASSWORD: ${{ secrets.MAVEN_PASSWORD }}
+      SIGN_KEY_ALIAS: ${{ secrets.SIGN_KEY_ALIAS }}
+      SIGN_KEY_PASSWORD: ${{ secrets.SIGN_KEY_PASSWORD }}
+      SIGN_KEYSTORE_PASSWORD: ${{ secrets.SIGN_KEYSTORE_PASSWORD }}
+      SIGN_KEYSTORE_DATA: ${{ secrets.SIGN_KEYSTORE_DATA }}

.gitignore

@@ -26,7 +26,6 @@
 /projects/mcp/
 /projects/clean/
 /projects/forge/
-#/patches/*
 
 #occupational hazards
 /projects/**/build/
@@ -35,20 +34,15 @@
 /projects/**/*.launch
 /repo/
 src/*/generated/**/.cache/
+
 # Generated by gradle every import
 **/src/main/resources/META-INF/MANIFEST.MF
 /fmlloader/src/main/resources/forge_version.json
 
-#Patch rejects
-#/patches-/
-#*.patch.rej
-#/projects/*/rejects/
-
-# FML changelog
-changelog.txt
-*.py
-*.7z
-/logs/
-
 /ForgeRoot.ipr
 /ForgeRoot.iws
+
+# APT stuff
+/*/.gitignore
+/*/.factorypath
+/*/.apt_generated/

.teamcity/pom.xml

@@ -1,104 +0,0 @@
-<?xml version="1.0"?>
-<project>
-  <modelVersion>4.0.0</modelVersion>
-  <name>MinecraftForge_Forge Config DSL Script</name>
-  <groupId>MinecraftForge_Forge</groupId>
-  <artifactId>MinecraftForge_Forge_dsl</artifactId>
-  <version>1.0-SNAPSHOT</version>
-
-  <parent>
-    <groupId>org.jetbrains.teamcity</groupId>
-    <artifactId>configs-dsl-kotlin-parent</artifactId>
-    <version>1.0-SNAPSHOT</version>
-  </parent>
-
-  <repositories>
-    <repository>
-      <id>jetbrains-all</id>
-      <url>https://download.jetbrains.com/teamcity-repository</url>
-      <snapshots>
-        <enabled>true</enabled>
-      </snapshots>
-    </repository>
-    <repository>
-      <id>teamcity-server</id>
-      <url>https://teamcity.minecraftforge.net/app/dsl-plugins-repository</url>
-      <snapshots>
-        <enabled>true</enabled>
-      </snapshots>
-    </repository>
-  </repositories>
-
-  <pluginRepositories>
-    <pluginRepository>
-      <id>JetBrains</id>
-      <url>https://download.jetbrains.com/teamcity-repository</url>
-    </pluginRepository>
-  </pluginRepositories>
-
-  <build>
-    <sourceDirectory>${basedir}</sourceDirectory>
-    <plugins>
-      <plugin>
-        <artifactId>kotlin-maven-plugin</artifactId>
-        <groupId>org.jetbrains.kotlin</groupId>
-        <version>${kotlin.version}</version>
-
-        <configuration/>
-        <executions>
-          <execution>
-            <id>compile</id>
-            <phase>process-sources</phase>
-            <goals>
-              <goal>compile</goal>
-            </goals>
-          </execution>
-          <execution>
-            <id>test-compile</id>
-            <phase>process-test-sources</phase>
-            <goals>
-              <goal>test-compile</goal>
-            </goals>
-          </execution>
-        </executions>
-      </plugin>
-      <plugin>
-        <groupId>org.jetbrains.teamcity</groupId>
-        <artifactId>teamcity-configs-maven-plugin</artifactId>
-        <version>${teamcity.dsl.version}</version>
-        <configuration>
-          <format>kotlin</format>
-          <dstDir>target/generated-configs</dstDir>
-        </configuration>
-      </plugin>
-    </plugins>
-  </build>
-
-  <dependencies>
-    <dependency>
-      <groupId>org.jetbrains.teamcity</groupId>
-      <artifactId>configs-dsl-kotlin</artifactId>
-      <version>${teamcity.dsl.version}</version>
-      <scope>compile</scope>
-    </dependency>
-    <dependency>
-      <groupId>org.jetbrains.teamcity</groupId>
-      <artifactId>configs-dsl-kotlin-plugins</artifactId>
-      <version>1.0-SNAPSHOT</version>
-      <type>pom</type>
-      <scope>compile</scope>
-    </dependency>
-    <dependency>
-      <groupId>org.jetbrains.kotlin</groupId>
-      <artifactId>kotlin-stdlib-jdk8</artifactId>
-      <version>${kotlin.version}</version>
-      <scope>compile</scope>
-    </dependency>
-    <dependency>
-      <groupId>org.jetbrains.kotlin</groupId>
-      <artifactId>kotlin-script-runtime</artifactId>
-      <version>${kotlin.version}</version>
-      <scope>compile</scope>
-    </dependency>
-  </dependencies>
-</project>

.teamcity/settings.kts

@@ -1,193 +0,0 @@
-import jetbrains.buildServer.configs.kotlin.v2019_2.*
-import jetbrains.buildServer.configs.kotlin.v2019_2.projectFeatures.githubIssues
-import jetbrains.buildServer.configs.kotlin.*
-import jetbrains.buildServer.configs.kotlin.v2019_2.buildSteps.gradle
-
-/*
-The settings script is an entry point for defining a TeamCity
-project hierarchy. The script should contain a single call to the
-project() function with a Project instance or an init function as
-an argument.
-
-VcsRoots, BuildTypes, Templates, and subprojects can be
-registered inside the project using the vcsRoot(), buildType(),
-template(), and subProject() methods respectively.
-
-To debug settings scripts in command-line, run the
-
-    mvnDebug org.jetbrains.teamcity:teamcity-configs-maven-plugin:generate
-
-command and attach your debugger to the port 8000.
-
-To debug in IntelliJ Idea, open the 'Maven Projects' tool window (View
--> Tool Windows -> Maven Projects), find the generate task node
-(Plugins -> teamcity-configs -> teamcity-configs:generate), the
-'Debug' option is available in the context menu for the task.
-*/
-
-version = "2021.2"
-
-project {
-
-    buildType(Build)
-    buildType(BuildSecondaryBranches)
-    buildType(PullRequests)
-    buildType(PullRequestChecks)
-    buildType(PullRequestCompatibility)
-
-    params {
-        text("docker_jdk_version", "21", label = "Gradle version", description = "The version of the JDK to use during execution of tasks in a JDK.", display = ParameterDisplay.HIDDEN, allowEmpty = false)
-        text("docker_gradle_version", "8.7", label = "Gradle version", description = "The version of Gradle to use during execution of Gradle tasks.", display = ParameterDisplay.HIDDEN, allowEmpty = false)
-        text("git_main_branch", "1.21.x", label = "Git Main Branch", description = "The git main or default branch to use in VCS operations.", display = ParameterDisplay.HIDDEN, allowEmpty = false)
-        text("git_branch_spec", """
-                +:refs/heads/(main*)
-                +:refs/heads/(master*)
-                +:refs/heads/(develop|release|staging|main|master)
-                +:refs/heads/(1.*)
-            """.trimIndent(), label = "The branch specification of the repository", description = "By default all main branches are build by the configuration. Modify this value to adapt the branches build.", display = ParameterDisplay.HIDDEN, allowEmpty = true)
-        text("github_repository_name", "MinecraftForge", label = "The github repository name. Used to connect to it in VCS Roots.", description = "This is the repository slug on github. So for example `MinecraftForge` or `MinecraftForge`. It is interpolated into the global VCS Roots.", display = ParameterDisplay.HIDDEN, allowEmpty = false)
-        text("env.PUBLISHED_JAVA_ARTIFACT_ID", "forge", label = "Published artifact id", description = "The maven coordinate artifact id that has been published by this build. Can not be empty.", allowEmpty = false)
-        text("env.PUBLISHED_JAVA_GROUP", "net.minecraftforge", label = "Published group", description = "The maven coordinate group that has been published by this build. Can not be empty.", allowEmpty = false)
-        //These are references and not actually keys
-        password("env.CROWDIN_KEY", "credentialsJSON:a3102dbe-805d-4177-9f54-3d2c2eb08fd5", display = ParameterDisplay.HIDDEN)
-        password("env.KEYSTORE_URL", "credentialsJSON:a7ae1c82-8058-4061-8d12-7f6bc2618d2e", display = ParameterDisplay.HIDDEN)
-        password("env.KEYSTORE_PASSWORD", "credentialsJSON:d7b964e3-a1fd-47a8-b892-6f601fe47479", display = ParameterDisplay.HIDDEN)
-        text("additional_publishing_gradle_parameters", "-PcrowdinKey=%env.CROWDIN_KEY% -PkeystoreKeyPass=%env.KEYSTORE_PASSWORD% -PkeystoreStorePass=%env.KEYSTORE_PASSWORD% -Pkeystore=%env.KEYSTORE_URL%", label = "Additional gradle parameters for publish", description = "Contains the additional gradle parameters used during publishing.", display = ParameterDisplay.HIDDEN, allowEmpty = true)
-
-        checkbox("should_execute_build", "false", label = "Should build", description = "Indicates if the build task should be executed.", display = ParameterDisplay.HIDDEN,
-            checked = "true", unchecked = "false")
-        checkbox("should_execute_test", "false", label = "Should build", description = "Indicates if the build task should be executed.", display = ParameterDisplay.HIDDEN,
-            checked = "true", unchecked = "false")
-    }
-
-    features {
-        githubIssues {
-            id = "MinecraftForge_MinecraftForge__IssueTracker"
-            displayName = "MinecraftForge/MinecraftForge"
-            repositoryURL = "https://github.com/MinecraftForge/MinecraftForge"
-        }
-    }
-}
-
-object Build : BuildType({
-    templates(AbsoluteId("MinecraftForge_SetupGradleUtilsCiEnvironmen"), AbsoluteId("MinecraftForge_BuildWithDiscordNotifications"), AbsoluteId("MinecraftForge_BuildMainBranches"), AbsoluteId("MinecraftForge_SetupProjectUsingGradle"), AbsoluteId("MinecraftForge_BuildUsingGradle"), AbsoluteId("MinecraftForge_PublishProjectUsingGradle"), AbsoluteId("MinecraftForge_TriggersStaticFilesWebpageGenerator"))
-    id("MinecraftForge_MinecraftForge__Build")
-    name = "Build"
-    description = "Builds and Publishes the main branches of the project."
-})
-
-object BuildSecondaryBranches : BuildType({
-    templates(AbsoluteId("MinecraftForge_ExcludesBuildingDefaultBranch"), AbsoluteId("MinecraftForge_SetupGradleUtilsCiEnvironmen"), AbsoluteId("MinecraftForge_BuildWithDiscordNotifications"), AbsoluteId("MinecraftForge_BuildMainBranches"), AbsoluteId("MinecraftForge_SetupProjectUsingGradle"), AbsoluteId("MinecraftForge_BuildUsingGradle"))
-    id("MinecraftForge_MinecraftForge__BuildSecondaryBranches")
-    name = "Build - Secondary Branches"
-    description = "Builds and Publishes the secondary branches of the project."
-    params {
-        text("git_branch_spec", """
-                +:refs/heads/(*)
-                -:refs/heads/noci*
-            """.trimIndent(), label = "The branch specification of the repository", description = "By default all main branches are build by the configuration. Modify this value to adapt the branches build.", display = ParameterDisplay.HIDDEN, allowEmpty = true)
-    }
-    vcs {
-        branchFilter = """
-            +:*
-            -:1.*
-            -:<default>
-        """.trimIndent()
-    }
-})
-
-object PullRequests : BuildType({
-    templates(AbsoluteId("MinecraftForge_BuildPullRequests"), AbsoluteId("MinecraftForge_SetupGradleUtilsCiEnvironmen"), AbsoluteId("MinecraftForge_BuildWithDiscordNotifications"), AbsoluteId("MinecraftForge_SetupProjectUsingGradle"), AbsoluteId("MinecraftForge_BuildUsingGradle"))
-    id("MinecraftForge_MinecraftForge__PullRequests")
-    name = "Pull Requests"
-    description = "Builds pull requests for the project"
-
-    params {
-        checkbox("should_execute_build", "true", label = "Should build", description = "Indicates if the build task should be executed.", display = ParameterDisplay.HIDDEN,
-            checked = "true", unchecked = "false")
-        text(
-            "gradle_build_task",
-            "assemble",
-            label = "Gradle build task to execute during build",
-            description = "Determines the build task that is executed to build the project.",
-            display = ParameterDisplay.HIDDEN,
-            allowEmpty = false
-        )
-    }
-
-    vcs {
-        branchFilter = """
-            +:*
-            -:1.*
-            -:<default>
-        """.trimIndent()
-    }
-})
-
-object PullRequestChecks : BuildType({
-    templates(AbsoluteId("MinecraftForge_BuildPullRequests"), AbsoluteId("MinecraftForge_SetupGradleUtilsCiEnvironmen"), AbsoluteId("MinecraftForge_BuildWithDiscordNotifications"), AbsoluteId("MinecraftForge_SetupProjectUsingGradle"))
-    id("MinecraftForge_MinecraftForge__PullRequestChecks")
-    name = "Pull Requests (Checks)"
-    description = "Checks pull requests for the project"
-
-    steps {
-        gradle {
-            name = "Check"
-            id = "RUNNER_10_Check"
-
-            tasks = "checkAll"
-            gradleParams = "--continue %gradle_custom_args%"
-            enableStacktrace = true
-            dockerImage = "%docker_gradle_image%"
-            dockerRunParameters = """
-                -v "/opt/cache/agent/gradle:/home/gradle/.gradle"
-                -v "/opt/cache/shared/gradle:/home/gradle/rocache:ro"
-                --network=host
-                -u 1000:1000
-                %docker_additional_args%
-            """.trimIndent()
-        }
-    }
-
-    vcs {
-        branchFilter = """
-            +:*
-            -:1.*
-            -:<default>
-        """.trimIndent()
-    }
-})
-
-object PullRequestCompatibility : BuildType({
-    templates(AbsoluteId("MinecraftForge_BuildPullRequests"), AbsoluteId("MinecraftForge_SetupGradleUtilsCiEnvironmen"), AbsoluteId("MinecraftForge_BuildWithDiscordNotifications"), AbsoluteId("MinecraftForge_SetupProjectUsingGradle"))
-    id("MinecraftForge_MinecraftForge__PullRequestCompatibility")
-    name = "Pull Requests (Compatibility)"
-    description = "Validates binary compatibility for pull requests made to the project"
-
-    steps {
-        gradle {
-            name = "Validate"
-            id = "RUNNER_10_Compatibility"
-
-            tasks = "checkJarCompatibility"
-            gradleParams = "--continue %gradle_custom_args%"
-            enableStacktrace = true
-            dockerImage = "%docker_gradle_image%"
-            dockerRunParameters = """
-                -v "/opt/cache/agent/gradle:/home/gradle/.gradle"
-                -v "/opt/cache/shared/gradle:/home/gradle/rocache:ro"
-                --network=host
-                -u 1000:1000
-                %docker_additional_args%
-            """.trimIndent()
-        }
-    }
-
-    vcs {
-        branchFilter = """
-            +:*
-            -:1.*
-            -:<default>
-        """.trimIndent()
-    }
-})

build.gradle

@@ -4,11 +4,11 @@ import net.minecraftforge.gradleutils.PomUtils
 plugins {
     id 'net.minecraftforge.licenser' version '1.0.1'
     id 'com.github.ben-manes.versions' version '0.46.0'
-    id 'net.minecraftforge.gradleutils' version '[2.3.0,2.4.0)'
+    id 'net.minecraftforge.gradleutils' version '[2.6.4,2.7)'
     id 'eclipse'
     id 'de.undercouch.download' version '5.4.0'
-    id 'net.minecraftforge.gradle.patcher' version '[6.0.22,6.2)' apply false
-    id 'net.minecraftforge.gradle.mcp' version '[6.0.22,6.2)' apply false
+    id 'net.minecraftforge.gradle.patcher' version '[6.0.46,6.2)' apply false
+    id 'net.minecraftforge.gradle.mcp' version '[6.0.46,6.2)' apply false
     id 'net.minecraftforge.gradlejarsigner' version '1.0.4'
     id 'org.barfuin.gradle.taskinfo' version '2.1.0'
 }
@@ -16,8 +16,7 @@ plugins {
 Util.init() //Init all our extension methods!
 
 ext {
-    GIT_INFO = gradleutils.gitInfo
-    VERSION = gradleutils.getFilteredMCTagOffsetBranchVersion(true, '[0-9]', MC_VERSION)
+    VERSION = gitversion.getMCTagOffsetBranch(MC_VERSION)
     FORGE_VERSION = VERSION.substring(MC_VERSION.length() + 1)
 }
 

buildSrc/build.gradle

@@ -4,10 +4,11 @@ repositories {
 }
 
 dependencies {
-    implementation 'org.ow2.asm:asm:9.7'
-    implementation 'org.ow2.asm:asm-tree:9.7'
+    implementation 'org.ow2.asm:asm:9.8'
+    implementation 'org.ow2.asm:asm-tree:9.8'
     implementation 'net.minecraftforge:srgutils:0.5.10'
+    implementation 'net.minecraftforge:JarJarMetadata:0.3.27'
     implementation 'commons-io:commons-io:2.13.0'
     implementation 'com.google.code.gson:gson:2.10.1'
-    implementation 'org.eclipse.jgit:org.eclipse.jgit:6.5.0.202303070854-r'
+    implementation 'org.eclipse.jgit:org.eclipse.jgit:6.7.0.202309050840-r'
 }

buildSrc/src/main/groovy/net/minecraftforge/forge/tasks/BundleList.groovy

@@ -21,6 +21,8 @@ abstract class BundleList extends DefaultTask {
         configure {
             dependsOn(project.tasks.universalJar)
             inputs.file(project.tasks.universalJar.archiveFile)
+            dependsOn(project.tasks.applyServerBinPatches)
+            inputs.file(project.tasks.applyServerBinPatches.output)
         }
     }
     

buildSrc/src/main/groovy/net/minecraftforge/forge/tasks/BytecodePredicateFinder.groovy

@@ -3,6 +3,7 @@ package net.minecraftforge.forge.tasks
 import groovy.transform.CompileStatic
 import org.gradle.api.provider.Property
 import org.gradle.api.tasks.Internal
+import org.objectweb.asm.Opcodes
 import org.objectweb.asm.tree.ClassNode
 import org.objectweb.asm.tree.MethodNode
 
@@ -12,13 +13,19 @@ abstract class BytecodePredicateFinder extends BytecodeFinder {
     @Internal
     abstract Property<Closure<Boolean>> getPredicate()
 
-    private final Set<String> matches = new HashSet<>()
+    private final Map<String, List<String>> matches = new TreeMap<>(Comparator.naturalOrder())
 
     @Override
     protected process(ClassNode parent, MethodNode node) {
         for (final current : node.instructions) {
             if (predicate.get().call(parent, node, current)) {
-                matches.add(parent.name)
+                var methods = matches.compute(parent.name, { k, v -> v ?: new ArrayList<>() })
+
+                // only add non-synthetic methods
+                if ((node.access & Opcodes.ACC_SYNTHETIC) == 0) {
+                    methods.add(node.name + node.desc)
+                }
+
                 return
             }
         }
@@ -27,6 +34,15 @@ abstract class BytecodePredicateFinder extends BytecodeFinder {
     @Internal
     @Override
     protected Object getData() {
-        return matches.toSorted(Comparator.naturalOrder()) ?: {throw new RuntimeException('Failed to find any targets, please ensure that method names and descriptors are correct.')}()
+        var array = new ArrayList<Object>()
+        matches.forEach { c, m ->
+            {
+                array.add(
+                        'class': c,
+                        'methods': m
+                )
+            }
+        }
+        return array ?: { throw new RuntimeException('Failed to find any targets, please ensure that method names and descriptors are correct.') }()
     }
 }

buildSrc/src/main/groovy/net/minecraftforge/forge/tasks/JarJarMetadataOptions.java

@@ -0,0 +1,415 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
+package net.minecraftforge.forge.tasks;
+
+import com.google.common.reflect.TypeToken;
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import net.minecraftforge.jarjar.metadata.ContainedJarIdentifier;
+import net.minecraftforge.jarjar.metadata.ContainedJarMetadata;
+import net.minecraftforge.jarjar.metadata.ContainedVersion;
+import net.minecraftforge.jarjar.metadata.Metadata;
+import net.minecraftforge.jarjar.metadata.MetadataIOHandler;
+import net.minecraftforge.jarjar.metadata.json.ArtifactVersionSerializer;
+import net.minecraftforge.jarjar.metadata.json.ContainedJarIdentifierSerializer;
+import net.minecraftforge.jarjar.metadata.json.ContainedJarMetadataSerializer;
+import net.minecraftforge.jarjar.metadata.json.ContainedVersionSerializer;
+import net.minecraftforge.jarjar.metadata.json.MetadataSerializer;
+import net.minecraftforge.jarjar.metadata.json.VersionRangeSerializer;
+import org.apache.maven.artifact.versioning.ArtifactVersion;
+import org.apache.maven.artifact.versioning.DefaultArtifactVersion;
+import org.apache.maven.artifact.versioning.InvalidVersionSpecificationException;
+import org.apache.maven.artifact.versioning.VersionRange;
+import org.codehaus.groovy.runtime.InvokerHelper;
+import org.gradle.api.Action;
+import org.gradle.api.DefaultTask;
+import org.gradle.api.artifacts.ConfigurationContainer;
+import org.gradle.api.artifacts.Dependency;
+import org.gradle.api.artifacts.ExternalModuleDependency;
+import org.gradle.api.artifacts.FileCollectionDependency;
+import org.gradle.api.artifacts.MinimalExternalModuleDependency;
+import org.gradle.api.artifacts.ModuleDependency;
+import org.gradle.api.artifacts.ModuleIdentifier;
+import org.gradle.api.artifacts.ModuleVersionIdentifier;
+import org.gradle.api.artifacts.ResolvedArtifact;
+import org.gradle.api.file.ProjectLayout;
+import org.gradle.api.file.RegularFileProperty;
+import org.gradle.api.provider.Provider;
+import org.gradle.api.provider.SetProperty;
+import org.gradle.api.tasks.Input;
+import org.gradle.api.tasks.OutputFile;
+import org.gradle.api.tasks.TaskAction;
+
+import javax.inject.Inject;
+import java.io.File;
+import java.io.IOException;
+import java.io.Serial;
+import java.io.Serializable;
+import java.nio.file.Files;
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Objects;
+import java.util.Set;
+import java.util.zip.ZipFile;
+
+// TODO SUPER SUPER SUPER UGLY, CLEAN UP IN FORGEDEV 7
+@Deprecated(forRemoval = true) // Will be moved to JarJar plugin in ForgeDev 7
+public abstract class JarJarMetadataOptions extends DefaultTask {
+    private static final Gson GSON = new GsonBuilder()
+        .registerTypeAdapter(VersionRange.class, new VersionRangeSerializer())
+        .registerTypeAdapter(ArtifactVersion.class, new ArtifactVersionSerializer())
+        .registerTypeAdapter(DefaultArtifactVersion.class, new ArtifactVersionSerializer())
+        .registerTypeAdapter(ContainedJarIdentifier.class, new ContainedJarIdentifierSerializer())
+        .registerTypeAdapter(ContainedJarMetadata.class, new ContainedJarMetadataSerializer())
+        .registerTypeAdapter(ContainedVersion.class, new ContainedVersionSerializer())
+        .registerTypeAdapter(Metadata.class, new MetadataSerializer())
+        .setPrettyPrinting()
+        .create();
+
+    protected abstract @Input SetProperty<ResolvedDependencyInfoImpl> getResolvedDependencies();
+
+    protected abstract @OutputFile RegularFileProperty getMetadataFile();
+
+    protected abstract @Inject ProjectLayout getLayout();
+
+    // NOTE: I'm not adding a non-provider version. please just use the version catalog entries for now.
+    public void add(Provider<MinimalExternalModuleDependency> dependency, Action<? super ResolvedDependencyInfo> action) {
+        this.getResolvedDependencies().add(dependency.map(d -> {
+            var ret = ResolvedDependencyInfoImpl.from(this.getProject().getConfigurations(), d);
+            action.execute(ret);
+            return ret;
+        }));
+    }
+
+    @Inject
+    public JarJarMetadataOptions() {
+        this.getMetadataFile().convention(this.getLayout().getBuildDirectory().file(this.getName() + "/options.json"));
+    }
+
+    @TaskAction
+    protected void exec() {
+        record ForgeLocaterOptions(String resource, String layer, String id, List<ContainedJarMetadata> deps, ContainedJarMetadata meta, boolean nested) { }
+
+        var resolved = this.getResolvedDependencies().get();
+        var jars = new ArrayList<ForgeLocaterOptions>(resolved.size());
+        for (var dependency : resolved) {
+            var deps = new ArrayList<ContainedJarMetadata>();
+            try (var zip = new ZipFile(dependency.artifact)) {
+                var entry = zip.getEntry("META-INF/jarjar/metadata.json");
+                if (entry != null) {
+                    try (var stream = zip.getInputStream(entry)) {
+                        var meta = MetadataIOHandler.fromStream(stream).orElse(null);
+                        if (meta == null)
+                            throw new IllegalStateException("Corrupt metadata.json in " + dependency.artifact.getAbsolutePath());
+                        for (var dep : meta.jars())
+                            deps.add(new ContainedJarMetadata(dep.identifier(), dep.version(), "", dep.isObfuscated()));
+                    }
+                }
+            } catch (IOException e) {
+                throw new RuntimeException(e);
+            }
+            jars.add(new ForgeLocaterOptions(
+                dependency.resource,
+                dependency.layer,
+                dependency.identifier,
+                deps,
+                new ContainedJarMetadata(
+                    new ContainedJarIdentifier(validateGroup(dependency), dependency.module.getName()),
+                    new ContainedVersion(null, parseVersion(dependency)),
+                    Objects.requireNonNull(dependency.path, "Dependency path is unspecified: " + dependency.asString),
+                    false
+                ),
+                dependency.nested
+            ));
+        }
+
+        try {
+            record Meta(List<ForgeLocaterOptions> options){}
+
+            Files.writeString(
+                this.getMetadataFile().getAsFile().get().toPath(),
+                GSON.toJson(new Meta(jars), Meta.class)
+            );
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private String validateGroup(ResolvedDependencyInfoImpl dependency) {
+        try {
+            return Objects.requireNonNull(dependency.module.getGroup());
+        } catch (NullPointerException e) {
+            throw new IllegalArgumentException("Module dependency has no group: " + dependency.asString, e);
+        }
+    }
+
+    private ArtifactVersion parseVersion(ResolvedDependencyInfoImpl resolved) {
+        try {
+            return VersionRange.createFromVersionSpec(Objects.requireNonNull(resolved.version)).getRecommendedVersion();
+        } catch (InvalidVersionSpecificationException e) {
+            throw new IllegalArgumentException("Version is invalid for: " + resolved.asString, e);
+        } catch (NullPointerException e) {
+            throw new IllegalArgumentException("Version is unspecified for: " + resolved.asString, e);
+        }
+    }
+
+    private VersionRange parseVersionRange(ResolvedDependencyInfoImpl dependency) {
+        if (dependency.hasManuallySpecifiedRange) {
+            try {
+                return VersionRange.createFromVersionSpec(dependency.versionRange);
+            } catch (InvalidVersionSpecificationException e) {
+                throw new IllegalArgumentException("Version is invalid for: " + dependency.asString, e);
+            }
+        } else {
+            try {
+                return VersionRange.createFromVersionSpec("[%s,)".formatted(Objects.requireNonNull(dependency.versionRange)));
+            } catch (InvalidVersionSpecificationException e) {
+                throw new IllegalArgumentException("Version range is invalid for: " + dependency.asString, e);
+            } catch (NullPointerException e) {
+                throw new IllegalArgumentException("Version is unspecified for: " + dependency.asString, e);
+            }
+        }
+    }
+
+    public interface ResolvedDependencyInfo {
+        void containedJarMetadata(Action<? super ContainedJarMetadataInfo> action);
+
+        void setResource(String resource);
+
+        void setLayer(String layer);
+
+        void setId(String identifier);
+
+        void setNested(boolean nested);
+
+        interface ContainedJarMetadataInfo {
+            void setGroup(String group);
+
+            void setName(String name);
+
+            void setPath(String version);
+        }
+    }
+
+    static final class ResolvedDependencyInfoImpl implements ResolvedDependencyInfo, ResolvedDependencyInfo.ContainedJarMetadataInfo, Serializable {
+        private static final @Serial long serialVersionUID = -7577318115877822993L;
+
+        final MinimalModuleVersionIdentifier module;
+        final String version;
+        String versionRange;
+        boolean hasManuallySpecifiedRange;
+        boolean nested;
+        final File artifact;
+        String path;
+        String resource;
+        String layer;
+        String identifier;
+        final String asString;
+
+        public ResolvedDependencyInfoImpl(MinimalModuleVersionIdentifier module, String version, File artifact, String asString) {
+            this.module = module;
+            this.version = version;
+            this.artifact = artifact;
+            this.asString = asString;
+        }
+
+        @Override
+        public void containedJarMetadata(Action<? super ContainedJarMetadataInfo> action) {
+            action.execute(this);
+        }
+
+        @Override
+        public void setGroup(String group) {
+            this.module.group = group;
+        }
+
+        @Override
+        public void setName(String name) {
+            this.module.name = name;
+        }
+
+        @Override
+        public void setPath(String path) {
+            this.path = path;
+        }
+
+        @Override
+        public void setResource(String resource) {
+            this.resource = resource;
+        }
+
+        @Override
+        public void setLayer(String layer) {
+            this.layer = layer;
+        }
+
+        @Override
+        public void setId(String identifier) {
+            this.identifier = identifier;
+        }
+
+        @Override
+		public void setNested(boolean nested) {
+			this.nested = nested;
+		}
+
+        static Set<File> getFiles(Set<ResolvedDependencyInfoImpl> resolvedDependencies) {
+            var ret = new HashSet<File>(resolvedDependencies.size());
+            for (var dependency : resolvedDependencies) {
+                ret.add(dependency.artifact);
+            }
+            return ret;
+        }
+
+        static ResolvedDependencyInfoImpl from(ConfigurationContainer configurations, Dependency dependency) {
+            var group = dependency.getGroup();
+            var name = dependency.getName();
+            var version = dependency.getVersion();
+
+            if (dependency instanceof FileCollectionDependency filesDependency) {
+                File artifact;
+                try {
+                    artifact = filesDependency.getFiles().getSingleFile();
+                } catch (IllegalStateException e) {
+                    // TODO fileCollectionDependencyIsNotSingleFile
+                    throw e;
+                }
+
+                return new ResolvedDependencyInfoImpl(
+                    new MinimalModuleVersionIdentifier(group, name, version),
+                    version,
+                    artifact,
+                    filesDependency.toString()
+                );
+            } else if (dependency instanceof ModuleDependency moduleDependency) {
+                moduleDependency = moduleDependency.copy();
+                if (moduleDependency instanceof ExternalModuleDependency externalModuleDependency) {
+                    externalModuleDependency.version(v -> v.strictly(version.toString()));
+                }
+
+                var detachedConfiguration = configurations.detachedConfiguration(moduleDependency);
+                detachedConfiguration.setTransitive(false);
+
+                ResolvedDependencyInfoImpl ret = null;
+                for (var artifact : detachedConfiguration.getResolvedConfiguration().getFirstLevelModuleDependencies().iterator().next().getModuleArtifacts()) {
+                    var fileName = getFileName(artifact);
+                    if (!fileName.endsWith(".jar"))
+                        continue;
+
+                    if (ret != null)
+                        throw new IllegalArgumentException("Module dependency has too many Jar artifacts: " + moduleDependency);
+
+                    ret = new ResolvedDependencyInfoImpl(
+                        new MinimalModuleVersionIdentifier(group, name, artifact.getModuleVersion().getId().getVersion()),
+                        version,
+                        artifact.getFile(),
+                        moduleDependency.toString()
+                    );
+                }
+                if (ret == null)
+                    throw new IllegalArgumentException("Module dependency has no Jar artifacts: " + moduleDependency);
+
+                return ret;
+            } else {
+                throw new IllegalArgumentException("Unsupported dependency type: " + dependency.getClass().getName() + " -- " + dependency);
+            }
+        }
+
+        private static String getFileName(ResolvedArtifact artifact) {
+            try {
+                return InvokerHelper.getProperty(artifact.getId(), "fileName").toString();
+            } catch (Throwable e) {
+                // NOTE: Why not just use this to begin with?
+                // ComponentArtifactIdentifier can have a getFileName() method, which doesn't necessarily resolve the file itself.
+                // This allows us to get the name of the file to be used without asking Gradle to download the file.
+                // So, if a file is not a JAR file, we can check the name without actually downloading it.
+                return artifact.getFile().getName();
+            }
+        }
+
+        @Override
+        public boolean equals(Object obj) {
+            if (obj == this) return true;
+            if (obj == null || obj.getClass() != this.getClass()) return false;
+            var that = (ResolvedDependencyInfoImpl) obj;
+            return Objects.equals(this.module, that.module) &&
+                Objects.equals(this.version, that.version) &&
+                Objects.equals(this.versionRange, that.versionRange) &&
+                Objects.equals(this.artifact, that.artifact);
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hash(module, version, versionRange, artifact);
+        }
+
+        @Override
+        public String toString() {
+            return "ResolvedDependencyInfo[" +
+                "module=" + module + ", " +
+                "fixedVersion=" + version + ", " +
+                "versionRange=" + versionRange + ", " +
+                "artifact=" + artifact + ']';
+        }
+
+        static final class MinimalModuleVersionIdentifier implements ModuleIdentifier, ModuleVersionIdentifier {
+            private static final @Serial long serialVersionUID = -955346236759069739L;
+
+            private String group;
+            private String name;
+            private final String version;
+
+            @Inject
+            public MinimalModuleVersionIdentifier(String group, String name, String version) {
+                this.group = group;
+                this.name = name;
+                this.version = version;
+            }
+
+            @Override
+            public ModuleIdentifier getModule() {
+                return this;
+            }
+
+            @Override
+            public String getGroup() {
+                return this.group;
+            }
+
+            @Override
+            public String getName() {
+                return this.name;
+            }
+
+            @Override
+            public String getVersion() {
+                return this.version;
+            }
+
+            @Override
+            public boolean equals(Object obj) {
+                return this == obj || obj instanceof MinimalModuleVersionIdentifier o
+                    && Objects.equals(this.group, o.group)
+                    && Objects.equals(this.name, o.name)
+                    && Objects.equals(this.version, o.version);
+            }
+
+            @Override
+            public int hashCode() {
+                return Objects.hash(group, name, version);
+            }
+
+            @Override
+            public String toString() {
+                return "MinimalModuleVersionIdentifier[" +
+                    "group=" + group + ", " +
+                    "name=" + name + ", " +
+                    "version=" + version + ']';
+            }
+        }
+    }
+}

build_forge.gradle

@@ -47,6 +47,7 @@ jarSigner.autoDetect('forge')
 applyPatches {
     level 'WARNING'
     failOnError = UPDATING != 'true'
+    rejects = rootProject.layout.projectDirectory.dir('rejects').asFile
 }
 
 sourceSets {
@@ -70,7 +71,7 @@ sourceSets {
     }
 }
 
-final String SPEC_VERSION = gradleutils.gitInfo.tag
+final String SPEC_VERSION = gitversion.info.tag
 
 // The new versioning sceme is <MCVersion>-<ForgeMC>.<RB>.<CommitsSinceRB>
 // ForgeMC is a unique identifier for every MC version we have supported.
@@ -91,18 +92,18 @@ final String MAVEN_PATH = ext.MAVEN_PATH
 final String BINPATCH_TOOL = 'net.minecraftforge:binarypatcher:1.2.0:fatjar'
 final String INSTALLER_TOOLS = 'net.minecraftforge:installertools:1.4.3'
 final String FART = 'net.minecraftforge:ForgeAutoRenamingTool:1.0.6'
-final String S2S_TOOL = 'net.minecraftforge:Srg2Source:8.1.0:fatjar'
+final String S2S_TOOL = 'net.minecraftforge:Srg2Source:8.1.1:fatjar'
 
 configurations {
     // Don't pull all libraries, if we're missing something, add it to the installer list so the installer knows to download it.
     bootstrap  { transitive = false }
-    installer { 
+    installer {
         extendsFrom(bootstrap)
-        transitive = false 
+        transitive = false
     }
-    installerextra { 
+    installerextra {
         extendsFrom(bootstrap)
-        transitive = false 
+        transitive = false
     }
     api.extendsFrom(installer)
 }
@@ -112,18 +113,19 @@ dependencies {
     // And this is only needed because custom file systems are REQUIRED to be on the boot classloader.
     // This has ASM/BootStrap/Unsafe all because I haven't gotten around to moving UnionFileSystem out to its own project.
     bootstrap(libs.jarjar.fs)     // JarInJar file system
+    bootstrap(libs.roimfs)        // JarInJar File System - FileSystems need to be on boot loader.
     bootstrap(libs.bundles.jimfs) // In memory file system used for ForgeDev launches
     bootstrap(libs.securemodules) // Has Union file system in it
     bootstrap(libs.unsafe)        // Needed by securemodules
     bootstrap(libs.bundles.asm)   // Needed by securemodules
-    
-    implementation(libs.jopt.simple) { version { strictly '5.0.4' } }
-    
+
+    implementation(libs.jopt.simple)
+
     installer(libs.bootstrap)
     installer(libs.bootstrap.api) // Needed by securemodules
     installer(libs.accesstransformers)
     installer(libs.eventbus)
-    installer(libs.typetools) // Dep of EventBus
+    installer(libs.jspecify) // Dep of EventBus
     installer(libs.forgespi)
     installer(libs.coremods)
     installer(libs.nashorn) // Dep of Coremods
@@ -133,7 +135,9 @@ dependencies {
     installer(libs.maven.artifact)
     installer(libs.bundles.terminalconsoleappender)
     installer(libs.mixin)
+    installer(libs.mixinextras.forge)
     installer(libs.bundles.jarjar)
+    installer(libs.roimfs)
 
     installer(project(':fmlcore'))
     installer(project(':fmlloader'))
@@ -141,11 +145,14 @@ dependencies {
     installer(project(':javafmllanguage'))
     installer(project(':lowcodelanguage'))
     installer(project(':mclanguage'))
+    installer(project(':forge-transformers'))
 
     installerextra("${MCP_ARTIFACT.group}:${MCP_ARTIFACT.name}:${MCP_ARTIFACT.version}:srg2off")
 
     runtimeOnly(libs.bootstrap)
     runtimeOnly(libs.bootstrap.dev)
+
+    annotationProcessor(libs.eventbus.validator)
 }
 
 tasks.named('extractRangeMap').configure {
@@ -165,7 +172,7 @@ patcher {
 
     runs {
         forge_client {
-            property 'eventbus.checkTypesOnDispatch', 'true'
+            property 'eventbus.api.strictRuntimeChecks', 'true'
             property 'org.lwjgl.system.SharedLibraryExtractDirectory', 'lwjgl_dll'
 
             args '--launchTarget', 'forge_dev_client',
@@ -194,6 +201,7 @@ patcher {
 
         forge_server_gametest {
             args '--launchTarget', 'forge_dev_server_gametest'
+            args '--uniqueWorld' // Unique world is used so that the world regenerates, as well as the world config isn't influenced by other runs
         }
 
         forge_server_gametest_test {
@@ -207,7 +215,6 @@ patcher {
                  '--all',
                  '--validate',
                  '--output', rootProject.file('src/main/generated/'),
-                 '--validate',
                  '--existing', sourceSets.main.resources.srcDirs[0],
                  '--assetsDir', downloadAssets.output,
                  '--assetIndex', "{asset_index}"
@@ -225,6 +232,30 @@ patcher {
                  '--assetsDir', downloadAssets.output,
                  '--assetIndex', "{asset_index}"
         }
+
+        forge_client_data {
+            args '--launchTarget', 'forge_dev_client_data',
+                 '--mod', 'forge',
+                 '--all',
+                 '--output', rootProject.file('src/main/generated/'),
+                 '--existing', sourceSets.main.resources.srcDirs[0],
+                 '--assetsDir', downloadAssets.output,
+                 '--assetIndex', "{asset_index}"
+        }
+
+        forge_client_data_test {
+            source sourceSets.test
+            args '--launchTarget', 'forge_dev',
+                 '--launchEntry', 'minecraft/net.minecraft.client.data.Main',
+                 '--launchData',
+                 '--mod', '.+',
+                 '--all',
+                 '--output', rootProject.file('src/test/generated/'),
+                 '--existing', sourceSets.main.resources.srcDirs[0],
+                 '--existing', sourceSets.test.resources.srcDirs[0],
+                 '--assetsDir', downloadAssets.output,
+                 '--assetIndex', "{asset_index}"
+        }
     }
 }
 
@@ -266,11 +297,16 @@ tasks.register('downloadCrowdin', Download) {
 tasks.userdevConfig.configure {
     configurations.installer.allDependencies.forEach {
         def dep = it.toString()
-        if (it instanceof ProjectDependency) 
+        if (it instanceof ProjectDependency)
             dep = "net.minecraftforge:$it.dependencyProject.name:$it.dependencyProject.version"
         libraries.add(dep)
     }
-    
+
+    // TODO [ForgeDev][UserDev] Split API/Runtime elements in userdev config
+    //      so we don't gotta keep making exceptions for MixinExtras
+    addCompileDependency(libs.mixinextras.common)
+    addAnnotationProcessorDependency(libs.mixinextras.common)
+
     inject = '' // We don't have a userdev sourceset anymore. Empty as a gradle workaround...
     runs {
         client {
@@ -282,6 +318,13 @@ tasks.userdevConfig.configure {
             args '--assetsDir', '{assets_root}'
         }
 
+        clientData {
+            environment 'MCP_MAPPINGS', '{mcp_mappings}'
+            args '--launchTarget', "forge_userdev_client_data"
+            args '--assetIndex', '{asset_index}'
+            args '--assetsDir', '{assets_root}'
+        }
+
         server {
             environment 'MCP_MAPPINGS', '{mcp_mappings}'
             property 'forge.enableGameTest', 'true'
@@ -379,14 +422,14 @@ tasks.register('extractInheritance', ExtractInheritance) {
     }
 }
 tasks.register("findFinalizeSpawnTargets", BytecodePredicateFinder) {
-    jar = createJoinedSRG.output
-    output = rootProject.file('src/main/resources/coremods/finalize_spawn_targets.json')
+    jar = createClientOfficial.output
+    output = rootProject.file('forge-transformers/src/main/resources/coremods/finalize_spawn_targets.json')
     predicate = {
         parent, node, insn ->
             return 'net/minecraft/world/level/BaseSpawner' != parent.name // Ignore this class as we special case it.
             && insn.getOpcode().equals(Opcodes.INVOKEVIRTUAL)
-            && insn.name == 'm_6518_'
-            && insn.desc == '(Lnet/minecraft/world/level/ServerLevelAccessor;Lnet/minecraft/world/DifficultyInstance;Lnet/minecraft/world/entity/MobSpawnType;Lnet/minecraft/world/entity/SpawnGroupData;)Lnet/minecraft/world/entity/SpawnGroupData;';
+            && insn.name == 'finalizeSpawn'
+            && insn.desc == '(Lnet/minecraft/world/level/ServerLevelAccessor;Lnet/minecraft/world/DifficultyInstance;Lnet/minecraft/world/entity/EntitySpawnReason;Lnet/minecraft/world/entity/SpawnGroupData;)Lnet/minecraft/world/entity/SpawnGroupData;';
     }
 }
 tasks.register('validateDeprecations', ValidateDeprecations) {
@@ -491,7 +534,7 @@ tasks.register('serverShimJar', Jar) {
         from {
             zipTree(downloadServerShim.output).find { it.name == 'MANIFEST.MF' }
         }
-        
+
         attributes('Class-Path': configurations.bootstrap.resolvedConfiguration.resolvedArtifacts.collect { "libraries/${Util.getMavenInfoFromDep(it).path}" }.join(' '))
     }
     archiveClassifier = 'shim'
@@ -584,7 +627,7 @@ tasks.register('checkJarCompatibility', CheckJarCompatibility) {
     baseLibraries.from(project.tasks.named('createJoinedSRG').flatMap { it.output })
 
     inputJar = project.tasks.named('reobfJar').flatMap { it.output }
-    
+
     commonLibraries.from(project.configurations.minecraftImplementation)
     commonLibraries.from(project.configurations.installer)
 }
@@ -605,11 +648,11 @@ tasks.register('launcherJson', LauncherJson).configure {
 
 tasks.register('installerJson', InstallerJson) {
     icon = rootProject.file('icon.ico')
-    
+
     // Json to install into the client's launcher
     dependsOn(launcherJson)
     input.from(launcherJson.output)
-    
+
     // Download Official Mappings
     dependsOn(downloadClientMappings, downloadServerMappings)
     input.from(downloadClientMappings.output, downloadServerMappings.output)
@@ -815,6 +858,9 @@ tasks.named('universalJar').configure {
     exclude '.cache'
 
     manifest {
+        attributes([
+            'Automatic-Module-Name': 'net.minecraftforge.forge'
+        ] as LinkedHashMap)
         attributes([
             'Specification-Title':   'Forge',
             'Specification-Vendor':  'Forge Development LLC',
@@ -918,6 +964,9 @@ tasks.register('mdkZip', Zip) {
         rename 'gitignore\\.txt', '.gitignore'
         rename 'gitattributes\\.txt', '.gitattributes'
     }
+    from(rootProject.file('src/test/java/com/example/examplemod/')) {
+        into('src/main/java/com/example/examplemod/')
+    }
     from(rootProject.file('src/test/generated/mdk_datagen/')) {
         into('src/main/resources/')
         exclude '**/.cache/'
@@ -957,7 +1006,7 @@ if (project.hasProperty('UPDATE_MAPPINGS')) {
 
 tasks.named('javadoc', Javadoc).configure {
     description 'Generates the combined javadocs for the FML projects and the main Forge project'
-    var includedProjects = [ ':fmlcore', ':fmlloader', ':javafmllanguage', ':mclanguage' ]
+    var includedProjects = [ ':fmlcore', ':fmlloader', ':javafmllanguage', ':mclanguage', ':forge-transformers' ]
     source includedProjects.collect { project(it).sourceSets.main.allJava }
     classpath = classpath + files(includedProjects.collect { project(it).sourceSets.main.compileClasspath })
 
@@ -1051,7 +1100,7 @@ publishing {
             license gradleutils.pom.Licenses.LGPLv2_1
         }
     }
-    
+
     repositories {
         maven gradleutils.publishingForgeMaven
     }

build_shared.gradle

@@ -38,13 +38,17 @@ tasks.register('generateResources') {
     dependsOn('writeManifest')
 }
 
+tasks.named('processResources') {
+    dependsOn(generateResources)
+}
+
 // Make sure out manifests get written before compiling the code, IDEA calls this task if you tell it to use the gradle build.
 tasks.withType(JavaCompile).configureEach {
     dependsOn 'generateResources'
     dependsOn 'processResources' // Needed because we merge the output of this with the output of the compile task. And gradle detects downstream tasks using the output without a hard dep
     options.encoding = 'UTF-8' // Use the UTF-8 charset for Java compilation
     options.warnings = false // Shutup deprecated for removal warnings
-    options.forkOptions.jvmArgs += '-Xmx3G' // Needed to make compiling faster, and not run out of heap space in some cases.
+    options.forkOptions.jvmArgs += '-Xmx6G' // Needed to make compiling faster, and not run out of heap space in some cases.
 }
 
 // Merge the resources and classes into the same directory. We'll need to split them at runtime because
@@ -75,3 +79,11 @@ eclipse {
     // Run when importing the project
     synchronizationTasks generateResources, copyEclipseSettings, eclipseClasspath, eclipseProject
 }
+
+idea {
+    module {
+        // IntelliJ IDEA does not do this by itself anymore...
+        downloadJavadoc = true
+        downloadSources = true
+    }
+}

docs/README.md

@@ -2,16 +2,15 @@
 
 MinecraftForge
 =============
-[![Stable Release](https://img.shields.io/badge/dynamic/json?url=https://files.minecraftforge.net/net/minecraftforge/forge/promotions_slim.json&label=Stable&prefix=1.20.6-&query=$.promos["1.20.6-recommended"]&color=brightgreen&logo=data:image/svg+xml;base64,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)][Download]
-[![Latest Release](https://img.shields.io/badge/dynamic/json?url=https://files.minecraftforge.net/net/minecraftforge/forge/promotions_slim.json&label=Latest&prefix=1.20.6-&query=$.promos["1.20.6-latest"]&color=blue&logo=data:image/svg+xml;base64,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
+[![Stable Release](https://img.shields.io/badge/dynamic/json?url=https://files.minecraftforge.net/net/minecraftforge/forge/promotions_slim.json&label=Stable&prefix=1.21.10-&query=$.promos["1.21.10-recommended"]&color=brightgreen&logo=data:image/svg+xml;base64,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)][Download]
+[![Latest Release](https://img.shields.io/badge/dynamic/json?url=https://files.minecraftforge.net/net/minecraftforge/forge/promotions_slim.json&label=Latest&prefix=1.21.10-&query=$.promos["1.21.10-latest"]&color=blue&logo=data:image/svg+xml;base64,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
 )][Download] [![Discord](https://img.shields.io/discord/313125603924639766.svg?color=%237289da&label=Discord&logo=discord&logoColor=%237289da)][Discord] [![Support](https://img.shields.io/badge/Patreon-Support-orange.svg?logo=Patreon)][Patreon]
 
 Forge is a free, open-source modding API all of your favourite mods use!
 
-| Version |    Support    |
-|---------| ------------- |
-| 1.20.x  |    Active     |
-| 1.19.x  |    Legacy     |
+| Version      | Support                     |
+|--------------|-----------------------------|
+| All versions | [Supported][Support-Policy] |
 
 * [Download]
 * [Forum]
@@ -31,6 +30,19 @@ You can download the installer for the *Recommended Build* or the
  
 For support and questions, visit [the Support Forum][Support-Forum] or [the Forge Discord server][Discord].
 
+## Required Java Versions
+
+We require the version of Java that Minecraft requires, which is currently:
+
+| Minecraft     | Java              |
+|---------------|-------------------|
+| 1.20.6+       | [21][Adoptium-21] |
+| 1.18 - 1.20.4 | [17][Adoptium-17] |
+| 1.17.1        | [16][Adoptium-16] |
+| 1.16.5-       | [8][Adoptium-8]   |
+
+**If you are on Windows and have difficulty using Java to launch JAR files, consider using [Jarfix by Johann Löfflmann][Jarfix].**
+
 # Creating Mods
 
 [See the "Getting Started" section in the Forge Documentation][Getting-Started].
@@ -58,13 +70,25 @@ Please ensure you have a valid email address associated with your GitHub account
  to use and modify. However, it costs money to run such a large project as this, so please consider 
  [becoming a patron][Patreon].*
 
+### Thanks
+[![YourKit](https://www.yourkit.com/images/yklogo.png)](https://www.yourkit.com/)
+
+YourKit for providing us accesss to their [YourKit Java Profiler] which helps identify bottlenecks and places for improvment.
+
 [Contributing]: ./CONTRIBUTING.md
 [CLA]: https://cla-assistant.io/MinecraftForge/MinecraftForge
 
 [Download]: https://files.minecraftforge.net/
 
+[Adoptium-21]: https://adoptium.net/temurin/releases/?version=21
+[Adoptium-17]: https://adoptium.net/temurin/releases/?version=17
+[Adoptium-16]: https://adoptium.net/temurin/releases/?version=16
+[Adoptium-8]: https://adoptium.net/temurin/releases/?version=8
+[Jarfix]: https://johann.loefflmann.net/en/software/jarfix/index.html
+
 [Forum]: https://forums.minecraftforge.net/
 [Support-Forum]: https://forums.minecraftforge.net/forum/18-support-bug-reports/
+[Support-Policy]: https://forums.minecraftforge.net/topic/144690-new-tiered-support-policy
 
 [Discord]: https://discord.minecraftforge.net/
 
@@ -74,3 +98,4 @@ Please ensure you have a valid email address associated with your GitHub account
 [Pull-Requests]: https://docs.minecraftforge.net/en/latest/forgedev/#making-changes-and-pull-requests
 
 [Patreon]: https://www.patreon.com/LexManos
+[YourKit Java Profiler]: https://www.yourkit.com/java/profiler/

fmlcore/build.gradle

@@ -10,9 +10,10 @@ plugins {
 apply from: rootProject.file('build_shared.gradle')
 
 dependencies {
-    compileOnly(libs.nulls)
+    compileOnly(libs.jetbrains.annotations)
 
     api(libs.eventbus)
+    annotationProcessor(libs.eventbus.validator)
 
     implementation(project(':fmlloader'))
     implementation(libs.commons.io)

fmlcore/src/main/java/net/minecraftforge/fml/Bindings.java

@@ -5,7 +5,7 @@
 
 package net.minecraftforge.fml;
 
-import net.minecraftforge.eventbus.api.IEventBus;
+import net.minecraftforge.eventbus.api.bus.BusGroup;
 import net.minecraftforge.fml.config.IConfigEvent;
 import net.minecraftforge.fml.loading.FMLLoader;
 
@@ -29,7 +29,7 @@ public class Bindings {
     /**
      * @return A supplier of net.minecraftforge.common.MinecraftForge#EVENT_BUS
      */
-    public static Supplier<IEventBus> getForgeBus() {
+    public static Supplier<BusGroup> getForgeBus() {
         return PROVIDER.getForgeBusSupplier();
     }
 

fmlcore/src/main/java/net/minecraftforge/fml/DeferredWorkQueue.java

@@ -57,7 +57,9 @@ public class DeferredWorkQueue
         LOGGER.debug(LOADING, "Dispatching synchronous work for work queue {}: {} jobs", modLoadingStage, tasks.size());
         RuntimeException aggregate = new RuntimeException();
         Stopwatch timer = Stopwatch.createStarted();
-        tasks.forEach(t -> makeRunnable(t, Runnable::run, aggregate));
+        for (TaskInfo t : tasks) {
+            makeRunnable(t, Runnable::run, aggregate);
+        }
         timer.stop();
         if (aggregate.getSuppressed().length > 0) {
             LOGGER.fatal(
@@ -114,7 +116,7 @@ public class DeferredWorkQueue
         return future;
     }
 
-    private static class TaskInfo {
+    private static final class TaskInfo {
         private final ModContainer owner;
         private Runnable task;
         private CompletableFuture<?> future;

fmlcore/src/main/java/net/minecraftforge/fml/DistExecutor.java

@@ -25,7 +25,18 @@ import java.util.function.Supplier;
  * <li>When you want to call one thing on one side, another thing on the other and return a result {@link #safeRunForDist(Supplier, Supplier)}</li>
  * <li>When you want to run something on one side {@link #safeRunWhenOn(Dist, Supplier)}</li>
  * </ul>
+ *
+ * @deprecated Historically, this allowed for safe execution of code on the correct side by exploiting a low-level
+ * detail in Java 8, but in newer versions a simple if check is enough.
+ * <br>
+ * For example:
+ * <pre>{@code
+ * if (FMLEnvironment.dist.isClient()) {
+ *     // client code here
+ * }
+ * }</pre>
  */
+@Deprecated(since = "1.21.5", forRemoval = true)
 public final class DistExecutor
 {
     private static final Logger LOGGER = LogManager.getLogger();

fmlcore/src/main/java/net/minecraftforge/fml/IBindingsProvider.java

@@ -5,13 +5,13 @@
 
 package net.minecraftforge.fml;
 
-import net.minecraftforge.eventbus.api.IEventBus;
+import net.minecraftforge.eventbus.api.bus.BusGroup;
 import net.minecraftforge.fml.config.IConfigEvent;
 
 import java.util.function.Supplier;
 
 public interface IBindingsProvider {
-    Supplier<IEventBus> getForgeBusSupplier();
+    Supplier<BusGroup> getForgeBusSupplier();
     Supplier<I18NParser> getMessageParser();
     Supplier<IConfigEvent.ConfigConfig> getConfigConfiguration();
 }

fmlcore/src/main/java/net/minecraftforge/fml/IModLoadingState.java

@@ -5,8 +5,6 @@
 
 package net.minecraftforge.fml;
 
-import net.minecraftforge.eventbus.api.Event;
-import net.minecraftforge.fml.event.IModBusEvent;
 import net.minecraftforge.fml.loading.progress.ProgressMeter;
 
 import java.util.Optional;
@@ -61,27 +59,27 @@ public interface IModLoadingState {
     /**
      * Builds the transition task for this state with a blank pre-sync and post-sync task.
      *
-     * @param <T>              a type of event fired on the mod-specific event bus
      * @param syncExecutor     a synchronous executor
      * @param parallelExecutor a parallel executor
      * @param progressBar      a progress meter for tracking progress
      * @return a transition task for this state
      * @see #buildTransition(Executor, Executor, ProgressMeter, Function, Function)
      */
-    default <T extends Event & IModBusEvent>
-    Optional<CompletableFuture<Void>> buildTransition(final Executor syncExecutor,
-                                                      final Executor parallelExecutor,
-                                                      final ProgressMeter progressBar) {
+    default Optional<CompletableFuture<Void>> buildTransition(
+        final Executor syncExecutor,
+        final Executor parallelExecutor,
+        final ProgressMeter progressBar
+    ) {
         return buildTransition(syncExecutor, parallelExecutor, progressBar,
-                e -> CompletableFuture.runAsync(() -> {}, e),
-                e -> CompletableFuture.runAsync(() -> {}, e));
+            e -> CompletableFuture.completedFuture(null),
+            e -> CompletableFuture.completedFuture(null)
+        );
     }
 
     /**
      * Builds the transition task for this state. The pre-sync and post-sync task functions allow the transition builder
      * to run these tasks on the same executor as the actual event dispatch and pre/post hooks.
      *
-     * @param <T>              a type of event fired on the mod-specific event bus
      * @param syncExecutor     a synchronous executor
      * @param parallelExecutor a parallel executor
      * @param progressBar      a progress meter for tracking progress
@@ -89,7 +87,6 @@ public interface IModLoadingState {
      * @param postSyncTask     a function which returns a task to run after event post-dispatch hook
      * @return a transition task for this state
      */
-    <T extends Event & IModBusEvent>
     Optional<CompletableFuture<Void>> buildTransition(final Executor syncExecutor,
                                                       final Executor parallelExecutor,
                                                       final ProgressMeter progressBar,

fmlcore/src/main/java/net/minecraftforge/fml/IModStateTransition.java

@@ -5,12 +5,9 @@
 
 package net.minecraftforge.fml;
 
-import net.minecraftforge.eventbus.api.Event;
 import net.minecraftforge.fml.event.IModBusEvent;
 import net.minecraftforge.fml.loading.progress.ProgressMeter;
 
-import java.util.ArrayList;
-import java.util.List;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.Executor;
 import java.util.function.BiFunction;
@@ -18,103 +15,67 @@ import java.util.function.Function;
 import java.util.function.Supplier;
 import java.util.stream.Stream;
 
-@SuppressWarnings("unchecked")
+import org.jetbrains.annotations.Nullable;
+
 public interface IModStateTransition {
+    /** Magic value to allow me to optimize the futures list by ignoring the default value without making old methods nullable. */
+    BiFunction<Executor, ? extends EventGenerator<?>, CompletableFuture<Void>> NULL_HOOK = (e, g) -> CompletableFuture.completedFuture(null);
+
     static IModStateTransition buildNoopTransition() {
-        return new NoopTransition();
+        return ModStateTransitionHelper.NOOP;
     }
 
-    default <T extends Event & IModBusEvent>
-    CompletableFuture<Void> build(final String name,
-                                  final Executor syncExecutor,
-                                  final Executor parallelExecutor,
-                                  final ProgressMeter progressBar,
-                                  final Function<Executor, CompletableFuture<Void>> preSyncTask,
-                                  final Function<Executor, CompletableFuture<Void>> postSyncTask) {
-        List<CompletableFuture<Void>> futures = new ArrayList<>();
-
-        this.eventFunctionStream().get()
-                .map(f -> (EventGenerator<T>) f)
-                .reduce((head, tail) -> addCompletableFutureTaskForModDispatch(syncExecutor, parallelExecutor, futures, progressBar, head, ModLoadingStage::currentState, tail))
-                .ifPresent(last -> addCompletableFutureTaskForModDispatch(syncExecutor, parallelExecutor, futures, progressBar, last, nextModLoadingStage(), null));
-
-        final CompletableFuture<Void> preSyncTaskCF = preSyncTask.apply(syncExecutor);
-        final CompletableFuture<Void> eventDispatchCF = ModList.gather(futures).thenCompose(ModList::completableFutureFromExceptionList);
-        final CompletableFuture<Void> postEventDispatchCF = preSyncTaskCF
-                .thenApplyAsync(n -> {
-                    progressBar.label(progressBar.name() + ": dispatching "+name);
-                    return null;
-                }, parallelExecutor)
-                .thenComposeAsync(n -> eventDispatchCF, parallelExecutor)
-                .thenApply(r -> {
-                    postSyncTask.apply(syncExecutor);
-                    return null;
-                });
-        return this.finalActivityGenerator().apply(syncExecutor, postEventDispatchCF);
+    default CompletableFuture<Void> build(
+        final String name,
+        final Executor syncExecutor,
+        final Executor parallelExecutor,
+        final ProgressMeter progressBar,
+        final Function<Executor, CompletableFuture<Void>> preSyncTask,
+        final Function<Executor, CompletableFuture<Void>> postSyncTask
+    ) {
+        return ModStateTransitionHelper.build(this, name, syncExecutor, parallelExecutor, progressBar, preSyncTask, postSyncTask);
     }
 
     default BiFunction<ModLoadingStage, Throwable, ModLoadingStage> nextModLoadingStage() {
         return ModLoadingStage::nextState;
     }
 
-    private <T extends Event & IModBusEvent>
-    EventGenerator<T> addCompletableFutureTaskForModDispatch(final Executor syncExecutor,
-                                                             final Executor parallelExecutor,
-                                                             final List<CompletableFuture<Void>> completableFutures,
-                                                             final ProgressMeter progressBar,
-                                                             final EventGenerator<T> eventGenerator,
-                                                             final BiFunction<ModLoadingStage, Throwable, ModLoadingStage> nextState,
-                                                             final EventGenerator<T> nextGenerator) {
-        final Executor selectedExecutor = threadSelector().apply(syncExecutor, parallelExecutor);
-
-        var preDispatchHook = (BiFunction<Executor, EventGenerator<T>, CompletableFuture<Void>>) preDispatchHook();
-        completableFutures.add(preDispatchHook.apply(selectedExecutor, eventGenerator));
-
-        completableFutures.add(ModList.get().futureVisitor(eventGenerator, progressBar, nextState).apply(threadSelector().apply(syncExecutor, parallelExecutor)));
-
-        var postDispatchHook = (BiFunction<Executor, EventGenerator<T>, CompletableFuture<Void>>) postDispatchHook();
-        completableFutures.add(postDispatchHook.apply(selectedExecutor, eventGenerator));
-
-        return nextGenerator;
+    /**
+     * This used to allow you to fire multiple events during the transition. However, in doing so it would cause issues with the default
+     * ModContainer's event handlers causing issues such as mod classes being constructed multiple times.
+     */
+    @Deprecated(since = "1.21.3", forRemoval = true)
+    default Supplier<Stream<EventGenerator<?>>> eventFunctionStream() {
+        return () -> Stream.ofNullable(eventFunction());
+    }
+
+    @Nullable
+    default <T extends IModBusEvent> EventGenerator<T> eventFunction() {
+        return null;
     }
 
-    Supplier<Stream<EventGenerator<?>>> eventFunctionStream();
     ThreadSelector threadSelector();
     BiFunction<Executor, CompletableFuture<Void>, CompletableFuture<Void>> finalActivityGenerator();
-    BiFunction<Executor, ? extends EventGenerator<?>, CompletableFuture<Void>> preDispatchHook();
-    BiFunction<Executor, ? extends EventGenerator<?>, CompletableFuture<Void>> postDispatchHook();
 
-    interface EventGenerator<T extends Event & IModBusEvent> extends Function<ModContainer, T> {
-        static <FN extends Event & IModBusEvent> EventGenerator<FN> fromFunction(Function<ModContainer, FN> fn) {
+    /**
+     * I think this was meant as a way to do some things for each mod container beforge/after the transition had been sent to the container.
+     * However, the Future returned by this was never linked to the main transition future in any way.  Which means that it was run
+     * in parallel and couldn't guarantee the state of the ModContainer.
+     * <p>
+     * Plus all existing code that I could find returned a completedFuture, so I don't think anyone ever used this.
+     * <p>
+     * If I were to add this back it would be a CompletableFuture wrap(ModContainer, CompletableFuture)
+     * <p>
+     * Added magic value NULL_HOOK to allow me to optimize the futures list by ignoring the default value without making this method nullable.
+     */
+    @Deprecated(since = "1.21.3", forRemoval = true)
+    default BiFunction<Executor, ? extends EventGenerator<?>, CompletableFuture<Void>> preDispatchHook() { return NULL_HOOK; }
+    @Deprecated(since = "1.21.3", forRemoval = true)
+    default BiFunction<Executor, ? extends EventGenerator<?>, CompletableFuture<Void>> postDispatchHook() { return NULL_HOOK; }
+
+    interface EventGenerator<T extends IModBusEvent> extends Function<ModContainer, T> {
+        static <FN extends IModBusEvent> EventGenerator<FN> fromFunction(Function<ModContainer, FN> fn) {
             return fn::apply;
         }
     }
-}
-
-record NoopTransition() implements IModStateTransition {
-
-    @Override
-    public Supplier<Stream<EventGenerator<?>>> eventFunctionStream() {
-        return Stream::of;
-    }
-
-    @Override
-    public ThreadSelector threadSelector() {
-        return ThreadSelector.SYNC;
-    }
-
-    @Override
-    public BiFunction<Executor, CompletableFuture<Void>, CompletableFuture<Void>> finalActivityGenerator() {
-        return (e, t) -> t.thenApplyAsync(Function.identity(), e);
-    }
-
-    @Override
-    public BiFunction<Executor, ? extends EventGenerator<?>, CompletableFuture<Void>> preDispatchHook() {
-        return (t, f)-> CompletableFuture.completedFuture(null);
-    }
-
-    @Override
-    public BiFunction<Executor, ? extends EventGenerator<?>, CompletableFuture<Void>> postDispatchHook() {
-        return (t, f)-> CompletableFuture.completedFuture(null);
-    }
 }

fmlcore/src/main/java/net/minecraftforge/fml/InterModComms.java

@@ -61,7 +61,7 @@ public class InterModComms
         }
     }
 
-    private static ConcurrentMap<String, ConcurrentLinkedQueue<IMCMessage>> containerQueues = new ConcurrentHashMap<>();
+    private static final ConcurrentMap<String, ConcurrentLinkedQueue<IMCMessage>> containerQueues = new ConcurrentHashMap<>();
 
     /**
      * Send IMC to remote. Sender will default to the active modcontainer, or minecraft if not.
@@ -115,16 +115,14 @@ public class InterModComms
         return getMessages(modId, s->Boolean.TRUE);
     }
 
-    private static class QueueFilteringSpliterator implements Spliterator<IMCMessage>
-    {
-        private final ConcurrentLinkedQueue<IMCMessage> queue;
-        private final Predicate<String> methodFilter;
-        private final Iterator<IMCMessage> iterator;
+    private record QueueFilteringSpliterator(
+            ConcurrentLinkedQueue<IMCMessage> queue,
+            Predicate<String> methodFilter,
+            Iterator<IMCMessage> iterator
+    ) implements Spliterator<IMCMessage> {
 
         public QueueFilteringSpliterator(final ConcurrentLinkedQueue<IMCMessage> queue, final Predicate<String> methodFilter) {
-            this.queue = queue;
-            this.iterator = queue.iterator();
-            this.methodFilter = methodFilter;
+            this(queue, methodFilter, queue.iterator());
         }
 
         @Override

fmlcore/src/main/java/net/minecraftforge/fml/ModContainer.java

@@ -5,22 +5,19 @@
 
 package net.minecraftforge.fml;
 
-import net.minecraftforge.eventbus.api.Event;
+import net.minecraftforge.eventbus.api.bus.BusGroup;
 import net.minecraftforge.fml.config.IConfigEvent;
 import net.minecraftforge.fml.config.ModConfig;
 import net.minecraftforge.fml.event.IModBusEvent;
-import net.minecraftforge.fml.loading.progress.ProgressMeter;
 import net.minecraftforge.forgespi.language.IModInfo;
 
 import java.util.EnumMap;
-import java.util.HashMap;
+import java.util.HashSet;
 import java.util.IdentityHashMap;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
-import java.util.concurrent.CompletableFuture;
-import java.util.concurrent.Executor;
-import java.util.function.BiFunction;
+import java.util.Set;
 import java.util.function.BiPredicate;
 import java.util.function.Consumer;
 import java.util.function.Supplier;
@@ -33,26 +30,24 @@ import java.util.function.Supplier;
  * a mechanism by which we can wrap actual mod code so that the loader and other
  * facilities can treat mods at arms length.
  * </p>
- *
- * @author cpw
- *
  */
-
-public abstract class ModContainer
-{
+public abstract class ModContainer {
     protected final String modId;
     protected final String namespace;
     protected final IModInfo modInfo;
     protected ModLoadingStage modLoadingStage;
     protected Supplier<?> contextExtension;
-    protected final Map<ModLoadingStage, Runnable> activityMap = new HashMap<>();
+    protected final Map<ModLoadingStage, Runnable> activityMap = new EnumMap<>(ModLoadingStage.class);
     protected final Map<Class<? extends IExtensionPoint<?>>, Supplier<?>> extensionPoints = new IdentityHashMap<>();
     protected final EnumMap<ModConfig.Type, ModConfig> configs = new EnumMap<>(ModConfig.Type.class);
-    @SuppressWarnings("OptionalUsedAsFieldOrParameterType")
+    final Set<ModContainer> dependencies = new HashSet<>();
+    /**
+     * If you want to handle the event, override {@link #dispatchConfigEvent(IConfigEvent)}
+     */
+    @Deprecated(since = "1.21.3", forRemoval = true)
     protected Optional<Consumer<IConfigEvent>> configHandler = Optional.empty();
 
-    public ModContainer(IModInfo info)
-    {
+    public ModContainer(IModInfo info) {
         this.modId = info.getModId();
         // TODO: Currently not reading namespace from configuration..
         this.namespace = this.modId;
@@ -82,58 +77,35 @@ public abstract class ModContainer
     /**
      * Errored container state, used for filtering. Does nothing.
      */
-    ModContainer()
-    {
+    ModContainer() {
         this.modLoadingStage = ModLoadingStage.ERROR;
         modId = "BROKEN";
         namespace = "BROKEN";
         modInfo = null;
     }
+
     /**
      * @return the modid for this mod
      */
-    public final String getModId()
-    {
+    public final String getModId() {
         return modId;
     }
 
     /**
      * @return the resource prefix for the mod
      */
-    public final String getNamespace()
-    {
+    public final String getNamespace() {
         return namespace;
     }
 
     /**
      * @return The current loading stage for this mod
      */
-    public ModLoadingStage getCurrentState()
-    {
+    public ModLoadingStage getCurrentState() {
         return modLoadingStage;
     }
 
-    public static <T extends Event & IModBusEvent> CompletableFuture<Void> buildTransitionHandler(
-            final ModContainer target,
-            final IModStateTransition.EventGenerator<T> eventGenerator,
-            final ProgressMeter progressBar,
-            final BiFunction<ModLoadingStage, Throwable, ModLoadingStage> stateChangeHandler,
-            final Executor executor) {
-        return CompletableFuture
-                .runAsync(() -> {
-                    ModLoadingContext.get().setActiveContainer(target);
-                    target.activityMap.getOrDefault(target.modLoadingStage, ()->{}).run();
-                    target.acceptEvent(eventGenerator.apply(target));
-                }, executor)
-                .whenComplete((mc, exception) -> {
-                    target.modLoadingStage = stateChangeHandler.apply(target.modLoadingStage, exception);
-                    progressBar.increment();
-                    ModLoadingContext.get().setActiveContainer(null);
-                });
-    }
-
-    public IModInfo getModInfo()
-    {
+    public IModInfo getModInfo() {
         return modInfo;
     }
 
@@ -142,8 +114,7 @@ public abstract class ModContainer
         return Optional.ofNullable((T)extensionPoints.getOrDefault(point,()-> null).get());
     }
 
-    public <T extends Record & IExtensionPoint<T>> void registerExtensionPoint(Class<? extends IExtensionPoint<T>> point, Supplier<T> extension)
-    {
+    public <T extends Record & IExtensionPoint<T>> void registerExtensionPoint(Class<? extends IExtensionPoint<T>> point, Supplier<T> extension) {
         extensionPoints.put(point, extension);
     }
 
@@ -168,7 +139,10 @@ public abstract class ModContainer
     }
 
     public void dispatchConfigEvent(IConfigEvent event) {
-        configHandler.ifPresent(configHandler->configHandler.accept(event));
+        var handler = configHandler.orElse(null);
+        if (handler != null) {
+            handler.accept(event);
+        }
     }
 
     /**
@@ -184,9 +158,17 @@ public abstract class ModContainer
      */
     public abstract Object getMod();
 
+    /**
+     * @return the mod bus group for this specific mod, or null if there is none.
+     *         Leave null if you use {@link BusGroup#DEFAULT} for your mod lifecycle events.
+     */
+    public BusGroup getModBusGroup() {
+        return null;
+    }
+
     /**
      * Accept an arbitrary event for processing by the mod. Probably posted to an event bus in the lower level container.
      * @param e Event to accept
      */
-    protected <T extends Event & IModBusEvent> void acceptEvent(T e) {}
+    protected <T extends IModBusEvent> void acceptEvent(T e) {}
 }

fmlcore/src/main/java/net/minecraftforge/fml/ModList.java

@@ -5,9 +5,6 @@
 
 package net.minecraftforge.fml;
 
-import net.minecraftforge.eventbus.api.Event;
-import net.minecraftforge.fml.event.IModBusEvent;
-import net.minecraftforge.fml.loading.progress.ProgressMeter;
 import net.minecraftforge.forgespi.language.IModFileInfo;
 import net.minecraftforge.forgespi.language.IModInfo;
 import net.minecraftforge.forgespi.language.ModFileScanData;
@@ -15,27 +12,15 @@ import net.minecraftforge.fml.loading.moddiscovery.ModFile;
 import net.minecraftforge.fml.loading.moddiscovery.ModFileInfo;
 import net.minecraftforge.fml.loading.moddiscovery.ModInfo;
 import net.minecraftforge.forgespi.locating.IModFile;
-import org.apache.logging.log4j.LogManager;
-import org.apache.logging.log4j.Logger;
-
-import java.util.AbstractMap;
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collection;
+import java.util.Collections;
 import java.util.Comparator;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
-import java.util.concurrent.CompletableFuture;
-import java.util.concurrent.CompletionException;
-import java.util.concurrent.CompletionStage;
-import java.util.concurrent.Executor;
-import java.util.concurrent.ForkJoinPool;
-import java.util.concurrent.ForkJoinWorkerThread;
 import java.util.function.BiConsumer;
-import java.util.function.BiFunction;
 import java.util.function.Consumer;
 import java.util.function.Function;
 import java.util.stream.Collectors;
@@ -45,27 +30,25 @@ import java.util.stream.Stream;
  * Master list of all mods - game-side version. This is classloaded in the game scope and
  * can dispatch game level events as a result.
  */
-public class ModList
-{
-    //private static final Logger LOGGER = LogManager.getLogger();
+public class ModList {
     private static ModList INSTANCE;
     private final List<IModFileInfo> modFiles;
     private final List<IModInfo> sortedList;
-    private final Map<String, ModFileInfo> fileById;
+    private final Map<String, IModFileInfo> fileById;
     private List<ModContainer> mods;
     private Map<String, ModContainer> indexedMods;
     private List<ModFileScanData> modFileScanData;
     private List<ModContainer> sortedContainers;
 
-    private ModList(final List<ModFile> modFiles, final List<ModInfo> sortedList)
-    {
-        this.modFiles = modFiles.stream().map(ModFile::getModFileInfo).map(ModFileInfo.class::cast).collect(Collectors.toList());
-        this.sortedList = sortedList.stream().
-                map(ModInfo.class::cast).
-                collect(Collectors.toList());
-        this.fileById = this.modFiles.stream().map(IModFileInfo::getMods).flatMap(Collection::stream).
-                map(ModInfo.class::cast).
-                collect(Collectors.toMap(ModInfo::getModId, ModInfo::getOwningFile));
+    private ModList(final List<ModFile> modFiles, final List<ModInfo> sortedList) {
+        var modFileInfos = this.modFiles = modFiles.stream().map(ModFile::getModFileInfo).toList();
+        this.sortedList = sortedList.stream().map(IModInfo.class::cast).toList();
+        var byId = new HashMap<String, IModFileInfo>();
+        for (var file : modFileInfos) {
+            for (var mod : file.getMods())
+                byId.put(mod.getModId(), mod.getOwningFile());
+        }
+        this.fileById = Map.copyOf(byId);
         CrashReportCallables.registerCrashCallable("Mod List", this::crashReport);
     }
 
@@ -74,19 +57,20 @@ public class ModList
     }
 
     private String fileToLine(IModFile mf) {
+        var mainMod = mf.getModInfos().getFirst();
         return String.format(Locale.ENGLISH, "%-50.50s|%-30.30s|%-30.30s|%-20.20s|%-10.10s|Manifest: %s", mf.getFileName(),
-                mf.getModInfos().get(0).getDisplayName(),
-                mf.getModInfos().get(0).getModId(),
-                mf.getModInfos().get(0).getVersion(),
-                getModContainerState(mf.getModInfos().get(0).getModId()),
+                mainMod.getDisplayName(),
+                mainMod.getModId(),
+                mainMod.getVersion(),
+                getModContainerState(mainMod.getModId()),
                 ((ModFileInfo)mf.getModFileInfo()).getCodeSigningFingerprint().orElse("NOSIGNATURE"));
     }
+
     private String crashReport() {
-        return "\n"+applyForEachModFile(this::fileToLine).collect(Collectors.joining("\n\t\t", "\t\t", ""));
+        return "\n" + applyForEachModFile(this::fileToLine).collect(Collectors.joining("\n\t\t", "\t\t", ""));
     }
 
-    public static ModList of(List<ModFile> modFiles, List<ModInfo> sortedList)
-    {
+    public static ModList of(List<ModFile> modFiles, List<ModInfo> sortedList) {
         INSTANCE = new ModList(modFiles, sortedList);
         return INSTANCE;
     }
@@ -95,123 +79,59 @@ public class ModList
         return INSTANCE;
     }
 
-    private static ForkJoinWorkerThread newForkJoinWorkerThread(ForkJoinPool pool) {
-        ForkJoinWorkerThread thread = ForkJoinPool.defaultForkJoinWorkerThreadFactory.newThread(pool);
-        thread.setName("modloading-worker-" + thread.getPoolIndex());
-        // The default sets it to the SystemClassloader, so copy the current one.
-        thread.setContextClassLoader(Thread.currentThread().getContextClassLoader());
-        return thread;
-    }
-
-    public List<IModFileInfo> getModFiles()
-    {
+    public List<IModFileInfo> getModFiles() {
         return modFiles;
     }
 
-    public IModFileInfo getModFileById(String modid)
-    {
+    public IModFileInfo getModFileById(String modid) {
         return this.fileById.get(modid);
     }
 
-    <T extends Event & IModBusEvent> Function<Executor, CompletableFuture<Void>> futureVisitor(
-            final IModStateTransition.EventGenerator<T> eventGenerator,
-            final ProgressMeter progressBar,
-            final BiFunction<ModLoadingStage, Throwable, ModLoadingStage> stateChange) {
-        return executor -> gather(
-                this.mods.stream()
-                .map(mod -> ModContainer.buildTransitionHandler(mod, eventGenerator, progressBar, stateChange, executor))
-                .toList()
-        ).thenComposeAsync(ModList::completableFutureFromExceptionList, executor);
-    }
-    static CompletionStage<Void> completableFutureFromExceptionList(List<? extends Map.Entry<?, Throwable>> t) {
-        if (t.stream().noneMatch(e->e.getValue()!=null)) {
-            return CompletableFuture.completedFuture(null);
-        } else {
-            final List<Throwable> throwables = t.stream().filter(e -> e.getValue() != null).map(Map.Entry::getValue).toList();
-            CompletableFuture<Void> cf = new CompletableFuture<>();
-            final RuntimeException accumulator = new RuntimeException();
-            cf.completeExceptionally(accumulator);
-            throwables.forEach(exception -> {
-                if (exception instanceof CompletionException) {
-                    exception = exception.getCause();
-                }
-                if (exception.getSuppressed().length!=0) {
-                    Arrays.stream(exception.getSuppressed()).forEach(accumulator::addSuppressed);
-                } else {
-                    accumulator.addSuppressed(exception);
-                }
-            });
-            return cf;
-        }
-    }
-
-    static <V> CompletableFuture<List<Map.Entry<V, Throwable>>> gather(List<? extends CompletableFuture<? extends V>> futures) {
-        List<Map.Entry<V, Throwable>> list = new ArrayList<>(futures.size());
-        CompletableFuture<?>[] results = new CompletableFuture[futures.size()];
-        futures.forEach(future -> {
-            int i = list.size();
-            list.add(null);
-            results[i] = future.whenComplete((result, exception) -> list.set(i, new AbstractMap.SimpleImmutableEntry<>(result, exception)));
-        });
-        return CompletableFuture.allOf(results).handle((r, th)->null).thenApply(res -> list);
-    }
-
-    void setLoadedMods(final List<ModContainer> modContainers)
-    {
+    void setLoadedMods(final List<ModContainer> modContainers) {
         this.mods = modContainers;
-        this.sortedContainers = modContainers.stream().sorted(Comparator.comparingInt(c->sortedList.indexOf(c.getModInfo()))).toList();
+        this.sortedContainers = modContainers.stream().sorted(Comparator.comparingInt(c -> sortedList.indexOf(c.getModInfo()))).toList();
         this.indexedMods = modContainers.stream().collect(Collectors.toMap(ModContainer::getModId, Function.identity()));
     }
 
     @SuppressWarnings("unchecked")
-    public <T> Optional<T> getModObjectById(String modId)
-    {
+    public <T> Optional<T> getModObjectById(String modId) {
         return getModContainerById(modId).map(ModContainer::getMod).map(o -> (T) o);
     }
 
-    public Optional<? extends ModContainer> getModContainerById(String modId)
-    {
+    public Optional<? extends ModContainer> getModContainerById(String modId) {
         return Optional.ofNullable(this.indexedMods.get(modId));
     }
 
-    public Optional<? extends ModContainer> getModContainerByObject(Object obj)
-    {
+    public Optional<? extends ModContainer> getModContainerByObject(Object obj) {
         return mods.stream().filter(mc -> mc.getMod() == obj).findFirst();
     }
 
-    public List<IModInfo> getMods()
-    {
+    public List<IModInfo> getMods() {
         return this.sortedList;
     }
 
-    public boolean isLoaded(String modTarget)
-    {
+    public boolean isLoaded(String modTarget) {
         return this.indexedMods.containsKey(modTarget);
     }
 
-    public int size()
-    {
+    public int size() {
         return mods.size();
     }
 
-    public List<ModFileScanData> getAllScanData()
-    {
-        if (modFileScanData == null)
-        {
+    public List<ModFileScanData> getAllScanData() {
+        if (modFileScanData == null) {
             modFileScanData = this.sortedList.stream().
                     map(IModInfo::getOwningFile).
                     filter(Objects::nonNull).
                     map(IModFileInfo::getFile).
                     distinct().
                     map(IModFile::getScanResult).
-                    collect(Collectors.toList());
+                    toList();
         }
         return modFileScanData;
-
     }
 
-    public void forEachModFile(Consumer<IModFile> fileConsumer)
-    {
+    public void forEachModFile(Consumer<IModFile> fileConsumer) {
         modFiles.stream().map(IModFileInfo::getFile).forEach(fileConsumer);
     }
 
@@ -227,13 +147,11 @@ public class ModList
         this.sortedContainers.forEach(containerConsumer);
     }
 
+    public List<ModContainer> getLoadedMods() {
+        return this.sortedContainers;
+    }
+
     public <T> Stream<T> applyForEachModContainer(Function<ModContainer, T> function) {
         return indexedMods.values().stream().map(function);
     }
-
-    private static class UncaughtModLoadingException extends ModLoadingException {
-        public UncaughtModLoadingException(ModLoadingStage stage, Throwable originalException) {
-            super(null, stage, "fml.modloading.uncaughterror", originalException);
-        }
-    }
 }

fmlcore/src/main/java/net/minecraftforge/fml/ModLoader.java

@@ -6,8 +6,7 @@
 package net.minecraftforge.fml;
 
 import com.google.common.collect.ImmutableList;
-import com.google.common.collect.Streams;
-import net.minecraftforge.eventbus.api.Event;
+import net.minecraftforge.eventbus.api.bus.BusGroup;
 import net.minecraftforge.fml.event.IModBusEvent;
 import net.minecraftforge.fml.loading.FMLEnvironment;
 import net.minecraftforge.fml.loading.FMLLoader;
@@ -33,8 +32,6 @@ import java.util.function.BiConsumer;
 import java.util.function.Consumer;
 import java.util.function.Function;
 import java.util.stream.Collectors;
-import java.util.stream.Stream;
-
 import static net.minecraftforge.fml.Logging.CORE;
 import static net.minecraftforge.fml.Logging.LOADING;
 
@@ -74,60 +71,68 @@ import static net.minecraftforge.fml.Logging.LOADING;
  *     and completes the mod loading sequence.</dd>
  * </dl>
  */
-public class ModLoader
-{
+public class ModLoader {
     private static final Logger LOGGER = LogManager.getLogger();
-    private static ModLoader INSTANCE;
     private final LoadingModList loadingModList;
 
     private final List<ModLoadingException> loadingExceptions;
+    private final Set<IModInfo> erroredModInfos;
     private final List<ModLoadingWarning> loadingWarnings;
     private final ModStateManager stateManager;
-    private boolean loadingStateValid;
-    @SuppressWarnings("OptionalUsedAsFieldOrParameterType")
-    private final Optional<Consumer<String>> statusConsumer = StartupNotificationManager.modLoaderConsumer();
+    private static boolean loadingStateValid;
+    private final Consumer<String> statusConsumer = StartupNotificationManager.modLoaderConsumer().orElse(msg -> {});
     private final Set<IModLoadingState> completedStates = new HashSet<>();
     private ModList modList;
 
-    private ModLoader()
-    {
-        INSTANCE = this;
-        this.loadingModList = FMLLoader.getLoadingModList();
-        this.loadingExceptions = this.loadingModList.getErrors().stream()
+    private ModLoader() {
+        var loadingModList = this.loadingModList = FMLLoader.getLoadingModList();
+        var loadingExceptions = this.loadingExceptions = loadingModList.getErrors().stream()
                 .flatMap(ModLoadingException::fromEarlyException)
                 .collect(Collectors.toList());
-        this.loadingWarnings = this.loadingModList.getBrokenFiles().stream()
+        this.loadingWarnings = loadingModList.getBrokenFiles().stream()
                 .map(file -> new ModLoadingWarning(null, ModLoadingStage.VALIDATE, InvalidModIdentifier.identifyJarProblem(file.getFilePath()).orElse("fml.modloading.brokenfile"), file.getFileName()))
                 .collect(Collectors.toList());
-        this.loadingModList.getModFiles().stream()
+        if (loadingExceptions.isEmpty()) {
+            this.erroredModInfos = Collections.emptySet();
+        } else {
+            this.erroredModInfos = Collections.newSetFromMap(new IdentityHashMap<>());
+            this.erroredModInfos.addAll(loadingExceptions.stream().map(ModLoadingException::getModInfo).toList());
+        }
+        loadingModList.getModFiles().stream()
                 .filter(ModFileInfo::missingLicense)
-                .filter(modFileInfo -> modFileInfo.getMods().stream().noneMatch(thisModInfo -> this.loadingExceptions.stream().map(ModLoadingException::getModInfo).anyMatch(otherInfo -> otherInfo == thisModInfo))) //Ignore files where any other mod already encountered an error
+                .filter(modFileInfo -> modFileInfo.getMods().stream().noneMatch(this.erroredModInfos::contains)) //Ignore files where any other mod already encountered an error
                 .map(modFileInfo -> new ModLoadingException(null, ModLoadingStage.VALIDATE, "fml.modloading.missinglicense", null, modFileInfo.getFile()))
                 .forEach(this.loadingExceptions::add);
         this.stateManager = new ModStateManager();
         CrashReportCallables.registerCrashCallable("ModLauncher", FMLLoader::getLauncherInfo);
         CrashReportCallables.registerCrashCallable("ModLauncher launch target", FMLLoader::launcherHandlerName);
         CrashReportCallables.registerCrashCallable("ModLauncher naming", FMLLoader::getNaming);
-        CrashReportCallables.registerCrashCallable("ModLauncher services", this::computeModLauncherServiceList);
-        CrashReportCallables.registerCrashCallable("FML Language Providers", this::computeLanguageList);
+        CrashReportCallables.registerCrashCallable("ModLauncher services", ModLoader::computeModLauncherServiceList);
+        CrashReportCallables.registerCrashCallable("FML Language Providers", ModLoader::computeLanguageList);
     }
 
-    private String computeLanguageList() {
-        return "\n"+FMLLoader.getLanguageLoadingProvider().applyForEach(lp->lp.name() +"@"+ lp.getClass().getPackage().getImplementationVersion()).collect(Collectors.joining("\n\t\t", "\t\t", ""));
+    private static String computeLanguageList() {
+        return "\n" + FMLLoader.getLanguageLoadingProvider()
+                .applyForEach(lp -> lp.name() + '@' + lp.getClass().getPackage().getImplementationVersion())
+                .collect(Collectors.joining("\n\t\t", "\t\t", ""));
     }
 
-    private String computeModLauncherServiceList() {
+    private static String computeModLauncherServiceList() {
         final List<Map<String, String>> mods = FMLLoader.modLauncherModList();
-        return "\n"+mods.stream().map(mod->mod.getOrDefault("file","nofile")+
-                " "+mod.getOrDefault("name", "missing")+
-                " "+mod.getOrDefault("type","NOTYPE")+
-                " "+mod.getOrDefault("description", "")).
+        return "\n" + mods.stream().map(mod -> mod.getOrDefault("file","nofile") +
+                ' ' + mod.getOrDefault("name", "missing") +
+                ' ' + mod.getOrDefault("type","NOTYPE") +
+                ' ' + mod.getOrDefault("description", "")).
                 collect(Collectors.joining("\n\t\t","\t\t",""));
     }
 
-    public static ModLoader get()
-    {
-        return INSTANCE == null ? INSTANCE = new ModLoader() : INSTANCE;
+    public static ModLoader get() {
+        return LazyInit.INSTANCE;
+    }
+
+    private static final class LazyInit {
+        private static final ModLoader INSTANCE = new ModLoader();
+        private LazyInit() {}
     }
 
     /**
@@ -144,21 +149,23 @@ public class ModLoader
         final ModList modList = ModList.of(loadingModList.getModFiles().stream().map(ModFileInfo::getFile).toList(),
                 loadingModList.getMods());
         if (!this.loadingExceptions.isEmpty()) {
-            LOGGER.fatal(CORE, "Error during pre-loading phase", loadingExceptions.get(0));
-            statusConsumer.ifPresent(c->c.accept("ERROR DURING MOD LOADING"));
+            LOGGER.fatal(CORE, "Error during pre-loading phase", loadingExceptions.getFirst());
+            statusConsumer.accept("ERROR DURING MOD LOADING");
             modList.setLoadedMods(Collections.emptyList());
             loadingStateValid = false;
             throw new LoadingFailedException(loadingExceptions);
         }
-        List<? extends ForgeFeature.Bound> failedBounds = loadingModList.getMods().stream()
-                .map(ModInfo::getForgeFeatures)
-                .flatMap(Collection::stream)
-                .filter(bound -> !ForgeFeature.testFeature(FMLEnvironment.dist, bound))
-                .toList();
+        var failedBounds = new ArrayList<ForgeFeature.Bound>();
+        for (var mod : loadingModList.getMods()) {
+            for (var feature : mod.getForgeFeatures()) {
+                if (!ForgeFeature.testFeature(FMLEnvironment.dist, feature))
+                    failedBounds.add(feature);
+            }
+        }
 
         if (!failedBounds.isEmpty()) {
             LOGGER.fatal(CORE, "Failed to validate feature bounds for mods: {}", failedBounds);
-            statusConsumer.ifPresent(c->c.accept("ERROR DURING MOD LOADING"));
+            statusConsumer.accept("ERROR DURING MOD LOADING");
             modList.setLoadedMods(Collections.emptyList());
             loadingStateValid = false;
             throw new LoadingFailedException(failedBounds.stream()
@@ -166,38 +173,79 @@ public class ModLoader
                     .toList());
         }
 
-        final List<ModContainer> modContainers = loadingModList.getModFiles().stream()
-                .map(ModFileInfo::getFile)
-                .map(this::buildMods)
-                .<ModContainer>mapMulti(Iterable::forEach)
-                .toList();
+        final var modContainers = new HashMap<String, ModContainer>();
+        for (var file : loadingModList.getModFiles()) {
+            var containers = this.buildMods(file.getFile());
+            for (var container : containers)
+                modContainers.put(container.getModId(), container);
+        }
+
         if (!loadingExceptions.isEmpty()) {
-            LOGGER.fatal(CORE, "Failed to initialize mod containers", loadingExceptions.get(0));
-            statusConsumer.ifPresent(c->c.accept("ERROR DURING MOD LOADING"));
+            LOGGER.fatal(CORE, "Failed to initialize mod containers", loadingExceptions.getFirst());
+            statusConsumer.accept("ERROR DURING MOD LOADING");
             modList.setLoadedMods(Collections.emptyList());
             loadingStateValid = false;
             throw new LoadingFailedException(loadingExceptions);
         }
-        modList.setLoadedMods(modContainers);
+
+        // Gather all dependencies, so we can make sure they have finished their transition events before we fire ours
+        for (var mod : modContainers.values()) {
+            for (var dep : mod.getModInfo().getDependencies()) {
+                var target = modContainers.get(dep.getModId());
+                if (target == null)
+                    continue;
+
+                switch (dep.getOrdering()) {
+                    case AFTER:
+                        mod.dependencies.add(target);
+                        break;
+                    case BEFORE:
+                        target.dependencies.add(mod);
+                        break;
+                    default:
+                        break;
+                }
+            }
+        }
+
+        modList.setLoadedMods(modContainers.values().stream().toList());
         this.modList = modList;
         var stateList = stateManager.getStates(ModLoadingPhase.GATHER);
-        var progress = StartupMessageManager.addProgressBar("Mod Gather", stateList.stream().mapToInt(mls -> mls.size().applyAsInt(modList)).sum());
-        stateList.forEach(mls->dispatchAndHandleError(mls, syncExecutor, parallelExecutor, periodicTask, progress));
+        var progress = StartupMessageManager.addProgressBar("Mod Gather", stateList.stream().mapToInt(mls -> mls.size().applyAsInt(this.modList)).sum());
+        for (IModLoadingState mls : stateList) {
+            dispatchAndHandleError(mls, syncExecutor, parallelExecutor, periodicTask, progress);
+        }
         progress.complete();
     }
 
     public void loadMods(final ModWorkManager.DrivenExecutor syncExecutor, final Executor parallelExecutor, final Runnable periodicTask) {
         var stateList = stateManager.getStates(ModLoadingPhase.LOAD);
         var progress = StartupMessageManager.addProgressBar("Mod Loading", stateList.stream().mapToInt(mls -> mls.size().applyAsInt(modList)).sum());
-        stateList.forEach(mls->dispatchAndHandleError(mls, syncExecutor, parallelExecutor, periodicTask, progress));
+        for (IModLoadingState mls : stateList) {
+            dispatchAndHandleError(mls, syncExecutor, parallelExecutor, periodicTask, progress);
+        }
         progress.complete();
     }
 
     public void finishMods(final ModWorkManager.DrivenExecutor syncExecutor, final Executor parallelExecutor, final Runnable periodicTask) {
         var stateList = stateManager.getStates(ModLoadingPhase.COMPLETE);
         var progress = StartupMessageManager.addProgressBar("Mod Complete", stateList.stream().mapToInt(mls -> mls.size().applyAsInt(modList)).sum());
-        stateList.forEach(mls->dispatchAndHandleError(mls, syncExecutor, parallelExecutor, periodicTask, progress));
-        statusConsumer.ifPresent(c->c.accept(String.format("Mod loading complete - %d mods loaded", this.modList.size())));
+        for (IModLoadingState mls : stateList) {
+            dispatchAndHandleError(mls, syncExecutor, parallelExecutor, periodicTask, progress);
+        }
+
+        var modBusGroups = Set.of(
+                modList.getLoadedMods().stream()
+                        .map(ModContainer::getModBusGroup)
+                        .filter(Objects::nonNull)
+                        .toArray(BusGroup[]::new)
+        );
+        for (var modBusGroup : modBusGroups) {
+            parallelExecutor.execute(modBusGroup::trim);
+        }
+        parallelExecutor.execute(BusGroup.DEFAULT::trim);
+
+        statusConsumer.accept("Mod loading complete - %d mods loaded".formatted(this.modList.size()));
         progress.complete();
     }
 
@@ -206,25 +254,32 @@ public class ModLoader
             LOGGER.error("Cowardly refusing to process mod state change request from {}", state);
             return;
         }
-        progressBar.label(progressBar.name()+ " working");
+        progressBar.label(progressBar.name() + " working");
         syncExecutor.drive(ticker);
-        state.inlineRunnable().ifPresent(a->this.handleInlineTransition(a, state, syncExecutor, ticker));
-        state.buildTransition(syncExecutor, parallelExecutor, progressBar).ifPresent(t->waitForTransition(state, syncExecutor, ticker, t));
+
+        var inlineRunnable = state.inlineRunnable().orElse(null);
+        if (inlineRunnable != null) handleInlineTransition(inlineRunnable, state, syncExecutor, ticker);
+
+        var transition = state.buildTransition(syncExecutor, parallelExecutor, progressBar).orElse(null);
+        if (transition != null) waitForTransition(state, syncExecutor, ticker, transition);
+
         completedStates.add(state);
     }
 
     private void handleInlineTransition(final Consumer<ModList> transition, final IModLoadingState state, final ModWorkManager.DrivenExecutor syncExecutor, final Runnable ticker) {
-        var pb = StartupMessageManager.addProgressBar("State transition " +state.name()+" running", 0);
+        var pb = StartupMessageManager.addProgressBar("State transition " + state.name() + " running", 0);
         syncExecutor.drive(ticker);
         transition.accept(this.modList);
         syncExecutor.drive(ticker);
         pb.complete();
         syncExecutor.drive(ticker);
     }
+
     private void waitForTransition(final IModLoadingState state, final ModWorkManager.DrivenExecutor syncExecutor, final Runnable ticker, final CompletableFuture<Void> transition) {
         while (!transition.isDone()) {
             syncExecutor.drive(ticker);
         }
+
         try {
             transition.join();
         } catch (CompletionException e) {
@@ -234,36 +289,38 @@ public class ModLoader
                     .anyMatch(obj -> !(obj instanceof ModLoadingException));
             if (hasNotModLoadingEx) {
                 LOGGER.fatal("Encountered non-modloading exceptions!", e);
-                statusConsumer.ifPresent(c->c.accept("ERROR DURING MOD LOADING"));
+                statusConsumer.accept("ERROR DURING MOD LOADING");
                 throw e;
             }
 
             final List<ModLoadingException> modLoadingExceptions = Arrays.stream(t.getSuppressed())
                     .filter(ModLoadingException.class::isInstance)
                     .map(ModLoadingException.class::cast)
-                    .collect(Collectors.toList());
+                    .toList();
             LOGGER.fatal(LOADING,"Failed to complete lifecycle event {}, {} errors found", state.name(), modLoadingExceptions.size());
-            statusConsumer.ifPresent(c->c.accept("ERROR DURING MOD LOADING"));
+            statusConsumer.accept("ERROR DURING MOD LOADING");
             throw new LoadingFailedException(modLoadingExceptions);
         }
     }
 
-    private List<ModContainer> buildMods(final IModFile modFile)
-    {
-        final Map<String, IModInfo> modInfoMap = modFile.getModFileInfo().getMods().stream().collect(Collectors.toMap(IModInfo::getModId, Function.identity()));
+    private List<ModContainer> buildMods(final IModFile modFile) {
+        final Map<String, IModInfo> modInfoMap = new HashMap<>();
+        for (var mod : modFile.getModFileInfo().getMods())
+            modInfoMap.put(mod.getModId(), mod);
 
         LOGGER.trace(LOADING, "ModContainer is {}", ModContainer.class.getClassLoader());
-        final List<ModContainer> containers = modFile.getScanResult().getTargets()
-                .entrySet()
-                .stream()
-                .map(e -> buildModContainerFromTOML(modFile, modInfoMap, e))
-                .filter(Objects::nonNull)
-                .toList();
+        final List<ModContainer> containers = new ArrayList<>();
+        for (var entry : modFile.getScanResult().getTargets().entrySet()) {
+            var container = buildModContainerFromTOML(modFile, modInfoMap, entry.getKey(), entry.getValue());
+            if (container != null)
+                containers.add(container);
+        }
+
         if (containers.size() != modInfoMap.size()) {
             var modIds = modInfoMap.values().stream().map(IModInfo::getModId).sorted().toList();
             var containerIds = containers.stream().map(c -> c != null ? c.getModId() : "(null)").sorted().toList();
 
-            LOGGER.fatal(LOADING,"File {} constructed {} mods: {}, but had {} mods specified: {}",
+            LOGGER.fatal(LOADING, "File {} constructed {} mods: {}, but had {} mods specified: {}",
                     modFile.getFilePath(),
                     containers.size(), containerIds,
                     modInfoMap.size(), modIds);
@@ -278,17 +335,20 @@ public class ModLoader
 
             loadingExceptions.add(new ModLoadingException(null, ModLoadingStage.CONSTRUCT, "fml.modloading.missingclasses", null, modFile.getFilePath()));
         }
+
         // remove errored mod containers
         return containers.stream().filter(mc -> mc.modLoadingStage != ModLoadingStage.ERROR).toList();
     }
 
-    private ModContainer buildModContainerFromTOML(final IModFile modFile, final Map<String, IModInfo> modInfoMap, final Map.Entry<String, ? extends IModLanguageProvider.IModLanguageLoader> idToProviderEntry) {
+    private ModContainer buildModContainerFromTOML(final IModFile modFile, final Map<String, IModInfo> modInfoMap,
+        final String modId, final IModLanguageProvider.IModLanguageLoader languageLoader
+    ) {
         try {
-            final String modId = idToProviderEntry.getKey();
-            final IModLanguageProvider.IModLanguageLoader languageLoader = idToProviderEntry.getValue();
-            IModInfo info = Optional.ofNullable(modInfoMap.get(modId)).
-                    // throw a missing metadata error if there is no matching modid in the modInfoMap from the mods.toml file
-                    orElseThrow(()->new ModLoadingException(null, ModLoadingStage.CONSTRUCT, "fml.modloading.missingmetadata", null, modId));
+            IModInfo info = modInfoMap.get(modId);
+            // throw a missing metadata error if there is no matching modid in the modInfoMap from the mods.toml file
+            if (info == null)
+                throw new ModLoadingException(null, ModLoadingStage.CONSTRUCT, "fml.modloading.missingmetadata", null, modId);
+
             return languageLoader.loadMod(info, modFile.getScanResult(), FMLLoader.getGameLayer());
         } catch (ModLoadingException mle) {
             // exceptions are caught and added to the error list for later handling
@@ -303,59 +363,73 @@ public class ModLoader
      * and don't want to cause extraneous crashes due to trying to do things that aren't possible in a "broken load"
      */
     public static boolean isLoadingStateValid() {
-        return get().loadingStateValid;
+        return loadingStateValid;
     }
 
+    /** @deprecated Use {@link #hasCompletedState(IModLoadingState)} instead */
+    @Deprecated(forRemoval = true)
     public boolean hasCompletedState(final String stateName) {
         IModLoadingState state = stateManager.findState(stateName);
         return completedStates.contains(state);
     }
 
-    public <T extends Event & IModBusEvent> void runEventGenerator(Function<ModContainer, T> generator) {
+    public boolean hasCompletedState(IModLoadingState state) {
+        return completedStates.contains(state);
+    }
+
+    public static <T extends IModBusEvent> void runEventGenerator(Function<ModContainer, T> generator) {
         if (!loadingStateValid) {
             LOGGER.error("Cowardly refusing to send event generator to a broken mod state");
             return;
         }
-        ModList.get().forEachModInOrder(mc -> mc.acceptEvent(generator.apply(mc)));
+        for (var mod : ModList.get().getLoadedMods())
+            mod.acceptEvent(generator.apply(mod));
     }
 
-    public <T extends Event & IModBusEvent> void postEvent(T e) {
+    public static <T extends IModBusEvent> void postEvent(T e) {
         if (!loadingStateValid) {
             LOGGER.error("Cowardly refusing to send event {} to a broken mod state", e.getClass().getName());
             return;
         }
-        ModList.get().forEachModInOrder(mc -> mc.acceptEvent(e));
+        for (var mod : ModList.get().getLoadedMods())
+            mod.acceptEvent(e);
     }
-    public <T extends Event & IModBusEvent> T postEventWithReturn(T e) {
+
+    public static <T extends IModBusEvent> T postEventWithReturn(T e) {
         if (!loadingStateValid) {
             LOGGER.error("Cowardly refusing to send event {} to a broken mod state", e.getClass().getName());
             return e;
         }
-        ModList.get().forEachModInOrder(mc -> mc.acceptEvent(e));
+        for (var mod : ModList.get().getLoadedMods())
+            mod.acceptEvent(e);
         return e;
     }
-    public <T extends Event & IModBusEvent> void postEventWrapContainerInModOrder(T event) {
-        postEventWithWrapInModOrder(event, (mc, e) -> ModLoadingContext.get().setActiveContainer(mc), (mc, e) -> ModLoadingContext.get().setActiveContainer(null));
+
+    @SuppressWarnings("removal")
+    public static <T extends IModBusEvent> void postEventWrapContainerInModOrder(T event) {
+        postEventWithWrapInModOrder(event,
+            (mc, e) -> ModLoadingContext.get().setActiveContainer(mc),
+            (mc, e) -> ModLoadingContext.get().setActiveContainer(null)
+        );
     }
-    public <T extends Event & IModBusEvent> void postEventWithWrapInModOrder(T e, BiConsumer<ModContainer, T> pre, BiConsumer<ModContainer, T> post) {
+
+    public static <T extends IModBusEvent> void postEventWithWrapInModOrder(T e, BiConsumer<ModContainer, T> pre, BiConsumer<ModContainer, T> post) {
         if (!loadingStateValid) {
             LOGGER.error("Cowardly refusing to send event {} to a broken mod state", e.getClass().getName());
             return;
         }
-        ModList.get().forEachModInOrder(mc -> {
-            pre.accept(mc, e);
-            mc.acceptEvent(e);
-            post.accept(mc, e);
-        });
+        for (var mod : ModList.get().getLoadedMods()) {
+            pre.accept(mod, e);
+            mod.acceptEvent(e);
+            post.accept(mod, e);
+        }
     }
 
-    public List<ModLoadingWarning> getWarnings()
-    {
+    public List<ModLoadingWarning> getWarnings() {
         return ImmutableList.copyOf(this.loadingWarnings);
     }
 
-    public void addWarning(ModLoadingWarning warning)
-    {
+    public void addWarning(ModLoadingWarning warning) {
         this.loadingWarnings.add(warning);
     }
 
@@ -365,7 +439,7 @@ public class ModLoader
         return runningDataGen;
     }
 
-    private static class ErroredModContainer extends ModContainer {
+    private static final class ErroredModContainer extends ModContainer {
         public ErroredModContainer() {
             super();
         }

fmlcore/src/main/java/net/minecraftforge/fml/ModLoadingContext.java

@@ -8,39 +8,63 @@ package net.minecraftforge.fml;
 import com.mojang.logging.LogUtils;
 import net.minecraftforge.fml.config.IConfigSpec;
 import net.minecraftforge.fml.config.ModConfig;
-import net.minecraftforge.fml.loading.FMLLoader;
 import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
 import java.util.function.BiPredicate;
 import java.util.function.Supplier;
 
-public class ModLoadingContext
-{
+public class ModLoadingContext {
     private static final Logger LOGGER = LogUtils.getLogger();
     private static final ThreadLocal<ModLoadingContext> context = ThreadLocal.withInitial(ModLoadingContext::new);
+    private ModContainer activeContainer;
     private Object languageExtension;
-    private ModLoadingStage stage;
 
+    /**
+     * @deprecated Use the context provided by your language loader in your mod's constructor. Example for Java mods: {@snippet :
+     * @Mod("examplemod")
+     * public final class ExampleMod {
+     *      public ExampleMod(FMLJavaModLoadingContext context) {
+     *           // Use context from the param instead of FMLJavaModLoadingContext.get() or ModLoadingContext.get()
+     *      }
+     * }}
+     */
+    @Deprecated(forRemoval = true, since="1.21.1")
     public static ModLoadingContext get() {
         return context.get();
     }
 
-    private ModContainer activeContainer;
-
+    /**
+     * @deprecated Going to be moved to ForgeHooks for Internal use.
+     */
+    @Deprecated(forRemoval = true, since="1.21.1")
     public void setActiveContainer(final ModContainer container) {
         this.activeContainer = container;
         this.languageExtension = container == null ? null : container.contextExtension.get();
     }
 
+    /**
+     * Going to be moved to ForgeHooks for Internal use.
+     * @deprecated Override/Use {@link ModLoadingContext#getContainer()}
+     */
+    @Deprecated(forRemoval = true, since="1.21.1")
     public ModContainer getActiveContainer() {
         return activeContainer == null ? ModList.get().getModContainerById("minecraft").orElseThrow(()->new RuntimeException("Where is minecraft???!")) : activeContainer;
     }
 
+    /**
+     * @deprecated Going to be moved to ForgeHooks for Internal use.
+     */
+    @Deprecated(forRemoval = true, since="1.21.1")
     public String getActiveNamespace() {
         return activeContainer == null ? "minecraft" : activeContainer.getNamespace();
     }
 
+    /**
+     * @return {@link ModLoadingContext#getActiveContainer()} by default.
+     */
+    public ModContainer getContainer() {
+        return getActiveContainer();
+    }
+
     /**
      * Register an {@link IExtensionPoint} with the mod container.
      * @param point The extension point to register
@@ -48,7 +72,7 @@ public class ModLoadingContext
      * @param <T> The type signature of the extension operator
      */
     public <T extends Record & IExtensionPoint<T>> void registerExtensionPoint(Class<? extends IExtensionPoint<T>> point, Supplier<T> extension) {
-        getActiveContainer().registerExtensionPoint(point, extension);
+        getContainer().registerExtensionPoint(point, extension);
     }
 
     /**
@@ -57,7 +81,7 @@ public class ModLoadingContext
      * @param displayTest The {@link IExtensionPoint.DisplayTest} to register
      */
     public void registerDisplayTest(IExtensionPoint.DisplayTest displayTest) {
-        getActiveContainer().registerDisplayTest(() -> displayTest);
+        getContainer().registerDisplayTest(() -> displayTest);
     }
 
     /**
@@ -66,7 +90,7 @@ public class ModLoadingContext
      * @param displayTest The {@link Supplier<IExtensionPoint.DisplayTest>} to register
      */
     public void registerDisplayTest(Supplier<IExtensionPoint.DisplayTest> displayTest) {
-        getActiveContainer().registerDisplayTest(displayTest);
+        getContainer().registerDisplayTest(displayTest);
     }
 
     /**
@@ -76,7 +100,7 @@ public class ModLoadingContext
      * @see IExtensionPoint.DisplayTest#DisplayTest(String, BiPredicate)
      */
     public void registerDisplayTest(String version, BiPredicate<String, Boolean> remoteVersionTest) {
-        getActiveContainer().registerDisplayTest(new IExtensionPoint.DisplayTest(version, remoteVersionTest));
+        getContainer().registerDisplayTest(new IExtensionPoint.DisplayTest(version, remoteVersionTest));
     }
 
     /**
@@ -86,29 +110,29 @@ public class ModLoadingContext
      * @see IExtensionPoint.DisplayTest#DisplayTest(Supplier, BiPredicate)
      */
     public void registerDisplayTest(Supplier<String> suppliedVersion, BiPredicate<String, Boolean> remoteVersionTest) {
-        getActiveContainer().registerDisplayTest(new IExtensionPoint.DisplayTest(suppliedVersion, remoteVersionTest));
+        getContainer().registerDisplayTest(new IExtensionPoint.DisplayTest(suppliedVersion, remoteVersionTest));
     }
 
     public void registerConfig(ModConfig.Type type, IConfigSpec<?> spec) {
         if (spec.isEmpty())
         {
             // This handles the case where a mod tries to register a config, without any options configured inside it.
-            LOGGER.debug("Attempted to register an empty config for type {} on mod {}", type, getActiveContainer().getModId());
+            LOGGER.debug("Attempted to register an empty config for type {} on mod {}", type, getContainer().getModId());
             return;
         }
 
-        getActiveContainer().addConfig(new ModConfig(type, spec, getActiveContainer()));
+        getContainer().addConfig(new ModConfig(type, spec, getContainer()));
     }
 
     public void registerConfig(ModConfig.Type type, IConfigSpec<?> spec, String fileName) {
         if (spec.isEmpty())
         {
             // This handles the case where a mod tries to register a config, without any options configured inside it.
-            LOGGER.debug("Attempted to register an empty config for type {} on mod {} using file name {}", type, getActiveContainer().getModId(), fileName);
+            LOGGER.debug("Attempted to register an empty config for type {} on mod {} using file name {}", type, getContainer().getModId(), fileName);
             return;
         }
 
-        getActiveContainer().addConfig(new ModConfig(type, spec, getActiveContainer(), fileName));
+        getContainer().addConfig(new ModConfig(type, spec, getContainer(), fileName));
     }
 
 

fmlcore/src/main/java/net/minecraftforge/fml/ModLoadingState.java

@@ -5,10 +5,9 @@
 
 package net.minecraftforge.fml;
 
-import net.minecraftforge.eventbus.api.Event;
-import net.minecraftforge.fml.event.IModBusEvent;
 import net.minecraftforge.fml.loading.progress.ProgressMeter;
 
+import java.util.Objects;
 import java.util.Optional;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.Executor;
@@ -26,20 +25,27 @@ import java.util.function.ToIntFunction;
  * @param inlineRunnable an optional runnable, which runs before starting the transition from this state to the next
  * @param transition     optional state transition information
  */
-public record ModLoadingState(String name, String previous,
-                              Function<ModList, String> message,
-                              ToIntFunction<ModList> size,
-                              ModLoadingPhase phase,
-                              Optional<Consumer<ModList>> inlineRunnable,
-                              Optional<IModStateTransition> transition) implements IModLoadingState {
+public record ModLoadingState(
+    String name,
+    String previous,
+    Function<ModList, String> message,
+    ToIntFunction<ModList> size,
+    ModLoadingPhase phase,
+    Optional<Consumer<ModList>> inlineRunnable,
+    Optional<IModStateTransition> transition
+) implements IModLoadingState {
     @Override
-    public <T extends Event & IModBusEvent>
-    Optional<CompletableFuture<Void>> buildTransition(final Executor syncExecutor,
-                                                      final Executor parallelExecutor,
-                                                      final ProgressMeter progressBar,
-                                                      final Function<Executor, CompletableFuture<Void>> preSyncTask,
-                                                      final Function<Executor, CompletableFuture<Void>> postSyncTask) {
-        return transition.map(t -> t.build(name, syncExecutor, parallelExecutor, progressBar, preSyncTask, postSyncTask));
+    public Optional<CompletableFuture<Void>> buildTransition(
+        final Executor syncExecutor,
+        final Executor parallelExecutor,
+        final ProgressMeter progressBar,
+        final Function<Executor, CompletableFuture<Void>> preSyncTask,
+        final Function<Executor, CompletableFuture<Void>> postSyncTask
+    ) {
+        var transition = this.transition.orElse(null);
+        return transition == null
+                ? Optional.empty()
+                : Optional.ofNullable(transition.build(name, syncExecutor, parallelExecutor, progressBar, preSyncTask, postSyncTask));
     }
 
     /**
@@ -49,9 +55,12 @@ public record ModLoadingState(String name, String previous,
      * @param name     the name of the state
      * @param previous the name of the immediately previous state to this state
      * @param phase    the mod loading phase the state belongs to
+     *
+     * @deprecated Use the builder
      */
+    @Deprecated(since = "1.21.3", forRemoval = true)
     public static ModLoadingState empty(final String name, final String previous, final ModLoadingPhase phase) {
-        return new ModLoadingState(name, previous, ml -> "", f->0, phase, Optional.empty(), Optional.empty());
+        return new ModLoadingState(name, previous, ml -> "", ml -> 0, phase, Optional.empty(), Optional.empty());
     }
 
     /**
@@ -62,11 +71,13 @@ public record ModLoadingState(String name, String previous,
      * @param previous   the name of the immediately previous state to this state
      * @param phase      the mod loading phase the state belongs to
      * @param transition the state transition information
-     * @return a mod loading state with state transition information and a default message
+     *
+     * @deprecated Use the builder
      */
+    @Deprecated(since = "1.21.3", forRemoval = true)
     public static ModLoadingState withTransition(final String name, final String previous, final ModLoadingPhase phase,
                                                  final IModStateTransition transition) {
-        return new ModLoadingState(name, previous, ml -> "Processing transition " + name, ModList::size, phase, Optional.empty(), Optional.of(transition));
+        return of(name, phase).after(previous).withTransition(transition);
     }
 
     /**
@@ -78,11 +89,14 @@ public record ModLoadingState(String name, String previous,
      * @param phase      the mod loading phase the state belongs to
      * @param transition the state transition information
      * @return a mod loading state with state transition information and a custom message
+     *
+     * @deprecated Use the builder
      */
+    @Deprecated(since = "1.21.3", forRemoval = true)
     public static ModLoadingState withTransition(final String name, final String previous,
                                                  final Function<ModList, String> message, final ModLoadingPhase phase,
                                                  final IModStateTransition transition) {
-        return new ModLoadingState(name, previous, message, ModList::size, phase, Optional.empty(), Optional.of(transition));
+        return of(name, phase).after(previous).message(message).withTransition(transition);
     }
 
     /**
@@ -94,9 +108,75 @@ public record ModLoadingState(String name, String previous,
      * @param phase    the mod loading phase the state belongs to
      * @param inline   an optional runnable, which runs before starting the transition from this state to the next
      * @return a mod loading state with an inline runnable and default message
+     *
+     * @deprecated Use the builder
      */
+    @Deprecated(since = "1.21.3", forRemoval = true)
     public static ModLoadingState withInline(final String name, final String previous, final ModLoadingPhase phase,
                                              final Consumer<ModList> inline) {
-        return new ModLoadingState(name, previous, ml -> "Processing work " + name, ml->0, phase, Optional.of(inline), Optional.empty());
+        return of(name, phase).after(previous).withInline(inline);
+    }
+
+    public static Builder of(final String name, final ModLoadingPhase phase) {
+        return new Builder(name, phase);
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        return o instanceof ModLoadingState that
+                && this.phase == that.phase
+                && this.name.equals(that.name)
+                && Objects.equals(this.previous, that.previous);
+    }
+
+    @Override
+    public int hashCode() {
+        int result = phase.hashCode();
+        result = 31 * result + name.hashCode();
+        result = 31 * result + Objects.hashCode(previous);
+        return result;
+    }
+
+    public static class Builder {
+        private final String name;
+        private final ModLoadingPhase phase;
+        private String after;
+        private Function<ModList, String> message = null;
+        private ToIntFunction<ModList> size = null;
+
+        private Builder(final String name, final ModLoadingPhase phase) {
+            this.name = name;
+            this.phase = phase;
+        }
+
+        public Builder after(final ModLoadingState value) { return after(value.name()); }
+        public Builder after(final String value) {
+            this.after = value;
+            return this;
+        }
+
+        public Builder message(final String value) { return message(ml -> value); }
+        public Builder message(final Function<ModList, String> value) {
+            this.message = value;
+            return this;
+        }
+
+        public Builder size(final int value) { return size(ml -> value); }
+        public Builder size(final ToIntFunction<ModList> value) {
+            this.size = value;
+            return this;
+        }
+
+        public ModLoadingState empty() {
+            return new ModLoadingState(name, after, message != null ? message : ml -> "", size != null ? size : ml -> 0, phase, Optional.empty(), Optional.empty());
+        }
+
+        public ModLoadingState withTransition(final IModStateTransition transition) {
+            return new ModLoadingState(name, after, message != null ? message : ml -> "Processing transition " + name, size != null ? size : ModList::size, phase, Optional.empty(), Optional.of(transition));
+        }
+
+        public ModLoadingState withInline(final Consumer<ModList> inline) {
+            return new ModLoadingState(name, after, message != null ? message : ml -> "Processing work " + name, size != null ? size : ml -> 0, phase, Optional.of(inline), Optional.empty());
+        }
     }
 }

fmlcore/src/main/java/net/minecraftforge/fml/ModStateManager.java

@@ -16,15 +16,13 @@ import java.util.stream.Collectors;
 
 @SuppressWarnings("UnstableApiUsage")
 public class ModStateManager {
-    static ModStateManager INSTANCE;
     private final EnumMap<ModLoadingPhase, List<IModLoadingState>> stateMap;
 
     public ModStateManager() {
-        INSTANCE = this;
         final var sp = ServiceLoader.load(FMLLoader.getGameLayer(), IModStateProvider.class);
         this.stateMap = ServiceLoaderUtils.streamWithErrorHandling(sp, sce->{})
                 .map(IModStateProvider::getAllStates)
-                .<IModLoadingState>mapMulti(Iterable::forEach)
+                .flatMap(List::stream)
                 .collect(Collectors.groupingBy(IModLoadingState::phase, ()->new EnumMap<>(ModLoadingPhase.class), Collectors.toUnmodifiableList()));
     }
 
@@ -36,16 +34,20 @@ public class ModStateManager {
         var dummy = ModLoadingState.empty("", "", phase);
         nodes.forEach(graph::addNode);
         graph.addNode(dummy);
-        nodes.forEach(n->graph.putEdge(lookup.getOrDefault(n.previous(), dummy), n));
+        for (IModLoadingState node : nodes) {
+            graph.putEdge(lookup.getOrDefault(node.previous(), dummy), node);
+        }
         return TopologicalSort.topologicalSort(graph, Comparator.comparingInt(nodes::indexOf)).stream().filter(st->st!=dummy).toList();
     }
 
     public IModLoadingState findState(final String stateName) {
-        return stateMap.values()
+        var result = stateMap.values()
                 .stream()
-                .flatMap(Collection::stream)
+                .flatMap(List::stream)
                 .filter(mls -> mls.name().equals(stateName))
                 .findFirst()
-                .orElseThrow(() -> new IllegalArgumentException("Unknown IModLoadingState: " + stateName));
+                .orElse(null);
+        if (result != null) return result;
+        else throw new IllegalArgumentException("Unknown IModLoadingState: " + stateName);
     }
 }

fmlcore/src/main/java/net/minecraftforge/fml/ModStateTransitionHelper.java

@@ -0,0 +1,184 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
+package net.minecraftforge.fml;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Objects;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
+import java.util.concurrent.CompletionStage;
+import java.util.concurrent.Executor;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+
+import org.jetbrains.annotations.ApiStatus;
+
+import net.minecraftforge.fml.IModStateTransition.EventGenerator;
+import net.minecraftforge.fml.event.IModBusEvent;
+import net.minecraftforge.fml.loading.progress.ProgressMeter;
+
+@ApiStatus.Internal
+class ModStateTransitionHelper {
+    static final IModStateTransition NOOP = new NoopTransition();
+    record NoopTransition() implements IModStateTransition {
+        @Override
+        public ThreadSelector threadSelector() {
+            return ThreadSelector.SYNC;
+        }
+
+        @Override
+        public BiFunction<Executor, CompletableFuture<Void>, CompletableFuture<Void>> finalActivityGenerator() {
+            return (e, t) -> t.thenApplyAsync(Function.identity(), e);
+        }
+    }
+
+    static <V> CompletionStage<Void> completableFutureFromExceptionList(List<FutureResult<V>> t) {
+        if (t.stream().noneMatch(e -> e.exception() != null)) {
+            return CompletableFuture.completedFuture(null);
+        } else {
+            final var throwables = t.stream().map(FutureResult::exception).filter(Objects::nonNull).toList();
+            CompletableFuture<Void> cf = new CompletableFuture<>();
+            final RuntimeException accumulator = new RuntimeException();
+            cf.completeExceptionally(accumulator);
+            for (Throwable exception : throwables) {
+                if (exception instanceof CompletionException) {
+                    exception = exception.getCause();
+                }
+                if (exception.getSuppressed().length != 0) {
+                    for (Throwable throwable : exception.getSuppressed()) {
+                        accumulator.addSuppressed(throwable);
+                    }
+                } else {
+                    accumulator.addSuppressed(exception);
+                }
+            }
+            return cf;
+        }
+    }
+
+    record FutureResult<V>(V value, Throwable exception){}
+
+    static <V> CompletableFuture<List<FutureResult<V>>> gather(Collection<? extends CompletableFuture<? extends V>> futures) {
+        var list = new ArrayList<FutureResult<V>>(futures.size());
+        var results = new CompletableFuture[futures.size()];
+
+        for (var future : futures) {
+            int i = list.size();
+            list.add(null);
+            @SuppressWarnings("unchecked") // Bypass a weird javac error with generic by forcing it to be the exact type we want.
+            var raw = ((CompletableFuture<V>)future);
+            results[i] = raw.whenComplete((result, exception) -> list.set(i, new FutureResult<>(result, exception)));
+        }
+
+        return CompletableFuture.allOf(results).handle((r, th)->null).thenApply(res -> list);
+    }
+
+    private static <T extends IModBusEvent> void addCompletableFutureTaskForModDispatch(
+        final IModStateTransition transition,
+        final Executor executor,
+        final List<CompletableFuture<Void>> completableFutures,
+        final ProgressMeter progressBar,
+        final EventGenerator<T> eventGenerator,
+        final BiFunction<ModLoadingStage, Throwable, ModLoadingStage> nextState
+     ) {
+
+        @SuppressWarnings("removal")
+        var preDispatchHook = getHook(transition.preDispatchHook(), executor, eventGenerator);
+        if (preDispatchHook != null)
+            completableFutures.add(preDispatchHook);
+
+        var modFutures = new LinkedHashMap<String, CompletableFuture<Void>>();
+        for (var mod : ModList.get().getLoadedMods()) {
+
+            CompletableFuture<Void> parent = null;
+            if (mod.dependencies.isEmpty()) {
+                parent = CompletableFuture.allOf();
+            } else {
+                var deps = new CompletableFuture[mod.dependencies.size()];
+                int idx = 0;
+                for (var depContainer : mod.dependencies) {
+                    var future = modFutures.get(depContainer.getModId());
+                    if (future == null)
+                        throw new IllegalStateException("Could not find dependency future " + depContainer.getModId() + " for " + mod.getModId());
+                    deps[idx++] = future;
+                }
+                parent = CompletableFuture.allOf(deps);
+            }
+
+            @SuppressWarnings("removal")
+            var dispatch = parent
+                .thenRunAsync(() -> {
+                    ModLoadingContext.get().setActiveContainer(mod);
+                    var handler = mod.activityMap.get(mod.modLoadingStage);
+                    if (handler != null)
+                        handler.run();
+                    mod.acceptEvent(eventGenerator.apply(mod));
+                }, executor)
+                .whenComplete((mc, exception) -> {
+                    mod.modLoadingStage = nextState.apply(mod.modLoadingStage, exception);
+                    progressBar.increment();
+                    ModLoadingContext.get().setActiveContainer(null);
+                });
+
+            modFutures.put(mod.getModId(), dispatch);
+        }
+
+        var dispatch = gather(modFutures.values()).thenComposeAsync(ModStateTransitionHelper::completableFutureFromExceptionList, executor);
+        completableFutures.add(dispatch);
+
+        @SuppressWarnings("removal")
+        var postDispatchHook = getHook(transition.preDispatchHook(), executor, eventGenerator);
+        if (postDispatchHook != null)
+            completableFutures.add(postDispatchHook);
+    }
+
+    private static <T extends IModBusEvent> CompletableFuture<Void> getHook(BiFunction<Executor, ? extends EventGenerator<?>, CompletableFuture<Void>> hook, Executor executor, EventGenerator<T> eventGenerator) {
+        if (hook == null || hook == IModStateTransition.NULL_HOOK) return null;
+        @SuppressWarnings("unchecked")
+        var hookTyped = (BiFunction<Executor, EventGenerator<T>, CompletableFuture<Void>>)hook;
+        return hookTyped.apply(executor, eventGenerator);
+    }
+
+    static <T extends IModBusEvent> CompletableFuture<Void> build(
+        final IModStateTransition transition,
+        final String name,
+        final Executor syncExecutor,
+        final Executor parallelExecutor,
+        final ProgressMeter progressBar,
+        final Function<Executor, CompletableFuture<Void>> preSyncTask,
+        final Function<Executor, CompletableFuture<Void>> postSyncTask
+    ) {
+        List<CompletableFuture<Void>> futures = new ArrayList<>();
+        final var executor = transition.threadSelector().apply(syncExecutor, parallelExecutor);
+
+        @SuppressWarnings({ "removal", "unchecked" })
+        var events = transition.eventFunctionStream().get().map(f -> (EventGenerator<T>)f).toList();
+        for (int x = 0; x < events.size(); x++) {
+            var gen = events.get(x);
+            BiFunction<ModLoadingStage, Throwable, ModLoadingStage> state = x == events.size() - 1
+                ? transition.nextModLoadingStage()
+                : ModLoadingStage::currentState;
+            addCompletableFutureTaskForModDispatch(transition, executor, futures, progressBar, gen, state);
+        }
+
+        final CompletableFuture<Void> preSyncTaskCF = preSyncTask.apply(syncExecutor);
+        final CompletableFuture<Void> eventDispatchCF = gather(futures).thenCompose(ModStateTransitionHelper::completableFutureFromExceptionList);
+        final CompletableFuture<Void> postEventDispatchCF = preSyncTaskCF
+            .thenApplyAsync(n -> {
+                progressBar.label(progressBar.name() + ": dispatching " + name);
+                return null;
+            }, parallelExecutor)
+            .thenComposeAsync(n -> eventDispatchCF, parallelExecutor)
+            .thenApply(r -> {
+                postSyncTask.apply(syncExecutor);
+                return null;
+            });
+        return transition.finalActivityGenerator().apply(syncExecutor, postEventDispatchCF);
+    }
+}

fmlcore/src/main/java/net/minecraftforge/fml/ModWorkManager.java

@@ -17,6 +17,7 @@ import static net.minecraftforge.fml.Logging.LOADING;
 public class ModWorkManager {
     private static final Logger LOGGER = LogManager.getLogger();
     private static final long PARK_TIME = TimeUnit.MILLISECONDS.toNanos(1);
+
     public interface DrivenExecutor extends Executor {
         boolean selfDriven();
         boolean driveOne();
@@ -33,8 +34,11 @@ public class ModWorkManager {
             }
         }
     }
-    private static class SyncExecutor implements DrivenExecutor {
-        private ConcurrentLinkedDeque<Runnable> tasks = new ConcurrentLinkedDeque<>();
+
+    private record SyncExecutor(ConcurrentLinkedDeque<Runnable> tasks) implements DrivenExecutor {
+        public SyncExecutor() {
+            this(new ConcurrentLinkedDeque<>());
+        }
 
         @Override
         public boolean driveOne() {
@@ -56,13 +60,7 @@ public class ModWorkManager {
         }
     }
 
-    private static class WrappingExecutor implements DrivenExecutor {
-        private final Executor wrapped;
-
-        public WrappingExecutor(final Executor executor) {
-            this.wrapped = executor;
-        }
-
+    private record WrappingExecutor(Executor wrapped) implements DrivenExecutor {
         @Override
         public boolean selfDriven() {
             return true;
@@ -79,11 +77,9 @@ public class ModWorkManager {
         }
     }
 
-    private static SyncExecutor syncExecutor;
+    private static final SyncExecutor syncExecutor = new SyncExecutor();
 
     public static DrivenExecutor syncExecutor() {
-        if (syncExecutor == null)
-            syncExecutor = new SyncExecutor();
         return syncExecutor;
     }
 
@@ -91,14 +87,8 @@ public class ModWorkManager {
         return new WrappingExecutor(executor);
     }
 
-    private static ForkJoinPool parallelThreadPool;
     public static Executor parallelExecutor() {
-        if (parallelThreadPool == null) {
-            final int loadingThreadCount = FMLConfig.getIntConfigValue(FMLConfig.ConfigValue.MAX_THREADS);
-            LOGGER.debug(LOADING, "Using {} threads for parallel mod-loading", loadingThreadCount);
-            parallelThreadPool = new ForkJoinPool(loadingThreadCount, ModWorkManager::newForkJoinWorkerThread, null, false);
-        }
-        return parallelThreadPool;
+        return LazyInit.PARALLEL_EXECUTOR;
     }
 
     private static ForkJoinWorkerThread newForkJoinWorkerThread(ForkJoinPool pool) {
@@ -109,4 +99,14 @@ public class ModWorkManager {
         return thread;
     }
 
+    private static final class LazyInit {
+        private LazyInit() {}
+        private static final ForkJoinPool PARALLEL_EXECUTOR;
+
+        static {
+            final int loadingThreadCount = FMLConfig.getIntConfigValue(FMLConfig.ConfigValue.MAX_THREADS);
+            LOGGER.debug(LOADING, "Using {} threads for parallel mod-loading", loadingThreadCount);
+            PARALLEL_EXECUTOR = new ForkJoinPool(loadingThreadCount, ModWorkManager::newForkJoinWorkerThread, null, false);
+        }
+    }
 }

fmlcore/src/main/java/net/minecraftforge/fml/OptionalMod.java

@@ -23,7 +23,7 @@ public final class OptionalMod<T>
         return new OptionalMod<>(modId);
     }
 
-    private static OptionalMod<?> EMPTY = new OptionalMod<>(true);
+    private static final OptionalMod<?> EMPTY = new OptionalMod<>(true);
     private static <T> OptionalMod<T> empty() {
         @SuppressWarnings("unchecked")
         OptionalMod<T> t = (OptionalMod<T>) EMPTY;
@@ -213,8 +213,8 @@ public final class OptionalMod<T>
     public boolean equals(Object obj)
     {
         if (this == obj) return true;
-        if (obj instanceof OptionalMod) {
-            return Objects.equals(((OptionalMod)obj).modId, modId);
+        if (obj instanceof OptionalMod<?> optionalMod) {
+            return Objects.equals(optionalMod.modId, modId);
         }
         return false;
     }

fmlcore/src/main/java/net/minecraftforge/fml/config/ConfigFileTypeHandler.java

@@ -14,6 +14,7 @@ import com.mojang.logging.LogUtils;
 import net.minecraftforge.fml.loading.FMLConfig;
 import net.minecraftforge.fml.loading.FMLPaths;
 import org.apache.commons.io.FilenameUtils;
+import org.jetbrains.annotations.Nullable;
 import org.slf4j.Logger;
 
 import java.io.IOException;
@@ -25,9 +26,66 @@ import static net.minecraftforge.fml.config.ConfigTracker.CONFIG;
 
 public class ConfigFileTypeHandler {
     private static final Logger LOGGER = LogUtils.getLogger();
-    static ConfigFileTypeHandler TOML = new ConfigFileTypeHandler();
     private static final Path defaultConfigPath = FMLPaths.GAMEDIR.get().resolve(FMLConfig.getConfigValue(FMLConfig.ConfigValue.DEFAULT_CONFIG_PATH));
 
+    private static final ConfigFileTypeHandler CLIENT = new ConfigFileTypeHandler(ModConfig.Type.CLIENT);
+    private static final ConfigFileTypeHandler COMMON = new ConfigFileTypeHandler(ModConfig.Type.COMMON);
+    private static final ConfigFileTypeHandler SERVER = new ConfigFileTypeHandler(ModConfig.Type.SERVER);
+
+    private final @Nullable ModConfig.Type type;
+    private @Nullable FileWatcher watcher;
+
+    // exists for bin compat
+    public ConfigFileTypeHandler() {
+        this(null);
+    }
+
+    private ConfigFileTypeHandler(@Nullable ModConfig.Type type) {
+        this.type = type;
+    }
+
+    /**
+     * Gets the handler for the given {@link ModConfig.Type}.
+     *
+     * @param type The type to get the handler for
+     * @return The handler
+     */
+    static ConfigFileTypeHandler get(ModConfig.Type type) {
+        return switch (type) {
+            case CLIENT -> CLIENT;
+            case COMMON -> COMMON;
+            case SERVER -> SERVER;
+        };
+    }
+
+    /**
+     * Gets the {@link FileWatcher} for this handler, creating it if it doesn't exist and/or has been stopped.
+     *
+     * @return The watcher
+     *
+     * @apiNote This is package-private so modders can't just call {@link FileWatcher#stop()} and fuck up everything.
+     */
+    FileWatcher getWatcher() {
+        if (this.watcher == null) {
+            LOGGER.debug(CONFIG, "Starting watcher for handler: {}", this);
+            this.watcher = new FileWatcher();
+        }
+
+        return this.watcher;
+    }
+
+    /**
+     * Stops the {@link FileWatcher} for this handler, and sets it to null afterward. Use this instead of
+     * {@link FileWatcher#stop()}.
+     */
+    void stopWatcher() {
+        if (this.watcher == null) return;
+
+        LOGGER.debug(CONFIG, "Stopping watcher for hander: {}", this);
+        this.watcher.stop();
+        this.watcher = null;
+    }
+
     public Function<ModConfig, CommentedFileConfig> reader(Path configBasePath) {
         return (c) -> {
             final Path configPath = configBasePath.resolve(c.getFileName());
@@ -37,7 +95,7 @@ public class ConfigFileTypeHandler {
                     onFileNotFound((newfile, configFormat)-> setupConfigFile(c, newfile, configFormat)).
                     writingMode(WritingMode.REPLACE).
                     build();
-            LOGGER.debug(CONFIG, "Built TOML config for {}", configPath.toString());
+            LOGGER.debug(CONFIG, "Built TOML config for {}", configPath);
             try
             {
                 configData.load();
@@ -46,9 +104,9 @@ public class ConfigFileTypeHandler {
             {
                 throw new ConfigLoadingException(c, ex);
             }
-            LOGGER.debug(CONFIG, "Loaded TOML config file {}", configPath.toString());
-            FileWatcher.defaultInstance().addWatch(configPath, new ConfigWatcher(c, configData, Thread.currentThread().getContextClassLoader()));
-            LOGGER.debug(CONFIG, "Watching TOML config file {} for changes", configPath.toString());
+            LOGGER.debug(CONFIG, "Loaded TOML config file {}", configPath);
+            this.getWatcher().addWatch(configPath, new ConfigWatcher(c, configData, Thread.currentThread().getContextClassLoader()));
+            LOGGER.debug(CONFIG, "Watching TOML config file {} for changes", configPath);
             return configData;
         };
     }
@@ -56,13 +114,13 @@ public class ConfigFileTypeHandler {
     public void unload(Path configBasePath, ModConfig config) {
         Path configPath = configBasePath.resolve(config.getFileName());
         try {
-            FileWatcher.defaultInstance().removeWatch(configBasePath.resolve(config.getFileName()));
+            this.getWatcher().removeWatch(configPath);
         } catch (RuntimeException e) {
-            LOGGER.error("Failed to remove config {} from tracker!", configPath.toString(), e);
+            LOGGER.error("Failed to remove config {} from tracker!", configPath, e);
         }
     }
 
-    private boolean setupConfigFile(final ModConfig modConfig, final Path file, final ConfigFormat<?> conf) throws IOException {
+    private static boolean setupConfigFile(final ModConfig modConfig, final Path file, final ConfigFormat<?> conf) throws IOException {
         if (!Files.isDirectory(file.getParent())) {
             Files.createDirectories(file.getParent());
         }
@@ -109,17 +167,16 @@ public class ConfigFileTypeHandler {
         }
     }
 
-    private static class ConfigWatcher implements Runnable {
-        private final ModConfig modConfig;
-        private final CommentedFileConfig commentedFileConfig;
-        private final ClassLoader realClassLoader;
-
-        ConfigWatcher(final ModConfig modConfig, final CommentedFileConfig commentedFileConfig, final ClassLoader classLoader) {
-            this.modConfig = modConfig;
-            this.commentedFileConfig = commentedFileConfig;
-            this.realClassLoader = classLoader;
-        }
+    @Override
+    public String toString() {
+        return "ConfigFileTypeHandler[" + (type != null ? type : "UNKNOWN") + "]";
+    }
 
+    private record ConfigWatcher(
+            ModConfig modConfig,
+            CommentedFileConfig commentedFileConfig,
+            ClassLoader realClassLoader
+    ) implements Runnable {
         @Override
         public void run() {
             // Force the regular classloader onto the special thread

fmlcore/src/main/java/net/minecraftforge/fml/config/ConfigTracker.java

@@ -8,6 +8,9 @@ package net.minecraftforge.fml.config;
 import com.electronwill.nightconfig.core.CommentedConfig;
 import com.electronwill.nightconfig.core.file.CommentedFileConfig;
 import com.mojang.logging.LogUtils;
+import net.minecraftforge.api.distmarker.Dist;
+import net.minecraftforge.fml.DistExecutor;
+import net.minecraftforge.fml.loading.FMLPaths;
 import org.slf4j.Logger;
 import org.slf4j.Marker;
 import org.slf4j.MarkerFactory;
@@ -47,15 +50,32 @@ public class ConfigTracker {
 
     public void loadConfigs(ModConfig.Type type, Path configBasePath) {
         LOGGER.debug(CONFIG, "Loading configs type {}", type);
-        this.configSets.get(type).forEach(config -> openConfig(config, configBasePath));
+        for (ModConfig config : this.configSets.get(type)) {
+            openConfig(config, configBasePath);
+        }
     }
 
+    // TODO: [FML] This is only called for the server (outside of forceUnload)
+    // rethink config implementation for eventual FML rewrite
     public void unloadConfigs(ModConfig.Type type, Path configBasePath) {
         LOGGER.debug(CONFIG, "Unloading configs type {}", type);
-        this.configSets.get(type).forEach(config -> closeConfig(config, configBasePath));
+        for (ModConfig config : this.configSets.get(type)) {
+            closeConfig(config, configBasePath);
+        }
+        ConfigFileTypeHandler.get(type).stopWatcher();
     }
 
-    private void openConfig(final ModConfig config, final Path configBasePath) {
+    // If there is a better way to do this, please tell me. Because this is FUCKED
+    public void forceUnload() {
+        // This is how ModStateProvider handles loading configs. So we're doing the same but with unloadConfigs instead
+        DistExecutor.unsafeRunWhenOn(Dist.CLIENT, () -> () -> this.unloadConfigs(ModConfig.Type.CLIENT, FMLPaths.CONFIGDIR.get()));
+        this.unloadConfigs(ModConfig.Type.COMMON, FMLPaths.CONFIGDIR.get());
+
+        // just in case server watcher is still alive somehow...
+        ConfigFileTypeHandler.get(ModConfig.Type.SERVER).stopWatcher();
+    }
+
+    private static void openConfig(final ModConfig config, final Path configBasePath) {
         LOGGER.trace(CONFIG, "Loading config file type {} at {} for {}", config.getType(), config.getFileName(), config.getModId());
         final CommentedFileConfig configData = config.getHandler().reader(configBasePath).apply(config);
         config.setConfigData(configData);
@@ -63,7 +83,7 @@ public class ConfigTracker {
         config.save();
     }
 
-    private void closeConfig(final ModConfig config, final Path configBasePath) {
+    private static void closeConfig(final ModConfig config, final Path configBasePath) {
         if (config.getConfigData() != null) {
             LOGGER.trace(CONFIG, "Closing config file type {} at {} for {}", config.getType(), config.getFileName(), config.getModId());
             // stop the filewatcher before we save the file and close it, so reload doesn't fire

fmlcore/src/main/java/net/minecraftforge/fml/config/IConfigEvent.java

@@ -5,7 +5,7 @@
 
 package net.minecraftforge.fml.config;
 
-import net.minecraftforge.eventbus.api.Event;
+import net.minecraftforge.eventbus.api.event.InheritableEvent;
 import net.minecraftforge.fml.Bindings;
 
 import java.util.function.Function;
@@ -29,7 +29,7 @@ public interface IConfigEvent {
     ModConfig getConfig();
 
     @SuppressWarnings("unchecked")
-    default <T extends Event & IConfigEvent> T self() {
+    default <T extends InheritableEvent & IConfigEvent> T self() {
         return (T) this;
     }
 }

fmlcore/src/main/java/net/minecraftforge/fml/config/ModConfig.java

@@ -24,14 +24,13 @@ public class ModConfig
     private final ModContainer container;
     private final ConfigFileTypeHandler configHandler;
     private CommentedConfig configData;
-    private Callable<Void> saveHandler;
 
     public ModConfig(final Type type, final IConfigSpec<?> spec, final ModContainer container, final String fileName) {
         this.type = type;
         this.spec = spec;
         this.fileName = fileName;
         this.container = container;
-        this.configHandler = ConfigFileTypeHandler.TOML;
+        this.configHandler = ConfigFileTypeHandler.get(type);
         ConfigTracker.INSTANCE.trackConfig(this);
     }
 

fmlcore/src/main/java/net/minecraftforge/fml/event/IModBusEvent.java

@@ -5,8 +5,33 @@
 
 package net.minecraftforge.fml.event;
 
+import net.minecraftforge.eventbus.api.bus.BusGroup;
+import net.minecraftforge.eventbus.api.bus.EventBus;
+import net.minecraftforge.eventbus.api.event.InheritableEvent;
+import org.jspecify.annotations.NonNull;
+
 /**
- * Marker interface for events dispatched on the ModLifecycle event bus instead of the primary event bus
+ * Marker interface for mod lifecycle events dispatched on the
+ * {@linkplain net.minecraftforge.fml.javafmlmod.FMLJavaModLoadingContext#getModBusGroup() mod BusGroup} instead
+ * of the {@linkplain BusGroup#DEFAULT default BusGroup}.
+ *
+ * @apiNote Each mod gets its own unique mod BusGroup instance, obtained from the mod loading context. Most events
+ *          should go on the default BusGroup.
  */
-public interface IModBusEvent {
+public interface IModBusEvent extends InheritableEvent {
+    /**
+     * @param modEventBusGroup Obtained from {@link net.minecraftforge.fml.javafmlmod.FMLJavaModLoadingContext#getModBusGroup()} or your language provider's equivalent.
+     * @param eventClass The event type you want to get the associated bus for.
+     */
+    static <T extends IModBusEvent> @NonNull EventBus<@NonNull T> getBus(@NonNull BusGroup modEventBusGroup, @NonNull Class<T> eventClass) {
+        // Do not copy! Temporary solution until the FML rewrite is complete. May throw in future
+        // without prior notice.
+        //
+        // Mods creating their own events should directly assign the result of the create method to a
+        // static final field in their event class, without wrapping or calling multiple times.
+        //
+        // Mods using existing events should instead use the existing static final BUS field in the
+        // event class (for most events) or getBus(BusGroup) method (for mod bus events).
+        return EventBus.create(modEventBusGroup, eventClass);
+    }
 }

fmlcore/src/main/java/net/minecraftforge/fml/util/thread/EffectiveSide.java

@@ -7,8 +7,11 @@ package net.minecraftforge.fml.util.thread;
 
 import net.minecraftforge.fml.LogicalSide;
 
-public class EffectiveSide
-{
+/**
+ * Attempts to determine the effect side of the current thread, based on know threads in networking.
+ * This is not guaranteed to be correct, and modders should use other methods to determine the logical side when possible.
+ */
+public class EffectiveSide {
     public static LogicalSide get() {
         final ThreadGroup group = Thread.currentThread().getThreadGroup();
         return group instanceof SidedThreadGroup ? ((SidedThreadGroup) group).getSide() : LogicalSide.CLIENT;

fmlcore/src/main/java/net/minecraftforge/fml/util/thread/SidedThreadGroups.java

@@ -7,11 +7,13 @@ package net.minecraftforge.fml.util.thread;
 
 import net.minecraftforge.fml.LogicalSide;
 
-public final class SidedThreadGroups
-{
+public final class SidedThreadGroups {
     public static final SidedThreadGroup CLIENT = new SidedThreadGroup(LogicalSide.CLIENT);
     public static final SidedThreadGroup SERVER = new SidedThreadGroup(LogicalSide.SERVER);
 
-    private SidedThreadGroups() {
+    public static SidedThreadGroup get(boolean client) {
+        return client ? CLIENT : SERVER;
     }
+
+    private SidedThreadGroups() { }
 }

fmlearlydisplay/build.gradle

@@ -28,7 +28,7 @@ java {
 }
 
 dependencies {
-    compileOnly(libs.nulls)
+    compileOnly(libs.jetbrains.annotations)
     implementation(project(':fmlloader'))
     implementation(project(':fmlcore'))
     implementation(libs.bundles.lwjgl)

fmlearlydisplay/src/main/java/net/minecraftforge/fml/earlydisplay/DisplayWindow.java

@@ -22,9 +22,7 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.awt.Desktop;
-import java.io.BufferedReader;
 import java.io.IOException;
-import java.io.InputStreamReader;
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
 import java.net.URI;
@@ -87,11 +85,17 @@ public class DisplayWindow implements ImmediateWindowProvider {
     private ScheduledFuture<?> initializationFuture;
 
     private PerformanceInfo performanceInfo;
+    @SuppressWarnings("unused")
     private ScheduledFuture<?> performanceTick;
     // The GL ID of the window. Used for all operations
     private long window;
     // The thread that contains and ticks the window while Forge is loading mods
-    private ScheduledExecutorService renderScheduler;
+    private static final ScheduledExecutorService renderScheduler = Executors.newSingleThreadScheduledExecutor(r -> {
+        final var thread = Executors.defaultThreadFactory().newThread(r);
+        thread.setName("EarlyDisplay");
+        thread.setDaemon(true);
+        return thread;
+    });
     private int fbWidth;
     private int fbHeight;
     private int fbScale;
@@ -150,7 +154,7 @@ public class DisplayWindow implements ImmediateWindowProvider {
         }
         this.maximized = parsed.has(maximizedopt) || FMLConfig.getBoolConfigValue(FMLConfig.ConfigValue.EARLY_WINDOW_MAXIMIZED);
 
-        StartupNotificationManager.modLoaderConsumer().ifPresent(c->c.accept("Forge loading " + forgeVersion));
+        StartupNotificationManager.modLoaderConsumer().ifPresent(c->c.accept("Forge loading " + FMLLoader.versionInfo().forgeVersion()));
         performanceInfo = new PerformanceInfo();
         return start(mcVersion, forgeVersion);
     }
@@ -239,7 +243,7 @@ public class DisplayWindow implements ImmediateWindowProvider {
 
         var date = Calendar.getInstance();
         if (FMLConfig.getBoolConfigValue(FMLConfig.ConfigValue.EARLY_WINDOW_SQUIR) || (date.get(Calendar.MONTH) == Calendar.APRIL && date.get(Calendar.DAY_OF_MONTH) == 1))
-            this.elements.add(0, RenderElement.squir());
+            this.elements.addFirst(RenderElement.squir());
 
         glEnable(GL_BLEND);
         glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
@@ -259,7 +263,11 @@ public class DisplayWindow implements ImmediateWindowProvider {
         glEnable(GL_BLEND);
         glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 
-        this.elements.removeIf(element -> !element.render(context, framecount));
+        for (var itr = this.elements.iterator(); itr.hasNext(); ) {
+            var element = itr.next();
+            if (!element.render(context, framecount))
+                itr.remove();
+        }
         if (animationTimerTrigger.compareAndSet(true, false)) // we only increment the framecount on a periodic basis
             framecount++;
     }
@@ -284,12 +292,6 @@ public class DisplayWindow implements ImmediateWindowProvider {
      * Start the window and Render Thread; we're ready to go.
      */
     public Runnable start(@Nullable String mcVersion, final String forgeVersion) {
-        renderScheduler = Executors.newSingleThreadScheduledExecutor(r -> {
-            final var thread = Executors.defaultThreadFactory().newThread(r);
-            thread.setName("EarlyDisplay");
-            thread.setDaemon(true);
-            return thread;
-        });
         initWindow(mcVersion);
         this.initializationFuture = renderScheduler.schedule(() -> initRender(mcVersion, forgeVersion), 1, TimeUnit.MILLISECONDS);
         return this::periodicTick;
@@ -301,14 +303,7 @@ public class DisplayWindow implements ImmediateWindowProvider {
         return this.glVersion;
     }
 
-    private void crashElegantly(String errorDetails) {
-        String qrText;
-        try (var is = new BufferedReader(new InputStreamReader(getClass().getResourceAsStream("/glfailure.txt")))) {
-            qrText = is.lines().collect(Collectors.joining("\n"));
-        } catch (IOException ioe) {
-            qrText = "";
-        }
-
+    private static void crashElegantly(String errorDetails) {
         StringBuilder msgBuilder = new StringBuilder(2000);
         msgBuilder.append("Failed to initialize graphics window with current settings.\n");
         msgBuilder.append("\n\n");
@@ -407,13 +402,13 @@ public class DisplayWindow implements ImmediateWindowProvider {
             if (showHelpLog && versidx == 0) {
                 LOGGER.info("""
                 If this message is the only thing at the bottom of your log before a crash, you probably have a driver issue.
-                
+
                 Possible solutions:
                 A) Make sure Minecraft is set to prefer high performance graphics in the OS and/or driver control panel
                 B) Check for driver updates on the graphics brand's website
                 C) Try reinstalling your graphics drivers
                 D) If still not working after trying all of the above, ask for further help on the Forge forums or Discord
-                
+
                 You can safely ignore this message if the game starts up successfully.""");
             }
             glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, GL_VERSIONS[versidx][0]); // we try our versions one at a time
@@ -497,10 +492,6 @@ public class DisplayWindow implements ImmediateWindowProvider {
         glfwPollEvents();
     }
 
-    private void badWindowHandler(final int code, final long desc) {
-        LOGGER.error("Got error from GLFW window init: "+code+ " "+MemoryUtil.memUTF8(desc));
-    }
-
     private void winResize(long window, int width, int height) {
         if (window == this.window && width != 0 && height != 0) {
             this.winWidth = width;
@@ -520,7 +511,7 @@ public class DisplayWindow implements ImmediateWindowProvider {
             this.winY = y;
         }
     }
-    private void handleLastGLFWError(BiConsumer<Integer, String> handler) {
+    private static void handleLastGLFWError(BiConsumer<Integer, String> handler) {
         try (MemoryStack memorystack = MemoryStack.stackPush()) {
             PointerBuffer pointerbuffer = memorystack.mallocPointer(1);
             int error = glfwGetError(pointerbuffer);
@@ -612,10 +603,25 @@ public class DisplayWindow implements ImmediateWindowProvider {
 
     @Override
     public void updateModuleReads(final ModuleLayer layer) {
-        var fm = layer.findModule("forge").orElseThrow();
-        getClass().getModule().addReads(fm);
-        var clz = FMLLoader.getGameLayer().findModule("forge").map(l->Class.forName(l, "net.minecraftforge.client.loading.ForgeLoadingOverlay")).orElseThrow();
-        loadingOverlay = Arrays.stream(clz.getDeclaredMethods()).filter(m-> Modifier.isStatic(m.getModifiers()) && m.getName().equals("newInstance")).findFirst().orElseThrow();
+        final var FORGE_MODULE = "net.minecraftforge.forge";
+        var forge_module = layer.findModule(FORGE_MODULE).orElse(null);
+        if (forge_module == null)
+            throw new IllegalStateException("Could not find " + FORGE_MODULE + " in " + layer);
+
+        getClass().getModule().addReads(forge_module);
+
+
+        var clz = Class.forName(forge_module, "net.minecraftforge.client.loading.ForgeLoadingOverlay");
+
+        for (var mtd : clz.getDeclaredMethods()) {
+            if (Modifier.isStatic(mtd.getModifiers()) && "newInstance".equals(mtd.getName())) {
+                this.loadingOverlay = mtd;
+                break;
+            }
+        }
+
+        if (loadingOverlay == null)
+            throw new IllegalStateException("Could not find static newInstace method in " + clz.getName());
     }
 
     public int getFramebufferTextureId() {
@@ -633,8 +639,7 @@ public class DisplayWindow implements ImmediateWindowProvider {
     }
 
     public void addMojangTexture(final int textureId) {
-        this.elements.add(0, RenderElement.mojang(textureId, framecount));
-//        this.elements.get(0).retire(framecount + 1);
+        this.elements.addFirst(RenderElement.mojang(textureId, framecount));
     }
 
     public void close() {

fmlearlydisplay/src/main/java/net/minecraftforge/fml/earlydisplay/PerformanceInfo.java

@@ -13,10 +13,10 @@ import java.lang.management.MemoryMXBean;
 import java.lang.management.MemoryUsage;
 
 public class PerformanceInfo {
+    private static final MemoryMXBean MEMORY_BEAN = ManagementFactory.getMemoryMXBean();
 
     private final boolean showCPUUsage;
     private final OperatingSystemMXBean osBean;
-    private final MemoryMXBean memoryBean;
 
     private float memory;
     private String text;
@@ -24,15 +24,14 @@ public class PerformanceInfo {
     PerformanceInfo() {
         showCPUUsage = FMLConfig.getBoolConfigValue(FMLConfig.ConfigValue.EARLY_WINDOW_SHOW_CPU);
         osBean = showCPUUsage ? ManagementFactory.getPlatformMXBean(OperatingSystemMXBean.class) : null;
-        memoryBean = ManagementFactory.getMemoryMXBean();
     }
 
     void update() {
-        final MemoryUsage heapusage = memoryBean.getHeapMemoryUsage();
+        final MemoryUsage heapusage = MEMORY_BEAN.getHeapMemoryUsage();
         memory = (float) heapusage.getUsed() / heapusage.getMax();
 
         if (!showCPUUsage) {
-            text = "Heap: %d/%d MB (%.1f%%) OffHeap: %d MB".formatted(heapusage.getUsed() >> 20, heapusage.getMax() >> 20, memory * 100.0, memoryBean.getNonHeapMemoryUsage().getUsed() >> 20);
+            text = "Memory: %d/%dMB (%.1f%%)".formatted(heapusage.getUsed() >>> 20, heapusage.getMax() >>> 20, memory * 100f);
             return;
         }
 
@@ -44,7 +43,7 @@ public class PerformanceInfo {
             cpuText = "CPU: %.1f%%".formatted(cpuLoad * 100f);
         }
 
-        text = "Heap: %d/%d MB (%.1f%%) OffHeap: %d MB  %s".formatted(heapusage.getUsed() >> 20, heapusage.getMax() >> 20, memory * 100.0, memoryBean.getNonHeapMemoryUsage().getUsed() >> 20, cpuText);
+        text = "Memory: %d/%dMB (%.1f%%)  %s".formatted(heapusage.getUsed() >>> 20, heapusage.getMax() >>> 20, memory * 100f, cpuText);
     }
 
     String text() {

fmlearlydisplay/src/main/java/net/minecraftforge/fml/earlydisplay/RenderElement.java

@@ -22,8 +22,8 @@ public class RenderElement {
     static int globalAlpha = 255;
     private int retireCount;
 
+    @FunctionalInterface
     interface Renderer {
-
         void accept(SimpleBufferBuilder bb, DisplayContext context, int frame);
 
         default Renderer then(Renderer r) {
@@ -38,6 +38,9 @@ public class RenderElement {
     interface TextureRenderer {
         void accept(SimpleBufferBuilder bb, DisplayContext context, int[] size, int frame);
     }
+
+    /** @deprecated Use {@link Renderer} directly. This was always eagerly resolved, making it an unnecessary wrapper. */
+    @Deprecated(since = "1.21.5", forRemoval = true)
     @FunctionalInterface
     interface Initializer extends Supplier<Renderer> {}
 
@@ -56,11 +59,18 @@ public class RenderElement {
         }
     }
 
+    /** @deprecated Use {@link RenderElement#RenderElement(Renderer)} instead */
+    @Deprecated(since = "1.21.5", forRemoval = true)
     public RenderElement(final Initializer rendererInitializer) {
         this.bb = new SimpleBufferBuilder(1);
         this.renderer = rendererInitializer.get();
     }
 
+    public RenderElement(Renderer renderer) {
+        this.bb = new SimpleBufferBuilder(1);
+        this.renderer = renderer;
+    }
+
     public boolean render(DisplayContext ctx, int count) {
         this.renderer.accept(bb, ctx, count);
         return this.retireCount == 0 || this.retireCount < count;
@@ -75,7 +85,7 @@ public class RenderElement {
         List<SimpleFont.DisplayText> texts = new ArrayList<>();
         for (int i = messages.size() - 1; i >= 0; i--) {
             final StartupNotificationManager.AgeMessage pair = messages.get(i);
-            final float fade = clamp((4000.0f - (float) pair.age() - ( i - 4 ) * 1000.0f) / 5000.0f, 0.0f, 1.0f);
+            final float fade = Math.clamp((4000.0f - (float) pair.age() - ( i - 4 ) * 1000.0f) / 5000.0f, 0.0f, 1.0f);
             if (fade <0.01f) continue;
             Message msg = pair.message();
             int colour = Math.min((int)(fade * 255f), globalAlpha) << 24 | 0xFFFFFF;
@@ -84,19 +94,9 @@ public class RenderElement {
 
         font.generateVerticesForTexts(10, context.scaledHeight() -  texts.size() * font.lineSpacing() + font.descent() - 10, bb, texts.toArray(SimpleFont.DisplayText[]::new));
     }
-    public static RenderElement monag() {
-        return new RenderElement(RenderElement.initializeTexture("monagstudios.png", 45000, 4, (bb, ctx, sz, frame) -> {
-            var size = 256;
-            var x0 = (ctx.width() - 2 * size) / 2;
-            var y0 = 64;
-            QuadHelper.loadQuad(bb, x0, x0+size, y0, y0+size/2f, 0f, 1f, 0f, 0.5f, 0xFFFFFFFF);
-            QuadHelper.loadQuad(bb, x0+size, x0+2*size, y0, y0+size/2f, 0f, 1f, 0.5f, 1f, 0xFFFFFFFF);
-        }));
-
-    }
 
     public static RenderElement mojang(final int textureId, final int frameStart) {
-        return new RenderElement(()->(bb, ctx, frame) -> {
+        return new RenderElement((bb, ctx, frame) -> {
             var size = 256 * ctx.scale();
             var x0 = (ctx.scaledWidth() - 2 * size) / 2;
             var y0 = 64 * ctx.scale() + 32;
@@ -148,11 +148,11 @@ public class RenderElement {
         }));
     }
     public static RenderElement progressBars(SimpleFont font) {
-        return new RenderElement(() -> (bb, ctx, frame) -> RenderElement.startupProgressBars(font, bb, ctx, frame));
+        return new RenderElement((bb, ctx, frame) -> RenderElement.startupProgressBars(font, bb, ctx, frame));
     }
 
     public static RenderElement performanceBar(SimpleFont font) {
-        return new RenderElement(() -> (bb, ctx, frame) -> RenderElement.memoryInfo(font, bb, ctx, frame));
+        return new RenderElement((bb, ctx, frame) -> RenderElement.memoryInfo(font, bb, ctx, frame));
     }
 
     public static void startupProgressBars(SimpleFont font, final SimpleBufferBuilder buffer, final DisplayContext context, final int frameNumber) {
@@ -187,10 +187,10 @@ public class RenderElement {
     }
     private static float[] indeterminateBar(int frame, boolean isActive) {
         if (RenderElement.globalAlpha != 0xFF || !isActive) {
-            return new float[] {0f,1f};
+            return new float[] { 0f, 1f };
         } else {
-            var progress = frame % 100;
-            return new float[]{clamp((progress - 2) / 100f, 0f, 1f), clamp((progress + 2) / 100f, 0f, 1f)};
+            int progress = frame % 100;
+            return new float[] { Math.clamp((progress - 2) / 100f, 0f, 1f), Math.clamp((progress + 2) / 100f, 0f, 1f) };
         }
     }
 
@@ -249,8 +249,8 @@ public class RenderElement {
         };
     }
 
-    private static Initializer initializeText(SimpleFont font, TextGenerator textGenerator) {
-        return () -> (bb, context, frame) -> renderText(font, textGenerator, bb, context);
+    private static Renderer initializeText(SimpleFont font, TextGenerator textGenerator) {
+        return (bb, context, frame) -> renderText(font, textGenerator, bb, context);
     }
 
     private static void renderText(final SimpleFont font, final TextGenerator textGenerator, final SimpleBufferBuilder bb, final DisplayContext context) {
@@ -264,14 +264,13 @@ public class RenderElement {
     private static TextGenerator text(int x, int y, String text, int colour) {
         return (bb, font, context) -> font.generateVerticesForTexts(x, y, bb, new SimpleFont.DisplayText(text, colour));
     }
-    private static Initializer initializeTexture(final String textureFileName, int size, int textureNumber, TextureRenderer positionAndColour) {
-        return ()->{
-            int[] imgSize = STBHelper.loadTextureFromClasspath(textureFileName, size, GL_TEXTURE0 + textureNumber + INDEX_TEXTURE_OFFSET);
-            return (bb, ctx, frame) -> {
-                ctx.elementShader().updateTextureUniform(textureNumber + INDEX_TEXTURE_OFFSET);
-                ctx.elementShader().updateRenderTypeUniform(ElementShader.RenderType.TEXTURE);
-                renderTexture(bb, ctx, frame, imgSize, positionAndColour);
-            };
+
+    private static Renderer initializeTexture(final String textureFileName, int size, int textureNumber, TextureRenderer positionAndColour) {
+        int[] imgSize = STBHelper.loadTextureFromClasspath(textureFileName, size, GL_TEXTURE0 + textureNumber + INDEX_TEXTURE_OFFSET);
+        return (bb, ctx, frame) -> {
+            ctx.elementShader().updateTextureUniform(textureNumber + INDEX_TEXTURE_OFFSET);
+            ctx.elementShader().updateRenderTypeUniform(ElementShader.RenderType.TEXTURE);
+            renderTexture(bb, ctx, frame, imgSize, positionAndColour);
         };
     }
 
@@ -281,21 +280,13 @@ public class RenderElement {
         bb.draw();
     }
 
-
+    @Deprecated(since = "1.21.5", forRemoval = true)
     public static float clamp(float num, float min, float max) {
-        if (num < min) {
-            return min;
-        } else {
-            return Math.min(num, max);
-        }
+        return Math.clamp(num, min, max);
     }
 
     public static int clamp(int num, int min, int max) {
-        if (num < min) {
-            return min;
-        } else {
-            return Math.min(num, max);
-        }
+        return Math.min(max, Math.max(num, min));
     }
 
     public static int hsvToRGB(float hue, float saturation, float value) {

fmlearlydisplay/src/main/java/net/minecraftforge/fml/earlydisplay/SimpleFont.java

@@ -11,8 +11,6 @@ import org.lwjgl.stb.STBTTFontinfo;
 import org.lwjgl.stb.STBTTPackContext;
 import org.lwjgl.stb.STBTTPackRange;
 import org.lwjgl.stb.STBTTPackedchar;
-import org.lwjgl.system.MemoryStack;
-
 import java.nio.ByteBuffer;
 import java.nio.charset.StandardCharsets;
 
@@ -24,8 +22,8 @@ public class SimpleFont {
     private final int textureNumber;
     private final int lineSpacing;
     private final int descent;
-    private final int GLYPH_COUNT = 127-32;
-    private Glyph[] glyphs;
+    private static final int GLYPH_COUNT = 127 - 32;
+    private final Glyph[] glyphs;
 
     private record Glyph(char c, int charwidth, int[] pos, float[] uv) {
         Pos loadQuad(Pos pos, int colour, SimpleBufferBuilder bb) {
@@ -122,7 +120,7 @@ public class SimpleFont {
                 case '\n', '\t' -> 0;
                 case ' ' -> glyphs[0].charwidth();
                 default -> {
-                    if (c - 32 < this.GLYPH_COUNT && c > 32) {
+                    if (c - 32 < GLYPH_COUNT && c > 32) {
                         yield this.glyphs[c - 32].charwidth();
                     } else {
                         yield 0;
@@ -153,7 +151,7 @@ public class SimpleFont {
                     case '\t' -> new Pos(pos.x()+font.glyphs[0].charwidth() * 4, pos.y(), pos.minx());
                     case ' ' -> new Pos(pos.x()+font.glyphs[0].charwidth(), pos.y(), pos.minx());
                     default -> {
-                        if (c-32 < font.GLYPH_COUNT && c > 32) {
+                        if (c-32 < GLYPH_COUNT && c > 32) {
                             pos = font.glyphs[c - 32].loadQuad(pos, colour(), bb);
                         }
                         yield pos;

fmlloader/build.gradle

@@ -5,6 +5,7 @@ plugins {
     id 'maven-publish'
     id 'net.minecraftforge.licenser'
     id 'net.minecraftforge.gradleutils'
+    alias(libs.plugins.apt)
 }
 
 apply from: rootProject.file('build_shared.gradle')
@@ -12,7 +13,7 @@ apply from: rootProject.file('build_shared.gradle')
 configurations.forEach{ it.transitive = false }
 
 dependencies {
-    compileOnly(libs.nulls)
+    compileOnly(libs.jetbrains.annotations)
 
     api(libs.bundles.asm) // Needed by all the black magic
     api(libs.forgespi)
@@ -35,11 +36,13 @@ dependencies {
     implementation(libs.accesstransformers)
     implementation(libs.terminalconsoleappender)
     implementation(libs.jimfs)
+    implementation(libs.roimfs)
 
+    // Needed because we have a custom log4j plugin, and they removed package scanning and require a data file to be generated
     implementation(libs.log4j.core)
     annotationProcessor(libs.bundles.log4j)
 
-    testCompileOnly(libs.nulls)
+    testCompileOnly(libs.jetbrains.annotations)
     testRuntimeOnly(libs.bootstrap)
 }
 
@@ -85,7 +88,7 @@ publishing {
             license PomUtils.Licenses.LGPLv2_1
         }
     }
-    
+
     repositories {
         maven gradleutils.publishingForgeMaven
     }
@@ -101,6 +104,44 @@ tasks.register('writeForgeVersionJson') {
     }
 }
 
-tasks.named('generateResources').configure {
-    dependsOn('writeForgeVersionJson')
+tasks.register('jarJarOptionsJson', net.minecraftforge.forge.tasks.JarJarMetadataOptions) {
+    metadataFile = project.file('src/main/resources/jarjar_options.json')
+    // This is resolved too early by cpw.mods.modlauncher.TransformationServicesHandler.discoverServices(DiscoveryData) But eventually...
+    //add(libs.mixin, 'org/spongepowered/asm/mixin/Mixin.class')
+    add(libs.mixinextras.forge) {
+        containedJarMetadata {
+            path = ''
+        }
+        resource = 'com/llamalad7/mixinextras/platform/forge/MixinExtrasConfigPlugin.class'
+        layer = 'GAMELIBRARY'
+        id = 'mixinextras'
+        nested = true
+    }
+}
+
+tasks.named('generateResources').configure {
+    dependsOn('eclipseJdt')
+    dependsOn('eclipseJdtApt')
+    dependsOn('eclipseFactorypath')
+    dependsOn('writeForgeVersionJson')
+    dependsOn('jarJarOptionsJson')
+}
+
+tasks.named('sourcesJar') {
+    dependsOn('jarJarOptionsJson')
+}
+
+eclipse {
+    classpath {
+       // We need to set the default output directory for the log4j annotation processor
+       // Ideally we'd just set the value, but the eclipse plugin deduplicates the output directories
+       // So we have to do a hacky whenMerged
+       //defaultOutputDir = file('bin/main')
+       file.whenMerged {
+           entries.each { entry ->
+               if (entry.kind == 'output' && entry.hasProperty('path'))
+                   entry.path = 'bin/main'
+           }
+       }
+    }
 }

fmlloader/src/main/java/net/minecraftforge/fml/common/asm/CapabilityTokenSubclass.java

@@ -34,11 +34,10 @@ import cpw.mods.modlauncher.serviceapi.ILaunchPluginService;
  *  }</code>
  * </pre>
  */
-public class CapabilityTokenSubclass implements ILaunchPluginService {
-
-    private final String FUNC_NAME = "getType";
-    private final String FUNC_DESC = "()Ljava/lang/String;";
-    private final String CAP_INJECT = "net/minecraftforge/common/capabilities/CapabilityToken"; //Don't directly reference this to prevent class loading.
+public final class CapabilityTokenSubclass implements ILaunchPluginService {
+    private static final String FUNC_NAME = "getType";
+    private static final String FUNC_DESC = "()Ljava/lang/String;";
+    private static final String CAP_INJECT = "net/minecraftforge/common/capabilities/CapabilityToken"; // Don't directly reference this to prevent class loading.
 
     @Override
     public String name() {
@@ -50,7 +49,17 @@ public class CapabilityTokenSubclass implements ILaunchPluginService {
 
     @Override
     public EnumSet<Phase> handlesClass(Type classType, boolean isEmpty) {
-        return isEmpty ? NAY : YAY;
+        if (isEmpty)
+            return NAY;
+
+        String internalName = classType.getInternalName();
+        if (internalName.startsWith("net/minecraft/") || internalName.startsWith("com/mojang/"))
+            return NAY;
+
+        if (internalName.startsWith("net/minecraftforge/common/capabilities/"))
+            return YAY;
+        
+        return internalName.contains("$") ? YAY : NAY; // Anonymous subclasses only
     }
 
     @Override
@@ -63,11 +72,11 @@ public class CapabilityTokenSubclass implements ILaunchPluginService {
             }
             return ComputeFlags.SIMPLE_REWRITE;
         } else if (CAP_INJECT.equals(classNode.superName)) {
-            Holder cls = new Holder();
+            var cls = new Object() { String value = null; };
 
             SignatureReader reader = new SignatureReader(classNode.signature); // Having a node version of this would probably be useful.
             reader.accept(new SignatureVisitor(Opcodes.ASM9) {
-                Deque<String> stack = new ArrayDeque<>();
+                final Deque<String> stack = new ArrayDeque<>();
 
                 @Override
                 public void visitClassType(final String name) {
@@ -99,8 +108,4 @@ public class CapabilityTokenSubclass implements ILaunchPluginService {
             return ComputeFlags.NO_REWRITE;
         }
     }
-
-    private static class Holder {
-        String value;
-    }
 }

fmlloader/src/main/java/net/minecraftforge/fml/common/asm/ObjectHolderDefinalize.java

@@ -1,111 +0,0 @@
-/*
- * Copyright (c) Forge Development LLC and contributors
- * SPDX-License-Identifier: LGPL-2.1-only
- */
-
-package net.minecraftforge.fml.common.asm;
-
-import java.util.EnumSet;
-import java.util.List;
-import java.util.Map;
-import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.function.Function;
-import java.util.stream.Collectors;
-import java.util.stream.Stream;
-
-import org.objectweb.asm.Opcodes;
-import org.objectweb.asm.Type;
-import org.objectweb.asm.tree.AnnotationNode;
-import org.objectweb.asm.tree.ClassNode;
-import cpw.mods.modlauncher.serviceapi.ILaunchPluginService;
-
-/**
- * Removes the final modifier from fields with the @ObjectHolder annotation, prevents the JITer from in lining them so our runtime replacements can work.
- * Will also de-finalize all fields in on class level annotations.
- */
-public class ObjectHolderDefinalize implements ILaunchPluginService {
-    // Hardcoded map of vanilla classes that should have object holders for each field of the given registry type.
-    // IMPORTANT: Updates to this collection must be reflected in ObjectHolderRegistry. Duplicated cuz classloaders, yay!
-    // Classnames are validated in ObjectHolderRegistry.
-    private static final Map<String, VanillaObjectHolderData> VANILLA_OBJECT_HOLDERS = Stream.of(
-            new VanillaObjectHolderData("net.minecraft.world.level.block.Blocks", "block", "net.minecraft.world.level.block.Block"),
-            new VanillaObjectHolderData("net.minecraft.world.item.Items", "item", "net.minecraft.world.item.Item"),
-            new VanillaObjectHolderData("net.minecraft.world.item.enchantment.Enchantments", "enchantment", "net.minecraft.world.item.enchantment.Enchantment"),
-            new VanillaObjectHolderData("net.minecraft.world.effect.MobEffects", "mob_effect", "net.minecraft.world.effect.MobEffect"),
-            new VanillaObjectHolderData("net.minecraft.core.particles.ParticleTypes", "particle_type", "net.minecraft.core.particles.ParticleType"),
-            new VanillaObjectHolderData("net.minecraft.sounds.SoundEvents", "sound_event", "net.minecraft.sounds.SoundEvent")
-    ).collect(Collectors.toMap(VanillaObjectHolderData::holderClass, Function.identity()));
-    private final String OBJECT_HOLDER = "Lnet/minecraftforge/registries/ObjectHolder;"; //Don't directly reference this to prevent class loading.
-
-    @Override
-    public String name() {
-        return "object_holder_definalize";
-    }
-
-    private static final EnumSet<Phase> YAY = EnumSet.of(Phase.AFTER);
-    private static final EnumSet<Phase> NAY = EnumSet.noneOf(Phase.class);
-
-    @Override
-    public EnumSet<Phase> handlesClass(Type classType, boolean isEmpty)
-    {
-        return isEmpty ? NAY : YAY;
-    }
-
-    private boolean hasHolder(List<AnnotationNode> lst)
-    {
-        return lst != null && lst.stream().anyMatch(n -> n.desc.equals(OBJECT_HOLDER));
-    }
-
-    @SuppressWarnings("unused")
-    private String getValue(List<AnnotationNode> lst)
-    {
-        AnnotationNode ann = lst.stream().filter(n -> n.desc.equals(OBJECT_HOLDER)).findFirst().get();
-        if (ann.values != null)
-        {
-            for (int x = 0; x < ann.values.size() - 1; x += 2) {
-                if (ann.values.get(x).equals("value")) {
-                    return (String)ann.values.get(x + 1);
-                }
-            }
-        }
-        return null;
-    }
-
-    @Override
-    public int processClassWithFlags(final Phase phase, final ClassNode classNode, final Type classType, final String reason)
-    {
-        final AtomicBoolean changes = new AtomicBoolean();
-        //Must be public static finals, and non-array objects
-        final int flags = Opcodes.ACC_PUBLIC | Opcodes.ACC_STATIC | Opcodes.ACC_FINAL;
-
-        //Fix Annotated Fields before injecting from class level
-        classNode.fields.stream().filter(f -> ((f.access & flags) == flags) && f.desc.startsWith("L") && hasHolder(f.visibleAnnotations)).forEach(f ->
-        {
-            int prev = f.access;
-            f.access &= ~Opcodes.ACC_FINAL; //Strip final
-            f.access |= Opcodes.ACC_SYNTHETIC; //Add Synthetic so we can check in runtime. ? Good idea?
-            changes.compareAndSet(false, prev != f.access);
-        });
-
-        if (VANILLA_OBJECT_HOLDERS.containsKey(classType.getClassName())) //Class level, de-finalize all fields and add @ObjectHolder to them!
-        {
-            classNode.fields.stream().filter(f -> ((f.access & flags) == flags) && f.desc.startsWith("L")).forEach(f ->
-            {
-                int prev = f.access;
-                f.access &= ~Opcodes.ACC_FINAL;
-                f.access |= Opcodes.ACC_SYNTHETIC;
-                /*if (!hasHolder(f.visibleAnnotations)) //Add field level annotation, doesn't do anything until after we figure out how ASMDataTable is gatherered
-                {
-                   if (value == null)
-                       f.visitAnnotation(OBJECT_HOLDER, true);
-                   else
-                       f.visitAnnotation(OBJECT_HOLDER, true).visit("value", value + ":" + f.name.toLowerCase());
-                }*/
-                changes.compareAndSet(false, prev != f.access);
-            });
-        }
-        return changes.get() ? ComputeFlags.SIMPLE_REWRITE : ComputeFlags.NO_REWRITE;
-    }
-
-    private record VanillaObjectHolderData(String holderClass, String registryName, String registryType) {}
-}

fmlloader/src/main/java/net/minecraftforge/fml/common/asm/RuntimeEnumExtender.java

@@ -7,9 +7,9 @@ package net.minecraftforge.fml.common.asm;
 
 import java.util.EnumSet;
 import java.util.List;
-import java.util.stream.Collectors;
 
 import com.mojang.logging.LogUtils;
+import net.minecraftforge.fml.loading.LoadingModList;
 import org.objectweb.asm.Label;
 import org.objectweb.asm.Opcodes;
 import org.objectweb.asm.Type;
@@ -28,15 +28,16 @@ import org.slf4j.Logger;
 public class RuntimeEnumExtender implements ILaunchPluginService {
 
     private static final Logger LOGGER = LogUtils.getLogger();
-    private final Type STRING = Type.getType(String.class);
-    private final Type ENUM = Type.getType(Enum.class);
-    private final Type MARKER_IFACE = Type.getType("Lnet/minecraftforge/common/IExtensibleEnum;");
-    private final Type ARRAY_UTILS = Type.getType("Lorg/apache/commons/lang3/ArrayUtils;"); //Don't directly reference this to prevent class loading.
-    private final String ADD_DESC = Type.getMethodDescriptor(Type.getType(Object[].class), Type.getType(Object[].class), Type.getType(Object.class));
-    private final Type UNSAFE_HACKS = Type.getType("Lnet/minecraftforge/fml/unsafe/UnsafeHacks;"); //Again, not direct reference to prevent class loading.
-    private final String CLEAN_DESC = Type.getMethodDescriptor(Type.VOID_TYPE, Type.getType(Class.class));
-    private final String NAME_DESC = Type.getMethodDescriptor(STRING);
-    private final String EQUALS_DESC = Type.getMethodDescriptor(Type.BOOLEAN_TYPE, STRING);
+    private static final Type STRING = Type.getType(String.class);
+    private static final Type ENUM = Type.getType(Enum.class);
+    private static final Type MARKER_IFACE = Type.getType("Lnet/minecraftforge/common/IExtensibleEnum;");
+    private static final Type ARRAY_UTILS = Type.getType("Lorg/apache/commons/lang3/ArrayUtils;"); //Don't directly reference this to prevent class loading.
+    private static final String ADD_DESC = Type.getMethodDescriptor(Type.getType(Object[].class), Type.getType(Object[].class), Type.getType(Object.class));
+    private static final Type UNSAFE_HACKS = Type.getType("Lnet/minecraftforge/fml/unsafe/UnsafeHacks;"); //Again, not direct reference to prevent class loading.
+    private static final String CLEAN_DESC = Type.getMethodDescriptor(Type.VOID_TYPE, Type.getType(Class.class));
+    private static final String NAME_DESC = Type.getMethodDescriptor(STRING);
+    private static final String EQUALS_DESC = Type.getMethodDescriptor(Type.BOOLEAN_TYPE, STRING);
+    private static final int FLAGS = Opcodes.ACC_PRIVATE | Opcodes.ACC_STATIC | Opcodes.ACC_FINAL | Opcodes.ACC_SYNTHETIC;
 
     @Override
     public String name() {
@@ -46,10 +47,21 @@ public class RuntimeEnumExtender implements ILaunchPluginService {
     private static final EnumSet<Phase> YAY = EnumSet.of(Phase.AFTER);
     private static final EnumSet<Phase> NAY = EnumSet.noneOf(Phase.class);
 
+    private static final class LazyInit {
+        private LazyInit() {}
+        private static final boolean ANY_MODS = LoadingModList.get().getMods().size() > 2; // 2: forge, minecraft
+    }
+
     @Override
-    public EnumSet<Phase> handlesClass(Type classType, boolean isEmpty)
-    {
-        return isEmpty ? NAY : YAY;
+    public EnumSet<Phase> handlesClass(Type classType, boolean isEmpty) {
+        if (isEmpty || !LazyInit.ANY_MODS)
+            return NAY;
+
+        String internalName = classType.getInternalName();
+        if (internalName.startsWith("net/minecraft/client/model") || internalName.startsWith("net/minecraft/world"))
+            return YAY;
+
+        return NAY;
     }
 
     @Override
@@ -58,25 +70,24 @@ public class RuntimeEnumExtender implements ILaunchPluginService {
         if ((classNode.access & Opcodes.ACC_ENUM) == 0)
             return ComputeFlags.NO_REWRITE;
 
-        Type array = Type.getType("[" + classType.getDescriptor());
-        final int flags = Opcodes.ACC_PRIVATE | Opcodes.ACC_STATIC | Opcodes.ACC_FINAL | Opcodes.ACC_SYNTHETIC;
-
-        FieldNode values = classNode.fields.stream().filter(f -> f.desc.contentEquals(array.getDescriptor()) && ((f.access & flags) == flags)).findFirst().orElse(null);
-
-        if (!classNode.interfaces.contains(MARKER_IFACE.getInternalName())) {
+        if (!classNode.interfaces.contains(MARKER_IFACE.getInternalName()))
             return ComputeFlags.NO_REWRITE;
-        }
+
+        Type array = Type.getType("[" + classType.getDescriptor());
+        String arrayDesc = array.getDescriptor();
+
+        FieldNode values = classNode.fields.stream().filter(f -> f.desc.equals(arrayDesc) && ((f.access & FLAGS) == FLAGS)).findFirst().orElse(null);
 
         //Static methods named "create" with first argument as a string
         List<MethodNode> candidates = classNode.methods.stream()
                 .filter(m -> ((m.access & Opcodes.ACC_STATIC) != 0) && m.name.equals("create"))
-                .collect(Collectors.toList());
+                .toList();
 
         if (candidates.isEmpty()) {
             throw new IllegalStateException("IExtensibleEnum has no candidate factory methods: " + classType.getClassName());
         }
 
-        candidates.forEach(mtd ->
+        for (var mtd : candidates)
         {
             Type[] args = Type.getArgumentTypes(mtd.desc);
             if (args.length == 0 || !args[0].equals(STRING)) {
@@ -108,8 +119,7 @@ public class RuntimeEnumExtender implements ILaunchPluginService {
             Type[] ctrArgs = new Type[args.length + 1];
             ctrArgs[0] = STRING;
             ctrArgs[1] = Type.INT_TYPE;
-            for (int x = 1; x < args.length; x++)
-                ctrArgs[1 + x] = args[x];
+            System.arraycopy(args, 1, ctrArgs, 2, args.length - 1);
 
             String desc = Type.getMethodDescriptor(Type.VOID_TYPE, ctrArgs);
 
@@ -231,7 +241,7 @@ public class RuntimeEnumExtender implements ILaunchPluginService {
                 ins.load(vars, classType);
                 ins.areturn(classType);
             }
-        });
+        }
         return ComputeFlags.COMPUTE_FRAMES;
     }
 

fmlloader/src/main/java/net/minecraftforge/fml/loading/BackgroundWaiter.java

@@ -6,14 +6,13 @@
 package net.minecraftforge.fml.loading;
 
 import java.util.concurrent.ExecutionException;
-import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
 
 public class BackgroundWaiter {
-    private static final ExecutorService runner = Executors.newSingleThreadExecutor();
 
     public static void runAndTick(Runnable r, Runnable tick) {
+        var runner = Executors.newSingleThreadExecutor();
         ImmediateWindowHandler.updateProgress("Loading bootstrap resources");
         final Future<?> work = runner.submit(r);
         do {

fmlloader/src/main/java/net/minecraftforge/fml/loading/FMLLoader.java

@@ -17,11 +17,9 @@ import net.minecraftforge.api.distmarker.Dist;
 import net.minecraftforge.fml.loading.targets.CommonLaunchHandler;
 import net.minecraftforge.forgespi.Environment;
 import net.minecraftforge.forgespi.coremod.ICoreModProvider;
-import org.apache.commons.lang3.tuple.Pair;
 import org.slf4j.Logger;
 
 import java.nio.file.Path;
-import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
@@ -36,7 +34,6 @@ import static net.minecraftforge.fml.loading.LogMarkers.SCAN;
 public class FMLLoader {
     private static final Logger LOGGER = LogUtils.getLogger();
     private static AccessTransformerService accessTransformer;
-    private static ModDiscoverer modDiscoverer;
     private static ICoreModProvider coreModProvider;
     private static LanguageLoadingProvider languageLoadingProvider;
     private static Dist dist;
@@ -59,10 +56,9 @@ public class FMLLoader {
 
         checkPackage(ITransformationService.class, "4.0", "ModLauncher");
         accessTransformer  = getPlugin(env, "accesstransformer",  "1.0", "AccessTransformer");
-        /*eventBus       =*/ getPlugin(env, "eventbus",           "1.0", "EventBus");
         runtimeDistCleaner = getPlugin(env, "runtimedistcleaner", "1.0", "RuntimeDistCleaner");
         coreModProvider = getSingleService(ICoreModProvider.class, "CoreMod");
-        LOGGER.debug(CORE,"FML found CoreMod version : {}", JarVersionLookupHandler.getInfo(coreModProvider.getClass()).impl().version().orElse("MISSING"));
+        LOGGER.debug(CORE, "FML found CoreMod version : {}", JarVersionLookupHandler.getInfo(coreModProvider.getClass()).impl().version().orElse("MISSING"));
         checkPackage(Environment.class, "2.0", "ForgeSPI");
 
         try {
@@ -74,14 +70,15 @@ public class FMLLoader {
         }
     }
 
+    @SuppressWarnings("unchecked")
     private static <T> T getPlugin(IEnvironment env, String id, String version, String name) throws IncompatibleEnvironmentException {
-        @SuppressWarnings("unchecked")
-        var plugin = (T)env.findLaunchPlugin(id).orElseThrow(() -> {
+        var plugin = env.findLaunchPlugin(id).orElse(null);
+        if (plugin == null) {
             LOGGER.error(CORE, "{} library is missing, we need this to run", name);
-            return new IncompatibleEnvironmentException("Missing " + name + ", cannot run");
-        });
+            throw new IncompatibleEnvironmentException("Missing " + name + ", cannot run");
+        }
         checkPackage(plugin.getClass(), version, name);
-        return plugin;
+        return (T) plugin;
     }
 
     private static void checkPackage(Class<?> cls, String version, String name) throws IncompatibleEnvironmentException {
@@ -137,21 +134,20 @@ public class FMLLoader {
         }
         commonLaunchHandler = (CommonLaunchHandler)launchHandler.get();
         launchHandlerName = launchHandler.get().name();
-        gamePath = environment.getProperty(IEnvironment.Keys.GAMEDIR.get()).orElse(Paths.get(".").toAbsolutePath());
+        gamePath = environment.getProperty(IEnvironment.Keys.GAMEDIR.get()).orElse(Path.of(".").toAbsolutePath());
 
         naming = commonLaunchHandler.getNaming();
         dist = commonLaunchHandler.getDist();
         production = commonLaunchHandler.isProduction();
 
-        accessTransformer.getExtension().accept(Pair.of(naming, "srg"));
+        accessTransformer.getExtension().accept(Map.entry(naming, "srg"));
 
         runtimeDistCleaner.getExtension().accept(dist);
     }
 
     public static List<ITransformationService.Resource> beginModScan(final Map<String,?> arguments) {
-        LOGGER.debug(SCAN,"Scanning for Mod Locators");
-        modDiscoverer = new ModDiscoverer(arguments);
-        modValidator = modDiscoverer.discoverMods();
+        LOGGER.debug(SCAN, "Scanning for Mod Locators");
+        modValidator = ModDiscoverer.discoverMods(arguments);
         var pluginResources = modValidator.getPluginResources();
         return List.of(pluginResources);
     }
@@ -172,10 +168,6 @@ public class FMLLoader {
         return languageLoadingProvider;
     }
 
-    static ModDiscoverer getModDiscoverer() {
-        return modDiscoverer;
-    }
-
     public static CommonLaunchHandler getLaunchHandler() {
         return commonLaunchHandler;
     }

fmlloader/src/main/java/net/minecraftforge/fml/loading/FMLServiceProvider.java

@@ -7,7 +7,6 @@ package net.minecraftforge.fml.loading;
 
 import com.mojang.logging.LogUtils;
 import cpw.mods.modlauncher.api.*;
-import joptsimple.OptionSpecBuilder;
 import net.minecraftforge.fml.loading.moddiscovery.ModFile;
 import net.minecraftforge.forgespi.Environment;
 import org.jetbrains.annotations.NotNull;
@@ -19,12 +18,11 @@ import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
-import java.util.function.BiFunction;
 import static net.minecraftforge.fml.loading.LogMarkers.CORE;
 
 public class FMLServiceProvider implements ITransformationService {
     private static final Logger LOGGER = LogUtils.getLogger();
-    private Map<String, Object> arguments;
+    private final Map<String, Object> arguments = new HashMap<>();
 
     public FMLServiceProvider() {
         var markers = System.getProperty("forge.logging.markers", "").split(",");
@@ -45,7 +43,6 @@ public class FMLServiceProvider implements ITransformationService {
         FMLConfig.load();
         LOGGER.debug(CORE, "Preparing ModFile");
         environment.computePropertyIfAbsent(Environment.Keys.MODFILEFACTORY.get(), k->ModFile::new);
-        arguments = new HashMap<>();
         LOGGER.debug(CORE, "Preparing launch handler");
         FMLLoader.setupLaunchHandler(environment, arguments);
         FMLEnvironment.setupInteropEnvironment(environment);
@@ -68,14 +65,6 @@ public class FMLServiceProvider implements ITransformationService {
         FMLLoader.onInitialLoad(environment, otherServices);
     }
 
-    @Override
-    public void arguments(BiFunction<String, String, OptionSpecBuilder> argumentBuilder) {
-    }
-
-    @Override
-    public void argumentValues(OptionResult option) {
-    }
-
     @SuppressWarnings("rawtypes")
     @Override
     public @NotNull List<ITransformer> transformers() {

fmlloader/src/main/java/net/minecraftforge/fml/loading/ImmediateWindowHandler.java

@@ -140,7 +140,7 @@ public class ImmediateWindowHandler {
 
         @Override
         public void updateModuleReads(final ModuleLayer layer) {
-            var fm = layer.findModule("forge");
+            var fm = layer.findModule("net.minecraftforge.forge");
             if (fm.isPresent()) {
                 getClass().getModule().addReads(fm.get());
                 var clz = fm.map(l -> Class.forName(l, "net.minecraftforge.client.loading.NoVizFallback")).orElseThrow();

fmlloader/src/main/java/net/minecraftforge/fml/loading/LoadingModList.java

@@ -5,31 +5,25 @@
 
 package net.minecraftforge.fml.loading;
 
-import cpw.mods.modlauncher.api.LamdbaExceptionUtils;
 import net.minecraftforge.fml.loading.moddiscovery.BackgroundScanHandler;
 import net.minecraftforge.fml.loading.moddiscovery.ModFile;
 import net.minecraftforge.fml.loading.moddiscovery.ModFileInfo;
 import net.minecraftforge.fml.loading.moddiscovery.ModInfo;
 import net.minecraftforge.forgespi.locating.IModFile;
 
-import java.net.URL;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Enumeration;
-import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
-import java.util.NoSuchElementException;
 import java.util.stream.Collectors;
 
 /**
  * Master list of all mods <em>in the loading context. This class cannot refer outside the
  * loading package</em>
  */
-public class LoadingModList
-{
+public class LoadingModList {
     private static LoadingModList INSTANCE;
     private final List<ModFileInfo> modFiles;
     private final List<ModInfo> sortedList;
@@ -37,15 +31,12 @@ public class LoadingModList
     private final List<EarlyLoadingException> preLoadErrors;
     private List<IModFile> brokenFiles;
 
-    private LoadingModList(final List<ModFile> modFiles, final List<ModInfo> sortedList)
-    {
+    private LoadingModList(final List<ModFile> modFiles, final List<ModInfo> sortedList) {
         this.modFiles = modFiles.stream()
                 .map(ModFile::getModFileInfo)
                 .map(ModFileInfo.class::cast)
-                .collect(Collectors.toList());
-        this.sortedList = sortedList.stream()
-                .map(ModInfo.class::cast)
-                .collect(Collectors.toList());
+                .toList();
+        this.sortedList = sortedList.stream().toList();
         this.fileById = this.modFiles.stream()
                 .map(ModFileInfo::getMods)
                 .flatMap(Collection::stream)
@@ -54,21 +45,18 @@ public class LoadingModList
         this.preLoadErrors = new ArrayList<>();
     }
 
-    public static LoadingModList of(List<ModFile> modFiles, List<ModInfo> sortedList, final EarlyLoadingException earlyLoadingException)
-    {
+    public static LoadingModList of(List<ModFile> modFiles, List<ModInfo> sortedList, final EarlyLoadingException earlyLoadingException) {
         INSTANCE = new LoadingModList(modFiles, sortedList);
         if (earlyLoadingException != null)
-        {
             INSTANCE.preLoadErrors.add(earlyLoadingException);
-        }
         return INSTANCE;
     }
 
     public static LoadingModList get() {
         return INSTANCE;
     }
-    public void addCoreMods()
-    {
+
+    public void addCoreMods() {
         modFiles.stream()
                 .map(ModFileInfo::getFile)
                 .map(ModFile::getCoreMods)
@@ -76,28 +64,28 @@ public class LoadingModList
                 .forEach(FMLLoader.getCoreModProvider()::addCoreMod);
     }
 
-    public void addAccessTransformers()
-    {
-        modFiles.stream()
-                .map(ModFileInfo::getFile)
-                .forEach(mod -> mod.getAccessTransformer().ifPresent(path -> FMLLoader.addAccessTransformer(path, mod)));
+    public void addAccessTransformers() {
+        for (ModFileInfo modFile : modFiles) {
+            ModFile mod = modFile.getFile();
+            var at = mod.getAccessTransformer().orElse(null);
+            if (at != null) {
+                FMLLoader.addAccessTransformer(at, mod);
+            }
+        }
     }
 
-    public void addForScanning(BackgroundScanHandler backgroundScanHandler)
-    {
+    public void addForScanning(BackgroundScanHandler backgroundScanHandler) {
         backgroundScanHandler.setLoadingModList(this);
         modFiles.stream()
                 .map(ModFileInfo::getFile)
                 .forEach(backgroundScanHandler::submitForScanning);
     }
 
-    public List<ModFileInfo> getModFiles()
-    {
+    public List<ModFileInfo> getModFiles() {
         return modFiles;
     }
 
-    public Path findResource(final String className)
-    {
+    public Path findResource(final String className) {
         for (ModFileInfo mf : modFiles) {
             final Path resource = mf.getFile().findResource(className);
             if (Files.exists(resource)) return resource;
@@ -105,55 +93,11 @@ public class LoadingModList
         return null;
     }
 
-    public Enumeration<URL> findAllURLsForResource(final String resName) {
-        final String resourceName;
-        // strip a leading slash
-        if (resName.startsWith("/")) {
-            resourceName = resName.substring(1);
-        } else {
-            resourceName = resName;
-        }
-        return new Enumeration<URL>() {
-            private final Iterator<ModFileInfo> modFileIterator = modFiles.iterator();
-            private URL next;
-            @Override
-            public boolean hasMoreElements() {
-                if (next!=null) return true;
-                next = findNextURL();
-                return next != null;
-            }
-
-            @Override
-            public URL nextElement() {
-                if (next == null) {
-                    next = findNextURL();
-                    if (next == null) throw new NoSuchElementException();
-                }
-                URL result = next;
-                next = null;
-                return result;
-            }
-
-            private URL findNextURL() {
-                while (modFileIterator.hasNext()) {
-                    final ModFileInfo next = modFileIterator.next();
-                    final Path resource = next.getFile().findResource(resourceName);
-                    if (Files.exists(resource)) {
-                        return LamdbaExceptionUtils.uncheck(()->new URL("modjar://" + next.getMods().get(0).getModId() + "/" + resourceName));
-                    }
-                }
-                return null;
-            }
-        };
-    }
-
-    public ModFileInfo getModFileById(String modid)
-    {
+    public ModFileInfo getModFileById(String modid) {
         return this.fileById.get(modid);
     }
 
-    public List<ModInfo> getMods()
-    {
+    public List<ModInfo> getMods() {
         return this.sortedList;
     }
 

fmlloader/src/main/java/net/minecraftforge/fml/loading/MCPNamingService.java

@@ -36,7 +36,7 @@ public class MCPNamingService implements INameMappingService {
 
     @Override
     public Map.Entry<String, String> understanding() {
-        return Pair.of("srg", "mcp");
+        return Map.entry("srg", "mcp");
     }
 
     @Override

fmlloader/src/main/java/net/minecraftforge/fml/loading/MavenCoordinateResolver.java

@@ -34,7 +34,7 @@ public class MavenCoordinateResolver {
                 (!extension.isEmpty() ? "." + extension : ".jar");
 
         String[] groups = groupId.split("\\.");
-        Path result = Paths.get(groups[0]);
+        Path result = Path.of(groups[0]);
         for (int i = 1; i < groups.length; i++) {
             result = result.resolve(groups[i]);
         }

fmlloader/src/main/java/net/minecraftforge/fml/loading/ModDirTransformerDiscoverer.java

@@ -7,8 +7,10 @@ package net.minecraftforge.fml.loading;
 
 import com.mojang.logging.LogUtils;
 import cpw.mods.jarhandling.SecureJar;
+import cpw.mods.modlauncher.Launcher;
 import cpw.mods.modlauncher.api.LamdbaExceptionUtils;
 import cpw.mods.modlauncher.api.NamedPath;
+import cpw.mods.modlauncher.api.TypesafeMap;
 import cpw.mods.modlauncher.serviceapi.ITransformerDiscoveryService;
 
 import org.jetbrains.annotations.ApiStatus;
@@ -40,6 +42,17 @@ public class ModDirTransformerDiscoverer implements ITransformerDiscoveryService
 
     @Override
     public void earlyInitialization(final String launchTarget, final String[] arguments) {
+        boolean isMixinEnabledInDev = false;
+        for (String arg : arguments) {
+            if (arg.startsWith("-mixin") || arg.startsWith("--mixin")) {
+                isMixinEnabledInDev = true;
+                break;
+            }
+        }
+        Launcher.INSTANCE.blackboard().putIfAbsent(
+            TypesafeMap.Key.getOrCreate(Launcher.INSTANCE.blackboard(), "isMixinEnabledInDev", Boolean.class),
+            isMixinEnabledInDev
+        );
         ImmediateWindowHandler.load(launchTarget, arguments);
     }
 

fmlloader/src/main/java/net/minecraftforge/fml/loading/ModSorter.java

@@ -8,7 +8,7 @@ package net.minecraftforge.fml.loading;
 import com.google.common.graph.GraphBuilder;
 import com.google.common.graph.MutableGraph;
 import com.mojang.logging.LogUtils;
-import net.minecraftforge.forgespi.language.IModInfo;
+import net.minecraftforge.forgespi.language.IModInfo.ModVersion;
 import net.minecraftforge.fml.loading.EarlyLoadingException.ExceptionData;
 import net.minecraftforge.fml.loading.moddiscovery.ModFile;
 import net.minecraftforge.fml.loading.moddiscovery.ModFileInfo;
@@ -20,229 +20,250 @@ import org.apache.maven.artifact.versioning.DefaultArtifactVersion;
 import org.slf4j.Logger;
 
 import java.util.ArrayList;
-import java.util.Collections;
+import java.util.Collection;
 import java.util.Comparator;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
-import java.util.concurrent.atomic.AtomicInteger;
-import java.util.function.Function;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
-import static java.util.stream.Collectors.*;
 import static net.minecraftforge.fml.loading.LogMarkers.LOADING;
 
-public class ModSorter
-{
+public class ModSorter {
     private static final Logger LOGGER = LogUtils.getLogger();
-    private final UniqueModListBuilder uniqueModListBuilder;
-    private List<ModFile> modFiles;
-    private List<ModInfo> sortedList;
-    private Map<String, IModInfo> modIdNameLookup;
-    private List<ModFile> systemMods;
 
-    private ModSorter(final List<ModFile> modFiles)
-    {
-        this.uniqueModListBuilder = new UniqueModListBuilder(modFiles);
-    }
+    private record State(List<ModFile> files, List<ModInfo> mods) {}
+
+    private ModSorter() {}
+
+    @SuppressWarnings("removal")
+    public static LoadingModList sort(List<ModFile> mods, final List<ExceptionData> errors) {
+        State systemMods = detectSystemMods(mods);
+        List<ModFile> modFiles;
 
-    public static LoadingModList sort(List<ModFile> mods, final List<ExceptionData> errors)
-    {
-        final ModSorter ms = new ModSorter(mods);
         try {
-            ms.buildUniqueList();
+            modFiles = UniqueModListBuilder.buildUniqueList(mods).modFiles();
         } catch (EarlyLoadingException e) {
             // We cannot build any list with duped mods. We have to abort immediately and report it
             // Note this will never actually throw an error because the duplicate checks are done in ModDiscovererer before we get to this phase
             // So all this is really doing is wasting time.
             // But i'm leaving it here until I rewrite all of cpw's mod loading code because its such a clusterfuck.
-            return LoadingModList.of(ms.systemMods, ms.systemMods.stream().map(mf->(ModInfo)mf.getModInfos().get(0)).collect(toList()), e);
+            return LoadingModList.of(systemMods.files(), systemMods.mods(), e);
         }
+
+        var named = new HashMap<String, ModInfo>();
+        for (var file : modFiles) {
+            for (var info : file.getModInfos())
+                named.put(info.getModId(), (ModInfo)info);
+        }
+
         // try and validate dependencies
-        final List<ExceptionData> failedList = Stream.concat(ms.verifyDependencyVersions().stream(), errors.stream()).toList();
+        final List<ExceptionData> failedList = Stream.concat(verifyDependencyVersions(modFiles).stream(), errors.stream()).toList();
+
         // if we miss one or the other, we abort now
         if (!failedList.isEmpty()) {
-            return LoadingModList.of(ms.systemMods, ms.systemMods.stream().map(mf->(ModInfo)mf.getModInfos().get(0)).collect(toList()), new EarlyLoadingException("failure to validate mod list", null, failedList));
+            return LoadingModList.of(systemMods.files(), systemMods.mods(), new EarlyLoadingException("failure to validate mod list", null, failedList));
         } else {
             // Otherwise, lets try and sort the modlist and proceed
-            EarlyLoadingException earlyLoadingException = null;
             try {
-                ms.sort();
+                var sorted = sort(modFiles, named);
+                return LoadingModList.of(sorted.files(), sorted.mods(), null);
             } catch (EarlyLoadingException e) {
-                earlyLoadingException = e;
+                // The only exception that can happen here is a cyclic exception, but fall back to system mods so we can display the nice screen.
+                return LoadingModList.of(systemMods.files(), systemMods.mods(), e);
             }
-            return LoadingModList.of(ms.modFiles, ms.sortedList, earlyLoadingException);
         }
     }
 
-    private void sort()
-    {
-        // lambdas are identity based, so sorting them is impossible unless you hold reference to them
-        final MutableGraph<ModFileInfo> graph = GraphBuilder.directed().build();
-        AtomicInteger counter = new AtomicInteger();
-        Map<ModFileInfo, Integer> infos = modFiles.stream()
-                .map(ModFile::getModFileInfo)
-                .filter(ModFileInfo.class::isInstance)
-                .map(ModFileInfo.class::cast)
-                .collect(toMap(Function.identity(), e -> counter.incrementAndGet()));
-        infos.keySet().forEach(graph::addNode);
-        modFiles.stream()
-                .map(ModFile::getModInfos)
-                .<IModInfo>mapMulti(Iterable::forEach)
-                .map(IModInfo::getDependencies)
-                .<IModInfo.ModVersion>mapMulti(Iterable::forEach)
-                .forEach(dep -> addDependency(graph, dep));
+    private static State sort(final List<ModFile> modFiles, final Map<String, ModInfo> named) {
+        final MutableGraph<ModInfo> graph = GraphBuilder.directed().build();
 
-        final List<ModFileInfo> sorted;
-        try
-        {
-            sorted = TopologicalSort.topologicalSort(graph, Comparator.comparing(infos::get));
-        }
-        catch (CyclePresentException e)
-        {
-            Set<Set<ModFileInfo>> cycles = e.getCycles();
-            if (LOGGER.isErrorEnabled(LOADING))
-            {
-                LOGGER.error(LOADING, "Mod Sorting failed.\nDetected Cycles: {}\n", cycles);
+        int counter = 0;
+        var infos = new HashMap<ModInfo, Integer>();
+        for (var file : modFiles) {
+            if (file.getModFileInfo() instanceof ModFileInfo info) {
+                for (var imod : info.getMods()) {
+                    var mod = (ModInfo)imod;
+                    infos.put(mod, counter++);
+                    graph.addNode(mod);
+                }
             }
-            var dataList = cycles.stream()
-                    .<ModFileInfo>mapMulti(Iterable::forEach)
-                    .<IModInfo>mapMulti((mf,c)->mf.getMods().forEach(c))
-                    .map(IModInfo::getModId)
-                    .map(list -> new ExceptionData("fml.modloading.cycle", list))
-                    .toList();
+        }
+
+        for (var file : modFiles) {
+            for (var info : file.getModInfos()) {
+                for (var dep : info.getDependencies()) {
+                    // Ordering isn't effected by sides, should it be?
+                    //if (!dep.getSide().isCorrectSide())
+                    //    continue;
+
+                    var target = named.get(dep.getModId());
+
+                    // soft dep that doesn't exist. No edge required.
+                    if (target == null)
+                        continue;
+
+                    var self = (ModInfo)dep.getOwner();
+
+                    switch (dep.getOrdering()) {
+                        case BEFORE -> graph.putEdge(self, target);
+                        case AFTER -> graph.putEdge(target, self);
+                        default -> {}
+                    }
+                }
+            }
+        }
+
+        final List<ModInfo> sorted;
+        try {
+            sorted = TopologicalSort.topologicalSort(graph, Comparator.comparing(infos::get));
+        } catch (CyclePresentException e) {
+            Set<Set<ModInfo>> cycles = e.getCycles();
+            var buf = new StringBuilder();
+            buf.append("Mod Sorting failed - Detected Cycles: \n");
+
+            var dataList = new ArrayList<ExceptionData>();
+            for (var cycle : cycles) {
+                buf.append("\tCycle:\n");
+                for (var mod : cycle) {
+                    var modDeps = new StringBuilder()
+                        .append(mod.getModId())
+                        .append(' ')
+                        .append(mod.getDependencies().stream()
+                            .filter(v -> cycle.stream().anyMatch(m -> m.getModId().equals(v.getModId())))
+                            .map(dep -> dep.getOrdering().name() + " " + dep.getModId())
+                            .collect(Collectors.joining(", "))
+                        );
+                    dataList.add(new ExceptionData("fml.modloading.cycle", modDeps.toString()));
+                    buf.append("\t\tMod: ").append(modDeps.toString()).append('\n');
+                }
+            }
+
+            LOGGER.error(LOADING, buf.toString());
+
             throw new EarlyLoadingException("Sorting error", e, dataList);
         }
-        this.sortedList = sorted.stream()
-                .map(ModFileInfo::getMods)
-                .<IModInfo>mapMulti(Iterable::forEach)
-                .map(ModInfo.class::cast)
-                .collect(toList());
-        this.modFiles = sorted.stream()
-                .map(ModFileInfo::getFile)
-                .collect(toList());
-    }
 
-    private void addDependency(MutableGraph<ModFileInfo> topoGraph, IModInfo.ModVersion dep)
-    {
-        final ModFileInfo self = (ModFileInfo)dep.getOwner().getOwningFile();
-        final IModInfo targetModInfo = modIdNameLookup.get(dep.getModId());
-        // soft dep that doesn't exist. Just return. No edge required.
-        if (targetModInfo == null || !(targetModInfo.getOwningFile() instanceof final ModFileInfo target)) return;
-        if (self == target)
-            return; // in case a jar has two mods that have dependencies between
-        switch (dep.getOrdering()) {
-            case BEFORE -> topoGraph.putEdge(self, target);
-            case AFTER -> topoGraph.putEdge(target, self);
-            default -> {}
+        var files = new LinkedHashSet<ModFile>();
+        var list = new ArrayList<ModInfo>();
+
+        for (var mod : sorted) {
+            files.add(mod.getOwningFile().getFile());
+            list.add(mod);
         }
+
+        return new State(files.stream().toList(), list);
     }
 
-    private void buildUniqueList()
-    {
-        final UniqueModListBuilder.UniqueModListData uniqueModListData = uniqueModListBuilder.buildUniqueList();
-
-        this.modFiles = uniqueModListData.modFiles();
-
-        detectSystemMods(uniqueModListData.modFilesByFirstId());
-
-        modIdNameLookup = uniqueModListData.modFilesByFirstId().entrySet().stream()
-                .filter(e -> !e.getValue().get(0).getModInfos().isEmpty())
-                .collect(Collectors.toMap(
-                    Map.Entry::getKey,
-                    e -> e.getValue().get(0).getModInfos().get(0)
-                  ));
-    }
-
-    private void detectSystemMods(final Map<String, List<ModFile>> modFilesByFirstId) {
+    private static State detectSystemMods(final List<ModFile> modFiles) {
         // Capture system mods (ex. MC, Forge) here, so we can keep them for later
         var systemMods = List.of("minecraft", "forge");
         LOGGER.debug("Configured system mods: {}", systemMods);
 
-        this.systemMods = new ArrayList<>();
+        var mods = new ArrayList<ModInfo>();
+        var files = new ArrayList<ModFile>();
         for (var systemMod : systemMods) {
-            var container = modFilesByFirstId.get(systemMod);
-            if (container != null && !container.isEmpty()) {
-                LOGGER.debug("Found system mod: {}", systemMod);
-                this.systemMods.add((ModFile) container.get(0));
-            } else {
+            var mod = findMod(modFiles, systemMod);
+            if (mod == null)
                 throw new IllegalStateException("Failed to find system mod: " + systemMod);
-            }
+
+            LOGGER.debug("Found system mod: {}", systemMod);
+            mods.add(mod.info());
+            files.add(mod.file());
         }
+
+        return new State(files, mods);
     }
 
-    private List<EarlyLoadingException.ExceptionData> verifyDependencyVersions()
-    {
-        final var modVersions = modFiles.stream()
-                .map(ModFile::getModInfos)
-                .<IModInfo>mapMulti(Iterable::forEach)
-                .collect(toMap(IModInfo::getModId, IModInfo::getVersion));
+    private record ModPair(ModFile file, ModInfo info) {}
+    private static ModPair findMod(final List<ModFile> modFiles, String name) {
+        for (var file : modFiles) {
+            for (var mod : file.getModFileInfo().getMods()) {
+                if (name.equals(mod.getModId()))
+                    return new ModPair(file, (ModInfo)mod);
+            }
+        }
+        return null;
+    }
 
-        final var modVersionDependencies = modFiles.stream()
-                .map(ModFile::getModInfos)
-                .<IModInfo>mapMulti(Iterable::forEach)
-                .collect(groupingBy(Function.identity(), flatMapping(e -> e.getDependencies().stream(), toList())));
+    private static List<ExceptionData> verifyDependencyVersions(final List<ModFile> files) {
+        final var modVersions = new HashMap<String, ArtifactVersion>();
+        final var modRequirements = new HashSet<ModVersion>();
+        int mandatoryRequired = 0;
 
-        final var modRequirements = modVersionDependencies.values().stream()
-                .<IModInfo.ModVersion>mapMulti(Iterable::forEach)
-                .filter(mv -> mv.getSide().isCorrectSide())
-                .collect(toSet());
+        for (var file : files) {
+            for (var info : file.getModInfos()) {
+                modVersions.put(info.getModId(), info.getVersion());
+                for (var dep : info.getDependencies()) {
+                    if (dep.getSide().isCorrectSide()) {
+                        if (modRequirements.add(dep) && dep.isMandatory())
+                            mandatoryRequired++;
+                    }
+                }
+            }
+        }
 
-        final long mandatoryRequired = modRequirements.stream().filter(IModInfo.ModVersion::isMandatory).count();
         LOGGER.debug(LOADING, "Found {} mod requirements ({} mandatory, {} optional)", modRequirements.size(), mandatoryRequired, modRequirements.size() - mandatoryRequired);
-        final var missingVersions = modRequirements.stream()
-                .filter(mv -> (mv.isMandatory() || modVersions.containsKey(mv.getModId())) && this.modVersionNotContained(mv, modVersions))
-                .collect(toSet());
-        final long mandatoryMissing = missingVersions.stream().filter(IModInfo.ModVersion::isMandatory).count();
-        LOGGER.debug(LOADING, "Found {} mod requirements missing ({} mandatory, {} optional)", missingVersions.size(), mandatoryMissing, missingVersions.size() - mandatoryMissing);
 
-        if (!missingVersions.isEmpty()) {
-            if (mandatoryMissing > 0) {
-                LOGGER.error(
-                        LOADING,
-                        "Missing or unsupported mandatory dependencies:\n{}",
-                        missingVersions.stream()
-                                .filter(IModInfo.ModVersion::isMandatory)
-                                .map(ver -> formatDependencyError(ver, modVersions))
-                                .collect(Collectors.joining("\n"))
-                );
-            }
-            if (missingVersions.size() - mandatoryMissing > 0) {
-                LOGGER.error(
-                        LOADING,
-                        "Unsupported installed optional dependencies:\n{}",
-                        missingVersions.stream()
-                                .filter(ver -> !ver.isMandatory())
-                                .map(ver -> formatDependencyError(ver, modVersions))
-                                .collect(Collectors.joining("\n"))
-                );
-            }
+        final var missingMandatory = new HashSet<ModVersion>();
+        final var missingOptional = new HashSet<ModVersion>();
 
-            return missingVersions.stream()
-                    .map(mv -> new ExceptionData(mv.isMandatory() ? "fml.modloading.missingdependency" : "fml.modloading.missingdependency.optional",
-                            mv.getOwner(), mv.getModId(), mv.getOwner().getModId(), mv.getVersionRange(),
-                            modVersions.getOrDefault(mv.getModId(), new DefaultArtifactVersion("null"))))
-                    .toList();
+        for (var dep : modRequirements) {
+            var modId = dep.getModId();
+            var existing = modVersions.get(modId);
+
+            if (!dep.isMandatory() && existing == null)
+                continue;
+
+            var range = dep.getVersionRange();
+            if (existing != null && (range.containsVersion(existing) || "0.0NONE".equals(existing.toString())))
+                continue;
+
+            if (!VersionSupportMatrix.testVersionSupportMatrix(range, modId, "mod"))
+                (dep.isMandatory() ? missingMandatory : missingOptional).add(dep);
         }
-        return Collections.emptyList();
+
+
+        LOGGER.debug(LOADING, "Found {} mod requirements missing ({} mandatory, {} optional)", missingMandatory.size() + missingOptional.size(), missingMandatory.size(), missingOptional.size());
+
+        var ret = new ArrayList<ExceptionData>();
+
+        if (!missingMandatory.isEmpty()) {
+            LOGGER.error(LOADING, "Missing or unsupported mandatory dependencies:\n{}", formatDependencyError(missingMandatory, modVersions));
+            for (var mv : missingMandatory)
+                ret.add(data(mv, modVersions, "fml.modloading.missingdependency"));
+        }
+
+        if (!missingOptional.isEmpty()) {
+            LOGGER.error(LOADING, "Unsupported installed optional dependencies:\n{}", formatDependencyError(missingMandatory, modVersions));
+            for (var mv : missingMandatory)
+                ret.add(data(mv, modVersions, "fml.modloading.missingdependency.optional"));
+        }
+
+        return ret;
     }
 
-    private static String formatDependencyError(IModInfo.ModVersion dependency, Map<String, ArtifactVersion> modVersions)
-    {
-        ArtifactVersion installed = modVersions.get(dependency.getModId());
-        return String.format(
+    private static String formatDependencyError(Collection<ModVersion> missing, Map<String, ArtifactVersion> modVersions) {
+        var ret = new ArrayList<String>();
+        for (var dep : missing) {
+            var installed = modVersions.get(dep.getModId());
+            ret.add(String.format(
                 "\tMod ID: '%s', Requested by: '%s', Expected range: '%s', Actual version: '%s'",
-                dependency.getModId(),
-                dependency.getOwner().getModId(),
-                dependency.getVersionRange(),
+                dep.getModId(),
+                dep.getOwner().getModId(),
+                dep.getVersionRange(),
                 installed != null ? installed.toString() : "[MISSING]"
-        );
+            ));
+        }
+        return String.join("\n", ret);
     }
 
-    private boolean modVersionNotContained(final IModInfo.ModVersion mv, final Map<String, ArtifactVersion> modVersions)
-    {
-        return !(VersionSupportMatrix.testVersionSupportMatrix(mv.getVersionRange(), mv.getModId(), "mod", (modId, range) -> modVersions.containsKey(modId) &&
-                (range.containsVersion(modVersions.get(modId)) || modVersions.get(modId).toString().equals("0.0NONE"))));
+    private static final ArtifactVersion NULL_VERSION = new DefaultArtifactVersion("null");
+    private static ExceptionData data(ModVersion mv, Map<String, ArtifactVersion> modVersions, String key) {
+        return new ExceptionData(key, mv.getOwner(), mv.getModId(), mv.getOwner().getModId(), mv.getVersionRange(), modVersions.getOrDefault(mv.getModId(), NULL_VERSION));
     }
 }

fmlloader/src/main/java/net/minecraftforge/fml/loading/RuntimeDistCleaner.java

@@ -8,14 +8,8 @@ package net.minecraftforge.fml.loading;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.EnumSet;
-import java.util.Iterator;
 import java.util.List;
-import java.util.Objects;
-import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Consumer;
-import java.util.stream.Collectors;
-
-import com.google.common.collect.Streams;
 import com.mojang.logging.LogUtils;
 import cpw.mods.modlauncher.serviceapi.ILaunchPluginService;
 import net.minecraftforge.api.distmarker.Dist;
@@ -28,212 +22,199 @@ import org.objectweb.asm.Type;
 import org.objectweb.asm.tree.AbstractInsnNode;
 import org.objectweb.asm.tree.AnnotationNode;
 import org.objectweb.asm.tree.ClassNode;
-import org.objectweb.asm.tree.FieldNode;
 import org.objectweb.asm.tree.MethodNode;
 import org.slf4j.Logger;
 import org.slf4j.Marker;
 import org.slf4j.MarkerFactory;
 
-public class RuntimeDistCleaner implements ILaunchPluginService
-{
+public final class RuntimeDistCleaner implements ILaunchPluginService {
     private static final Logger LOGGER = LogUtils.getLogger();
     private static final Marker DISTXFORM = MarkerFactory.getMarker("DISTXFORM");
     private static String DIST;
     private static final String ONLYIN = Type.getDescriptor(OnlyIn.class);
     private static final String ONLYINS = Type.getDescriptor(OnlyIns.class);
+    private static final String MOD = "Lnet/minecraftforge/fml/common/Mod;";
+
     @Override
-    public String name()
-    {
+    public String name() {
         return "runtimedistcleaner";
     }
 
-    @Override
-    public int processClassWithFlags(final Phase phase, final ClassNode classNode, final Type classType, final String reason)
-    {
-        AtomicBoolean changes = new AtomicBoolean();
-        if (remove(classNode.visibleAnnotations, DIST))
-        {
-            LOGGER.error(DISTXFORM, "Attempted to load class {} for invalid dist {}", classNode.name, DIST);
-            throw new RuntimeException("Attempted to load class "+ classNode.name  + " for invalid dist "+ DIST);
-        }
-
-        if (!FMLEnvironment.production && hasOnlyInWithModAnnotation(classNode.visibleAnnotations))
-        {
-            LOGGER.error(DISTXFORM, "Attempted to load class {} with @Mod and @OnlyIn/@OnlyIns annotations", classNode.name);
-            throw new RuntimeException("Found @OnlyIn on @Mod class "+ classNode.name  + " - this is not allowed as it causes crashes. Remove the OnlyIn and consider setting clientSideOnly=true in the root of your mods.toml instead");
-        }
-
-        if (classNode.interfaces != null )
-        {
-            unpack(classNode.visibleAnnotations).stream()
-                .filter(ann->Objects.equals(ann.desc, ONLYIN))
-                .filter(ann-> ann.values.contains("_interface"))
-                .filter(ann->!Objects.equals(((String[])ann.values.get(ann.values.indexOf("value") + 1))[1], DIST))
-                .map(ann -> ((Type)ann.values.get(ann.values.indexOf("_interface") + 1)).getInternalName())
-                .forEach(intf -> {
-                    if (classNode.interfaces.remove(intf)) {
-                        LOGGER.debug(DISTXFORM,"Removing Interface: {} implements {}", classNode.name, intf);
-                        changes.compareAndSet(false, true);
-                    }
-                });
-
-            //Remove Class level @OnlyIn/@OnlyIns annotations, this is important if anyone gets ambitious and tries to reflect an annotation with _interface set.
-            if (classNode.visibleAnnotations != null) {
-                Iterator<AnnotationNode> itr = classNode.visibleAnnotations.iterator();
-                while (itr.hasNext()) {
-                    AnnotationNode ann = itr.next();
-                    if (Objects.equals(ann.desc, ONLYIN) || Objects.equals(ann.desc, ONLYINS)) {
-                        LOGGER.debug(DISTXFORM,"Removing Class Annotation: {} @{}", classNode.name, ann.desc);
-                        itr.remove();
-                        changes.compareAndSet(false, true);
-                    }
-                }
-            }
-        }
-
-        Iterator<FieldNode> fields = classNode.fields.iterator();
-        while(fields.hasNext())
-        {
-            FieldNode field = fields.next();
-            if (remove(field.visibleAnnotations, DIST))
-            {
-                LOGGER.debug(DISTXFORM,"Removing field: {}.{}", classNode.name, field.name);
-                fields.remove();
-                changes.compareAndSet(false, true);
-            }
-        }
-
-        LambdaGatherer lambdaGatherer = new LambdaGatherer();
-        Iterator<MethodNode> methods = classNode.methods.iterator();
-        while(methods.hasNext())
-        {
-            MethodNode method = methods.next();
-            if (remove(method.visibleAnnotations, DIST))
-            {
-                LOGGER.debug(DISTXFORM,"Removing method: {}.{}{}", classNode.name, method.name, method.desc);
-                methods.remove();
-                lambdaGatherer.accept(method);
-                changes.compareAndSet(false, true);
-            }
-        }
-
-        // remove dynamic synthetic lambda methods that are inside of removed methods
-        for (List<Handle> dynamicLambdaHandles = lambdaGatherer.getDynamicLambdaHandles();
-            !dynamicLambdaHandles.isEmpty(); dynamicLambdaHandles = lambdaGatherer.getDynamicLambdaHandles())
-        {
-            lambdaGatherer = new LambdaGatherer();
-            methods = classNode.methods.iterator();
-            while (methods.hasNext())
-            {
-                MethodNode method = methods.next();
-                if ((method.access & Opcodes.ACC_SYNTHETIC) == 0) continue;
-                for (Handle dynamicLambdaHandle : dynamicLambdaHandles)
-                {
-                    if (method.name.equals(dynamicLambdaHandle.getName()) && method.desc.equals(dynamicLambdaHandle.getDesc()))
-                    {
-                        LOGGER.debug(DISTXFORM,"Removing lambda method: {}.{}{}", classNode.name, method.name, method.desc);
-                        methods.remove();
-                        lambdaGatherer.accept(method);
-                        changes.compareAndSet(false, true);
-                    }
-                }
-            }
-        }
-        return changes.get() ? ComputeFlags.SIMPLE_REWRITE : ComputeFlags.NO_REWRITE;
-    }
-
-    @SuppressWarnings("unchecked")
-    private static List<AnnotationNode> unpack(final List<AnnotationNode> anns)
-    {
-        if (anns == null)
-        {
-            return Collections.emptyList();
-        }
-
-        List<AnnotationNode> unpacked = new ArrayList<>();
-
-        for (var annotationNode : anns)
-        {
-            if (Objects.equals(annotationNode.desc, ONLYINS))
-            {
-                unpacked.add(annotationNode);
-
-                if (annotationNode.values != null)
-                {
-                    List<AnnotationNode> subNodes = (List<AnnotationNode>) annotationNode.values.get(annotationNode.values.indexOf("value") + 1);
-
-                    if (subNodes != null)
-                    {
-                        unpacked.addAll(subNodes);
-                    }
-                }
-            }
-        }
-
-        return unpacked;
-    }
-
-    private boolean remove(final List<AnnotationNode> anns, final String side)
-    {
-        var onlyIns = unpack(anns);
-
-        for (var onlyIn : onlyIns)
-        {
-            if (!Objects.equals(onlyIn.desc, ONLYINS) || onlyIn.values.contains("_interface"))
-            {
-                continue;
-            }
-
-            if (!Objects.equals(((String[])onlyIn.values.get(onlyIn.values.indexOf("value") + 1))[1], side))
-            {
-                return true;
-            }
-        }
-
-        return false;
-    }
-
-    private boolean hasOnlyInWithModAnnotation(final List<AnnotationNode> anns)
-    {
-        if (anns == null)
-        {
-            return false;
-        }
-
-        var foundModAnnotation = false;
-        var foundOnlyIn = false;
-
-        for (var ann : anns)
-        {
-            if (ann.desc.equals("Lnet/minecraftforge/fml/common/Mod;"))
-            {
-                foundModAnnotation = true;
-            } else if (Objects.equals(ann.desc, ONLYIN) || Objects.equals(ann.desc, ONLYINS))
-            {
-                foundOnlyIn = true;
-            }
-        }
-
-        return foundModAnnotation && foundOnlyIn;
-    }
-
-    @SuppressWarnings("unchecked")
-    @Override
-    public Consumer<Dist> getExtension()
-    {
-        return (s)-> {
-            DIST = s.name();
-            LOGGER.debug(DISTXFORM, "Configuring for Dist {}", DIST);
-        };
-    }
-
     private static final EnumSet<Phase> YAY = EnumSet.of(Phase.AFTER);
     private static final EnumSet<Phase> NAY = EnumSet.noneOf(Phase.class);
 
     @Override
-    public EnumSet<Phase> handlesClass(Type classType, boolean isEmpty)
-    {
-        return isEmpty ? NAY : YAY;
+    public EnumSet<Phase> handlesClass(Type classType, boolean isEmpty) {
+        if (isEmpty)
+            return NAY;
+
+        String internalName = classType.getInternalName();
+        if (internalName.startsWith("net/minecraftforge/"))
+            return NAY;
+
+        // No Vanilla classes use @OnlyIn(Dist.SERVER), so we can skip them entirely when we're running on a client
+        if (FMLEnvironment.dist.isClient() && (internalName.startsWith("net/minecraft/") || internalName.startsWith("com/mojang/")))
+            return NAY;
+
+        return YAY;
+    }
+
+    @Override
+    public int processClassWithFlags(final Phase phase, final ClassNode classNode, final Type classType, final String reason) {
+        var changed = false;
+
+        var annotations = unpack(classNode.visibleAnnotations);
+
+        if (remove(annotations, DIST)) {
+            LOGGER.error(DISTXFORM, "Attempted to load class {} for invalid dist {}", classNode.name, DIST);
+            throw new RuntimeException("Attempted to load class "+ classNode.name  + " for invalid dist "+ DIST);
+        }
+
+        if (!FMLEnvironment.production && !annotations.isEmpty() && hasModAnnotation(classNode.visibleAnnotations)) {
+            LOGGER.error(DISTXFORM, "Attempted to load class {} with @Mod and @OnlyIn/@OnlyIns annotations", classNode.name);
+            throw new RuntimeException("Found @OnlyIn on @Mod class "+ classNode.name  + " - this is not allowed as it causes crashes. Remove the OnlyIn and consider setting clientSideOnly=true in the root of your mods.toml instead");
+        }
+
+        if (classNode.interfaces != null && !classNode.interfaces.isEmpty()) {
+            for (var ann : annotations) {
+                if (ann.intf == null || DIST.equals(ann.side))
+                    continue;
+
+                if (classNode.interfaces.remove(ann.intf)) {
+                    LOGGER.debug(DISTXFORM,"Removing Interface: {} implements {}", classNode.name, ann.intf);
+                    changed = true;
+                }
+            }
+
+            //Remove Class level @OnlyIn/@OnlyIns annotations, this is important if anyone gets ambitious and tries to reflect an annotation with _interface set.
+            if (classNode.visibleAnnotations != null) {
+                for (var itr = classNode.visibleAnnotations.iterator(); itr.hasNext(); ) {
+                    var ann = itr.next();
+                    if (ONLYIN.equals(ann.desc) || ONLYINS.equals(ann.desc)) {
+                        LOGGER.debug(DISTXFORM, "Removing Class Annotation: {} @{}", classNode.name, ann.desc);
+                        itr.remove();
+                        changed = true;
+                    }
+                }
+            }
+        }
+
+        for (var itr = classNode.fields.iterator(); itr.hasNext(); ) {
+            var field = itr.next();
+            if (remove(unpack(field.visibleAnnotations), DIST)) {
+                LOGGER.debug(DISTXFORM, "Removing field: {}.{}", classNode.name, field.name);
+                itr.remove();
+                changed = true;
+            }
+        }
+
+        var lambdaGatherer = new LambdaGatherer();
+        for (var itr = classNode.methods.iterator(); itr.hasNext(); ) {
+            var method = itr.next();
+            if (remove(unpack(method.visibleAnnotations), DIST)) {
+                LOGGER.debug(DISTXFORM, "Removing method: {}.{}{}", classNode.name, method.name, method.desc);
+                itr.remove();
+                lambdaGatherer.accept(method);
+                changed = true;
+            }
+        }
+
+        // remove dynamic synthetic lambda methods that are inside of removed methods
+        for (List<Handle> handles = lambdaGatherer.getDynamicLambdaHandles();
+            !handles.isEmpty(); handles = lambdaGatherer.getDynamicLambdaHandles()) {
+            lambdaGatherer = new LambdaGatherer();
+            for (var itr = classNode.methods.iterator(); itr.hasNext(); ) {
+                MethodNode method = itr.next();
+                if ((method.access & Opcodes.ACC_SYNTHETIC) == 0)
+                    continue;
+
+                for (var handle : handles) {
+                    if (method.name.equals(handle.getName()) && method.desc.equals(handle.getDesc())) {
+                        LOGGER.debug(DISTXFORM, "Removing lambda method: {}.{}{}", classNode.name, method.name, method.desc);
+                        itr.remove();
+                        lambdaGatherer.accept(method);
+                        changed = true;
+                    }
+                }
+            }
+        }
+
+        return changed ? ComputeFlags.SIMPLE_REWRITE : ComputeFlags.NO_REWRITE;
+    }
+
+    private static record Target(String side, String intf) {
+        static Target from(final AnnotationNode node) {
+            var idx = node.values.indexOf("value");
+            var value = (String[])node.values.get(idx + 1); // Enums are stored as [Type, Value]
+
+            idx = node.values.indexOf("_interface");
+            if (idx == -1)
+                return new Target(value[1], null);
+
+            var intf = (Type)node.values.get(idx + 1);
+            return new Target(value[1], intf.getInternalName());
+        }
+    }
+
+    /**
+     * Unpack any OnlyIn or OnlyIns annotations to Target objects.
+     */
+    @SuppressWarnings("unchecked")
+    private static List<Target> unpack(final List<AnnotationNode> anns) {
+        if (anns == null || anns.isEmpty())
+            return Collections.emptyList();
+
+        var ret = new ArrayList<Target>();
+        for (var node : anns) {
+            if (ONLYIN.equals(node.desc))
+                ret.add(Target.from(node));
+            else if (ONLYINS.equals(node.desc)) {
+                if (node.values == null || node.values.isEmpty())
+                    continue;
+
+                int idx = node.values.indexOf("value");
+                if (idx == -1)
+                    continue;
+
+                var subNodes = (List<AnnotationNode>)node.values.get(idx + 1);
+                if (subNodes != null) {
+                    for (var sub : subNodes)
+                        ret.add(Target.from(sub));
+                }
+            }
+        }
+
+        return ret;
+    }
+
+    private static boolean remove(final List<Target> targets, final String side) {
+        for (var target : targets) {
+            if (target.intf == null && !side.equals(target.side))
+                return true;
+        }
+
+        return false;
+    }
+
+    private static boolean hasModAnnotation(final List<AnnotationNode> anns) {
+        if (anns == null || anns.isEmpty())
+            return false;
+
+        for (var ann : anns) {
+            if (ann.desc.equals(MOD))
+                return true;
+        }
+
+        return false;
+    }
+
+    @SuppressWarnings("unchecked")
+    @Override
+    public Consumer<Dist> getExtension() {
+        return s -> {
+            DIST = s.name();
+            LOGGER.debug(DISTXFORM, "Configuring for Dist {}", DIST);
+        };
     }
 
     private static class LambdaGatherer extends MethodVisitor {
@@ -248,23 +229,21 @@ public class RuntimeDistCleaner implements ILaunchPluginService
         }
 
         public void accept(MethodNode method) {
-            Streams.stream(method.instructions.iterator()).
-                    filter(insnNode->insnNode.getType() == AbstractInsnNode.INVOKE_DYNAMIC_INSN).
-                    forEach(insnNode->insnNode.accept(this));
-        }
-
-        @Override
-        public void visitInvokeDynamicInsn(String name, String desc, Handle bsm, Object... bsmArgs)
-        {
-            if (META_FACTORY.equals(bsm))
-            {
-                Handle dynamicLambdaHandle = (Handle) bsmArgs[1];
-                dynamicLambdaHandles.add(dynamicLambdaHandle);
+            for (var insn : method.instructions) {
+                if (insn.getType() == AbstractInsnNode.INVOKE_DYNAMIC_INSN)
+                    insn.accept(this);
             }
         }
 
-        public List<Handle> getDynamicLambdaHandles()
-        {
+        @Override
+        public void visitInvokeDynamicInsn(String name, String desc, Handle bsm, Object... bsmArgs) {
+            if (META_FACTORY.equals(bsm)) {
+                var handle = (Handle)bsmArgs[1];
+                dynamicLambdaHandles.add(handle);
+            }
+        }
+
+        public List<Handle> getDynamicLambdaHandles() {
             return dynamicLambdaHandles;
         }
     }

fmlloader/src/main/java/net/minecraftforge/fml/loading/StringSubstitutor.java

@@ -14,16 +14,17 @@ import org.apache.commons.lang3.text.StrSubstitutor;
 
 @SuppressWarnings("deprecation")
 public class StringSubstitutor {
+    private static final Map<String, String> GLOBALS = Map.of(
+        "mcVersion", FMLLoader.versionInfo().mcVersion(),
+        "forgeVersion", FMLLoader.versionInfo().forgeVersion()
+    );
+
     public static String replace(final String in, final ModFile file) {
         return new StrSubstitutor(getStringLookup(file)).replace(in);
     }
 
     private static StrLookup<String> getStringLookup(final ModFile file) {
-        var globals = Map.of(
-            "mcVersion", FMLLoader.versionInfo().mcVersion(),
-            "forgeVersion", FMLLoader.versionInfo().forgeVersion()
-        );
-        return new StrLookup<String>() {
+        return new StrLookup<>() {
             @Override
             public String lookup(String key) {
                 var parts = key.split("\\.");
@@ -32,7 +33,7 @@ public class StringSubstitutor {
                 var pfx = parts[0];
 
                 if ("global".equals(pfx))
-                    return globals.get(parts[1]);
+                    return GLOBALS.get(parts[1]);
                 else if ("file".equals(pfx) && file != null)
                     return String.valueOf(file.getSubstitutionMap().get().get(parts[1]));
 

fmlloader/src/main/java/net/minecraftforge/fml/loading/UniqueModListBuilder.java

@@ -9,6 +9,7 @@ import com.mojang.logging.LogUtils;
 import net.minecraftforge.fml.loading.moddiscovery.ModFile;
 import net.minecraftforge.forgespi.language.IModInfo;
 import org.apache.maven.artifact.versioning.ArtifactVersion;
+import org.jetbrains.annotations.ApiStatus;
 import org.slf4j.Logger;
 
 import java.util.ArrayList;
@@ -16,26 +17,19 @@ import java.util.Collection;
 import java.util.Comparator;
 import java.util.List;
 import java.util.Map;
-import java.util.function.Function;
-import java.util.stream.Collectors;
 
 import static java.util.stream.Collectors.groupingBy;
 import static java.util.stream.Collectors.joining;
 import static net.minecraftforge.fml.loading.LogMarkers.LOADING;
 
-public class UniqueModListBuilder
-{
-    private final static Logger LOGGER = LogUtils.getLogger();
+@ApiStatus.Internal
+@Deprecated(since = "1.21.3", forRemoval = true) // TODO: [FML][Loading] Convert to package private in 1.22
+public final class UniqueModListBuilder {
+    private UniqueModListBuilder() {}
 
-    private final List<ModFile> modFiles;
-
-    public UniqueModListBuilder(final List<ModFile> modFiles) {this.modFiles = modFiles;}
-
-    public UniqueModListData buildUniqueList()
-    {
-        List<ModFile> uniqueModList;
-        List<ModFile> uniqueLibListWithVersion;
+    private static final Logger LOGGER = LogUtils.getLogger();
 
+    public static UniqueModListData buildUniqueList(List<ModFile> modFiles) {
         // Collect mod files by module name. This will be used for deduping purposes
         final Map<String, List<ModFile>> modFilesByFirstId = modFiles.stream()
                 .filter(mf -> mf.getModFileInfo() != null)
@@ -46,13 +40,13 @@ public class UniqueModListBuilder
                 .collect(groupingBy(UniqueModListBuilder::getModId));
 
         // Select the newest by artifact version sorting of non-unique files thus identified
-        uniqueModList = modFilesByFirstId.entrySet().stream()
-                .map(this::selectNewestModInfo)
+        final List<ModFile> uniqueModList = modFilesByFirstId.entrySet().stream()
+                .map(UniqueModListBuilder::selectNewestModInfo)
                 .toList();
 
         // Select the newest by artifact version sorting of non-unique files thus identified
-        uniqueLibListWithVersion = libFilesWithVersionByModuleName.entrySet().stream()
-                .map(this::selectNewestModInfo)
+        final List<ModFile> uniqueLibListWithVersion = libFilesWithVersionByModuleName.entrySet().stream()
+                .map(UniqueModListBuilder::selectNewestModInfo)
                 .toList();
 
         // Transform to the full mod id list
@@ -63,43 +57,40 @@ public class UniqueModListBuilder
                 .collect(groupingBy(IModInfo::getModId));
 
         // Transform to the full lib id list
-        final Map<String, List<ModFile>> versionedLibIds = uniqueLibListWithVersion.stream()
+        final List<List<ModFile>> versionedLibs = uniqueLibListWithVersion.stream()
                 .map(UniqueModListBuilder::getModId)
-                .collect(Collectors.toMap(
-                    Function.identity(),
-                    libFilesWithVersionByModuleName::get
-                ));
+                .map(libFilesWithVersionByModuleName::get)
+                .toList();
 
         // Its theoretically possible that some mod has somehow moved an id to a secondary place, thus causing a dupe.
         // We can't handle this
         final List<String> dupedModErrors = modIds.values().stream()
                 .filter(modInfos -> modInfos.size() > 1)
                 .map(mods -> String.format("\tMod ID: '%s' from mod files: %s",
-                        mods.get(0).getModId(),
+                        mods.getFirst().getModId(),
                         mods.stream()
                                 .map(modInfo -> modInfo.getOwningFile().getFile().getFileName()).collect(joining(", "))
                 )).toList();
 
         if (!dupedModErrors.isEmpty()) {
-            LOGGER.error(LOADING, "Found duplicate mods:\n{}", dupedModErrors.stream().collect(joining("\n")));
+            LOGGER.error(LOADING, "Found duplicate mods:\n{}", String.join("\n", dupedModErrors));
             throw new EarlyLoadingException("Duplicate mods found", null, dupedModErrors.stream()
-                    .map(s -> new EarlyLoadingException.ExceptionData(s))
+                    .map(EarlyLoadingException.ExceptionData::new)
                     .toList());
         }
 
 
-        final List<String> dupedLibErrors = versionedLibIds.values().stream()
-                .filter(modFiles -> modFiles.size() > 1)
+        final List<String> dupedLibErrors = versionedLibs.stream()
+                .filter(libModFiles -> libModFiles.size() > 1)
                 .map(mods -> String.format("\tLibrary: '%s' from files: %s",
-                        getModId(mods.get(0)),
-                        mods.stream()
-                                .map(modFile -> modFile.getFileName()).collect(joining(", "))
+                        getModId(mods.getFirst()),
+                        mods.stream().map(ModFile::getFileName).collect(joining(", "))
                 )).toList();
 
         if (!dupedLibErrors.isEmpty()) {
-            LOGGER.error(LOADING, "Found duplicate plugins or libraries:\n{}", dupedLibErrors.stream().collect(joining("\n")));
+            LOGGER.error(LOADING, "Found duplicate plugins or libraries:\n{}", String.join("\n", dupedLibErrors));
             throw new EarlyLoadingException("Duplicate plugins or libraries found", null, dupedLibErrors.stream()
-                    .map(s -> new EarlyLoadingException.ExceptionData(s))
+                    .map(EarlyLoadingException.ExceptionData::new)
                     .toList());
         }
 
@@ -107,30 +98,28 @@ public class UniqueModListBuilder
         final Map<String, List<ModFile>> uniqueModFilesByFirstId = uniqueModList.stream()
                 .collect(groupingBy(UniqueModListBuilder::getModId));
 
-        final List<ModFile> loadedList = new ArrayList<>();
-        loadedList.addAll(uniqueModList);
+        final List<ModFile> loadedList = new ArrayList<>(uniqueModList);
         loadedList.addAll(uniqueLibListWithVersion);
 
         return new UniqueModListData(loadedList, uniqueModFilesByFirstId);
     }
 
-    private ModFile selectNewestModInfo(Map.Entry<String, List<ModFile>> fullList) {
+    private static ModFile selectNewestModInfo(Map.Entry<String, List<ModFile>> fullList) {
         List<ModFile> modInfoList = fullList.getValue();
         if (modInfoList.size() > 1) {
             LOGGER.debug("Found {} mods for first modid {}, selecting most recent based on version data", modInfoList.size(), fullList.getKey());
-            modInfoList.sort(Comparator.comparing(this::getVersion).reversed());
-            LOGGER.debug("Selected file {} for modid {} with version {}", modInfoList.get(0).getFileName(), fullList.getKey(), this.getVersion(modInfoList.get(0)));
+            modInfoList.sort(Comparator.comparing(UniqueModListBuilder::getVersion).reversed());
+            LOGGER.debug("Selected file {} for modid {} with version {}", modInfoList.getFirst().getFileName(), fullList.getKey(), getVersion(modInfoList.getFirst()));
         }
-        return modInfoList.get(0);
+        return modInfoList.getFirst();
     }
 
-    private ArtifactVersion getVersion(final ModFile mf)
-    {
+    private static ArtifactVersion getVersion(final ModFile mf) {
         if (mf.getModFileInfo() == null || mf.getModInfos() == null || mf.getModInfos().isEmpty()) {
             return mf.getJarVersion();
         }
 
-        return mf.getModInfos().get(0).getVersion();
+        return mf.getModInfos().getFirst().getVersion();
     }
 
     private static String getModId(ModFile modFile) {
@@ -138,9 +127,8 @@ public class UniqueModListBuilder
             return modFile.getSecureJar().name();
         }
 
-        return modFile.getModFileInfo().moduleName();
+        return modFile.getModFileInfo().getMods().getFirst().getModId();
     }
 
     public record UniqueModListData(List<ModFile> modFiles, Map<String, List<ModFile>> modFilesByFirstId) {}
-
 }

fmlloader/src/main/java/net/minecraftforge/fml/loading/VersionSupportMatrix.java

@@ -5,33 +5,53 @@
 
 package net.minecraftforge.fml.loading;
 
-import net.minecraftforge.forgespi.language.MavenVersionAdapter;
 import org.apache.maven.artifact.versioning.ArtifactVersion;
 import org.apache.maven.artifact.versioning.DefaultArtifactVersion;
 import org.apache.maven.artifact.versioning.VersionRange;
+import org.jetbrains.annotations.ApiStatus;
 
-import java.util.ArrayList;
-import java.util.HashMap;
+import java.util.Collections;
 import java.util.List;
+import java.util.Map;
 import java.util.function.BiPredicate;
 
+@ApiStatus.Internal // since 1.21.1, will be made non-public in a later MC version
 public class VersionSupportMatrix {
-    private static final HashMap<String, List<ArtifactVersion>> overrideVersions = new HashMap<>();
+    private static final Map<String, List<ArtifactVersion>> OVERRIDE_VERSIONS;
+
     static {
-         final ArtifactVersion version = new DefaultArtifactVersion(FMLLoader.versionInfo().mcVersion());
-         if (MavenVersionAdapter.createFromVersionSpec("[1.19.2]").containsVersion(version)) {
-             // 1.19.2 is Compatible with 1.19.1
-             add("languageloader.javafml", "42");
-             add("mod.minecraft",          "1.19.1");
-             add("mod.forge",              "42.0.9");
+        if ("1.21.1".equals(FMLLoader.versionInfo().mcVersion())) {
+            OVERRIDE_VERSIONS = Map.ofEntries(
+                    // 1.21.1 is compatible with 1.21
+                    entry("languageloader.javafml", "51"),
+                    entry("mod.minecraft",          "1.21"),
+                    entry("mod.forge",              "51.0.33")
+            );
+        } else {
+            OVERRIDE_VERSIONS = Collections.emptyMap();
         }
     }
-    private static void add(String key, String value) {
-        overrideVersions.computeIfAbsent(key, k -> new ArrayList<>()).add(new DefaultArtifactVersion(value));
-    }
-    public static <T> boolean testVersionSupportMatrix(VersionRange declaredRange, String lookupId, String type, BiPredicate<String, VersionRange> standardLookup) {
+
+    /**
+     * @deprecated Use {@link #testVersionSupportMatrix(VersionRange, String, String)} instead, unwrapping your BiPredicate.
+     */
+    @Deprecated(forRemoval = true, since = "1.21.1")
+    public static boolean testVersionSupportMatrix(VersionRange declaredRange, String lookupId, String type, BiPredicate<String, VersionRange> standardLookup) {
         if (standardLookup.test(lookupId, declaredRange)) return true;
-        List<ArtifactVersion> custom = overrideVersions.get(type + "." + lookupId);
-        return custom == null ? false  : custom.stream().anyMatch(declaredRange::containsVersion);
+        return testVersionSupportMatrix(declaredRange, lookupId, type);
+    }
+
+    public static boolean testVersionSupportMatrix(VersionRange declaredRange, String lookupId, String type) {
+        if (OVERRIDE_VERSIONS.isEmpty()) return false;
+        List<ArtifactVersion> custom = OVERRIDE_VERSIONS.get(type + "." + lookupId);
+        return custom != null && custom.stream().anyMatch(declaredRange::containsVersion);
+    }
+
+    private static Map.Entry<String, List<ArtifactVersion>> entry(String typeAndLookupId, String declaredRange) {
+        return Map.entry(typeAndLookupId, List.of(new DefaultArtifactVersion(declaredRange)));
+    }
+
+    private static Map.Entry<String, List<ArtifactVersion>> entry(String typeAndLookupId, List<String> declaredRanges) {
+        return Map.entry(typeAndLookupId, declaredRanges.stream().map(DefaultArtifactVersion::new).map(it -> (ArtifactVersion) it).toList());
     }
 }

fmlloader/src/main/java/net/minecraftforge/fml/loading/log4j/ForgeHighlight.java

@@ -18,9 +18,7 @@ import org.apache.logging.log4j.util.PerformanceSensitive;
 import org.jetbrains.annotations.Nullable;
 
 import java.lang.reflect.Method;
-import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.List;
 
 /**
  * A wrapper for {@link HighlightConverter} that auto-disables ANSI when the terminal doesn't support it.
@@ -49,10 +47,7 @@ public class ForgeHighlight {
             LOGGER.warn("Failed to invoke initializeTerminal on TCA", e);
         }
         if (!TerminalConsoleAppender.isAnsiSupported() && Arrays.stream(options).noneMatch(s -> s.equals("disableAnsi=true"))) {
-            List<String> optionList = new ArrayList<>();
-            optionList.add(options[0]);
-            optionList.add("disableAnsi=true");
-            options = optionList.toArray(new String[0]);
+            options = new String[] { options[0], "disableAnsi=true" };
         }
         return HighlightConverter.newInstance(config, options);
     }

fmlloader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/AbstractModProvider.java

@@ -6,6 +6,7 @@
 package net.minecraftforge.fml.loading.moddiscovery;
 
 import com.mojang.logging.LogUtils;
+
 import cpw.mods.jarhandling.JarMetadata;
 import cpw.mods.jarhandling.SecureJar;
 import net.minecraftforge.fml.loading.LogMarkers;
@@ -22,19 +23,25 @@ import org.jetbrains.annotations.Nullable;
 import org.slf4j.Logger;
 
 import java.io.IOException;
+import java.lang.module.InvalidModuleDescriptorException;
+import java.lang.module.ModuleDescriptor;
+import java.lang.module.ModuleDescriptor.Version;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.Collections;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
 import java.util.function.Consumer;
 import java.util.jar.JarFile;
+import java.util.stream.Collectors;
 
 @ApiStatus.Internal
 public abstract class AbstractModProvider implements IModProvider {
-    private static final   Logger LOGGER    = LogUtils.getLogger();
-    protected static final String MODS_TOML = "META-INF/mods.toml";
+    private static final   Logger LOGGER      = LogUtils.getLogger();
+    protected static final String MODS_TOML   = "META-INF/mods.toml";
+    protected static final String MODULE_INFO = "module-info.class";
 
     protected IModLocator.ModFileOrException createMod(Path path) {
         return createMod(path, false);
@@ -42,16 +49,22 @@ public abstract class AbstractModProvider implements IModProvider {
 
     @Nullable
     protected IModLocator.ModFileOrException createMod(Path path, boolean ignoreUnknown) {
-        return createMod(path, false, getDefaultJarModType());
+        return createMod(path, ignoreUnknown, getDefaultJarModType());
     }
 
     @Nullable
     protected IModLocator.ModFileOrException createMod(Path path, boolean ignoreUnknown, String defaultType) {
+        var debug = path.toString();
+        if (debug.equals("/"))
+            debug = path.toUri().toString();
+
         var mjm = new ModJarMetadata();
-        var sj = SecureJar.from(
-            jar -> jar.moduleDataProvider().findFile(MODS_TOML).isPresent() ? mjm : JarMetadata.from(jar, path),
-            path
-        );
+        SecureJar sj = null;
+        try {
+            sj = SecureJar.from(jar -> loadMetaFromJar(jar, mjm), path);
+        } catch (Throwable t) {
+            return new IModLocator.ModFileOrException(null, new ModFileLoadingException("Failed to create secure jar for \"" + debug + "\" - " + t.getMessage()));
+        }
 
         IModFile mod;
         var type = sj.moduleDataProvider().getManifest().getMainAttributes().getValue(ModFile.TYPE);
@@ -59,32 +72,89 @@ public abstract class AbstractModProvider implements IModProvider {
             type = defaultType;
 
         if (sj.moduleDataProvider().findFile(MODS_TOML).isPresent()) {
-            LOGGER.debug(LogMarkers.SCAN, "Found {} mod of type {}: {}", MODS_TOML, type, path);
+            LOGGER.debug(LogMarkers.SCAN, "Found {} mod of type {}: {}", MODS_TOML, type, debug);
             mod = new ModFile(sj, this, ModFileParser::modsTomlParser);
+            // ModJarMetadata is only used when loading mods.toml mods as ModJarMetadata
+            mjm.setModFile(mod);
             if (mod.getModFileInfo().getFileProperties().containsKey(ModFileInfo.NOT_A_FORGE_MOD_PROP)) {
                 LOGGER.error(LogMarkers.SCAN, "Unable to load file \"{}\" because its mods.toml is requesting an invalid javafml loaderVersion (use \"*\" if you want to allow all versions) and is missing a forge modId dependency declaration (see the sample mods.toml in the MDK).", path);
                 return new IModLocator.ModFileOrException(null, new ModFileLoadingException("File \"%s\" is not a Forge mod and cannot be loaded. Look for a Forge version of this mod or consider alternative mods.".formatted(mod.getFileName())));
             }
         } else if (type != null) {
-            LOGGER.debug(LogMarkers.SCAN, "Found {} mod of type {}: {}", JarFile.MANIFEST_NAME, type, path);
+            LOGGER.debug(LogMarkers.SCAN, "Found {} mod of type {}: {}", JarFile.MANIFEST_NAME, type, debug);
             mod = new ModFile(sj, this, this::manifestParser, type);
         } else if (ignoreUnknown) {
             return null;
         } else
-            return new IModLocator.ModFileOrException(null, new ModFileLoadingException("Invalid mod file found " + path));
+            return new IModLocator.ModFileOrException(null, new ModFileLoadingException("Invalid mod file found " + debug));
 
-        mjm.setModFile(mod);
         return new IModLocator.ModFileOrException(mod, null);
     }
 
+    protected static JarMetadata loadMetaFromJar(SecureJar jar, ModJarMetadata mjm) {
+        var info = jar.moduleDataProvider().open(MODULE_INFO).orElse(null);
+        if (info != null) {
+            try {
+                var desc = ModuleDescriptor.read(info, jar::getPackages);
+                var all = new HashSet<>(jar.getPackages());
+                all.removeAll(desc.packages());
+                if (!all.isEmpty()) {
+                    var missing = all.stream().sorted().collect(Collectors.joining(", "));
+                    LOGGER.error("Invalid module-info, missing packages " + missing);
+                    throw new ModFileLoadingException("Invalid module-info, missing packages " + missing);
+                } else {
+                    return new JarMetadata() {
+                        @Override
+                        public String name() {
+                            return desc.name();
+                        }
+
+                        @Override
+                        public String version() {
+                            return desc.version().map(Version::toString).or(desc::rawVersion).orElse(null);
+                        }
+
+                        @Override
+                        public ModuleDescriptor descriptor() {
+                            return desc;
+                        }
+                    };
+                }
+            } catch (InvalidModuleDescriptorException | IOException e) {
+                LOGGER.error("Failed to parse " + jar.getPrimaryPath() + " module-info", e);
+                throw new ModFileLoadingException("Invalid module-info: " + e.getMessage());
+            } finally {
+                try {
+                    info.close();
+                } catch (IOException e) {}
+            }
+        }
+
+        if (jar.moduleDataProvider().findFile(MODS_TOML).isEmpty())
+            return JarMetadata.from(jar, jar.getPrimaryPath());
+
+        return mjm;
+    }
+
     protected IModFileInfo manifestParser(final IModFile mod) {
         var mf = mod.getSecureJar().moduleDataProvider().getManifest().getMainAttributes();
         var license = mf.getValue("LICENSE");
         var dummy = new IConfigurable() {
+            @Override
+            public <T> Optional<T> getConfigElement(String key) {
+                return Optional.empty();
+            }
+
             @Override
             public <T> Optional<T> getConfigElement(String... key) {
                 return Optional.empty();
             }
+
+            @Override
+            public List<? extends IConfigurable> getConfigList(String key) {
+                return Collections.emptyList();
+            }
+
             @Override
             public List<? extends IConfigurable> getConfigList(String... key) {
                 return Collections.emptyList();
@@ -140,10 +210,11 @@ public abstract class AbstractModProvider implements IModProvider {
     }
 
     private static final class Holder<T> {
-        T value;
+        private T value;
     }
 
     private record DefaultModFileInfo(IModFile mod, String license, IConfigurable configurable) implements IModFileInfo, IConfigurable {
+        @Override public <T> Optional<T> getConfigElement(final String string) { return Optional.empty(); }
         @Override public <T> Optional<T> getConfigElement(final String... strings) { return Optional.empty(); }
         @Override public List<? extends IConfigurable> getConfigList(final String... strings) { return null; }
         @Override public List<IModInfo> getMods() { return Collections.emptyList(); }

fmlloader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/BackgroundScanHandler.java

@@ -29,6 +29,7 @@ public class BackgroundScanHandler
     }
 
     private static final Logger LOGGER = LogUtils.getLogger();
+    private static final boolean DEBUG = LOGGER.isErrorEnabled(LogMarkers.SCAN);
     private final ExecutorService modContentScanner;
     private final List<ModFile> modFiles;
     private ScanStatus status;
@@ -55,16 +56,16 @@ public class BackgroundScanHandler
         }
         status = ScanStatus.RUNNING;
         ImmediateWindowHandler.updateProgress("Scanning mod candidates");
-        final CompletableFuture<ModFileScanData> future = CompletableFuture.supplyAsync(file::compileContent, modContentScanner)
-                .whenComplete(file::setScanResult)
-                .whenComplete((r,t)-> this.addCompletedFile(file,r,t));
+        CompletableFuture<ModFileScanData> future = CompletableFuture.supplyAsync(file::compileContent, modContentScanner)
+                .whenComplete(file::setScanResult);
+        if (DEBUG) future = future.whenComplete((r, t) -> addCompletedFile(file, t));
         file.setFutureScanResult(future);
     }
 
-    private void addCompletedFile(final ModFile file, final ModFileScanData modFileScanData, final Throwable throwable) {
+    private void addCompletedFile(final ModFile file, final Throwable throwable) {
         if (throwable != null) {
             status = ScanStatus.ERRORED;
-            LOGGER.error(LogMarkers.SCAN,"An error occurred scanning file {}", file, throwable);
+            LOGGER.error(LogMarkers.SCAN, "An error occurred scanning file {}", file, throwable);
         }
     }
 

fmlloader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/ClasspathLocator.java

@@ -18,9 +18,9 @@ import java.io.IOException;
 import java.net.URI;
 import java.net.URL;
 import java.nio.file.Path;
-import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.Comparator;
 import java.util.HashSet;
 import java.util.List;
 import java.util.jar.Attributes;
@@ -28,7 +28,7 @@ import java.util.jar.JarFile;
 import java.util.jar.Manifest;
 
 @ApiStatus.Internal
-public class ClasspathLocator extends AbstractModProvider implements IModLocator {
+public final class ClasspathLocator extends AbstractModProvider implements IModLocator {
     private static final Logger LOGGER = LogUtils.getLogger();
     private static final Attributes.Name MOD_TYPE = new Attributes.Name("FMLModType");
 
@@ -74,17 +74,18 @@ public class ClasspathLocator extends AbstractModProvider implements IModLocator
         var ret = new ArrayList<ModFileOrException>();
         for (var path : claimed) {
             // Filter out anything found by the ServiceLoader
-            if (!ModDirTransformerDiscoverer.isServiceProvider(path))
+            if (!ModDirTransformerDiscoverer.isServiceProvider(path)
+                && !JarInJarDependencyLocator.isOption(path))
                 ret.add(createMod(path));
         }
         return ret;
     }
 
-    private List<URL> getUrls(ClassLoader cl, String resource) {
+    private static List<URL> getUrls(ClassLoader cl, String resource) {
         try {
             var lst = Collections.list(cl.getResources(resource));
             if (LOGGER.isDebugEnabled(LogMarkers.SCAN)) {
-                Collections.sort(lst, (a, b) -> a.toString().compareTo(b.toString()));
+                lst.sort(Comparator.comparing(URL::toString));
                 LOGGER.debug(LogMarkers.SCAN, "Scanning Classloader: {} for {}", cl, resource);
                 for (var url : lst)
                     LOGGER.debug(LogMarkers.SCAN, "\t{}", url);
@@ -104,11 +105,10 @@ public class ClasspathLocator extends AbstractModProvider implements IModLocator
             len += 2;
         }
         str = str.substring(0, str.length() - len);
-        var path = Paths.get(URI.create(str));
-        return path;
+        return Path.of(URI.create(str));
     }
 
-    private static Path getPathFromResource(ClassLoader cl, String resource) {
+    static Path getPathFromResource(ClassLoader cl, String resource) {
         var url = cl.getResource(resource);
         if (url == null)
             return null;

fmlloader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/CoreModFile.java

@@ -15,7 +15,7 @@ import java.nio.file.Path;
 import org.jetbrains.annotations.ApiStatus;
 
 @ApiStatus.Internal
-public class CoreModFile implements ICoreModFile {
+public final class CoreModFile implements ICoreModFile {
     private final Path internalPath;
     private final ModFile file;
     private final String name;

fmlloader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/InvalidModIdentifier.java

@@ -9,7 +9,6 @@ import cpw.mods.modlauncher.api.LamdbaExceptionUtils.Supplier_WithExceptions;
 import net.minecraftforge.fml.loading.StringUtils;
 
 import java.nio.file.Path;
-import java.util.Arrays;
 import java.util.Optional;
 import java.util.function.BiPredicate;
 import java.util.stream.Stream;

fmlloader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/JarInJarDependencyLocator.java

@@ -5,37 +5,60 @@
 
 package net.minecraftforge.fml.loading.moddiscovery;
 
-import com.google.common.collect.ImmutableMap;
-import com.google.common.collect.Lists;
+import com.electronwill.nightconfig.core.UnmodifiableConfig;
+import com.electronwill.nightconfig.core.file.FileConfig;
 import com.mojang.logging.LogUtils;
+
+import cpw.mods.modlauncher.Launcher;
+import cpw.mods.modlauncher.api.TypesafeMap;
 import net.minecraftforge.fml.loading.EarlyLoadingException;
+import net.minecraftforge.fml.loading.EarlyLoadingException.ExceptionData;
+import net.minecraftforge.fml.loading.FMLEnvironment;
 import net.minecraftforge.forgespi.language.IModInfo;
 import net.minecraftforge.forgespi.locating.IDependencyLocator;
 import net.minecraftforge.forgespi.locating.IModFile;
-import net.minecraftforge.forgespi.locating.ModFileLoadingException;
+import net.minecraftforge.forgespi.locating.IModFile.Type;
+import net.minecraftforge.jarjar.metadata.ContainedJarIdentifier;
+import net.minecraftforge.jarjar.metadata.ContainedJarMetadata;
+import net.minecraftforge.jarjar.metadata.ContainedVersion;
+import net.minecraftforge.jarjar.metadata.MetadataIOHandler;
 import net.minecraftforge.jarjar.selection.JarSelector;
-import org.apache.maven.artifact.versioning.ArtifactVersion;
+
+import org.apache.maven.artifact.versioning.InvalidVersionSpecificationException;
 import org.apache.maven.artifact.versioning.VersionRange;
 import org.jetbrains.annotations.ApiStatus;
-import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 import org.slf4j.Logger;
+import org.slf4j.Marker;
+import org.slf4j.MarkerFactory;
 
+import java.io.IOException;
 import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.lang.module.ModuleDescriptor;
 import java.net.URI;
+import java.net.URISyntaxException;
 import java.nio.file.FileSystem;
 import java.nio.file.FileSystems;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
-import java.util.Optional;
+import java.util.StringJoiner;
+import java.util.TreeMap;
+import java.util.jar.Attributes;
+import java.util.jar.JarFile;
+import java.util.jar.Manifest;
 import java.util.stream.Collectors;
-import java.util.stream.Stream;
 
 @ApiStatus.Internal
 public class JarInJarDependencyLocator extends AbstractModProvider implements IDependencyLocator {
+    private static final String ROIMFS = "roimfs";
     private static final String COLOR_CODE = "\u00a7";
     private static final String RESET  = COLOR_CODE + "r";
     private static final String YELLOW = COLOR_CODE + "e";
@@ -43,32 +66,238 @@ public class JarInJarDependencyLocator extends AbstractModProvider implements ID
     private static final String GREEN  = COLOR_CODE + "2";
 
     private static final Logger LOGGER = LogUtils.getLogger();
+    private static final Marker MARKER = MarkerFactory.getMarker("JAR-JAR"); // LogMarkers.SCAN;
+
+    private static final Map<Path, Option> OPTIONS = new HashMap<>();
+    private static volatile boolean optionsLoaded = false;
+
+    private static final Attributes.Name MIXIN_CONFIGS_ATTR = new Attributes.Name("MixinConfigs");
+    private static final Attributes.Name MIXIN_CONNECTOR_ATTR = new Attributes.Name("MixinConnector");
+    private static final ContainedJarMetadata MIXIN_EXTRAS_DEPENDENCY = makeMixinExtraDependency();
+
+    private static ContainedJarMetadata makeMixinExtraDependency() {
+        VersionRange range = null;
+        try {
+            range = VersionRange.createFromVersionSpec("[0,)");
+        } catch (InvalidVersionSpecificationException e) {
+            throw new RuntimeException("Failed to create version range for mixinextras-forge dependency", e);
+        }
+
+        return new ContainedJarMetadata(
+            new ContainedJarIdentifier("io.github.llamalad7", "mixinextras-forge"),
+            new ContainedVersion(range, null),
+            null, false
+        );
+    }
 
     @Override
     public String name() {
         return "JarInJar";
     }
 
+    private int fsID = 0;
+    private synchronized int nextId() {
+        return fsID++;
+    }
+
     @Override
     public List<IModFile> scanMods(Iterable<IModFile> loadedMods) {
-        final List<IModFile> sources = Lists.newArrayList();
-        loadedMods.forEach(sources::add);
+        var mods = new ArrayList<IModFile>();
+        loadedMods.forEach(mods::add);
 
-        var dependenciesToLoad = JarSelector.detectAndSelect(
-            sources,
-            this::loadResourceFromModFile,
-            this::loadModFileFrom,
-            this::identifyMod,
-            this::exception
-        );
+        var selector = new Selector(mods);
 
-        if (dependenciesToLoad.isEmpty()) {
+        // Add a synthetic Mixin-Extras dependency if we detect anyone using Mixin
+        if (anyMixinsLoaded(mods)) {
+            if (!selector.isRequired(MIXIN_EXTRAS_DEPENDENCY.identifier()))
+                selector.addRequirement(MIXIN_EXTRAS_DEPENDENCY);
+        } else if (selector.entries.size() == mods.size()) {
             LOGGER.info("No dependencies to load found. Skipping!");
             return Collections.emptyList();
         }
 
-        LOGGER.info("Found {} dependencies adding them to mods collection", dependenciesToLoad.size());
-        return dependenciesToLoad;
+        loadOptions();
+
+        // Ideally, the json would be in order so we only have to loop once. But its written this way just in case.
+        var seen = new HashSet<Option>();
+        var added = false;
+        do {
+            added = false;
+            for (var entry : OPTIONS.values()) {
+                if (seen.contains(entry) || !selector.isRequired(entry.meta.identifier()))
+                    continue;
+
+                seen.add(entry);
+
+                entry.addTo(selector);
+
+                if (entry.deps != null && !entry.deps.isEmpty()) {
+                    added = true;
+                    for (var dep : entry.deps)
+                        selector.addRequirement(dep);
+                }
+            }
+        } while (added);
+
+        var selected = selector.select();
+
+        if (LOGGER.isDebugEnabled()) {
+            var ids = new TreeMap<String, List<Entry>>();
+            for (var entry : selector.entries.values()) {
+                if (entry != FAILED && entry.coord != null)
+                    ids.computeIfAbsent(entry.coord, id -> new ArrayList<>()).add(entry);
+            }
+
+            for (var entry : ids.entrySet()) {
+                LOGGER.info(MARKER, "JarJar Candidated for {}", entry.getKey());
+                Collections.sort(entry.getValue());
+                for (var option : entry.getValue())
+                    LOGGER.info(MARKER, "\t{}{}", selected.contains(option) ? '*' : ' ', option);
+            }
+        }
+
+        if (selected.isEmpty()) {
+            LOGGER.info("No dependencies to load found. Skipping!");
+            return Collections.emptyList();
+        }
+
+        /* Since Java 11, the JRE decompresses all zip files to memory when getting a ByteChannel for them.
+         * JarJar only targets Minecraft 1.18+ which is Java17+ Which means we can exploit the fact that
+         * these are Disjointed file systems, and close all unselected libraries.
+         *
+         * https://github.com/openjdk/jdk11u/blob/25a9b9e5594e88c9e1e66f95c7ca45d5a9da8854/src/jdk.zipfs/share/classes/jdk/nio/zipfs/ZipFileSystem.java#L703
+         *
+         * Combined with the fact that the JarJarFileSystem has always simply called into FileSystems.newFileSystem for its wrapped targets.
+         * https://github.com/MinecraftForge/JarJar/blame/b39b2051439c81519d826d38898778bf3081356f/src/main/java/net/minecraftforge/jarjar/nio/pathfs/PathFileSystem.java#L38
+         *
+         * This effectively means that JarJar has ALWAYS been a wrapper around in-memory copies of every jar it scans.
+         *
+         * It also never closes these FileSystems, which potentially means they are leaked if the GC can't inherently GC them.
+         *
+         * Ideally we would extract these contained jars to a temp folder, so that we can use the nice optimizations Java has for ZipFile/JarFile.
+         * But in order to do that we would need to write the file to a place that could potentially have conflicts.
+         * To resolve those conflicts we should take a hint out of maven/gradle/minecraft's book and key the filepath based on a hash of the file being extracted.
+         * However, because that hash is no available in existing metadata we would need to re-calculate it.
+         *
+         * To do it in an efficient way we I needed to be able to share the single opened FileSystem with both the SecureJar implementation, and with our recursive search.
+         * So I use my new ReadOnlyInMemoryFileSystem which is specifically designed to use the same backing array for the JarInJar search as it does with the resulting dependency
+         * selected SecureJars.
+         *
+         * This means that if we wanted to we could rather efficiently calculate a hash for extracting the file. However, it also means that we don't have to extract to file to
+         * support ZipFileSystem caching properly. So as long as we are okay with not using the JRE's optimized ZipFile implementation, or we want to support legacy JarInJar metadata,
+         * using this efficient in memory file system is the best option performance wise. Extracting the files during launch without an efficient caching/unique identifier system
+         * would incur a lot of Disc IO which can be super slow depending on your setup.
+         *
+         * So, it is a stated goal of our future re-write to extract files into a cache directory to gain the benefits of JRE optimizations, using a FileSystem much simpler then
+         * the existing JarInJarFileSystem is good enough.
+         */
+
+        // Lets close all unselected FileSystems
+        var wasSelected = new HashSet<>(selected);
+        for (var entry : selector.entries.values())
+            entry.cleanup(wasSelected.contains(entry));
+
+        LOGGER.info(MARKER, "Found {} dependencies adding them to mods collection", selected.size());
+        var ret = new ArrayList<IModFile>(selected.size());
+
+        // Now lets build the actual mod files
+        for (var entry : selected) {
+            try {
+                var root = entry.getFinalPath();
+                var mod = createMod(root, false, entry.type.name());
+
+                if (mod.ex() != null)
+                    throw fail("Failed to load JarInJar file " + entry, mod.ex());
+
+                ret.add(mod.file());
+            } catch (EarlyLoadingException e) {
+                throw e;
+            } catch (Throwable e) {
+                throw fail("Failed to load JarInJar file " + entry, e);
+            }
+        }
+
+        return ret;
+    }
+
+    private static Boolean anyMixinsLoaded = null;
+    private static boolean anyMixinsLoaded(List<IModFile> mods) {
+        var ret = anyMixinsLoaded;
+        if (ret != null) return ret;
+
+        if (!FMLEnvironment.production
+                && Launcher.INSTANCE.blackboard().get(TypesafeMap.Key.getOrCreate(Launcher.INSTANCE.blackboard(), "isMixinEnabledInDev", Boolean.class)).orElse(false)) {
+            anyMixinsLoaded = true;
+            return true;
+        }
+
+        for (var mod : mods) {
+            var attributes = mod.getSecureJar().moduleDataProvider().getManifest().getMainAttributes();
+            if (attributes.getValue(MIXIN_CONFIGS_ATTR) != null || attributes.getValue(MIXIN_CONNECTOR_ATTR) != null) {
+                anyMixinsLoaded = true;
+                return true;
+            }
+        }
+
+        anyMixinsLoaded = false;
+        return false;
+    }
+
+    private record Options(List<OptionMetadata> options) {}
+    private record OptionMetadata(String resource, Type layer, String id, List<ContainedJarMetadata> deps, ContainedJarMetadata meta, boolean nested) {}
+
+    private static void loadOptions() {
+        if (optionsLoaded)
+            return;
+
+        synchronized (OPTIONS) {
+            if (optionsLoaded)
+                return;
+
+            optionsLoaded = true;
+
+            var self = JarInJarDependencyLocator.class;
+
+            try (var stream = self.getModule().getResourceAsStream("/jarjar_options.json")) {
+                if (stream == null) {
+                    LOGGER.error(MARKER, "Failed to find jarjar_options.json");
+                    return;
+                }
+
+                var meta = MetadataIOHandler.getGson().fromJson(new InputStreamReader(stream), Options.class);
+                //var meta = MetadataIOHandler.fromStream(stream).orElse(null);
+                if (meta == null) {
+                    LOGGER.error(MARKER, "Corrupted jarjar_options.json");
+                    return;
+                }
+
+                for (var jar : meta.options()) {
+                    Path path = ClasspathLocator.getPathFromResource(self.getClassLoader(), jar.resource());
+                    if (path == null) {
+                        LOGGER.error(MARKER, "Failed to find JarJar option for {}", jar.resource());
+                        continue;
+                    }
+
+                    LOGGER.debug(MARKER, "Found JarJar Option: {}", path.toAbsolutePath());
+                    if (jar.nested())
+                        OPTIONS.put(path, new NestedOption(jar.id(), path, jar.layer(), jar.meta(), jar.deps()));
+                    else
+                        OPTIONS.put(path, new Option(jar.id(), path, jar.layer(), jar.meta(), jar.deps()));
+                }
+            } catch (Throwable e) {
+                LOGGER.error(MARKER, "Failed to read JarJar Options file", e);
+            }
+        }
+    }
+
+    static boolean isOption(Path path) {
+        loadOptions();
+        return OPTIONS.containsKey(path);
+    }
+
+    private static EarlyLoadingException fail(String message, @Nullable Throwable cause) {
+        LOGGER.error(MARKER, message);
+        return new EarlyLoadingException(message, cause, Collections.emptyList());
     }
 
     @Override
@@ -76,89 +305,7 @@ public class JarInJarDependencyLocator extends AbstractModProvider implements ID
         return IModFile.Type.GAMELIBRARY.name();
     }
 
-    protected Optional<IModFile> loadModFileFrom(IModFile file, Path path) {
-        try {
-            final Path pathInModFile = file.findResource(path.toString());
-            final URI filePathUri = new URI("jij:" + (pathInModFile.toAbsolutePath().toUri().getRawSchemeSpecificPart())).normalize();
-            final Map<String, ?> outerFsArgs = ImmutableMap.of("packagePath", pathInModFile);
-            final FileSystem zipFS = FileSystems.newFileSystem(filePathUri, outerFsArgs);
-            final Path pathInFS = zipFS.getPath("/");
-            final IModFile.Type parentType = file.getType();
-            final String modType;
-            if (parentType == IModFile.Type.LIBRARY || parentType == IModFile.Type.LANGPROVIDER) {
-                modType = IModFile.Type.LIBRARY.name();
-            } else {
-                modType = IModFile.Type.GAMELIBRARY.name();
-            }
-            return Optional.of(createMod(pathInFS, false, modType).file());
-        } catch (Exception e) {
-            LOGGER.error("Failed to load mod file {} from {}", path, file.getFileName());
-            final RuntimeException exception = new ModFileLoadingException("Failed to load mod file " + file.getFileName());
-            exception.initCause(e);
-            throw exception;
-        }
-    }
-
-    protected EarlyLoadingException exception(Collection<JarSelector.ResolutionFailureInformation<IModFile>> failedDependencies) {
-        final List<EarlyLoadingException.ExceptionData> errors = failedDependencies.stream()
-               .filter(entry -> !entry.sources().isEmpty()) //Should never be the case, but just to be sure
-               .map(this::buildExceptionData)
-               .toList();
-
-        return new EarlyLoadingException(failedDependencies.size() + " Dependency restrictions were not met.", null, errors);
-    }
-
-    @NotNull
-    private EarlyLoadingException.ExceptionData buildExceptionData(JarSelector.ResolutionFailureInformation<IModFile> entry) {
-        return new EarlyLoadingException.ExceptionData(
-                getErrorTranslationKey(entry),
-                entry.identifier().group() + ":" + entry.identifier().artifact(),
-                entry.sources()
-                     .stream()
-                     .flatMap(this::getModWithVersionRangeStream)
-                     .map(this::formatError)
-                     .collect(Collectors.joining(", "))
-        );
-    }
-
-    @NotNull
-    private String getErrorTranslationKey(JarSelector.ResolutionFailureInformation<IModFile> entry) {
-        return entry.failureReason() == JarSelector.FailureReason.VERSION_RESOLUTION_FAILED ?
-                       "fml.dependencyloading.conflictingdependencies" :
-                       "fml.dependencyloading.mismatchedcontaineddependencies";
-    }
-
-    @NotNull
-    private Stream<ModWithVersionRange> getModWithVersionRangeStream(JarSelector.SourceWithRequestedVersionRange<IModFile> file) {
-        return file.sources()
-                   .stream()
-                   .map(IModFile::getModFileInfo)
-                   .flatMap(modFileInfo -> modFileInfo.getMods().stream())
-                   .map(modInfo -> new ModWithVersionRange(modInfo, file.requestedVersionRange(), file.includedVersion()));
-    }
-
-    protected Optional<InputStream> loadResourceFromModFile(IModFile modFile, Path path) {
-        try {
-            var pathInModFile = modFile.findResource(path.toString());
-            if (!Files.exists(pathInModFile)) {
-                LOGGER.debug("Failed to load resource {} from {}, it does not contain dependency information.", path, modFile.getFileName());
-                return Optional.empty();
-            }
-            return Optional.of(Files.newInputStream(pathInModFile));
-        } catch (Exception e) {
-            LOGGER.error("Failed to load resource {} from mod {}, cause {}", path, modFile.getFileName(), e);
-            return Optional.empty();
-        }
-    }
-
-    @NotNull
-    private String formatError(ModWithVersionRange modWithVersionRange){
-        return YELLOW + modWithVersionRange.modInfo().getModId() + RESET + " - " +
-               RED + modWithVersionRange.versionRange().toString() + RESET + " - " +
-               GREEN + modWithVersionRange.artifactVersion().toString() + RESET;
-    }
-
-    protected String identifyMod(IModFile modFile) {
+    protected static String identifyMod(IModFile modFile) {
         if (modFile.getModFileInfo() != null && !modFile.getModInfos().isEmpty())
             return modFile.getModInfos().stream().map(IModInfo::getModId).collect(Collectors.joining());
 
@@ -169,5 +316,377 @@ public class JarInJarDependencyLocator extends AbstractModProvider implements ID
         return modFile.getFileName();
     }
 
-    private record ModWithVersionRange(IModInfo modInfo, VersionRange versionRange, ArtifactVersion artifactVersion) {}
+    private static final Entry FAILED = new Entry("FAILED ENTRY", Path.of(""), Type.LIBRARY, null);
+    private static sealed class Entry implements Comparable<Entry> {
+        final String id;
+        final Path path;
+        final Type type;
+        final @Nullable String coord;
+
+        private Entry(String id, Path path, Type type, @Nullable String coord) {
+            this.id = id;
+            this.path = path;
+            this.type = type;
+            this.coord = coord;
+        }
+
+        Path getFinalPath() {
+            return path;
+        }
+
+        void cleanup(boolean selected) {
+        }
+
+        @Override
+        public String toString() {
+            if (path.getFileName() == null)
+                return path.toUri().toString();
+            return path.getFileName().toString();
+        }
+
+        @Nullable
+        Path getResource(String path) {
+            return null;
+        }
+
+        @Override
+        public int compareTo(Entry o) {
+            return o.toString().compareTo(toString());
+        }
+    }
+
+    private static final class ModEntry extends Entry {
+        private final IModFile mod;
+
+        ModEntry(IModFile mod) {
+            super(identifyMod(mod), mod.getFilePath(), mod.getType(), null);
+            this.mod = mod;
+        }
+
+        @Override
+        @Nullable
+        Path getResource(String path) {
+            return mod.findResource(path);
+        }
+    }
+
+    private static sealed class Option extends Entry {
+        final ContainedJarMetadata meta;
+        final List<ContainedJarMetadata> deps;
+
+        private Option(String id, Path path, Type type, ContainedJarMetadata meta, List<ContainedJarMetadata> deps) {
+            super(id, path, type, meta.identifier().group() + ':' + meta.identifier().artifact());
+            this.meta = meta;
+            this.deps = deps;
+        }
+
+        public void addTo(Selector selector) {
+            selector.option(this, meta);
+        }
+    }
+
+    private static final class NestedOption extends Option {
+        private FileSystem zip;
+        private Path root;
+
+        private NestedOption(String id, Path path, Type type, ContainedJarMetadata meta, List<ContainedJarMetadata> deps) {
+            super(id, path, type, meta, deps);
+        }
+
+        @Override
+        public void addTo(Selector selector) {
+            super.addTo(selector);
+            selector.add(this);
+        }
+
+        @Override
+        void cleanup(boolean selected) {
+            if (this.zip != null) {
+                try {
+                    zip.close();
+                } catch (IOException e) {
+                    LOGGER.error(MARKER, "Failed to close unselected FileSystem {}", this, e);
+                }
+            }
+        }
+
+        @Nullable
+        Path getResource(String path) {
+            if (zip == null) {
+                try {
+                    this.zip = FileSystems.newFileSystem(this.path);
+                    this.root = zip.getRootDirectories().iterator().next();
+                } catch (IOException e) {
+                    LOGGER.error(MARKER, "Failed to open FileSystem for option root {}", this, e);
+                    return null;
+                }
+            }
+
+            var target = root.resolve(path);
+            if (Files.exists(target))
+                return target;
+
+            return null;
+        }
+    }
+
+
+    private static final class Nested extends Entry {
+        private final Entry parent;
+        private final String nestedPath;
+        private final Path zipPath;
+
+        Nested(String id, Path path, Type type, String coords, Entry parent, String nestedPath, Path zipPath) {
+            super(id, path, type, coords);
+            this.parent = parent;
+            this.nestedPath = nestedPath;
+            this.zipPath = zipPath;
+        }
+
+        /*
+         * Due to a bug in Mixin, anything that is not on the DefaultFileSystem MUST be a directory.
+         * Or else it can't resolve resources correctly. So for anything we put on the roimfs we need
+         * to return the nested zip file system.
+         *
+         * This will be an annoying to backport, but we can cross that bridge when we come to it.
+         *
+         * See: https://github.com/SpongePowered/Mixin/blob/4053421aa10aaac6127d969028a29c94fe3054f6/src/main/java/org/spongepowered/asm/launch/platform/MainAttributes.java#L102
+         */
+        @Override
+        public Path getFinalPath() {
+            return zipPath;
+        }
+
+        @Override
+        void cleanup(boolean selected) {
+            if (selected)
+                return;
+
+            LOGGER.info(MARKER, "Closeing unselected FileSystem {}", this);
+            try {
+                zipPath.getFileSystem().close();
+                path.getFileSystem().close();
+            } catch (IOException e) {
+                LOGGER.error(MARKER, "Failed to close unselected FileSystem {}", this, e);
+            }
+        }
+
+        @Override
+        @Nullable
+        Path getResource(String path) {
+            return zipPath.resolve(path);
+        }
+
+        @Override
+        public String toString() {
+            return parent + "!/" + nestedPath;
+        }
+    }
+
+    private record Key(Entry parent, String path) {}
+
+    private final class Selector extends JarSelector<Entry> {
+        private final HashMap<Key, Entry> entries = new HashMap<>();
+        private final HashMap<Entry, HashMap<String, String>> children = new HashMap<>();
+
+        private Selector(Iterable<IModFile> mods) {
+            for (var mod : mods)
+                this.force(new ModEntry(mod));
+        }
+
+        @Override
+        public void force(Entry entry) {
+            super.force(entry);
+            entries.put(new Key(entry, ""), entry);
+        }
+
+        @Override
+        public void option(Entry entry, ContainedJarMetadata meta) {
+            super.option(entry, meta);
+            entries.put(new Key(entry, ""), entry);
+        }
+
+        @Override
+        public void add(Entry entry) {
+            super.add(entry);
+            entries.put(new Key(entry, ""), entry);
+        }
+
+        @Override
+        @Nullable
+        protected InputStream getResource(Entry source, String path) {
+            try {
+                Path target = source.getResource(path);
+                if (target == null || !Files.exists(target)) {
+                    LOGGER.debug(MARKER, "Failed to load resource {} from {}, it does not contain dependency information.", path, source);
+                    return null;
+                }
+
+                // Read the metadata file and store identifiers so we can group them later.
+                if (JarSelector.CONTAINED_JARS_METADATA_PATH.equals(path)) {
+                    try (var is = Files.newInputStream(target)) {
+                        var meta = MetadataIOHandler.fromStream(is).orElse(null);
+                        if (meta == null)
+                            return Files.newInputStream(target);
+                        var children = new HashMap<String, String>();
+                        for (var child : meta.jars())
+                            children.put(child.path().replace('\\', '/'), child.identifier().group() + ':' + child.identifier().artifact());
+                        this.children.put(source, children);
+                    }
+                }
+
+                return Files.newInputStream(target);
+            } catch (Exception e) {
+                LOGGER.error(MARKER, "Failed to load resource {} from {}, cause {}", path, source, e);
+                return null;
+            }
+        }
+
+
+        @Override
+        protected Entry getNested(Entry source, String path) {
+            var cleaned = path.replace('\\', '/');
+            var key = new Key(source, cleaned);
+            var entry = entries.get(key);
+            if (entry == null) {
+                entry = createNested(source, path, cleaned);
+                if (entry == null)
+                    entry = FAILED;
+                entries.put(key, entry);
+            }
+            return entry == FAILED ? null : entry;
+        }
+
+        private Entry createNested(Entry source, String path, String cleaned) {
+            var targetPath = source.getResource(path);
+
+            if (targetPath == null || !Files.isRegularFile(targetPath))
+                return null;
+
+            Path roimfsPath = null;
+            Path zipPath = null;
+            try {
+                // Lets copy the uncompressed file to memory, and then create a ReadOnlyInMemorryFileSystem for it, this allows us to reference it by URI.
+                // Which is needed because a lot of things require navigation via URI.
+                // And ZipFileSystem only caches the FileSystem instance when accessed via URI.
+                byte[] data = Files.readAllBytes(targetPath);
+                String filename = targetPath.getFileName().toString();
+                URI uri = new URI(ROIMFS, "jar-jar-" + nextId() + "/" + filename, null);
+                var roimfs = FileSystems.newFileSystem(uri, Collections.singletonMap("data", data));
+                roimfsPath = roimfs.getPath(filename);
+                var zip = FileSystems.newFileSystem(new URI("jar:" + roimfsPath.toUri()), Collections.emptyMap());
+                zipPath = zip.getRootDirectories().iterator().next(); // Get first root, which on ZipFileSystem is the only root
+            } catch (IOException | URISyntaxException e) {
+                LOGGER.error(MARKER, "Failed to create FileSystem for nested jar {}", source, e);
+                return null;
+            }
+
+            var mf = new Manifest();
+            var mfPath = zipPath.resolve(JarFile.MANIFEST_NAME);
+            if (Files.exists(mfPath)) {
+                try (var is = Files.newInputStream(mfPath)) {
+                    mf = new Manifest(is);
+                } catch (IOException e) {
+                    LOGGER.error(MARKER, "Failed to read manifest from {}", source, e);
+                }
+            }
+
+            IModFile.Type type = null;
+            String id = null;
+            var tomlPath = zipPath.resolve(MODS_TOML);
+            if (Files.exists(tomlPath)) {
+                var cfg = FileConfig.builder(tomlPath).build();
+                cfg.load();
+                cfg.close();
+                if (cfg.getOrElse("mods", null) instanceof Collection collection) {
+                    @SuppressWarnings("unchecked")
+                    var mods = (Collection<UnmodifiableConfig>)collection;
+                    if (!mods.isEmpty()) {
+                        var first = mods.iterator().next();
+                        var modId = first.getOrElse("modId", null);
+                        if (modId instanceof String str)
+                            id = str;
+                    }
+                }
+                var value = mf.getMainAttributes().getValue(ModFile.TYPE);
+                if (value != null)
+                    type = IModFile.Type.valueOf(value);
+                else
+                    type = IModFile.Type.MOD;
+            } else {
+                var value = mf.getMainAttributes().getValue(ModFile.TYPE);
+                if (value != null)
+                    type = IModFile.Type.valueOf(value);
+                else {
+                    // No mods.toml, no entry value, so decide based on the container's type
+                    if (source.type == IModFile.Type.LIBRARY || source.type == IModFile.Type.LANGPROVIDER)
+                        type = IModFile.Type.LIBRARY;
+                    else
+                        type = IModFile.Type.GAMELIBRARY;
+                }
+            }
+
+            if (id == null) {
+                var modulePath = zipPath.resolve(MODULE_INFO);
+                if (Files.exists(modulePath)) {
+                    try (var is = Files.newInputStream(modulePath)) {
+                        var module = ModuleDescriptor.read(is);
+                        id = module.name();
+                    } catch (IOException e) {
+                        LOGGER.error(MARKER, "Failed to read module-info.class from {}", source, e);
+                    }
+                }
+            }
+
+            if (id == null)
+                id = mf.getMainAttributes().getValue("Automatic-Module-Name");
+
+            if (id == null)
+                id = Path.of(path).getFileName().toString();
+
+            String coords = null;
+            var child = this.children.get(source);
+            if (child != null)
+                coords = child.get(cleaned);
+
+            return new Nested(id, roimfsPath, type, coords, source, cleaned, zipPath);
+        }
+
+        @Override
+        protected String getIdentifier(Entry entry) {
+            return entry.id;
+        }
+
+        @Override
+        protected Throwable getFailureException(Collection<ResolutionFailureInformation<Entry>> failures) {
+            var errors = new ArrayList<ExceptionData>();
+            for (var failure : failures) {
+                var message = failure.failureReason() == JarSelector.FailureReason.VERSION_RESOLUTION_FAILED ? "fml.dependencyloading.conflictingdependencies" : "fml.dependencyloading.mismatchedcontaineddependencies";
+                var joiner = new StringJoiner(", ");
+                for (var source : failure.sources()) {
+                    String paths = null;
+                    if (source.sources().size() == 0) {
+                        paths = "[No Sources]";
+                    } else if (source.sources().size() == 1) {
+                        var entry = source.sources().iterator().next();
+                        paths = entry.toString();
+                    } else {
+                        var j = new StringJoiner(", ", "[", "]");
+                        for (var entry : source.sources())
+                            j.add(entry.toString());
+                        paths = j.toString();
+                    }
+
+                    var error = YELLOW + paths + RESET + " - " +
+                                RED + source.requestedVersionRange() + RESET + " - " +
+                                GREEN + source.includedVersion() + RESET;
+                    joiner.add(error);
+                }
+
+                errors.add(new ExceptionData(message, failure.identifier().group() + ":" + failure.identifier().artifact(), joiner.toString()));
+            }
+
+            return new EarlyLoadingException(failures.size() + " Dependency restrictions were not met.", null, errors);
+        }
+    }
 }

fmlloader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/MinecraftLocator.java

@@ -18,24 +18,22 @@ import java.util.List;
 import org.jetbrains.annotations.ApiStatus;
 
 @ApiStatus.Internal
-public class MinecraftLocator extends AbstractModProvider implements IModLocator {
+public final class MinecraftLocator extends AbstractModProvider implements IModLocator {
     @Override
     public List<IModLocator.ModFileOrException> scanMods() {
         var minecraft = FMLLoader.getLaunchHandler().getMinecraftPaths();
+        var paths = minecraft.toArray(Path[]::new);
 
         // Minecraft itself.
         var meta = new ModJarMetadata();
-        var mcjar = SecureJar.from(
-            jar -> meta,
-            minecraft.toArray(Path[]::new)
-        );
-        var mc = ModFileFactory.FACTORY.build(mcjar, this, this::buildMinecraftTOML);
+        var mcjar = SecureJar.from(jar -> meta, paths);
+        var mc = ModFileFactory.FACTORY.build(mcjar, this, MinecraftLocator::buildMinecraftTOML);
         meta.setModFile(mc);
 
         return List.of(new ModFileOrException(mc, null));
     }
 
-    private IModFileInfo buildMinecraftTOML(final IModFile iModFile) {
+    private static IModFileInfo buildMinecraftTOML(final IModFile iModFile) {
         // We haven't changed this in years, and I can't be asked right now to special case this one file in the path.
         final var conf = Config.inMemory();
         conf.set("modLoader", "minecraft");
@@ -45,14 +43,14 @@ public class MinecraftLocator extends AbstractModProvider implements IModLocator
         mods.set("modId", "minecraft");
         mods.set("version", FMLLoader.versionInfo().mcVersion());
         mods.set("displayName", "Minecraft");
-        mods.set("logoFile", "mcplogo.png");
-        mods.set("credits", "Mojang, deobfuscated by MCP");
-        mods.set("authors", "MCP: Searge,ProfMobius,IngisKahn,Fesh0r,ZeuX,R4wk,LexManos,Bspkrs");
-        mods.set("description", "Minecraft, decompiled and deobfuscated with MCP technology");
+        //mods.set("logoFile", "mcplogo.png");
+        //mods.set("credits", "Mojang, deobfuscated by MCP");
+        //mods.set("authors", "MCP: Searge,ProfMobius,IngisKahn,Fesh0r,ZeuX,R4wk,LexManos,Bspkrs");
+        mods.set("description", "The base Minecraft game, published by Mojang decompiled and deobfuscated by Forge");
         conf.set("mods", List.of(mods));
 
         var configWrapper = new NightConfigWrapper(conf);
-        return new ModFileInfo((ModFile)iModFile, configWrapper, configWrapper::setFile, List.of());
+        return new ModFileInfo((ModFile) iModFile, configWrapper, configWrapper::setFile);
     }
 
     @Override

fmlloader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/ModDiscoverer.java

@@ -5,8 +5,6 @@
 
 package net.minecraftforge.fml.loading.moddiscovery;
 
-import com.google.common.collect.ImmutableList;
-import com.google.common.collect.Maps;
 import com.mojang.logging.LogUtils;
 import cpw.mods.modlauncher.Launcher;
 import cpw.mods.modlauncher.api.IModuleLayerManager;
@@ -28,6 +26,7 @@ import org.jetbrains.annotations.ApiStatus;
 import org.slf4j.Logger;
 
 import java.util.ArrayList;
+import java.util.EnumMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -35,38 +34,36 @@ import java.util.ServiceLoader;
 import java.util.stream.Collectors;
 
 @ApiStatus.Internal
-public class ModDiscoverer {
-    private static final Logger LOGGER = LogUtils.getLogger();
-    private final ServiceLoader<IModLocator> modLocators;
-    private final ServiceLoader<IDependencyLocator> dependencyLocators;
-    private final List<IModLocator>          modLocatorList;
-    private final List<IDependencyLocator>   dependencyLocatorList;
+public final class ModDiscoverer {
+    private ModDiscoverer() {}
 
-    public ModDiscoverer(Map<String, ?> arguments) {
+    private static final Logger LOGGER = LogUtils.getLogger();
+
+    @SuppressWarnings("removal")
+    public static ModValidator discoverMods(Map<String, ?> arguments) {
         Launcher.INSTANCE.environment().computePropertyIfAbsent(Environment.Keys.MODDIRECTORYFACTORY.get(), v->ModsFolderLocator::new);
         Launcher.INSTANCE.environment().computePropertyIfAbsent(Environment.Keys.PROGRESSMESSAGE.get(), v-> StartupNotificationManager.locatorConsumer().orElseGet(()-> s->{}));
         final var moduleLayerManager = Launcher.INSTANCE.environment().findModuleLayerManager().orElseThrow();
-        modLocators = ServiceLoader.load(moduleLayerManager.getLayer(IModuleLayerManager.Layer.SERVICE).orElseThrow(), IModLocator.class);
-        dependencyLocators = ServiceLoader.load(moduleLayerManager.getLayer(IModuleLayerManager.Layer.SERVICE).orElseThrow(), IDependencyLocator.class);
-        modLocatorList = ServiceLoaderUtils.streamServiceLoader(()-> modLocators, sce->LOGGER.error("Failed to load mod locator list", sce)).collect(Collectors.toList());
-        modLocatorList.forEach(l->l.initArguments(arguments));
-        dependencyLocatorList = ServiceLoaderUtils.streamServiceLoader(()-> dependencyLocators, sce->LOGGER.error("Failed to load dependency locator list", sce)).collect(Collectors.toList());
-        dependencyLocatorList.forEach(l->l.initArguments(arguments));
-        if (LOGGER.isDebugEnabled(LogMarkers.CORE))
-        {
+        ServiceLoader<IModLocator> modLocators = ServiceLoader.load(moduleLayerManager.getLayer(IModuleLayerManager.Layer.SERVICE).orElseThrow(), IModLocator.class);
+        ServiceLoader<IDependencyLocator> dependencyLocators = ServiceLoader.load(moduleLayerManager.getLayer(IModuleLayerManager.Layer.SERVICE).orElseThrow(), IDependencyLocator.class);
+        List<IModLocator> modLocatorList = ServiceLoaderUtils.streamWithErrorHandling(modLocators, sce -> LOGGER.error("Failed to load mod locator list", sce)).toList();
+        for (IModLocator iModLocator : modLocatorList) {
+            iModLocator.initArguments(arguments);
+        }
+        List<IDependencyLocator> dependencyLocatorList = ServiceLoaderUtils.streamWithErrorHandling(dependencyLocators, sce -> LOGGER.error("Failed to load dependency locator list", sce)).toList();
+        for (IDependencyLocator l : dependencyLocatorList) {
+            l.initArguments(arguments);
+        }
+        if (LOGGER.isDebugEnabled(LogMarkers.CORE)) {
             LOGGER.debug(LogMarkers.CORE, "Found Mod Locators : {}", modLocatorList.stream()
-                                                                       .map(modLocator -> "(%s:%s)".formatted(modLocator.name(),
-                                                                         modLocator.getClass().getPackage().getImplementationVersion())).collect(Collectors.joining(",")));
-        }
-        if (LOGGER.isDebugEnabled(LogMarkers.CORE))
-        {
-            LOGGER.debug(LogMarkers.CORE, "Found Dependency Locators : {}", dependencyLocatorList.stream()
-                                                                       .map(dependencyLocator -> "(%s:%s)".formatted(dependencyLocator.name(),
-                                                                         dependencyLocator.getClass().getPackage().getImplementationVersion())).collect(Collectors.joining(",")));
-        }
-    }
+                    .map(modLocator -> "(%s:%s)".formatted(modLocator.name(),
+                            modLocator.getClass().getPackage().getImplementationVersion())).collect(Collectors.joining(",")));
+
+            LOGGER.debug(LogMarkers.CORE, "Found Dependency Locators : {}", dependencyLocatorList.stream()
+                    .map(dependencyLocator -> "(%s:%s)".formatted(dependencyLocator.name(),
+                            dependencyLocator.getClass().getPackage().getImplementationVersion())).collect(Collectors.joining(",")));
+        }
 
-    public ModValidator discoverMods() {
         LOGGER.debug(LogMarkers.SCAN,"Scanning for mods and other resources to load. We know {} ways to find mods", modLocatorList.size());
         List<ModFile> loadedFiles = new ArrayList<>();
         List<EarlyLoadingException.ExceptionData> discoveryErrorData = new ArrayList<>();
@@ -114,7 +111,7 @@ public class ModDiscoverer {
                 }
 
                 LOGGER.debug(LogMarkers.SCAN, "Locator {} found {} valid mod files", locator, locatedFiles.size());
-                handleLocatedFiles(loadedFiles, locatedFiles);
+                handleLocatedFiles(loadedFiles, locatedFiles, locator);
             } catch (InvalidModFileException imfe) {
                 // We don't generally expect this exception, since it should come from the candidates stream above and be handled in the Locator, but just in case.
                 LOGGER.error(LogMarkers.SCAN, "Locator {} found an invalid mod file {}", locator, imfe.getBrokenFile(), imfe);
@@ -126,15 +123,14 @@ public class ModDiscoverer {
         }
 
         //First processing run of the mod list. Any duplicates will cause resolution failure and dependency loading will be skipped.
-        Map<IModFile.Type, List<ModFile>> modFilesMap = Maps.newHashMap();
+        Map<IModFile.Type, List<ModFile>> modFilesMap = new EnumMap<>(IModFile.Type.class);
         try {
-            final UniqueModListBuilder modsUniqueListBuilder = new UniqueModListBuilder(loadedFiles);
-            final UniqueModListBuilder.UniqueModListData uniqueModsData = modsUniqueListBuilder.buildUniqueList();
+            final UniqueModListBuilder.UniqueModListData uniqueModsData = UniqueModListBuilder.buildUniqueList(loadedFiles);
 
             //Grab the temporary results.
             //This allows loading to continue to a base state, in case dependency loading fails.
             modFilesMap = uniqueModsData.modFiles().stream()
-                            .collect(Collectors.groupingBy(IModFile::getType));
+                            .collect(Collectors.groupingBy(IModFile::getType, () -> new EnumMap<>(IModFile.Type.class), Collectors.toList()));
             loadedFiles = uniqueModsData.modFiles();
         }
         catch (EarlyLoadingException exception) {
@@ -149,14 +145,10 @@ public class ModDiscoverer {
             for (IDependencyLocator locator : dependencyLocatorList) {
                 try {
                     LOGGER.debug(LogMarkers.SCAN,"Trying locator {}", locator);
-                    final List<IModFile> locatedMods = ImmutableList.copyOf(loadedFiles);
+                    final List<IModFile> locatedMods = List.copyOf(loadedFiles);
 
                     var locatedFiles = locator.scanMods(locatedMods);
-                    if (locatedFiles.stream().anyMatch(file -> !(file instanceof ModFile))) {
-                        LOGGER.error(LogMarkers.SCAN, "A dependency locator returned a file which is not a ModFile instance!. They will be skipped!");
-                    }
-
-                    handleLocatedFiles(loadedFiles, locatedFiles);
+                    handleLocatedFiles(loadedFiles, locatedFiles, locator);
                 }
                 catch (EarlyLoadingException exception) {
                     LOGGER.error(LogMarkers.SCAN, "Failed to load dependencies with locator {}", locator, exception);
@@ -166,16 +158,15 @@ public class ModDiscoverer {
 
             //Second processing run of the mod list. Any duplicates will cause resolution failure and only the mods list will be loaded.
             try {
-                final UniqueModListBuilder modsAndDependenciesUniqueListBuilder = new UniqueModListBuilder(loadedFiles);
-                final UniqueModListBuilder.UniqueModListData uniqueModsAndDependenciesData = modsAndDependenciesUniqueListBuilder.buildUniqueList();
+                final UniqueModListBuilder.UniqueModListData uniqueModsAndDependenciesData = UniqueModListBuilder.buildUniqueList(loadedFiles);
 
                 //We now only need the mod files map, not the list.
                 modFilesMap = uniqueModsAndDependenciesData.modFiles().stream()
-                                .collect(Collectors.groupingBy(IModFile::getType));
+                                .collect(Collectors.groupingBy(IModFile::getType, () -> new EnumMap<>(IModFile.Type.class), Collectors.toList()));
             } catch (EarlyLoadingException exception) {
                 LOGGER.error(LogMarkers.SCAN, "Failed to build unique mod list after dependency discovery.", exception);
                 discoveryErrorData.addAll(exception.getAllData());
-                modFilesMap = loadedFiles.stream().collect(Collectors.groupingBy(IModFile::getType));
+                modFilesMap = loadedFiles.stream().collect(Collectors.groupingBy(IModFile::getType, () -> new EnumMap<>(IModFile.Type.class), Collectors.toList()));
             }
         }
         else {
@@ -190,12 +181,14 @@ public class ModDiscoverer {
         return validator;
     }
 
-    private void handleLocatedFiles(final List<ModFile> loadedFiles, final List<IModFile> locatedFiles)
-    {
-        var locatedModFiles = locatedFiles.stream().filter(ModFile.class::isInstance).map(ModFile.class::cast).toList();
-        for (IModFile mf : locatedModFiles) {
-            LOGGER.info(LogMarkers.SCAN, "Found mod file {} of type {} with provider {}", mf.getFileName(), mf.getType(), mf.getProvider());
+    private static void handleLocatedFiles(final List<ModFile> loadedFiles, final List<IModFile> locatedFiles, final Object locator) {
+        for (IModFile mf : locatedFiles) {
+            if (mf instanceof ModFile modFile) {
+                LOGGER.info(LogMarkers.SCAN, "Found mod file {} of type {} with provider {}", mf.getFileName(), mf.getType(), mf.getProvider());
+                loadedFiles.add(modFile);
+            } else {
+                LOGGER.error(LogMarkers.SCAN, "Skipping mod file {} found by {}, as it was not a ModFile instance!", mf.getFileName(), locator);
+            }
         }
-        loadedFiles.addAll(locatedModFiles);
     }
 }

fmlloader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/ModFile.java

@@ -21,13 +21,13 @@ import org.apache.maven.artifact.versioning.ArtifactVersion;
 import org.apache.maven.artifact.versioning.DefaultArtifactVersion;
 import org.slf4j.Logger;
 
+import java.nio.file.FileSystems;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
-import java.util.Objects;
 import java.util.Optional;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutionException;
@@ -39,15 +39,13 @@ import java.util.jar.Manifest;
 public class ModFile implements IModFile {
     private static final Logger LOGGER = LogUtils.getLogger();
     private final String jarVersion;
-    private final ModFileFactory.ModFileInfoParser parser;
     private Map<String, Object> fileProperties;
     private List<IModLanguageProvider> loaders;
     private Throwable scanError;
     private final SecureJar jar;
     private final Type modFileType;
-    private final Manifest     manifest;
     private final IModProvider provider;
-    private       IModFileInfo modFileInfo;
+    private final IModFileInfo modFileInfo;
     private ModFileScanData fileModFileScanData;
     private CompletableFuture<ModFileScanData> futureScanResult;
     private List<CoreModFile> coreMods;
@@ -63,12 +61,11 @@ public class ModFile implements IModFile {
     public ModFile(final SecureJar jar, final IModProvider provider, final ModFileFactory.ModFileInfoParser parser, String type) {
         this.provider = provider;
         this.jar = jar;
-        this.parser = parser;
 
-        manifest = this.jar.moduleDataProvider().getManifest();
+        var manifest = this.jar.moduleDataProvider().getManifest();
         modFileType = Type.valueOf(type);
         jarVersion = Optional.ofNullable(manifest.getMainAttributes().getValue(Attributes.Name.IMPLEMENTATION_VERSION)).orElse("0.0NONE");
-        this.modFileInfo = ModFileParser.readModList(this, this.parser);
+        this.modFileInfo = ModFileParser.readModList(this, parser);
     }
 
     @Override
@@ -100,11 +97,13 @@ public class ModFile implements IModFile {
     }
 
     public boolean identifyMods() {
-        this.modFileInfo = ModFileParser.readModList(this, this.parser);
         if (this.modFileInfo == null) return this.getType() != Type.MOD;
-        LOGGER.debug(LogMarkers.LOADING,"Loading mod file {} with languages {}", this.getFilePath(), this.modFileInfo.requiredLanguageLoaders());
+        LOGGER.debug(LogMarkers.LOADING,"Loading mod file {} with languages {}", this.getFileName(), this.modFileInfo.requiredLanguageLoaders());
         this.coreMods = ModFileParser.getCoreMods(this);
-        this.coreMods.forEach(mi-> LOGGER.debug(LogMarkers.LOADING,"Found coremod {}", mi.getPath()));
+        if (!this.coreMods.isEmpty())
+            LOGGER.warn("Mod file {} contains javascript coremods! JS CoreMods are deprecated and will be removed in a future release. Consider using Mixin or ModLauncher transformers.", this.getFileName());
+        for (var mi : this.coreMods)
+            LOGGER.debug(LogMarkers.LOADING, "Found coremod {}", mi.getPath());
         this.accessTransformer = findResource("META-INF", "accesstransformer.cfg");
         return true;
     }
@@ -180,12 +179,28 @@ public class ModFile implements IModFile {
 
     @Override
     public String toString() {
-        return "Mod File: " + Objects.toString(this.jar.getPrimaryPath());
+        var path = getFilePath();
+        return "Mod File: " + path == null ? "null" : path.toUri().toString();
     }
 
     @Override
     public String getFileName() {
-        return getFilePath().getFileName().toString();
+        // This is only used for debugging, so lets try and make it a useful debug
+        var path = getFilePath();
+        var filename = path.getFileName();
+
+        // ZipFileSystem toString will return the outer file path
+        var ret = filename == null ? path.getFileSystem().toString() : filename.toString();
+
+        // If it's a directory on the default file system, return the full path
+        if (Files.isDirectory(path) && path.getFileSystem() == FileSystems.getDefault())
+            ret = path.toAbsolutePath().toString();
+
+        // If we are in a FileSystem 'root' like UnionFS, return the full uri
+        if (ret.isEmpty() || ret.equals("/"))
+            ret = path.toUri().toString();
+
+        return ret;
     }
 
     @Override

fmlloader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/ModFileInfo.java

@@ -104,11 +104,11 @@ public class ModFileInfo implements IModFileInfo, IConfigurable {
         this.modFile.setFileProperties(this.properties);
 
         final List<? extends IConfigurable> modConfigs = config.getConfigList("mods");
-        if (modConfigs.isEmpty())
+        if (modConfigs == null || modConfigs.isEmpty())
             throw new InvalidModFileException("Missing mods list", this);
 
         this.mods = modConfigs.stream()
-                .map(mi-> (IModInfo)new ModInfo(this, mi))
+                .map(mi -> (IModInfo) ModInfo.of(this, mi))
                 .toList();
 
         if (LOGGER.isDebugEnabled(LogMarkers.LOADING)) {
@@ -158,6 +158,11 @@ public class ModFileInfo implements IModFileInfo, IConfigurable {
         return this.showAsDataPack;
     }
 
+    @Override
+    public <T> Optional<T> getConfigElement(final String key) {
+        return this.config.getConfigElement(key);
+    }
+
     @Override
     public <T> Optional<T> getConfigElement(final String... key) {
         return this.config.getConfigElement(key);
@@ -186,7 +191,7 @@ public class ModFileInfo implements IModFileInfo, IConfigurable {
         return Strings.isNullOrEmpty(license);
     }
 
-    private final char[] HEX = "0123456789ABCDEF".toCharArray();
+    private static final char[] HEX = "0123456789ABCDEF".toCharArray();
     public Optional<String> getCodeSigningFingerprint() {
         var signers = this.modFile.getSecureJar().getManifestSigners();
         if (signers == null)
@@ -254,12 +259,12 @@ public class ModFileInfo implements IModFileInfo, IConfigurable {
 
     @Override
     public String moduleName() {
-        return getMods().get(0).getModId();
+        return this.modFile.getSecureJar().name();
     }
 
     @Override
     public String versionString()  {
-        return getMods().get(0).getVersion().toString();
+        return getMods().getFirst().getVersion().toString();
     }
 
     @Override

fmlloader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/ModInfo.java

@@ -27,211 +27,181 @@ import java.util.Optional;
 import java.util.regex.Pattern;
 
 @ApiStatus.Internal
-public class ModInfo implements IModInfo, IConfigurable {
+public record ModInfo(
+        ModFileInfo getOwningFile,
+        IConfigurable getConfig,
+
+        String getModId,
+        String getNamespace,
+        ArtifactVersion getVersion,
+
+        String getDisplayName,
+        String getDescription,
+        Optional<String> getLogoFile,
+        boolean getLogoBlur,
+        Optional<URL> getUpdateURL,
+        Optional<URL> getModURL,
+
+        Holder<List<? extends ModVersion>> dependencies,
+        Holder<List<ForgeFeature.Bound>> forgeFeatures,
+        Map<String, Object> getModProperties
+) implements IModInfo, IConfigurable {
     private static final Logger LOGGER = LogUtils.getLogger();
     private static final DefaultArtifactVersion DEFAULT_VERSION = new DefaultArtifactVersion("1");
     private static final Pattern VALID_MODID = Pattern.compile("^[a-z][a-z0-9_]{1,63}$");
     private static final Pattern VALID_NAMESPACE = Pattern.compile("^[a-z][a-z0-9_.-]{1,63}$");
     private static final Pattern VALID_VERSION = Pattern.compile("^\\d+.*");
 
-    private final ModFileInfo owningFile;
-    private final String modId;
-    private final String namespace;
-    private final ArtifactVersion version;
-    private final String displayName;
-    private final String description;
-    private final Optional<String> logoFile;
-    private final boolean logoBlur;
-    private final Optional<URL> updateJSONURL;
-    private final List<? extends IModInfo.ModVersion> dependencies;
-
-    private final List<ForgeFeature.Bound> features;
-    private final Map<String,Object> properties;
-    private final IConfigurable config;
-    private final Optional<URL> modUrl;
-
-    public ModInfo(final ModFileInfo owningFile, final IConfigurable config) {
-        Optional<ModFileInfo> ownFile = Optional.ofNullable(owningFile);
-        this.owningFile = owningFile;
-        this.config = config;
-
+    public static ModInfo of(ModFileInfo owningFile, IConfigurable config) {
         // These are sourced from the mod specific [[mod]] entry
-        this.modId = config.<String>getConfigElement("modId")
-                .orElseThrow(() -> new InvalidModFileException("Missing modId", owningFile));
+        String modId = config.<String>getConfigElement("modId").orElse(null);
+        if (modId == null)
+            throw new InvalidModFileException("Missing modId", owningFile);
 
         // verify we have a valid modid
-        if (!VALID_MODID.matcher(this.modId).matches()) {
-            LOGGER.error(LogUtils.FATAL_MARKER, "Invalid modId found in file {} - {} does not match the standard: {}", this.owningFile.getFile().getFilePath(), this.modId, VALID_MODID.pattern());
-            throw new InvalidModFileException("Invalid modId found : " + this.modId, owningFile);
+        if (!VALID_MODID.matcher(modId).matches()) {
+            LOGGER.error(LogUtils.FATAL_MARKER, "Invalid modId found in file {} - {} does not match the standard: {}", owningFile.getFile().getFilePath(), modId, VALID_MODID.pattern());
+            throw new InvalidModFileException("Invalid modId found : " + modId, owningFile);
         }
 
-        this.namespace = config.<String>getConfigElement("namespace")
-                .orElse(this.modId);
+        String namespace = config.<String>getConfigElement("namespace")
+                .orElse(modId);
 
         // verify our namespace is valid
-        if (!VALID_NAMESPACE.matcher(this.namespace).matches()) {
-            LOGGER.error(LogUtils.FATAL_MARKER, "Invalid override namespace found in file {} - {} does not match the standard: {}", this.owningFile.getFile().getFilePath(), this.namespace, VALID_NAMESPACE.pattern());
-            throw new InvalidModFileException("Invalid override namespace found : " + this.namespace, owningFile);
+        if (!VALID_NAMESPACE.matcher(namespace).matches()) {
+            LOGGER.error(LogUtils.FATAL_MARKER, "Invalid override namespace found in file {} - {} does not match the standard: {}", owningFile.getFile().getFilePath(), namespace, VALID_NAMESPACE.pattern());
+            throw new InvalidModFileException("Invalid override namespace found : " + namespace, owningFile);
         }
 
-        this.version = config.<String>getConfigElement("version")
-                .map(s -> StringSubstitutor.replace(s, ownFile.map(ModFileInfo::getFile).orElse(null)))
+        ArtifactVersion version = config.<String>getConfigElement("version")
+                .map(s -> StringSubstitutor.replace(s, owningFile.getFile()))
                 .map(DefaultArtifactVersion::new)
                 .orElse(DEFAULT_VERSION);
 
         // verify we have a valid mod version
-        if (!VALID_VERSION.matcher(this.version.toString()).matches())
-            throw new InvalidModFileException("Illegal version number specified " + this.version, this.getOwningFile());
+        if (!VALID_VERSION.matcher(version.toString()).matches())
+            throw new InvalidModFileException("Illegal version number specified " + version, owningFile);
 
         // The remaining properties all default to sensible values and are not essential
-        this.displayName = config.<String>getConfigElement("displayName")
-                .orElse(this.modId);
-        this.description = config.<String>getConfigElement("description")
+        String displayName = config.<String>getConfigElement("displayName")
+                .orElse(modId);
+
+        String description = config.<String>getConfigElement("description")
                 .orElse("MISSING DESCRIPTION")
                 .replace("\r\n", "\n").stripIndent();
-        this.logoFile = Optional.ofNullable(config.<String>getConfigElement("logoFile")
-                .orElseGet(() -> ownFile.flatMap(mf -> mf.<String>getConfigElement("logoFile"))
-                        .orElse(null)));
-        this.logoBlur = config.<Boolean>getConfigElement("logoBlur")
-                .orElseGet(() -> ownFile.flatMap(mf -> mf.<Boolean>getConfigElement("logoBlur"))
-                        .orElse(true));
-        this.updateJSONURL = config.<String>getConfigElement("updateJSONURL")
-                .map(StringUtils::toURL);
-        this.modUrl = config.<String>getConfigElement("modUrl")
+
+        Optional<String> logoFile = Optional.ofNullable(
+                config.<String>getConfigElement("logoFile")
+                        .orElseGet(() -> owningFile.<String>getConfigElement("logoFile").orElse(null))
+        );
+
+        Boolean logoBlur = config.<Boolean>getConfigElement("logoBlur").orElse(null);
+        if (logoBlur == null)
+            logoBlur = owningFile.<Boolean>getConfigElement("logoBlur").orElse(true);
+
+        Optional<URL> updateJSONURL = config.<String>getConfigElement("updateJSONURL")
                 .map(StringUtils::toURL);
 
-        // These are sourced from the file rather than the mod-specific block, but with a modid tag
-        if (ownFile.isEmpty()) {
-            this.dependencies = Collections.emptyList();
-            this.features = Collections.emptyList();
-            this.properties = Collections.emptyMap();
-        } else {
-            var deps = this.owningFile.getConfigList("dependencies", this.modId);
-            if (deps == null || deps.isEmpty()) {
-                this.dependencies = Collections.emptyList();
-            } else {
-                var tmp = new ArrayList<ModVersion>();
-                for (var dep : deps)
-                    tmp.add(new ModVersion(this, dep));
-                this.dependencies = Collections.unmodifiableList(tmp);
-            }
+        Optional<URL> modUrl = config.<String>getConfigElement("modUrl")
+                .map(StringUtils::toURL);
 
-            var feats = this.owningFile.<Map<String, Object>>getConfigElement("features", this.modId).orElse(null);
-            if (feats == null) {
-                this.features = Collections.emptyList();
-            } else {
-                var tmp = new ArrayList<ForgeFeature.Bound>();
-                for (var entry : feats.entrySet()) {
-                    if (!(entry.getValue() instanceof String val))
-                        throw new InvalidModFileException("Invalid feature bound {" + entry.getValue() + "} for key {" + entry.getKey() + "} only strings are accepted", this.owningFile);
-                    tmp.add(new ForgeFeature.Bound(entry.getKey(), val, this));
-                }
-                this.features = Collections.unmodifiableList(tmp);
-            }
+        // dependencies and features are done after the constructor as they need to reference the ModInfo we are creating
+        List<? extends ModVersion> dependencies = Collections.emptyList();
+        List<ForgeFeature.Bound> forgeFeatures = Collections.emptyList();
 
-            var props = this.owningFile.<Map<String, Object>>getConfigElement("modproperties", this.modId).orElse(null);
-            if (props == null)
-                this.properties = Collections.emptyMap();
-            else
-                this.properties = Collections.unmodifiableMap(props);
+        Map<String, Object> modProperties = owningFile.<Map<String, Object>>getConfigElement("modproperties", modId)
+                .map(Collections::unmodifiableMap)
+                .orElse(Collections.emptyMap());
+
+        return new ModInfo(
+                owningFile, config,
+                modId, namespace, version,
+                displayName, description, logoFile, logoBlur, updateJSONURL, modUrl,
+                new Holder<>(dependencies), new Holder<>(forgeFeatures), modProperties
+        ).setupDependencies().setupForgeFeatures();
+    }
+
+    private ModInfo setupDependencies() {
+        var deps = getOwningFile.getConfigList("dependencies", getModId);
+        if (deps == null || deps.isEmpty()) {
+            dependencies.value = Collections.emptyList();
+            return this;
         }
+
+        var tmp = new ModVersion[deps.size()];
+        for (int i = 0; i < deps.size(); i++) {
+            tmp[i] = ModVersion.of(this, deps.get(i));
+        }
+        dependencies.value = List.of(tmp);
+        return this;
     }
 
-    @Override
-    public ModFileInfo getOwningFile() {
-        return owningFile;
-    }
+    private ModInfo setupForgeFeatures() {
+        var feats = getOwningFile.<Map<String, Object>>getConfigElement("features", getModId).orElse(null);
+        if (feats == null) {
+            forgeFeatures.value = Collections.emptyList();
+            return this;
+        }
 
-    @Override
-    public String getModId() {
-        return modId;
-    }
-
-    @Override
-    public String getDisplayName() {
-        return this.displayName;
-    }
-
-    @Override
-    public String getDescription() {
-        return this.description;
-    }
-
-    @Override
-    public ArtifactVersion getVersion() {
-        return version;
-    }
-
-    @Override
-    public List<? extends IModInfo.ModVersion> getDependencies() {
-        return this.dependencies;
-    }
-
-    @Override
-    public String getNamespace() {
-        return this.namespace;
-    }
-
-    @Override
-    public Map<String, Object> getModProperties() {
-        return this.properties;
-    }
-
-    @Override
-    public Optional<URL> getUpdateURL() {
-        return this.updateJSONURL;
-    }
-
-    @Override
-    public Optional<String> getLogoFile() {
-        return this.logoFile;
-    }
-
-    @Override
-    public boolean getLogoBlur() {
-        return this.logoBlur;
-    }
-
-    @Override
-    public IConfigurable getConfig() {
+        var tmp = new ArrayList<ForgeFeature.Bound>();
+        for (var entry : feats.entrySet()) {
+            if (!(entry.getValue() instanceof String val))
+                throw new InvalidModFileException("Invalid feature bound {" + entry.getValue() + "} for key {" + entry.getKey() + "} only strings are accepted", getOwningFile);
+            tmp.add(new ForgeFeature.Bound(entry.getKey(), val, this));
+        }
+        forgeFeatures.value = List.copyOf(tmp);
         return this;
     }
 
     @Override
-    public List<? extends ForgeFeature.Bound> getForgeFeatures() {
-        return this.features;
+    public <T> Optional<T> getConfigElement(String key) {
+        return getConfig.getConfigElement(key);
     }
 
     @Override
-    public <T> Optional<T> getConfigElement(final String... key) {
-        return this.config.getConfigElement(key);
+    public <T> Optional<T> getConfigElement(String... key) {
+        return getConfig.getConfigElement(key);
     }
 
     @Override
-    public List<? extends IConfigurable> getConfigList(final String... key) {
+    public List<? extends IConfigurable> getConfigList(String... key) {
         return null;
     }
 
     @Override
-    public Optional<URL> getModURL() {
-        return modUrl;
+    public List<? extends IModInfo.ModVersion> getDependencies() {
+        return dependencies.value;
     }
 
-    class ModVersion implements net.minecraftforge.forgespi.language.IModInfo.ModVersion {
-        private IModInfo owner;
-        private final String modId;
-        private final VersionRange versionRange;
-        private final boolean mandatory;
-        private final Ordering ordering;
-        private final DependencySide side;
-        private final Optional<URL> referralUrl;
+    @Override
+    public List<? extends ForgeFeature.Bound> getForgeFeatures() {
+        return forgeFeatures.value;
+    }
 
-        public ModVersion(final IModInfo owner, final IConfigurable config) {
-            this.owner = owner;
-            this.modId = config.<String>getConfigElement("modId")
-                    .orElseThrow(()->new InvalidModFileException("Missing required field modid in dependency", getOwningFile()));
+    private static final class Holder<T> {
+        private T value;
 
-            if (this.modId.equals("forge")) {
+        public Holder(T value) {
+            this.value = value;
+        }
+    }
+
+    private record ModVersion(
+            Holder<IModInfo> owner,
+
+            String getModId,
+            VersionRange getVersionRange,
+            boolean isMandatory,
+            Ordering getOrdering,
+            DependencySide getSide,
+            Optional<URL> getReferralURL
+    ) implements IModInfo.ModVersion {
+        public static ModVersion of(IModInfo owner, IConfigurable config) {
+            var modId = config.<String>getConfigElement("modId").orElse(null);
+            if (modId == null)
+                throw new InvalidModFileException("Missing required field modid in dependency", owner.getOwningFile());
+
+            if (modId.equals("forge")) {
                 var fileProps = owner.getOwningFile().getFileProperties();
                 // Checking containsKey to avoid a possible exception if the property is not present (due to Collections.emptyMap())
                 if (!fileProps.isEmpty() && fileProps.containsKey(ModFileInfo.NOT_A_FORGE_MOD_PROP)) {
@@ -241,65 +211,41 @@ public class ModInfo implements IModInfo, IConfigurable {
                 }
             }
 
-            var mandatory = config.<Boolean>getConfigElement("mandatory");
-            if (mandatory.isPresent())
-                this.mandatory = mandatory.get();
+            boolean mandatory;
+            var mandatoryValue = config.<Boolean>getConfigElement("mandatory");
+            if (mandatoryValue.isPresent())
+                mandatory = mandatoryValue.get();
             else if (owner.getOwningFile().getFileProperties().containsKey(ModFileInfo.NOT_A_FORGE_MOD_PROP))
-                this.mandatory = true;
+                mandatory = true;
             else
-                throw new InvalidModFileException("Missing required field mandatory in dependency", getOwningFile());
+                throw new InvalidModFileException("Missing required field mandatory in dependency", owner.getOwningFile());
 
-            this.versionRange = config.<String>getConfigElement("versionRange")
+            var versionRange = config.<String>getConfigElement("versionRange")
                     .map(MavenVersionAdapter::createFromVersionSpec)
                     .orElse(UNBOUNDED);
-            this.ordering = config.<String>getConfigElement("ordering")
+            var ordering = config.<String>getConfigElement("ordering")
                     .map(Ordering::valueOf)
                     .orElse(Ordering.NONE);
-            this.side = config.<String>getConfigElement("side")
+            var side = config.<String>getConfigElement("side")
                     .map(DependencySide::valueOf)
                     .orElse(DependencySide.BOTH);
-            this.referralUrl = config.<String>getConfigElement("referralUrl")
+            var referralUrl = config.<String>getConfigElement("referralUrl")
                     .map(StringUtils::toURL);
-        }
 
-        @Override
-        public String getModId() {
-            return modId;
-        }
-
-        @Override
-        public VersionRange getVersionRange() {
-            return versionRange;
-        }
-
-        @Override
-        public boolean isMandatory() {
-            return mandatory;
-        }
-
-        @Override
-        public Ordering getOrdering() {
-            return ordering;
-        }
-
-        @Override
-        public DependencySide getSide() {
-            return side;
-        }
-
-        @Override
-        public void setOwner(final IModInfo owner) {
-            this.owner = owner;
+            return new ModVersion(
+                    new Holder<>(owner),
+                    modId, versionRange, mandatory, ordering, side, referralUrl
+            );
         }
 
         @Override
         public IModInfo getOwner() {
-            return owner;
+            return owner.value;
         }
 
         @Override
-        public Optional<URL> getReferralURL() {
-            return referralUrl;
+        public void setOwner(IModInfo newOwner) {
+            owner.value = newOwner;
         }
     }
 }

fmlloader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/ModJarMetadata.java

@@ -9,49 +9,64 @@ import cpw.mods.jarhandling.JarMetadata;
 import net.minecraftforge.forgespi.locating.IModFile;
 import java.lang.module.ModuleDescriptor;
 import java.util.Objects;
-
 import org.jetbrains.annotations.ApiStatus;
 
 @ApiStatus.Internal
 public final class ModJarMetadata implements JarMetadata {
+    private static final String AUTOMATIC_MODULE_NAME = "Automatic-Module-Name";
     private IModFile modFile;
+    private String name;
+    private String version;
     private ModuleDescriptor descriptor;
 
-    ModJarMetadata() {
-    }
+    ModJarMetadata() { }
 
     public void setModFile(IModFile file) {
         this.modFile = file;
+        var mods = this.modFile.getModFileInfo().getMods();
+
+        if (!mods.isEmpty()) {
+            var main = mods.get(0);
+            this.name = main.getModId();
+            this.version = main.getVersion().toString();
+        }
+
+        var jar = file.getSecureJar();
+        var aname = jar.moduleDataProvider().getManifest().getMainAttributes().getValue(AUTOMATIC_MODULE_NAME);
+        if (aname != null)
+            this.name = aname;
     }
 
     @Override
     public String name() {
-        return modFile.getModFileInfo().moduleName();
+        return this.name;
     }
 
     @Override
     public String version() {
-        return modFile.getModFileInfo().versionString();
+        return this.version;
     }
 
     @Override
     public ModuleDescriptor descriptor() {
-        if (descriptor != null) return descriptor;
+        if (descriptor != null)
+            return descriptor;
+
         var bld = ModuleDescriptor.newAutomaticModule(name())
-                .version(version())
-                .packages(modFile.getSecureJar().getPackages());
-        modFile.getSecureJar().getProviders().stream()
-                .filter(p -> !p.providers().isEmpty())
-                .forEach(p -> bld.provides(p.serviceName(), p.providers()));
-        modFile.getModFileInfo().usesServices().forEach(bld::uses);
+            .version(version())
+            .packages(modFile.getSecureJar().getPackages());
+
+        for (var provider : modFile.getSecureJar().getProviders()) {
+            if (provider.providers().isEmpty())
+                continue;
+
+            bld.provides(provider.serviceName(), provider.providers());
+        }
+
         descriptor = bld.build();
         return descriptor;
     }
 
-    public IModFile modFile() {
-        return modFile;
-    }
-
     @Override
     public boolean equals(Object obj) {
         if (obj == this) return true;

fmlloader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/ModValidator.java

@@ -34,7 +34,6 @@ public class ModValidator {
     private LoadingModList loadingModList;
     private final List<IModFile> brokenFiles = new ArrayList<>();
     private final List<EarlyLoadingException.ExceptionData> discoveryErrorData;
-    private final List<ModFileLoadingException> modFileLoadingExceptions;
 
     public ModValidator(Map<IModFile.Type, List<ModFile>> modFiles, List<IModFileInfo> brokenFiles, List<EarlyLoadingException.ExceptionData> discoveryErrorData, List<ModFileLoadingException> modFileLoadingExceptions) {
         this.candidateMods = lst(modFiles.get(IModFile.Type.MOD));
@@ -44,7 +43,6 @@ public class ModValidator {
         this.candidatePlugins.addAll(lst(modFiles.get(IModFile.Type.LIBRARY)));
         this.discoveryErrorData = discoveryErrorData;
         this.brokenFiles.addAll(brokenFiles.stream().map(IModFileInfo::getFile).toList());
-        this.modFileLoadingExceptions = modFileLoadingExceptions;
     }
 
     public ModValidator(Map<IModFile.Type, List<ModFile>> modFiles, List<IModFileInfo> brokenFiles, List<EarlyLoadingException.ExceptionData> discoveryErrorData) {
@@ -52,7 +50,9 @@ public class ModValidator {
     }
 
     private static List<ModFile> lst(List<ModFile> files) {
-        return files == null ? new ArrayList<>() : new ArrayList<>(files);
+        if (files == null) return new ArrayList<>();
+        if (files instanceof ArrayList) return files;
+        return new ArrayList<>(files);
     }
 
     public void stage1Validation() {
@@ -60,11 +60,11 @@ public class ModValidator {
         if (LOGGER.isDebugEnabled(LogMarkers.SCAN)) {
             LOGGER.debug(LogMarkers.SCAN, "Found {} mod files with {} mods", candidateMods.size(), candidateMods.stream().mapToInt(mf -> mf.getModInfos().size()).sum());
         }
-        ImmediateWindowHandler.updateProgress("Found "+candidateMods.size()+" mod candidates");
+        ImmediateWindowHandler.updateProgress("Found " + candidateMods.size() + " mod candidates");
     }
 
     @NotNull
-    private List<ModFile> validateFiles(final List<ModFile> mods) {
+    private static List<ModFile> validateFiles(final List<ModFile> mods) {
         final List<ModFile> brokenFiles = new ArrayList<>();
         for (Iterator<ModFile> iterator = mods.iterator(); iterator.hasNext();) {
             ModFile modFile = iterator.next();
@@ -106,8 +106,8 @@ public class ModValidator {
 
     private List<EarlyLoadingException.ExceptionData> validateLanguages() {
         List<EarlyLoadingException.ExceptionData> errorData = new ArrayList<>();
-        for (Iterator<ModFile> iterator = this.candidateMods.iterator(); iterator.hasNext(); ) {
-            final ModFile modFile = iterator.next();
+        for (Iterator<ModFile> iterator = this.candidateMods.iterator(); iterator.hasNext();) {
+            var modFile = iterator.next();
             try {
                 modFile.identifyLanguage();
             } catch (EarlyLoadingException e) {

fmlloader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/ModsFolderLocator.java

@@ -17,7 +17,6 @@ import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
-import java.util.Comparator;
 import java.util.List;
 import java.util.Locale;
 

fmlloader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/NightConfigWrapper.java

@@ -18,11 +18,12 @@ import java.util.Optional;
 import java.util.stream.Collectors;
 
 import org.jetbrains.annotations.ApiStatus;
+import org.jetbrains.annotations.Nullable;
 
 import static java.util.Arrays.asList;
 
 @ApiStatus.Internal
-class NightConfigWrapper implements IConfigurable {
+final class NightConfigWrapper implements IConfigurable {
     private final UnmodifiableConfig config;
     private IModFileInfo file;
 
@@ -30,39 +31,51 @@ class NightConfigWrapper implements IConfigurable {
         this.config = config;
     }
 
-    NightConfigWrapper setFile(IModFileInfo file) {
+    private NightConfigWrapper(UnmodifiableConfig config, IModFileInfo file) {
+        this.config = config;
+        this.file = file;
+    }
+
+    void setFile(IModFileInfo file) {
         this.file = file;
-        return this;
     }
 
     @Override
-    @SuppressWarnings("unchecked")
+    public <T> Optional<T> getConfigElement(String key) {
+        var path = List.of(key);
+        return Optional.ofNullable(validate(this.config.get(path), path));
+    }
+
+    @Override
     public <T> Optional<T> getConfigElement(final String... key) {
         var path = asList(key);
-        return this.config.getOptional(path).map(value -> {
-            if (value instanceof UnmodifiableConfig cfg) {
-                // New Night config doesn't implement valueMap(), so do a copy.
-                var builder = ImmutableMap.builder();
-                for (var e: cfg.entrySet())
-                    builder.put(e.getKey(), e.getValue());
-                return (T)builder.build();
-            } else if (value instanceof ArrayList<?> al && al.size() > 0 && al.get(0) instanceof UnmodifiableConfig) {
-                throw new InvalidModFileException("The configuration path " + path + " is invalid. I wasn't expecting a multi-object list - remove one of the [[ ]]", file);
-            }
-            return (T) value;
-        });
+        return Optional.ofNullable(validate(this.config.get(path), path));
+    }
+
+    @SuppressWarnings("unchecked")
+    private <T> T validate(@Nullable T value, List<String> path) {
+        if (value instanceof UnmodifiableConfig cfg) {
+            // New Night config doesn't implement valueMap(), so do a copy.
+            var entries = cfg.entrySet();
+            var builder = ImmutableMap.builderWithExpectedSize(entries.size());
+            for (var e : entries)
+                builder.put(e.getKey(), e.getValue());
+            return (T) builder.build();
+        } else if (value instanceof ArrayList<?> al && !al.isEmpty() && al.getFirst() instanceof UnmodifiableConfig) {
+            throw new InvalidModFileException("The configuration path " + path + " is invalid. I wasn't expecting a multi-object list - remove one of the [[ ]]", file);
+        }
+        return value;
     }
 
     @Override
     public List<? extends IConfigurable> getConfigList(final String... key) {
         final List<String> path = asList(key);
         if (this.config.contains(path) && !(this.config.get(path) instanceof Collection)) {
-            throw new InvalidModFileException("The configuration path "+path+" is invalid. Expecting a collection!", file);
+            throw new InvalidModFileException("The configuration path " + path + " is invalid. Expecting a collection!", file);
         }
         final Collection<UnmodifiableConfig> nestedConfigs = this.config.getOrElse(path, ArrayList::new);
         return nestedConfigs.stream()
-                .map(NightConfigWrapper::new)
-                .map(cw->cw.setFile(file))
+                .map(conf -> new NightConfigWrapper(conf, file))
                 .collect(Collectors.toList());
     }
 }

fmlloader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/Scanner.java

@@ -21,37 +21,36 @@ import java.nio.file.Path;
 import java.util.List;
 
 @ApiStatus.Internal
-class Scanner {
+record Scanner(ModFile fileToScan, ModFileScanData result) {
     private static final Logger LOGGER = LogUtils.getLogger();
-    private final ModFile fileToScan;
+    private static final boolean DEBUG = LOGGER.isDebugEnabled(LogMarkers.SCAN);
 
-    public Scanner(final ModFile fileToScan) {
-        this.fileToScan = fileToScan;
+    public Scanner(ModFile fileToScan) {
+        this(fileToScan, new ModFileScanData());
     }
 
     public ModFileScanData scan() {
-        ModFileScanData result = new ModFileScanData();
         result.addModFileInfo(fileToScan.getModFileInfo());
-        fileToScan.scanFile(p -> fileVisitor(p, result));
+        fileToScan.scanFile(this::fileVisitor);
         final List<IModLanguageProvider> loaders = fileToScan.getLoaders();
         if (loaders != null) {
-            loaders.forEach(loader -> {
-                LOGGER.debug(LogMarkers.SCAN, "Scanning {} with language loader {}", fileToScan.getFilePath(), loader.name());
+            for (IModLanguageProvider loader : loaders) {
+                if (DEBUG) LOGGER.debug("Scanning {} with language loader {}", fileToScan.getFilePath(), loader.name());
                 loader.getFileVisitor().accept(result);
-            });
+            }
         }
         return result;
     }
 
-    private void fileVisitor(final Path path, final ModFileScanData result) {
-        LOGGER.debug(LogMarkers.SCAN,"Scanning {} path {}", fileToScan, path);
-        try (InputStream in = Files.newInputStream(path)){
+    private void fileVisitor(final Path path) {
+        try (InputStream in = Files.newInputStream(path)) {
             ModClassVisitor mcv = new ModClassVisitor();
             ClassReader cr = new ClassReader(in);
-            cr.accept(mcv, 0);
+            cr.accept(mcv, ClassReader.SKIP_CODE | ClassReader.SKIP_DEBUG | ClassReader.SKIP_FRAMES);
             mcv.buildData(result.getClasses(), result.getAnnotations());
         } catch (IOException | IllegalArgumentException e) {
             // mark path bad
+            if (DEBUG) LOGGER.warn("Failed scanning {} path {}", fileToScan, path);
         }
     }
 }

fmlloader/src/main/java/net/minecraftforge/fml/loading/targets/ArgumentList.java

@@ -24,8 +24,8 @@ import java.util.function.Supplier;
 @ApiStatus.Internal
 class ArgumentList {
     private static final Logger LOGGER = LogUtils.getLogger();
-    private List<Supplier<String[]>> entries = new ArrayList<>();
-    private Map<String, EntryValue> values = new HashMap<>();
+    private final List<Supplier<String[]>> entries = new ArrayList<>();
+    private final Map<String, EntryValue> values = new HashMap<>();
 
     public static ArgumentList from(String... args) {
         ArgumentList ret = new ArgumentList();
@@ -77,8 +77,12 @@ class ArgumentList {
 
     public String[] getArguments() {
         return entries.stream()
-            .flatMap(e -> Arrays.asList(e.get()).stream())
-            .toArray(size -> new String[size]);
+            .flatMap(e -> Arrays.stream(e.get()))
+            .toArray(String[]::new);
+    }
+
+    public boolean has(String key) {
+        return this.values.containsKey(key);
     }
 
     public boolean hasValue(String key) {
@@ -122,7 +126,7 @@ class ArgumentList {
         return ent.getValue();
     }
 
-    private class EntryValue implements Supplier<String[]> {
+    private static final class EntryValue implements Supplier<String[]> {
         private final String prefix;
         private final String key;
         private final boolean split;

fmlloader/src/main/java/net/minecraftforge/fml/loading/targets/CommonDevLaunchHandler.java

@@ -22,6 +22,10 @@ abstract class CommonDevLaunchHandler extends CommonLaunchHandler {
         super(type, prefix);
     }
 
+    protected CommonDevLaunchHandler(String name) {
+        super(name);
+    }
+
     @Override public String getNaming() { return "mcp"; }
     @Override public boolean isProduction() { return false; }
 
@@ -29,18 +33,40 @@ abstract class CommonDevLaunchHandler extends CommonLaunchHandler {
     protected String[] preLaunch(String[] arguments, ModuleLayer layer) {
         super.preLaunch(arguments, layer);
 
+        var args = ArgumentList.from(arguments);
+
+        if (this.module == null) {
+            var entry = args.get("launchEntry");
+            if (entry == null)
+                throw new IllegalArgumentException("When using " + this.name() + " launch target you must specify a --launchEntry argument");
+
+            args.remove("launchEntry");
+
+            int idx = entry.indexOf('/');
+            if (idx == -1) {
+                this.module = "minecraft";
+                this.main = entry;
+            } else {
+                this.module = entry.substring(0, idx);
+                this.main = entry.substring(idx + 1);
+            }
+
+            if (args.has("launchData")) {
+                args.remove("launchData");
+                this.isData = true;
+            }
+        }
+
         if (getDist().isDedicatedServer())
-            return arguments;
+            return args.getArguments();
 
         if (isData())
-            return arguments;
-
-        var args = ArgumentList.from(arguments);
+            return args.getArguments();
 
         String username = args.get("username");
         if (username != null) { // Replace '#' placeholders with random numbers
             Matcher m = Pattern.compile("#+").matcher(username);
-            StringBuffer replaced = new StringBuffer();
+            StringBuilder replaced = new StringBuilder();
             while (m.find()) {
                 m.appendReplacement(replaced, getRandomNumbers(m.group().length()));
             }

fmlloader/src/main/java/net/minecraftforge/fml/loading/targets/CommonLaunchHandler.java

@@ -7,7 +7,6 @@ package net.minecraftforge.fml.loading.targets;
 
 import com.mojang.logging.LogUtils;
 import cpw.mods.modlauncher.api.ILaunchHandlerService;
-import cpw.mods.modlauncher.api.ITransformingClassLoaderBuilder;
 import cpw.mods.modlauncher.api.ServiceRunner;
 import net.minecraftforge.fml.loading.FMLLoader;
 import net.minecraftforge.api.distmarker.Dist;
@@ -19,7 +18,6 @@ import org.slf4j.Logger;
 import java.io.IOException;
 import java.net.URI;
 import java.nio.file.Path;
-import java.nio.file.Paths;
 import java.util.List;
 
 /**
@@ -31,26 +29,32 @@ import java.util.List;
 public abstract class CommonLaunchHandler implements ILaunchHandlerService {
     protected static final Logger LOGGER = LogUtils.getLogger();
 
-    protected final LaunchType type;
-    private final String prefix;
+    private final String name;
+    protected Dist dist = Dist.CLIENT;
+    protected boolean isData = false;
+    protected String module;
+    protected String main;
 
     protected CommonLaunchHandler(LaunchType type, String prefix) {
-        this.type = type;
-        this.prefix = prefix;
+        this(prefix + type.name());
+        this.dist = type.dist();
+        this.isData = type.data();
+        this.module = type.module();
+        this.main = type.main();
     }
 
-    @Override public String name() { return this.prefix + this.type.name(); }
-    public Dist getDist() { return this.type.dist(); }
-    public boolean isData() { return this.type.data(); }
+    protected CommonLaunchHandler(String name) {
+        this.name = name;
+    }
+
+    @Override public String name() { return this.name; }
+    public Dist getDist() { return this.dist; }
+    public boolean isData() { return this.isData; }
     public boolean isProduction() { return false; }
     public abstract String getNaming();
 
     public abstract List<Path> getMinecraftPaths();
 
-    @Override
-    public void configureTransformationClassLoader(final ITransformingClassLoaderBuilder builder) {
-    }
-
     protected String[] preLaunch(String[] arguments, ModuleLayer layer) {
         URI uri;
         try (var reader = layer.configuration().findModule("net.minecraftforge.fmlloader").orElseThrow().reference().open()) {
@@ -72,14 +76,15 @@ public abstract class CommonLaunchHandler implements ILaunchHandlerService {
     }
 
     protected ServiceRunner makeService(final String[] arguments, final ModuleLayer gameLayer) {
-        return () -> runTarget(this.type.module(), this.type.main(), arguments, gameLayer);
+        return () -> runTarget(this.module, this.main, arguments, gameLayer);
     }
 
     protected record LaunchType(String name, String module, String main, Dist dist, boolean data) {};
     protected static final LaunchType CLIENT          = new LaunchType("client", "minecraft", "net.minecraft.client.main.Main", Dist.CLIENT, false);
+    protected static final LaunchType CLIENT_DATA     = new LaunchType("client_data", "minecraft", "net.minecraft.client.data.Main", Dist.CLIENT, true);
     protected static final LaunchType DATA            = new LaunchType("data",   "minecraft", "net.minecraft.data.Main", Dist.CLIENT, true);
     protected static final LaunchType SERVER          = new LaunchType("server", "minecraft", "net.minecraft.server.Main", Dist.DEDICATED_SERVER, false);
-    protected static final LaunchType SERVER_GAMETEST = new LaunchType("server_gametest", "forge", "net.minecraftforge.gametest.GameTestMain", Dist.DEDICATED_SERVER, false);
+    protected static final LaunchType SERVER_GAMETEST = new LaunchType("server_gametest", "minecraft", "net.minecraft.gametest.Main", Dist.DEDICATED_SERVER, false);
 
     protected void runTarget(String module, String target, final String[] arguments, final ModuleLayer layer) throws Throwable {
         var mod = layer.findModule(module).orElse(null);
@@ -107,7 +112,7 @@ public abstract class CommonLaunchHandler implements ILaunchHandlerService {
             len += 2;
         }
         str = str.substring(0, str.length() - len);
-        var path = Paths.get(URI.create(str));
+        var path = Path.of(URI.create(str));
         return path;
     }
 }

fmlloader/src/main/java/net/minecraftforge/fml/loading/targets/ForgeDevLaunchHandler.java

@@ -9,17 +9,19 @@ import java.util.List;
 import org.jetbrains.annotations.ApiStatus;
 
 @ApiStatus.Internal
-abstract class ForgeDevLaunchHandler extends CommonDevLaunchHandler {
+sealed abstract class ForgeDevLaunchHandler extends CommonDevLaunchHandler {
     private ForgeDevLaunchHandler(LaunchType type) {
         super(type, "forge_dev_");
     }
 
+    private ForgeDevLaunchHandler(String name) {
+        super(name);
+    }
+
     @Override
     public List<Path> getMinecraftPaths() {
-
-        // The extra jar is on the classpath, so try and pull it out of the legacy classpath
-        var legacyCP = findClassPath();
-        var extra = findJarOnClasspath(legacyCP, "client-extra");
+        // The client extra jar is on the classpath we can try locating it using the .mcassetsroot which vanilla uses for loading data
+        var extra = getPathFromResource("assets/.mcassetsroot");
         // Minecraft is an exploded directory, so find it.
         var minecraft = getPathFromResource("net/minecraft/client/Minecraft.class");
         var forge = getPathFromResource("net/minecraftforge/common/MinecraftForge.class");
@@ -33,27 +35,39 @@ abstract class ForgeDevLaunchHandler extends CommonDevLaunchHandler {
         return List.of(filtered);
     }
 
-    public static class Client extends ForgeDevLaunchHandler {
+    public static final class Client extends ForgeDevLaunchHandler {
         public Client() {
             super(CLIENT);
         }
     }
 
-    public static class Data extends ForgeDevLaunchHandler {
+    public static final class ClientData extends ForgeDevLaunchHandler {
+        public ClientData() {
+            super(CLIENT_DATA);
+        }
+    }
+
+    public static final class Data extends ForgeDevLaunchHandler {
         public Data() {
             super(DATA);
         }
     }
 
-    public static class Server extends ForgeDevLaunchHandler {
+    public static final class Server extends ForgeDevLaunchHandler {
         public Server() {
             super(SERVER);
         }
     }
 
-    public static class ServerGameTest extends ForgeDevLaunchHandler {
+    public static final class ServerGameTest extends ForgeDevLaunchHandler {
         public ServerGameTest() {
             super(SERVER_GAMETEST);
         }
     }
+
+    public static final class Custom extends ForgeDevLaunchHandler {
+        public Custom() {
+            super("forge_dev");
+        }
+    }
 }

fmlloader/src/main/java/net/minecraftforge/fml/loading/targets/ForgeDevLocator.java

@@ -35,7 +35,7 @@ import net.minecraftforge.fml.loading.moddiscovery.AbstractModProvider;
 import net.minecraftforge.forgespi.locating.IModLocator;
 
 @ApiStatus.Internal
-public class ForgeDevLocator extends AbstractModProvider implements IModLocator {
+public final class ForgeDevLocator extends AbstractModProvider implements IModLocator {
     private static final String PACK_META = "pack.mcmeta";
 
     @Override
@@ -60,7 +60,7 @@ public class ForgeDevLocator extends AbstractModProvider implements IModLocator
         return ret;
     }
 
-    private List<Path> getMods() {
+    private static List<Path> getMods() {
         // Forge is an exploded directory as well
         var minecraft = ForgeDevLaunchHandler.getPathFromResource("net/minecraft/client/Minecraft.class");
         var forge = ForgeDevLaunchHandler.getPathFromResource("net/minecraftforge/common/MinecraftForge.class");
@@ -84,30 +84,31 @@ public class ForgeDevLocator extends AbstractModProvider implements IModLocator
         return ret;
     }
 
-    private List<Path> explodeTestMods(Path path) {
+    private static List<Path> explodeTestMods(Path path) {
         var mod = new ArrayList<Path>();
         var memory = Jimfs.newFileSystem();
 
         // First lets find all class files, that have the @Mod annotation and map packages to modids.
         var packages = findTestModPackages(path);
         for (var entry : packages.entrySet()) {
-            var pkg = entry.getKey();
+            var pkg = entry.getKey() + '/';
             var modids = entry.getValue();
 
             // Find resource directories for every mod in this group
-            var resourcePaths = new LinkedHashSet<Path>();
-            for (var modid : modids) {
+            var paths = new LinkedHashSet<Path>();
+            for (var modid : modids.stream().sorted().toList()) {
                 var rsc = path.resolve(modid);
                 if (Files.exists(rsc))
-                    resourcePaths.add(rsc);
+                    paths.add(rsc);
             }
 
             var root = memory.getPath(modids.iterator().next()); // use the first modid as our root
-            buildModsToml(resourcePaths, modids, root);
-            buildPackMeta(resourcePaths, root);
+            buildModsToml(paths, modids, root, pkg.startsWith("net/minecraftforge/debug/client/"));
+            buildPackMeta(paths, root);
+            moveModuleInfo(paths, root);
 
             if (Files.exists(root))
-                resourcePaths.add(root);
+                paths.add(root);
 
             // We want just the class files from the root of the input paths. So make a new union with a filter.
             var classes = UnionHelper.newFileSystem(
@@ -121,14 +122,10 @@ public class ForgeDevLocator extends AbstractModProvider implements IModLocator
                 }, new Path[] { path }
             );
 
-            // And we want the resources, and none of the classes, just in case things get kinda fucky and somehow a package overlaps a sub package {shading?}
-            var resources = UnionHelper.newFileSystem((name, base) -> !name.endsWith(".class"), resourcePaths.toArray(Path[]::new));
+            paths.addFirst(classes.getRootDirectories().iterator().next());
 
             // Union of unions, Yay!
-            var union = UnionHelper.newFileSystem(null, new Path[] {
-                classes.getRootDirectories().iterator().next(),
-                resources.getRootDirectories().iterator().next()
-            });
+            var union = UnionHelper.newFileSystem(null, paths.stream().toArray(Path[]::new));
             mod.add(union.getRootDirectories().iterator().next());
         }
 
@@ -137,7 +134,7 @@ public class ForgeDevLocator extends AbstractModProvider implements IModLocator
 
     // Find all the @Mods so we can generate tomls, and so we can pick packages. Right now it doesn't allow mods in parent directories,
     // I could make it merge all the way up, but I think this would be fine.
-    private Map<String, Set<String>> findTestModPackages(Path path) {
+    private static Map<String, Set<String>> findTestModPackages(Path path) {
         var mods = new HashMap<String, Set<String>>();
         try (var files = Files.walk(path)) {
             var classes = files
@@ -190,7 +187,7 @@ public class ForgeDevLocator extends AbstractModProvider implements IModLocator
     }
 
     // Builds or update the mods.toml file for all @Mods in this package
-    private void buildModsToml(Set<Path> resources, Set<String> modids, Path root) {
+    private static void buildModsToml(Set<Path> resources, Set<String> modids, Path root, boolean clientOnly) {
         var toml = resources.stream()
             .map(p -> p.resolve(MODS_TOML))
             .filter(Files::exists)
@@ -208,7 +205,8 @@ public class ForgeDevLocator extends AbstractModProvider implements IModLocator
         var defaults = Map.of(
             "modLoader", "javafml",
             "loaderVersion", "[0,)",
-            "license", "Doesnt fucking matter"
+            "license", "Doesnt fucking matter",
+            "clientSideOnly", clientOnly
         );
 
         for (var key : defaults.keySet()) {
@@ -226,7 +224,7 @@ public class ForgeDevLocator extends AbstractModProvider implements IModLocator
         }
 
         for (var modid : modids) {
-            if (!modlist.stream().anyMatch(c -> modid.equals(c.get("modId")))) {
+            if (modlist.stream().noneMatch(c -> modid.equals(c.get("modId")))) {
                 modified = true;
                 var tmp = Config.inMemory();
                 tmp.set("modId", modid);
@@ -248,7 +246,7 @@ public class ForgeDevLocator extends AbstractModProvider implements IModLocator
     }
 
     // This is optional, it just hides a warning screen when starting up. I should probably remove this once I restructure how data gen for test mods work and make it generate there.
-    private void buildPackMeta(Set<Path> paths, Path root) {
+    private static void buildPackMeta(Set<Path> paths, Path root) {
         var existing = paths.stream()
                 .map(p -> p.resolve(PACK_META))
                 .filter(Files::exists)
@@ -274,6 +272,25 @@ public class ForgeDevLocator extends AbstractModProvider implements IModLocator
         }
     }
 
+    private static void moveModuleInfo(Set<Path> paths, Path root) {
+        var existing = paths.stream()
+            .map(p -> p.resolve("module-info.dat"))
+            .filter(Files::exists)
+            .findFirst()
+            .orElse(null);
+
+        if (existing == null)
+            return;
+
+        var target = root.resolve("module-info.class");
+        try {
+            Files.createDirectories(target.getParent());
+            Files.copy(existing, target);
+        } catch (IOException e) {
+            throw new IllegalStateException("Failed to copy module-info.dat to memory: " + target, e);
+        }
+    }
+
     @SuppressWarnings("unchecked")
     private static <E extends Throwable, R> R sneak(Throwable e) throws E {
         throw (E)e;

fmlloader/src/main/java/net/minecraftforge/fml/loading/targets/ForgeProdLaunchHandler.java

@@ -10,7 +10,7 @@ import java.util.List;
 import org.jetbrains.annotations.ApiStatus;
 
 @ApiStatus.Internal
-abstract class ForgeProdLaunchHandler extends CommonLaunchHandler {
+sealed abstract class ForgeProdLaunchHandler extends CommonLaunchHandler {
     protected ForgeProdLaunchHandler(LaunchType type) {
         super(type, "forge_");
     }
@@ -18,7 +18,7 @@ abstract class ForgeProdLaunchHandler extends CommonLaunchHandler {
     @Override public String getNaming() { return "mcp"; }
     @Override public boolean isProduction() { return true; }
 
-    public static class Client extends ForgeProdLaunchHandler {
+    public static final class Client extends ForgeProdLaunchHandler {
         public Client() {
             super(CLIENT);
         }
@@ -29,7 +29,7 @@ abstract class ForgeProdLaunchHandler extends CommonLaunchHandler {
         }
     }
 
-    public static class Server extends ForgeProdLaunchHandler {
+    public static final class Server extends ForgeProdLaunchHandler {
         public Server() {
             super(SERVER);
         }

fmlloader/src/main/java/net/minecraftforge/fml/loading/targets/ForgeUserdevLaunchHandler.java

@@ -8,17 +8,18 @@ package net.minecraftforge.fml.loading.targets;
 import net.minecraftforge.fml.loading.FMLLoader;
 import java.nio.file.Path;
 import java.util.List;
-import java.util.function.BiPredicate;
 import org.jetbrains.annotations.ApiStatus;
 
-import cpw.mods.jarhandling.SecureJar;
-
 @ApiStatus.Internal
-abstract class ForgeUserdevLaunchHandler extends CommonDevLaunchHandler {
+sealed abstract class ForgeUserdevLaunchHandler extends CommonDevLaunchHandler {
     private ForgeUserdevLaunchHandler(LaunchType type) {
         super(type, "forge_userdev_");
     }
 
+    private ForgeUserdevLaunchHandler(String name) {
+        super(name);
+    }
+
     @Override
     public List<Path> getMinecraftPaths() {
         var legacyCP = findClassPath();
@@ -26,34 +27,46 @@ abstract class ForgeUserdevLaunchHandler extends CommonDevLaunchHandler {
 
         // Minecraft is extra jar {resources} + forge jar {patches}
         // The MC extra and forge jars are on the classpath, so try and pull them out
-        var extra = findJarOnClasspath(legacyCP, "client-extra");
+        var extra = findJarOnClasspath(legacyCP, "client-extra"); // This should be "client-" + vers.mcAndMCPVersion() + "-extra" but FG6 qwerks
         var forge = findJarOnClasspath(legacyCP, "forge-" + vers.mcAndForgeVersion());
         // We need to filter the forge jar to just MC code
         var minecraft = CommonDevLaunchHandler.getMinecraftOnly(extra, forge);
         return List.of(minecraft);
     }
 
-    public static class Client extends ForgeUserdevLaunchHandler {
+    public static final class Client extends ForgeUserdevLaunchHandler {
         public Client() {
             super(CLIENT);
         }
     }
 
-    public static class Data extends ForgeUserdevLaunchHandler {
+    public static final class ClientData extends ForgeUserdevLaunchHandler {
+        public ClientData() {
+            super(CLIENT_DATA);
+        }
+    }
+
+    public static final class Data extends ForgeUserdevLaunchHandler {
         public Data() {
             super(DATA);
         }
     }
 
-    public static class Server extends ForgeUserdevLaunchHandler {
+    public static final class Server extends ForgeUserdevLaunchHandler {
         public Server() {
             super(SERVER);
         }
     }
 
-    public static class ServerGameTest extends ForgeUserdevLaunchHandler {
+    public static final class ServerGameTest extends ForgeUserdevLaunchHandler {
         public ServerGameTest() {
             super(SERVER_GAMETEST);
         }
     }
+
+    public static final class Custom extends ForgeUserdevLaunchHandler {
+        public Custom() {
+            super("forge_userdev");
+        }
+    }
 }

fmlloader/src/main/java/net/minecraftforge/fml/loading/targets/ForgeUserdevLocator.java

@@ -12,7 +12,7 @@ import net.minecraftforge.fml.loading.moddiscovery.AbstractModProvider;
 import net.minecraftforge.forgespi.locating.IModLocator;
 
 @ApiStatus.Internal
-public class ForgeUserdevLocator extends AbstractModProvider implements IModLocator {
+public final class ForgeUserdevLocator extends AbstractModProvider implements IModLocator {
     @Override
     public String name() {
         return "forge_userdev_locator";

fmlloader/src/main/java/net/minecraftforge/fml/loading/toposort/StronglyConnectedComponentDetector.java

@@ -25,7 +25,7 @@ import java.util.Set;
  */
 public class StronglyConnectedComponentDetector<T> {
     private final Graph<T> graph;
-    private Map<T, Integer> ids;
+    private final Map<T, Integer> ids = new HashMap<>();
     private T[] elements;
     private int[] dfn;
     private int[] low;
@@ -49,7 +49,6 @@ public class StronglyConnectedComponentDetector<T> {
     private void calculate() {
         components = new HashSet<>();
         int t = 0;
-        ids = new HashMap<>();
         Set<T> nodes = graph.nodes();
         elements = (T[]) new Object[nodes.size()];
         for (T node : nodes) {

fmlloader/src/main/resources/META-INF/services/cpw.mods.modlauncher.api.ILaunchHandlerService

@@ -4,12 +4,16 @@ net.minecraftforge.fml.loading.targets.ForgeProdLaunchHandler$Server
 
 # Mod Developers
 net.minecraftforge.fml.loading.targets.ForgeUserdevLaunchHandler$Client
+net.minecraftforge.fml.loading.targets.ForgeUserdevLaunchHandler$ClientData
+net.minecraftforge.fml.loading.targets.ForgeUserdevLaunchHandler$Custom
 net.minecraftforge.fml.loading.targets.ForgeUserdevLaunchHandler$Data
 net.minecraftforge.fml.loading.targets.ForgeUserdevLaunchHandler$Server
 net.minecraftforge.fml.loading.targets.ForgeUserdevLaunchHandler$ServerGameTest
 
 #Working on Forge itself
 net.minecraftforge.fml.loading.targets.ForgeDevLaunchHandler$Client
+net.minecraftforge.fml.loading.targets.ForgeDevLaunchHandler$ClientData
+net.minecraftforge.fml.loading.targets.ForgeDevLaunchHandler$Custom
 net.minecraftforge.fml.loading.targets.ForgeDevLaunchHandler$Data
 net.minecraftforge.fml.loading.targets.ForgeDevLaunchHandler$Server
 net.minecraftforge.fml.loading.targets.ForgeDevLaunchHandler$ServerGameTest

fmlloader/src/main/resources/META-INF/services/cpw.mods.modlauncher.serviceapi.ILaunchPluginService

@@ -1,5 +1,4 @@
 net.minecraftforge.fml.loading.log4j.SLF4JFixerLaunchPluginService
 net.minecraftforge.fml.loading.RuntimeDistCleaner
 net.minecraftforge.fml.common.asm.RuntimeEnumExtender
-net.minecraftforge.fml.common.asm.ObjectHolderDefinalize
 net.minecraftforge.fml.common.asm.CapabilityTokenSubclass

fmlloader/src/main/resources/jarjar_options.json

@@ -0,0 +1,35 @@
+{
+  "options": [
+    {
+      "resource": "com/llamalad7/mixinextras/platform/forge/MixinExtrasConfigPlugin.class",
+      "layer": "GAMELIBRARY",
+      "id": "mixinextras",
+      "deps": [
+        {
+          "identifier": {
+            "group": "com.github.LlamaLad7",
+            "artifact": "MixinExtras"
+          },
+          "version": {
+            "range": "[0.5.0,)",
+            "artifactVersion": "0.5.0"
+          },
+          "path": "",
+          "isObfuscated": false
+        }
+      ],
+      "meta": {
+        "identifier": {
+          "group": "io.github.llamalad7",
+          "artifact": "mixinextras-forge"
+        },
+        "version": {
+          "artifactVersion": "0.5.0"
+        },
+        "path": "",
+        "isObfuscated": false
+      },
+      "nested": true
+    }
+  ]
+}

fmlloader/src/main/resources/log4j2.xml

@@ -4,7 +4,7 @@
     SPDX-License-Identifier: LGPL-2.1-only
 -->
 
-<Configuration status="warn" packages="net.minecrell.terminalconsole,net.minecrell.terminalconsole.util,com.mojang.util,cpw.mods.modlauncher.log,net.minecraftforge.fml.loading.log4j" shutdownHook="disable">
+<Configuration status="warn" shutdownHook="disable">
     <filters>
         <ThresholdFilter level="WARN" onMatch="ACCEPT" onMismatch="NEUTRAL"/>
         <MarkerFilter marker="NETWORK_PACKETS" onMatch="${sys:forge.logging.marker.networking:-DENY}" onMismatch="NEUTRAL"/>

forge-transformers/build.gradle

@@ -0,0 +1,73 @@
+import net.minecraftforge.gradleutils.PomUtils
+
+plugins {
+    id 'java-library'
+    id 'maven-publish'
+    id 'net.minecraftforge.licenser'
+    id 'net.minecraftforge.gradleutils'
+    alias(libs.plugins.apt)
+}
+
+apply from: rootProject.file('build_shared.gradle')
+
+configurations.forEach{ it.transitive = false }
+
+dependencies {
+    compileOnly(libs.jetbrains.annotations)
+
+    implementation(libs.bundles.asm) // Needed by all the black magic
+    implementation(libs.log4j.api)
+    implementation(libs.gson)
+    implementation(libs.modlauncher)
+    implementation(libs.coremods) // Used for ASMAPI (for now)
+
+    testCompileOnly(libs.jetbrains.annotations)
+}
+
+java {
+    toolchain.languageVersion = JavaLanguageVersion.of(JAVA_VERSION)
+    withSourcesJar()
+}
+
+tasks.named('jar', Jar) {
+    manifest {
+        attributes([
+            'Automatic-Module-Name': 'net.minecraftforge.forge.transformers',
+            'Forge-Module-Layer':    'boot'
+        ] as LinkedHashMap)
+        attributes([
+            'Specification-Title':   'Forge Transformers',
+            'Specification-Vendor':  'Forge Development LLC',
+            'Specification-Version': '1',
+            'Implementation-Title':  'Forge Transformers',
+            'Implementation-Vendor': 'Forge Development LLC',
+            'Implementation-Version': FORGE_VERSION
+        ] as LinkedHashMap, 'net/minecraftforge/forge/transformers/')
+    }
+}
+
+tasks.withType(JavaCompile).configureEach {
+    options.compilerArgs << '-Xlint:unchecked'
+}
+
+license {
+    header = rootProject.file('LICENSE-header.txt')
+}
+
+publishing {
+    publications.register('mavenJava', MavenPublication) {
+        from components.java
+        artifactId = 'forge-transformers'
+        pom {
+            name = project.name
+            description = 'Forge-specific transformers unrelated to the FML project.'
+            url = 'https://github.com/MinecraftForge/MinecraftForge'
+            PomUtils.setGitHubDetails(pom, 'MinecraftForge')
+            license PomUtils.Licenses.LGPLv2_1
+        }
+    }
+
+    repositories {
+        maven gradleutils.publishingForgeMaven
+    }
+}

forge-transformers/src/main/java/net/minecraftforge/forge/transformers/FieldToMethodTransformer.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
+package net.minecraftforge.forge.transformers;
+
+import cpw.mods.modlauncher.api.ITransformer;
+import cpw.mods.modlauncher.api.ITransformerVotingContext;
+import cpw.mods.modlauncher.api.TransformerVoteResult;
+import net.minecraftforge.coremod.api.ASMAPI;
+import org.jetbrains.annotations.NotNull;
+import org.objectweb.asm.tree.ClassNode;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+record FieldToMethodTransformer(String className, Map<String, String> fields) implements ITransformer<ClassNode> {
+    // TODO [Forge][Transformer] Make this properly data driven or configurable.
+    //      It was hard-coded like this before when using JS CoreMods, though.
+    static final Map<String, Map<String, String>> TARGETS = Map.of(
+        "net.minecraft.world.level.biome.Biome",
+        Map.of(
+            "climateSettings", "getModifiedClimateSettings",
+            "specialEffects", "getModifiedSpecialEffects"
+        ),
+
+        "net.minecraft.world.effect.MobEffectInstance",
+        Map.of(
+            "effect", "getEffect"
+        ),
+
+        "net.minecraft.world.level.block.LiquidBlock",
+        Map.of(
+            "fluid", "getFluid"
+        ),
+
+        "net.minecraft.world.item.BucketItem",
+        Map.of(
+            "content", "getFluid"
+        ),
+
+        "net.minecraft.world.level.block.FlowerPotBlock",
+        Map.of(
+            "potted", "getPotted"
+        )
+    );
+
+    @SuppressWarnings("rawtypes")
+    static List<ITransformer> getAll() {
+        var ret = new ArrayList<ITransformer>(TARGETS.size());
+        for (var entry : TARGETS.entrySet()) {
+            ret.add(new FieldToMethodTransformer(entry.getKey(), entry.getValue()));
+        }
+        return ret;
+    }
+
+    @Override
+    public @NotNull ClassNode transform(ClassNode input, ITransformerVotingContext context) {
+        for (var entry : this.fields.entrySet()) {
+            ASMAPI.redirectFieldToMethod(input, entry.getKey(), entry.getValue());
+        }
+
+        return input;
+    }
+
+    @Override
+    public @NotNull TransformerVoteResult castVote(ITransformerVotingContext context) {
+        return TransformerVoteResult.YES;
+    }
+
+    @Override
+    public @NotNull Set<Target> targets() {
+        return Set.of(Target.targetClass(this.className));
+    }
+}

forge-transformers/src/main/java/net/minecraftforge/forge/transformers/ForgeModTransformers.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
+package net.minecraftforge.forge.transformers;
+
+import cpw.mods.modlauncher.api.IEnvironment;
+import cpw.mods.modlauncher.api.ITransformationService;
+import cpw.mods.modlauncher.api.ITransformer;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.List;
+import java.util.Set;
+
+public record ForgeModTransformers(String name) implements ITransformationService {
+    public ForgeModTransformers() {
+        this("forge");
+    }
+
+    @Override
+    public void initialize(IEnvironment environment) { }
+
+    @Override
+    public void onLoad(IEnvironment env, Set<String> otherServices) { }
+
+    @Override
+    @SuppressWarnings("rawtypes")
+    public @NotNull List<ITransformer> transformers() {
+        List<ITransformer> transformers = FieldToMethodTransformer.getAll();
+        transformers.add(new MethodRedirector());
+        return transformers;
+    }
+}

forge-transformers/src/main/java/net/minecraftforge/forge/transformers/MethodRedirector.java

@@ -0,0 +1,142 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
+package net.minecraftforge.forge.transformers;
+
+import com.google.gson.Gson;
+import com.google.gson.annotations.SerializedName;
+import cpw.mods.modlauncher.api.ITransformer;
+import cpw.mods.modlauncher.api.ITransformerVotingContext;
+import cpw.mods.modlauncher.api.TransformerVoteResult;
+import net.minecraftforge.coremod.api.ASMAPI;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.jetbrains.annotations.NotNull;
+import org.objectweb.asm.Opcodes;
+import org.objectweb.asm.tree.AbstractInsnNode;
+import org.objectweb.asm.tree.ClassNode;
+import org.objectweb.asm.tree.MethodInsnNode;
+
+import java.io.InputStreamReader;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.Callable;
+import java.util.function.UnaryOperator;
+import java.util.stream.Collectors;
+
+// NOTE: THIS IS A SINGLETON!
+record MethodRedirector() implements ITransformer<ClassNode> {
+    private static final Logger LOGGER = LogManager.getLogger();
+    private static final Gson GSON = new Gson();
+
+    private static final Replacement[] REPLACEMENTS = {
+        new Replacement(
+            // finalizeSpawn redirection to ForgeEventFactory.onFinalizeSpawn
+            ASMAPI.MethodType.VIRTUAL,
+            "finalizeSpawn",
+            "(Lnet/minecraft/world/level/ServerLevelAccessor;Lnet/minecraft/world/DifficultyInstance;Lnet/minecraft/world/entity/EntitySpawnReason;Lnet/minecraft/world/entity/SpawnGroupData;)Lnet/minecraft/world/entity/SpawnGroupData;",
+            GSON.fromJson(new InputStreamReader(sneak(() -> MethodRedirector.class.getModule().getResourceAsStream("coremods/finalize_spawn_targets.json"))), Target[].class),
+            insn -> ASMAPI.buildMethodCall(
+                ASMAPI.MethodType.STATIC,
+                "net/minecraftforge/event/ForgeEventFactory",
+                "onFinalizeSpawn",
+                "(Lnet/minecraft/world/entity/Mob;Lnet/minecraft/world/level/ServerLevelAccessor;Lnet/minecraft/world/DifficultyInstance;Lnet/minecraft/world/entity/EntitySpawnReason;Lnet/minecraft/world/entity/SpawnGroupData;)Lnet/minecraft/world/entity/SpawnGroupData;"
+            )
+        )
+    };
+
+    private static <T> T sneak(Callable<T> callable) {
+        try {
+            return callable.call();
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    record Replacement(
+        ASMAPI.MethodType type,
+        String name,
+        String desc,
+        Target[] targets,
+        UnaryOperator<MethodInsnNode> factory
+    ) { }
+
+    record Target(
+        @SerializedName("class") String className,
+        String[] methods
+    ) { }
+
+    @Override
+    public @NotNull TransformerVoteResult castVote(ITransformerVotingContext context) {
+        return TransformerVoteResult.YES;
+    }
+
+    @Override
+    public @NotNull Set<ITransformer.Target> targets() {
+        return Arrays
+            .stream(REPLACEMENTS)
+            .map(Replacement::targets)
+            .flatMap(Arrays::stream)
+            .map(Target::className)
+            .map(ITransformer.Target::targetClass)
+            .collect(Collectors.toUnmodifiableSet());
+    }
+
+    @Override
+    public @NotNull ClassNode transform(ClassNode clazz, ITransformerVotingContext context) {
+        for (var replacement : REPLACEMENTS) {
+            for (var methodString : getClassTargetMethods(clazz, replacement)) {
+                // cut up the string since we've put both the name and desc as the target
+                var splitPos = methodString.indexOf('(');
+                var methodName = methodString.substring(0, splitPos);
+                var methodDesc = methodString.substring(splitPos);
+                var method = ASMAPI.findMethodNode(clazz, methodName, methodDesc);
+
+                if (method == null) {
+                    LOGGER.error("Failed to redirect method call for {}! Method {} not found in class {}! This is a Forge bug, and is likely due to a Minecraft update changing something.", replacement.name, methodString, clazz.name);
+                    continue;
+                }
+
+                for (var insn : method.instructions) {
+                    if (!shouldReplace(insn, replacement)) continue;
+
+                    var methodInsn = (MethodInsnNode) insn;
+                    var redirection = replacement.factory.apply(methodInsn);
+                    LOGGER.debug("Redirecting method call {}{} to {}{} inside of {}.{}", methodInsn.name, methodInsn.desc, redirection.name, redirection.desc, clazz.name, method.name);
+                    ASMAPI.insertInsn(method, methodInsn, redirection, ASMAPI.InsertMode.REMOVE_ORIGINAL);
+                }
+            }
+        }
+
+        return clazz;
+    }
+
+    private static boolean shouldReplace(AbstractInsnNode insn, Replacement replacement) {
+        return insn.getOpcode() == replacement.type.toOpcode()
+            && replacement.name.equals(((MethodInsnNode) insn).name)
+            && replacement.desc.equals(((MethodInsnNode) insn).desc);
+    }
+
+    private static List<String> getClassTargetMethods(ClassNode clazz, Replacement replacement) {
+        for (var t : replacement.targets) {
+            if (!t.className.equals(clazz.name)) continue;
+
+            // declared methods
+            var targets = new ArrayList<>(Arrays.asList(t.methods));
+
+            // synthetic methods
+            for (var method : clazz.methods) {
+                if ((method.access & Opcodes.ACC_SYNTHETIC) != 0)
+                    targets.add(method.name + method.desc);
+            }
+
+            return targets;
+        }
+
+        return List.of();
+    }
+}

forge-transformers/src/main/resources/META-INF/services/cpw.mods.modlauncher.api.ITransformationService

@@ -0,0 +1 @@
+net.minecraftforge.forge.transformers.ForgeModTransformers

forge-transformers/src/main/resources/coremods/finalize_spawn_targets.json

@@ -0,0 +1,168 @@
+[
+    {
+        "class": "net/minecraft/gametest/framework/GameTestHelper",
+        "methods": [
+            "spawn(Lnet/minecraft/world/entity/EntityType;Lnet/minecraft/world/phys/Vec3;Lnet/minecraft/world/entity/EntitySpawnReason;)Lnet/minecraft/world/entity/Entity;"
+        ]
+    },
+    {
+        "class": "net/minecraft/server/commands/RaidCommand",
+        "methods": [
+            "spawnLeader(Lnet/minecraft/commands/CommandSourceStack;)I"
+        ]
+    },
+    {
+        "class": "net/minecraft/server/commands/SummonCommand",
+        "methods": [
+            "createEntity(Lnet/minecraft/commands/CommandSourceStack;Lnet/minecraft/core/Holder$Reference;Lnet/minecraft/world/phys/Vec3;Lnet/minecraft/nbt/CompoundTag;Z)Lnet/minecraft/world/entity/Entity;"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/entity/EntityType",
+        "methods": [
+            "create(Lnet/minecraft/server/level/ServerLevel;Ljava/util/function/Consumer;Lnet/minecraft/core/BlockPos;Lnet/minecraft/world/entity/EntitySpawnReason;ZZ)Lnet/minecraft/world/entity/Entity;"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/entity/ai/village/VillageSiege",
+        "methods": [
+            "trySpawn(Lnet/minecraft/server/level/ServerLevel;)V"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/entity/animal/equine/SkeletonTrapGoal",
+        "methods": [
+            "createHorse(Lnet/minecraft/world/DifficultyInstance;)Lnet/minecraft/world/entity/animal/equine/AbstractHorse;",
+            "createSkeleton(Lnet/minecraft/world/DifficultyInstance;Lnet/minecraft/world/entity/animal/equine/AbstractHorse;)Lnet/minecraft/world/entity/monster/skeleton/Skeleton;"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/entity/animal/equine/ZombieHorse",
+        "methods": [
+            "finalizeSpawn(Lnet/minecraft/world/level/ServerLevelAccessor;Lnet/minecraft/world/DifficultyInstance;Lnet/minecraft/world/entity/EntitySpawnReason;Lnet/minecraft/world/entity/SpawnGroupData;)Lnet/minecraft/world/entity/SpawnGroupData;"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/entity/animal/frog/Tadpole",
+        "methods": [
+            
+        ]
+    },
+    {
+        "class": "net/minecraft/world/entity/monster/Strider",
+        "methods": [
+            "spawnJockey(Lnet/minecraft/world/level/ServerLevelAccessor;Lnet/minecraft/world/DifficultyInstance;Lnet/minecraft/world/entity/Mob;Lnet/minecraft/world/entity/SpawnGroupData;)Lnet/minecraft/world/entity/SpawnGroupData;"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/entity/monster/illager/Evoker$EvokerSummonSpellGoal",
+        "methods": [
+            "performSpellCasting()V"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/entity/monster/spider/Spider",
+        "methods": [
+            "finalizeSpawn(Lnet/minecraft/world/level/ServerLevelAccessor;Lnet/minecraft/world/DifficultyInstance;Lnet/minecraft/world/entity/EntitySpawnReason;Lnet/minecraft/world/entity/SpawnGroupData;)Lnet/minecraft/world/entity/SpawnGroupData;"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/entity/monster/zombie/Drowned",
+        "methods": [
+            "finalizeSpawn(Lnet/minecraft/world/level/ServerLevelAccessor;Lnet/minecraft/world/DifficultyInstance;Lnet/minecraft/world/entity/EntitySpawnReason;Lnet/minecraft/world/entity/SpawnGroupData;)Lnet/minecraft/world/entity/SpawnGroupData;"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/entity/monster/zombie/Husk",
+        "methods": [
+            "finalizeSpawn(Lnet/minecraft/world/level/ServerLevelAccessor;Lnet/minecraft/world/DifficultyInstance;Lnet/minecraft/world/entity/EntitySpawnReason;Lnet/minecraft/world/entity/SpawnGroupData;)Lnet/minecraft/world/entity/SpawnGroupData;"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/entity/monster/zombie/Zombie",
+        "methods": [
+            "hurtServer(Lnet/minecraft/server/level/ServerLevel;Lnet/minecraft/world/damagesource/DamageSource;F)Z",
+            "finalizeSpawn(Lnet/minecraft/world/level/ServerLevelAccessor;Lnet/minecraft/world/DifficultyInstance;Lnet/minecraft/world/entity/EntitySpawnReason;Lnet/minecraft/world/entity/SpawnGroupData;)Lnet/minecraft/world/entity/SpawnGroupData;"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/entity/monster/zombie/ZombieVillager",
+        "methods": [
+            
+        ]
+    },
+    {
+        "class": "net/minecraft/world/entity/npc/CatSpawner",
+        "methods": [
+            "spawnCat(Lnet/minecraft/core/BlockPos;Lnet/minecraft/server/level/ServerLevel;Z)V"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/entity/npc/villager/Villager",
+        "methods": [
+            "getBreedOffspring(Lnet/minecraft/server/level/ServerLevel;Lnet/minecraft/world/entity/AgeableMob;)Lnet/minecraft/world/entity/npc/villager/Villager;"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/entity/raid/Raid",
+        "methods": [
+            "joinRaid(Lnet/minecraft/server/level/ServerLevel;ILnet/minecraft/world/entity/raid/Raider;Lnet/minecraft/core/BlockPos;Z)V"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/level/NaturalSpawner",
+        "methods": [
+            "spawnCategoryForPosition(Lnet/minecraft/world/entity/MobCategory;Lnet/minecraft/server/level/ServerLevel;Lnet/minecraft/world/level/chunk/ChunkAccess;Lnet/minecraft/core/BlockPos;Lnet/minecraft/world/level/NaturalSpawner$SpawnPredicate;Lnet/minecraft/world/level/NaturalSpawner$AfterSpawnCallback;)V",
+            "spawnMobsForChunkGeneration(Lnet/minecraft/world/level/ServerLevelAccessor;Lnet/minecraft/core/Holder;Lnet/minecraft/world/level/ChunkPos;Lnet/minecraft/util/RandomSource;)V"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/level/block/entity/trialspawner/TrialSpawner",
+        "methods": [
+            "spawnMob(Lnet/minecraft/server/level/ServerLevel;Lnet/minecraft/core/BlockPos;)Ljava/util/Optional;"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/level/levelgen/PatrolSpawner",
+        "methods": [
+            "spawnPatrolMember(Lnet/minecraft/server/level/ServerLevel;Lnet/minecraft/core/BlockPos;Lnet/minecraft/util/RandomSource;Z)Z"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/level/levelgen/PhantomSpawner",
+        "methods": [
+            "tick(Lnet/minecraft/server/level/ServerLevel;Z)V"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/level/levelgen/structure/structures/OceanMonumentPieces$OceanMonumentPiece",
+        "methods": [
+            "spawnElder(Lnet/minecraft/world/level/WorldGenLevel;Lnet/minecraft/world/level/levelgen/structure/BoundingBox;III)V"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/level/levelgen/structure/structures/OceanRuinPieces$OceanRuinPiece",
+        "methods": [
+            "handleDataMarker(Ljava/lang/String;Lnet/minecraft/core/BlockPos;Lnet/minecraft/world/level/ServerLevelAccessor;Lnet/minecraft/util/RandomSource;Lnet/minecraft/world/level/levelgen/structure/BoundingBox;)V"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/level/levelgen/structure/structures/SwampHutPiece",
+        "methods": [
+            "postProcess(Lnet/minecraft/world/level/WorldGenLevel;Lnet/minecraft/world/level/StructureManager;Lnet/minecraft/world/level/chunk/ChunkGenerator;Lnet/minecraft/util/RandomSource;Lnet/minecraft/world/level/levelgen/structure/BoundingBox;Lnet/minecraft/world/level/ChunkPos;Lnet/minecraft/core/BlockPos;)V",
+            "spawnCat(Lnet/minecraft/world/level/ServerLevelAccessor;Lnet/minecraft/world/level/levelgen/structure/BoundingBox;)V"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/level/levelgen/structure/structures/WoodlandMansionPieces$WoodlandMansionPiece",
+        "methods": [
+            "handleDataMarker(Ljava/lang/String;Lnet/minecraft/core/BlockPos;Lnet/minecraft/world/level/ServerLevelAccessor;Lnet/minecraft/util/RandomSource;Lnet/minecraft/world/level/levelgen/structure/BoundingBox;)V"
+        ]
+    },
+    {
+        "class": "net/minecraft/world/level/levelgen/structure/templatesystem/StructureTemplate",
+        "methods": [
+            
+        ]
+    }
+]

gradle.properties

@@ -1,17 +1,17 @@
 # Sets default memory used for gradle commands. Can be overridden by user or command line properties.
 # This is required to provide enough memory for the Minecraft decompilation process.
-org.gradle.jvmargs=-Xmx3G
+org.gradle.jvmargs=-Xmx6G
 org.gradle.daemon=false
 org.gradle.parallel=true
 
 JAVA_VERSION=21
-MC_VERSION=1.21.1
+MC_VERSION=1.21.11
 MC_NEXT_VERSION=1.22
-MCP_VERSION=20240808.132146
+MCP_VERSION=20251209.095502
 MAPPING_CHANNEL=official
-MAPPING_VERSION=1.21.1
+MAPPING_VERSION=1.21.11
 
-// Set to true before the first build of a new MC version, so we don't do compatibility checks
+# Set to true before the first build of a new MC version, so we don't do compatibility checks
 CHECK_COMPATIBILITY=false
-// Set to true to allow for fuzzy patching. Useful during updateing
-UPDATING=true
+# Set to true to allow for fuzzy patching. Useful during updateing
+UPDATING=false

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,7 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.7-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.12.1-bin.zip
 networkTimeout=10000
+validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists

gradlew

@@ -83,7 +83,8 @@ done
 # This is normally unused
 # shellcheck disable=SC2034
 APP_BASE_NAME=${0##*/}
-APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
+APP_HOME=$( cd "${APP_HOME:-./}" > /dev/null && pwd -P ) || exit
 
 # Use the maximum available, or set MAX_FD != -1 to use that value.
 MAX_FD=maximum
@@ -130,10 +131,13 @@ location of your Java installation."
     fi
 else
     JAVACMD=java
-    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+    if ! command -v java >/dev/null 2>&1
+    then
+        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
 
 Please set the JAVA_HOME variable in your environment to match the
 location of your Java installation."
+    fi
 fi
 
 # Increase the maximum file descriptors if we can.
@@ -141,7 +145,7 @@ if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
     case $MAX_FD in #(
       max*)
         # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
-        # shellcheck disable=SC3045
+        # shellcheck disable=SC2039,SC3045
         MAX_FD=$( ulimit -H -n ) ||
             warn "Could not query maximum file descriptor limit"
     esac
@@ -149,7 +153,7 @@ if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
       '' | soft) :;; #(
       *)
         # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
-        # shellcheck disable=SC3045
+        # shellcheck disable=SC2039,SC3045
         ulimit -n "$MAX_FD" ||
             warn "Could not set maximum file descriptor limit to $MAX_FD"
     esac
@@ -198,11 +202,11 @@ fi
 # Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
 DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
 
-# Collect all arguments for the java command;
-#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
-#     shell script including quotes and variable substitutions, so put them in
-#     double quotes to make sure that they get re-expanded; and
-#   * put everything else in single quotes, so that it's not re-expanded.
+# Collect all arguments for the java command:
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#     and any embedded shellness will be escaped.
+#   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
+#     treated as '${Hostname}' itself on the command line.
 
 set -- \
         "-Dorg.gradle.appname=$APP_BASE_NAME" \

gradlew.bat

@@ -43,11 +43,11 @@ set JAVA_EXE=java.exe
 %JAVA_EXE% -version >NUL 2>&1
 if %ERRORLEVEL% equ 0 goto execute
 
-echo.
-echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
-echo.
-echo Please set the JAVA_HOME variable in your environment to match the
-echo location of your Java installation.
+echo. 1>&2
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
 
 goto fail
 
@@ -57,11 +57,11 @@ set JAVA_EXE=%JAVA_HOME%/bin/java.exe
 
 if exist "%JAVA_EXE%" goto execute
 
-echo.
-echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
-echo.
-echo Please set the JAVA_HOME variable in your environment to match the
-echo location of your Java installation.
+echo. 1>&2
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME% 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
 
 goto fail