Update to 1.17

Update to Official classnames
Patchwork
Make the game compile and run
Merge in the new HUD overlay API
Merge in the new render properties API
PEEL
Use Gradle 7.2 snapshot to fix eclipse integration bug in 7.1, Would use 7.0 but FG needs 7.1 for some reason.
New FML installer
Update to 1.17.1

Co-authored-by: LexManos <[email protected]>
Co-authored-by: SizableShrimp <[email protected]>
Co-authored-by: cpw <[email protected]>
Co-authored-by: Curle <[email protected]>
Co-authored-by: Unnoen <[email protected]>
Co-authored-by: covers1624 <[email protected]>
Co-authored-by: DaemonUmbra <[email protected]>
Co-authored-by: gigaherz <[email protected]>
Signed-off-by: SizableShrimp <[email protected]>

.gitattributes

@@ -14,3 +14,10 @@
 *.cfg text eol=lf
 *.py text eol=lf
 *.jks binary
+
+# Disable autocrlf on generated files, they always generate with LF
+src/generated/**/.cache/cache text eol=lf
+src/generated/**/*.json text eol=lf
+src/generated_test/**/.cache/cache text eol=lf
+src/generated_test/**/*.json text eol=lf
+

.github/workflows/publish.yml

@@ -1,28 +0,0 @@
-name: Publish
-
-on:
-  push:
-    branches: [ '1.14.x' ]
-
-permissions:
-  contents: read
-
-jobs:
-  build:
-    uses: MinecraftForge/SharedActions/.github/workflows/gradle.yml@main
-    with:
-      java: 8
-      gradle_tasks: 'setup 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 }}
-      # Unused for now until we upgrade gradle
-      # 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

@@ -9,36 +9,38 @@
 
 #idea
 /.idea
+/*/out
 /classes
 *.iml
 
 #gradle
 /build
 /.gradle
-/**/.gradle
-/**/build
+/*/build
+/*/.gradle
 
-#occupational hazards
+# Projects repo, either ignore it, or ignore patches.
 /projects/mcp/
 /projects/clean/
 /projects/forge/
+/projects/fmlonly/
+#/patches/
+
+#occupational hazards
 /projects/**/build/
 /projects/**/out/
 /projects/**/run/
 /projects/**/*.launch
 /repo/
-/buildSrc
 src/generated/resources/.cache/
 
 #Patch rejects
 /patches-/
-*.patch.rej
+#*.patch.rej
+/projects/*/rejects/
 
 # FML changelog
 changelog.txt
 *.py
 *.7z
 /logs/
-
-gradle.properties
-!/mdk/gradle.properties

Jenkinsfile

@@ -0,0 +1,114 @@
+@Library('forge-shared-library')_
+
+pipeline {
+    options {
+        disableConcurrentBuilds()
+    }
+    agent {
+        docker {
+            image 'gradle:7-jdk16'
+            args '-v forgegc:/home/gradle/.gradle/'
+        }
+    }
+    environment {
+        GRADLE_ARGS = '--no-daemon --console=plain' // No daemon for now as FG3 kinda derps. //'-Dorg.gradle.daemon.idletimeout=5000'
+        DISCORD_WEBHOOK = credentials('forge-discord-jenkins-webhook')
+        DISCORD_PREFIX = "Job: Forge Branch: ${BRANCH_NAME} Build: #${BUILD_NUMBER}"
+        JENKINS_HEAD = 'https://wiki.jenkins-ci.org/download/attachments/2916393/headshot.png'
+    }
+
+    stages {
+        stage('notify_start') {
+            when {
+                not {
+                    changeRequest()
+                }
+            }
+            steps {
+                discordSend(
+                    title: "${DISCORD_PREFIX} Started",
+                    successful: true,
+                    result: 'ABORTED', //White border
+                    thumbnail: JENKINS_HEAD,
+                    webhookURL: DISCORD_WEBHOOK
+                )
+            }
+        }
+        stage('setup') {
+            steps {
+                withGradle {
+                    sh './gradlew ${GRADLE_ARGS} --refresh-dependencies --continue setup'
+                }
+                script {
+                    env.MYVERSION = sh(returnStdout: true, script: './gradlew :forge:properties -q | grep "^version:" | cut -d" " -f2').trim()
+                }
+            }
+        }
+        stage('changelog') {
+            when {
+                not {
+                    changeRequest()
+                }
+            }
+            steps {
+                writeChangelog(currentBuild, 'build/changelog.txt')
+            }
+        }
+        stage('publish') {
+            when {
+                not {
+                    changeRequest()
+                }
+            }
+            environment {
+                CROWDIN = credentials('forge-crowdin')
+                KEYSTORE = credentials('forge-jenkins-keystore-old')
+                KEYSTORE_KEYPASS = credentials('forge-jenkins-keystore-old-keypass')
+                KEYSTORE_STOREPASS = credentials('forge-jenkins-keystore-old-keypass')
+            }
+            steps {
+                withCredentials([usernamePassword(credentialsId: 'maven-forge-user', usernameVariable: 'MAVEN_USER', passwordVariable: 'MAVEN_PASSWORD')]) {
+                    withGradle {
+                        sh './gradlew ${GRADLE_ARGS} publish -PkeystoreKeyPass=${KEYSTORE_KEYPASS} -PkeystoreStorePass=${KEYSTORE_STOREPASS} -Pkeystore=${KEYSTORE} -PcrowdinKey=${CROWDIN}'
+                    }
+                }
+            }
+            post {
+                success {
+                    build job: 'filegenerator', parameters: [string(name: 'COMMAND', value: "promote net.minecraftforge:forge ${env.MYVERSION} latest")], propagate: false, wait: false
+                }
+            }
+        }
+        stage('test_publish_pr') { //Publish to local repo to test full process, but don't include credentials so it can't sign/publish to maven
+            when {
+                changeRequest()
+            }
+            environment {
+                CROWDIN = credentials('forge-crowdin')
+            }
+            steps {
+                withGradle {
+                    sh './gradlew ${GRADLE_ARGS} publish -PcrowdinKey=${CROWDIN}'
+                }
+            }
+        }
+    }
+    post {
+        always {
+            script {
+                archiveArtifacts artifacts: 'projects/forge/build/libs/**/*.*', fingerprint: true, onlyIfSuccessful: true, allowEmptyArchive: true
+
+                if (env.CHANGE_ID == null) { // This is unset for non-PRs
+                    discordSend(
+                        title: "${DISCORD_PREFIX} Finished ${currentBuild.currentResult}",
+                        description: '```\n' + getChanges(currentBuild) + '\n```',
+                        successful: currentBuild.resultIsBetterOrEqualTo("SUCCESS"),
+                        result: currentBuild.currentResult,
+                        thumbnail: JENKINS_HEAD,
+                        webhookURL: DISCORD_WEBHOOK
+                    )
+                }
+            }
+        }
+    }
+}

LICENSE-header.txt

@@ -1,2 +1,16 @@
-Copyright (c) Forge Development LLC and contributors
-SPDX-License-Identifier: LGPL-2.1-only
+Minecraft Forge
+Copyright (c) 2016-${year}.
+
+This library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Lesser General Public
+License as published by the Free Software Foundation version 2.1
+of the License.
+
+This library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with this library; if not, write to the Free Software
+Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

buildSrc/.gitignore

@@ -0,0 +1,3 @@
+/.gradle/
+/build/
+/out/

buildSrc/build.gradle

@@ -0,0 +1,9 @@
+repositories {
+    maven { url = 'https://maven.minecraftforge.net/' }
+	mavenCentral()
+}
+dependencies {
+	implementation 'org.ow2.asm:asm:9.1'
+	implementation 'org.ow2.asm:asm-tree:9.1'
+    implementation 'net.minecraftforge:srgutils:0.4.+'
+}

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

@@ -0,0 +1,64 @@
+package net.minecraftforge.forge.tasks
+
+import groovy.json.JsonBuilder
+import org.gradle.api.DefaultTask
+import org.gradle.api.file.RegularFileProperty
+import org.gradle.api.tasks.InputFile
+import org.gradle.api.tasks.OutputFile
+import org.gradle.api.tasks.TaskAction
+import org.objectweb.asm.ClassReader
+import org.objectweb.asm.Opcodes
+import org.objectweb.asm.tree.ClassNode
+import org.objectweb.asm.tree.FieldNode
+import org.objectweb.asm.tree.MethodNode
+
+import java.util.zip.ZipEntry
+import java.util.zip.ZipInputStream
+
+abstract class BytecodeFinder extends DefaultTask {
+    @InputFile abstract RegularFileProperty getJar()
+    @OutputFile abstract RegularFileProperty getOutput()
+
+    BytecodeFinder() {
+        output.convention(project.layout.buildDirectory.dir(name).map { it.file("output.json") })
+    }
+
+    @TaskAction
+    protected void exec() {
+        Util.init()
+
+        def outputFile = output.get().asFile
+        if (outputFile.exists())
+            outputFile.delete()
+
+        pre()
+
+        jar.get().asFile.withInputStream { i ->
+            new ZipInputStream(i).withCloseable { zin ->
+                ZipEntry zein
+                while ((zein = zin.nextEntry) != null) {
+                    if (zein.name.endsWith('.class')) {
+                        def node = new ClassNode(Opcodes.ASM9)
+                        new ClassReader(zin).accept(node, 0)
+                        process(node)
+                    }
+                }
+            }
+        }
+
+        post()
+        outputFile.text = new JsonBuilder(getData()).toPrettyString()
+    }
+
+
+    protected process(ClassNode node) {
+        if (node.fields != null) node.fields.each { process(node, it) }
+        if (node.methods != null) node.methods.each { process(node, it) }
+    }
+
+    protected pre() {}
+    protected process(ClassNode parent, FieldNode node) {}
+    protected process(ClassNode parent, MethodNode node) {}
+    protected post() {}
+    protected abstract Object getData()
+}

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

@@ -0,0 +1,267 @@
+package net.minecraftforge.forge.tasks
+
+import net.minecraftforge.srgutils.IMappingFile
+import org.gradle.api.file.ConfigurableFileCollection
+import org.gradle.api.file.RegularFileProperty
+
+import org.gradle.api.DefaultTask
+import org.gradle.api.tasks.InputFile
+import org.gradle.api.tasks.InputFiles
+import org.gradle.api.tasks.Optional
+import org.gradle.api.tasks.TaskAction
+import org.objectweb.asm.Opcodes
+
+abstract class CheckATs extends DefaultTask {
+	@InputFile abstract RegularFileProperty getInheritance()
+	@InputFiles abstract ConfigurableFileCollection getAts()
+    @InputFile @Optional abstract RegularFileProperty getMappings()
+	
+    @TaskAction
+    protected void exec() {
+        def mappings = mappings.map { IMappingFile.load(it.asFile) }.getOrNull()
+		Util.init()
+		def parse = { line ->
+			def idx = line.indexOf('#')
+			def comment = idx == -1 ? null : line.substring(idx)
+			if (idx != -1) line = line.substring(0, idx - 1)
+			def (modifier, cls, desc) = (line.trim() + '     ').split(' ', -1)
+			def key = cls + (desc.isEmpty() ? '' : ' ' + desc)
+			return [modifier, cls, desc, comment, key]
+		}
+		def accessLevel = { access ->
+			if ((access & Opcodes.ACC_PUBLIC)    != 0) return 3
+			if ((access & Opcodes.ACC_PROTECTED) != 0) return 2
+			if ((access & Opcodes.ACC_PRIVATE)   != 0) return 0
+			return 1
+		}
+		def accessStr = { access ->
+			if (access.endsWith('-f') || access.endsWith('+f'))
+				return 4
+			switch (access.toLowerCase()) {
+				case 'public':    return 3
+				case 'protected': return 2
+				case 'default':   return 1
+				case 'private':   return 0
+				default:          return -1
+			}
+		}
+		def json = inheritance.get().asFile.json()
+		
+		ats.each { f -> 
+			TreeMap lines = [:]
+			def group = null
+			for (def line : f.readLines()) {
+				if (line.isEmpty()) continue
+				if (line.startsWith('#group ')) {
+					def (modifier, cls, desc, comment, key) = parse.call(line.substring(7))
+					
+					if (desc != '*' && desc != '*()' && desc != '<init>')
+						throw new IllegalStateException('Invalid group: ' + line)
+					
+					group = [modifier: modifier, cls: cls, desc: desc, comment: comment, 
+						existing: [] as Set,
+						children: [] as TreeSet,
+						group: true
+					]
+					if (lines.containsKey(key))
+						throw new IllegalStateException('Duplicate group: ' + line)
+					
+					lines[key] = group
+				} else if (group != null) {
+					if (line.startsWith('#endgroup')) {
+						group = null
+					} else {
+						def (modifier, cls, desc, comment, key) = parse.call(line)
+						group['existing'].add(key)
+					}
+				} else if (line.startsWith('#endgroup')) {
+					throw new IllegalStateException('Invalid group ending: ' + line)
+				} else if (line.startsWith('#')) {
+					//Nom
+				} else {
+					def (modifier, cls, desc, comment, key) = parse.call(line)
+					if (lines.containsKey(key)) {
+						println('Duplicate: ' + line)
+						continue
+					}
+					lines[key] = [modifier: modifier, cls: cls, desc: desc, comment: comment, group: false]
+				}
+			}
+			
+			// Process Groups, this will remove any entries outside the group that is covered by the group
+			for (def key : new ArrayList<>(lines.keySet())) {
+				def entry = lines.get(key)
+				if (entry != null && entry['group']) {
+					def cls = entry['cls']
+					def jcls = json.get(cls.replaceAll('\\.', '/'))
+					if (jcls == null) {
+						lines.remove(key)
+						println('Invalid Group: ' + key)
+					} else if ('*' == entry['desc']) {
+						if (!jcls.containsKey('fields')) {
+							lines.remove(key)
+							println('Invalid Group, Class has no fields: ' + key)
+						} else {
+							jcls['fields'].each { field, value ->
+								def fkey = cls + ' ' + field
+								if (accessLevel.call(value['access']) < accessStr.call(entry['modifier'])) {
+									if (lines.containsKey(fkey)) {
+										lines.remove(fkey)
+									} else if (!entry['existing'].contains(fkey)) {
+										println('Added: ' + fkey)
+									}
+									entry['children'].add(fkey)
+								} else if (lines.containsKey(fkey)) {
+									lines.remove(fkey)
+									println('Removed: ' + fkey)
+								}
+							}
+							entry['existing'].stream().findAll{ !entry['children'].contains(it) }.each{ println('Removed: ' + it) }
+						}
+					} else if ('*()' == entry['desc']) {
+						if (!jcls.containsKey('methods')) {
+							lines.remove(key)
+							println('Invalid Group, Class has no methods: ' + key)
+						} else {
+							jcls['methods'].each{ mtd, value ->
+								if (mtd.startsWith('<clinit>') || mtd.startsWith('lambda$'))
+									return
+								key = cls + ' ' + mtd.replace(' ', '')
+								if (accessLevel.call(value['access']) < accessStr.call(entry['modifier'])) {
+									if (lines.containsKey(key)) {
+										lines.remove(key)
+									} else if (!entry['existing'].contains(key)) {
+										println('Added: ' + key)
+									}
+									entry['children'].add(key)
+								} else if (lines.containsKey(key)) {
+									lines.remove(key)
+									println('Removed: ' + key)
+								}
+							}
+							entry['existing'].stream().findAll{ !entry['children'].contains(it) }.each{ println('Removed: ' + it) }
+						}
+					} else if ('<init>' == entry['desc']) { //Make all public non-abstract subclasses
+						json.each{ tcls,value -> 
+							if (!value.containsKey('methods') || ((value['access'] & Opcodes.ACC_ABSTRACT) != 0))
+								return
+							def parents = [] as Set
+							def parent = tcls
+							while (parent != null && json.containsKey(parent)) {
+								parents.add(parent)
+								def p = json[parent]
+								parent = p == null ? null : p['superName']
+							}
+							if (parents.contains(cls.replaceAll('\\.', '/'))) {
+								value['methods'].each{ mtd, v -> 
+									if (mtd.startsWith('<init>')) {
+										def child = tcls.replaceAll('/', '\\.') + ' ' + mtd.replace(' ', '')
+										if (accessLevel.call(v['access']) < 3) {
+											if (lines.containsKey(child)) {
+												lines.remove(child)
+											} else if (!entry['existing'].contains(child)) {
+												println('Added: ' + child)
+											}
+											entry['children'].add(child)
+										} else if (lines.containsKey(child)) {
+											lines.remove(child)
+											println('Removed: ' + child)
+										}
+									}
+								}
+							}
+						}
+						entry['existing'].stream().findAll{ !entry['children'].contains(it) }.each{ println('Removed: ' + it) }
+					}
+				}
+			}
+			
+			// Process normal lines, remove invalid and remove narrowing
+			for (def key : new ArrayList<>(lines.keySet())) {
+				def entry = lines.get(key)
+				if (entry != null && !entry['group']) {
+					def cls = entry['cls']
+					def jcls = json.get(cls.replaceAll('\\.', '/'))
+					if (jcls == null) {
+						lines.remove(key)
+						println('Invalid: ' + key)
+					} else if (entry['desc'] == '') {
+						if (accessLevel.call(jcls['access']) > accessStr.call(entry['modifier']) && (entry.comment == null || !entry.comment.startsWith('#force '))) {
+							lines.remove(key)
+							println('Invalid Narrowing: ' + key)
+						}
+					} else if (!entry['desc'].contains('(')) {
+						if (!jcls.containsKey('fields') || !jcls['fields'].containsKey(entry['desc'])) {
+							lines.remove(key)
+							println('Invalid: ' + key)
+						} else {
+							def value = jcls['fields'][entry['desc']]
+							if (accessLevel.call(value['access']) > accessStr.call(entry['modifier']) && (entry.comment == null || !entry.comment.startsWith('#force '))) {
+								lines.remove(key)
+								println('Invalid Narrowing: ' + key)
+								println(entry.comment)
+							}
+						}
+					} else {
+						def jdesc = entry['desc'].replace('(', ' (')
+						if (!jcls.containsKey('methods') || !jcls['methods'].containsKey(jdesc)) {
+							lines.remove(key)
+							println('Invalid: ' + key)
+						} else {
+							def value = jcls['methods'][jdesc]
+							if (accessLevel.call(value['access']) > accessStr.call(entry['modifier']) && (entry.comment == null || !entry.comment.startsWith('#force '))) {
+								lines.remove(key)
+								println('Invalid Narrowing: ' + key)
+							}
+						}
+					}
+				}
+			}
+
+			
+			def data = []
+            def remapComment = { entry ->
+                if (!mappings || !entry || !entry.desc) return null
+                def comment = entry.comment?.substring(1)?.trim()
+                def jsonCls = json.get(entry.cls.replaceAll('\\.', '/'))
+                def mappingsClass = mappings?.getClass(jsonCls.name)
+                if (!mappingsClass) return entry.comment
+                def idx = entry.desc.indexOf('(')
+                def mappedName = idx == -1
+                        ? mappingsClass.remapField(entry.desc)
+                        : mappingsClass.remapMethod(entry.desc.substring(0, idx), entry.desc.substring(idx))
+                if (!mappedName) return entry.comment
+                if (mappedName == '<init>')
+                    mappedName = 'constructor'
+
+                if (comment?.startsWith(mappedName))
+                    return '# ' + comment
+                if (comment && comment.indexOf(' ') != -1) {
+                    def split = comment.split(" - ").toList()
+                    if (split[0].indexOf(' ') != -1)
+                        // The first string is more than one word, so append before it
+                        return "# ${mappedName} - ${comment}"
+                    split.remove(0)
+                    return "# ${mappedName} - ${String.join(' - ', split)}"
+                }
+                return '# ' + mappedName
+            }
+			lines.each { key,value -> 
+				if (!value.group) {
+                    def comment = remapComment.call(value)
+					data.add(value.modifier + ' ' + key + (comment ? ' ' + comment : ''))
+				} else {
+					data.add('#group ' + value.modifier + ' ' + key + (value.comment == null ? '' : ' ' + value.comment))
+					value.children.each {
+                        def line = value.modifier + ' ' + it
+                        def (modifier, cls, desc, comment) = parse.call(line)
+                        comment = remapComment.call([modifier: modifier, cls: cls, desc: desc, comment: comment])
+                        data.add(line + (comment ? ' ' + comment : ''))
+                    }
+					data.add('#endgroup')
+				}
+			}
+			f.text = data.join('\n')
+		}
+	}
+}

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

@@ -0,0 +1,94 @@
+package net.minecraftforge.forge.tasks
+
+import org.gradle.api.file.ConfigurableFileCollection
+import org.gradle.api.file.RegularFileProperty
+
+import org.gradle.api.DefaultTask
+import org.gradle.api.tasks.InputFile
+import org.gradle.api.tasks.InputFiles
+import org.gradle.api.tasks.TaskAction
+
+import org.objectweb.asm.ClassReader
+import org.objectweb.asm.ClassVisitor
+import org.objectweb.asm.MethodVisitor
+import org.objectweb.asm.Opcodes
+import org.objectweb.asm.Type
+
+import java.util.zip.ZipEntry
+import java.util.zip.ZipInputStream
+
+abstract class CheckExcs extends DefaultTask {
+	@InputFile abstract RegularFileProperty getBinary()
+	@InputFiles abstract ConfigurableFileCollection getExcs()
+	
+    @TaskAction
+    protected void exec() {
+		Util.init()
+		def known = []
+		binary.get().asFile.withInputStream { i ->
+			new ZipInputStream(i).withCloseable { zin ->
+				def visitor = new ClassVisitor(Opcodes.ASM9) {
+					private String cls
+					@Override
+					public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) {
+						this.cls = name
+					}
+					
+					@Override
+					public MethodVisitor visitMethod(int access, String name, String descriptor, String signature, String[] exceptions) {
+						known.add(this.cls + '.' + name + descriptor)
+						super.visitMethod(access, name, descriptor, signature, exceptions)
+					}
+				}
+				ZipEntry zein
+				while ((zein = zin.nextEntry) != null) {
+					if (zein.name.endsWith('.class')) {
+						ClassReader reader = new ClassReader(zin)
+						reader.accept(visitor, ClassReader.SKIP_CODE | ClassReader.SKIP_DEBUG | ClassReader.SKIP_FRAMES)
+					}
+				}
+			}
+		}
+		
+		excs.each { f -> 
+			def lines = []
+			f.eachLine { line ->
+				def idx = line.indexOf('#')
+				if (idx == 0 || line.isEmpty()) {
+					return
+				}
+				
+				def comment = idx == -1 ? null : line.substring(idx)
+				if (idx != -1) line = line.substring(0, idx - 1)
+				
+				if (!line.contains('=')) {
+					println('Invalid: ' + line)
+					return
+				}
+				
+				def (key, value) = line.split('=', 2)
+				if (!known.contains(key)) {
+					println('Unknown: ' + line)
+					return
+				}
+				
+				def (cls, desc) = key.split('\\.', 2)
+				if (!desc.contains('(')) {
+					println('Invalid: ' + line)
+					return
+				}
+				def name = desc.split('\\(', 2)[0]
+				desc = '(' + desc.split('\\(', 2)[1]
+				
+				def (exceptions, args) = value.contains('|') ? value.split('|', 2) : [value, '']
+				
+				if (args.split(',').length != Type.getArgumentTypes(desc).length) {
+					println('Invalid: ' + line)
+					return
+				}
+				lines.add(line)
+			}
+			f.text = lines.sort().join('\n')
+		}
+	}
+}

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

@@ -0,0 +1,219 @@
+package net.minecraftforge.forge.tasks
+
+import org.gradle.api.DefaultTask
+import org.gradle.api.file.DirectoryProperty
+import org.gradle.api.tasks.Input
+import org.gradle.api.tasks.InputDirectory
+import org.gradle.api.tasks.TaskAction
+
+import java.nio.file.Files
+import java.nio.file.Paths
+import java.util.regex.Pattern
+
+abstract class CheckPatches extends DefaultTask {
+    @InputDirectory abstract DirectoryProperty getPatchDir()
+    @Input boolean autoFix = false
+
+    @TaskAction
+    protected void exec() {
+        def hasS2SArtifact = [
+                Paths.get("patches/minecraft/net/minecraft/client/renderer/ViewArea.java.patch"),
+                Paths.get("patches/minecraft/net/minecraft/data/models/blockstates/Variant.java.patch")
+        ]
+
+        def verified = true;
+        patchDir.get().asFileTree.each { patch ->
+            def patchPath = project.rootDir.toPath().relativize(patch.toPath())
+            verified &= verifyPatch(patch, autoFix, patchPath.toString(), hasS2SArtifact.contains(patchPath))
+        }
+
+        if (!verified)
+            throw new RuntimeException('One or more patches failed verification. Check the log for errors.')
+    }
+
+    def verifyPatch(patch, fix, patchPath, hasS2SArtifact) {
+        def hunk_start_pattern = Pattern.compile('^@@ -[0-9,]* \\+[0-9,_]* @@$')
+        def white_space_pattern = Pattern.compile('^[+\\-]\\s*$')
+        def import_pattern = Pattern.compile('^[+\\-]\\s*import.*')
+        def field_pattern = Pattern.compile('^[+\\-][\\s]*((public|protected|private)[\\s]*)?(static[\\s]*)?(final)?([^=;]*)(=.*)?;\\s*$')
+        def method_pattern = Pattern.compile('^[+\\-][\\s]*((public|protected|private)[\\s]*)?(static[\\s]*)?(final)?([^(]*)[(]([^)]*)?[)]\\s*[{]\\s*$')
+        def class_pattern = Pattern.compile('^[+\\-][\\s]*((public|protected|private)[\\s]*)?(static[\\s]*)?(final[\\s]*)?(class|interface)([^{]*)[{]\\s*$')
+
+        def accessMap = [("private"):0, (null):1, ("protected"):2, ("public"):3]
+
+        def hasProblem = false;
+        def lines = patch.readLines()
+
+        def hunksStart = 0
+        def onlyWhiteSpace = false
+
+        def didFix = false
+        def newLines = []
+        def whiteSpaceErrors = []
+
+        // First two lines are file name ++/-- and we do not care
+        newLines.add(lines[0] + '\n')
+        newLines.add(lines[1] + '\n')
+
+        int i = 2
+        for (; i < lines.size(); ++i) {
+            def line = lines[i]
+            newLines.add(line + '\n')
+
+            if (hunk_start_pattern.matcher(line).find()) {
+                if (onlyWhiteSpace) {
+                    if (fix || hasS2SArtifact) {
+                        logger.lifecycle("Removing white space hunk starting at line {}, file: {}", hunksStart + 1, patchPath)
+                        def toRemove = i - hunksStart;
+                        while (toRemove-- > 0)
+                            newLines.remove(newLines.size() - 1)
+                        didFix = true
+                    }
+                    else {
+                        logger.lifecycle("Patch contains only white space hunk starting at line {}, file: {}", hunksStart + 1, patchPath)
+                        hasProblem = true
+                    }
+                }
+                else {
+                    if (!whiteSpaceErrors.empty)
+                        hasProblem = true
+                    whiteSpaceErrors.each { error -> logger.lifecycle(error) }
+                    whiteSpaceErrors.clear()
+                }
+                hunksStart = i
+                onlyWhiteSpace = true
+                continue
+            }
+
+            if (line.startsWithAny('+','-')) {
+                def prefixChange = false
+                def prevLine = lines[i - 1]
+
+                if (line.charAt(0) == (char)'+' && prevLine.charAt(0) == (char)'-') {
+                    def prevTrim = prevLine.substring(1).replaceAll("\\s", "")
+                    def currTrim = line.substring(1).replaceAll("\\s", "")
+
+                    if (prevTrim.equals(currTrim)) {
+                        prefixChange = true
+                    }
+
+                    def pMatcher = field_pattern.matcher(prevLine)
+                    def cMatcher = field_pattern.matcher(line)
+
+                    if (pMatcher.find() && cMatcher.find() &&
+                            pMatcher.group(6) == cMatcher.group(6) && // = ...
+                            pMatcher.group(5) == cMatcher.group(5) && // field name
+                            pMatcher.group(3) == cMatcher.group(3) && // static
+                            (accessMap[pMatcher.group(2)] < accessMap[cMatcher.group(2)] || pMatcher.group(4) != cMatcher.group(4))) {
+                        logger.lifecycle("Patch contains access changes or final removal at line {}, file: {}", i + 1, patchPath)
+                        hasProblem = true
+                    }
+
+                    pMatcher = method_pattern.matcher(prevLine)
+                    cMatcher = method_pattern.matcher(line)
+
+                    if (pMatcher.find() && cMatcher.find() &&
+                            pMatcher.group(6) == cMatcher.group(6) && // params
+                            pMatcher.group(5) == cMatcher.group(5) && // <T> void name
+                            pMatcher.group(3) == cMatcher.group(3) && // static
+                            (accessMap[pMatcher.group(2)] < accessMap[cMatcher.group(2)] || pMatcher.group(4) != cMatcher.group(4))) {
+                        logger.lifecycle("Patch contains access changes or final removal at line {}, file: {}", i + 1, patchPath)
+                        hasProblem = true
+                    }
+
+                    pMatcher = class_pattern.matcher(prevLine)
+                    cMatcher = class_pattern.matcher(line)
+
+                    if (pMatcher.find() && cMatcher.find() &&
+                            pMatcher.group(6) == cMatcher.group(6) && // ClassName<> extends ...
+                            pMatcher.group(5) == cMatcher.group(5) && // class | interface
+                            pMatcher.group(3) == cMatcher.group(3) && // static
+                            (accessMap[pMatcher.group(2)] < accessMap[cMatcher.group(2)] || pMatcher.group(4) != cMatcher.group(4))) {
+                        logger.lifecycle("Patch contains access changes or final removal at line {}, file: {}", i + 1, patchPath)
+                        hasProblem = true
+                    }
+                }
+
+                if (line.charAt(0) == (char)'-' && i + 1 < lines.size()) {
+                    def nextLine = lines[i + 1]
+                    if (nextLine.charAt(0) == (char)'+') {
+                        def nextTrim = nextLine.substring(1).replaceAll("\\s", "")
+                        def currTrim = line.substring(1).replaceAll("\\s", "")
+
+                        if (nextTrim.equals(currTrim)) {
+                            prefixChange = true
+                        }
+                    }
+                }
+
+                def isWhiteSpaceChange = white_space_pattern.matcher(line).find()
+
+                if (!prefixChange && !isWhiteSpaceChange) {
+                    onlyWhiteSpace = hasS2SArtifact && import_pattern.matcher(line).find()
+                }
+                else if (isWhiteSpaceChange) {
+                    def prevLineChange = prevLine.startsWithAny('+','-')
+                    def nextLineChange = i + 1 < lines.size() && lines[i + 1].startsWithAny('+','-')
+
+                    if (!prevLineChange && !nextLineChange) {
+                        whiteSpaceErrors.add(String.format("Patch contains white space change in valid hunk at line %d (cannot auto fix), file: %s", i + 1, patchPath))
+                    }
+                }
+
+                if (line.contains("\t")) {
+                    if (!fix) {
+                        logger.lifecycle("Patch contains tabs on line {}, file: {}", i + 1, patchPath)
+                        hasProblem = true
+                    }
+                    else {
+                        logger.lifecycle("Fixing tabs on line {}, file: {}", i + 1, patchPath)
+                        line = line.replaceAll('\t', '    ')
+                        newLines.remove(newLines.size() - 1)
+                        newLines.add(line + '\n')
+                        didFix = true
+                    }
+                }
+
+                if (import_pattern.matcher(line).find() && !hasS2SArtifact) {
+                    logger.lifecycle("Patch contains import change on line {}, file: {}", i + 1, patchPath)
+                    hasProblem = true
+                }
+            }
+        }
+
+        if (onlyWhiteSpace) {
+            if (fix || hasS2SArtifact) {
+                logger.lifecycle("Removing white space hunk starting at line {}, file: {}", hunksStart + 1, patchPath)
+                def toRemove = i - hunksStart;
+                while (toRemove-- > 0)
+                    newLines.remove(newLines.size() - 1)
+                didFix = true
+            }
+            else {
+                logger.lifecycle("Patch contains only white space hunk starting at line {}, file: {}", hunksStart + 1, patchPath)
+                hasProblem = true
+            }
+        }
+        else {
+            if (!whiteSpaceErrors.empty)
+                hasProblem = true
+            whiteSpaceErrors.each { error -> logger.lifecycle(error) }
+        }
+
+        if (didFix) {
+            if (newLines.size() <= 2) {
+                logger.lifecycle("Patch is now empty removing, file: {}", patchPath)
+                Files.delete(patch.toPath())
+            }
+            else {
+                if (!hasS2SArtifact)
+                    logger.lifecycle("*** Updating patch file. Please run setup then genPatches again. ***")
+                patch.withWriter('UTF-8') { writer ->
+                    newLines.each { l -> writer.write(l) }
+                }
+            }
+        }
+
+        return !hasProblem
+    }
+}

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

@@ -0,0 +1,63 @@
+package net.minecraftforge.forge.tasks
+
+import org.gradle.api.file.ConfigurableFileCollection
+import org.gradle.api.file.RegularFileProperty
+
+import org.gradle.api.DefaultTask
+import org.gradle.api.tasks.InputFile
+import org.gradle.api.tasks.InputFiles
+import org.gradle.api.tasks.TaskAction
+
+abstract class CheckSAS extends DefaultTask {
+	@InputFile abstract RegularFileProperty getInheritance()
+	@InputFiles abstract ConfigurableFileCollection getSass()
+	
+    @TaskAction
+    protected void exec() {
+		Util.init()
+		def json = inheritance.get().asFile.json()
+		
+		sass.each { f -> 
+			def lines = []
+			f.eachLine { line ->
+				if (line[0] == '\t') return //Skip any tabbed lines, those are ones we add
+				def idx = line.indexOf('#')
+				if (idx == 0 || line.isEmpty()) {
+					lines.add(line)
+					return
+				}
+				def comment = idx == -1 ? null : line.substring(idx)
+				if (idx != -1) line = line.substring(0, idx - 1)
+				def (cls, desc) = (line.trim() + '    ').split(' ', -1)
+				cls = cls.replaceAll('\\.', '/')
+				desc = desc.replace('(', ' (')
+
+				if (json[cls] == null || (!desc.isEmpty() && (json[cls]['methods'] == null || json[cls]['methods'][desc] == null))) {
+					println('Invalid: ' + line)
+					return
+				}
+
+				//Class SAS
+				if (desc.isEmpty()) {
+					lines.add(cls + (comment == null ? '' : ' ' + comment))
+					if (json[cls]['methods'] != null)
+						(json[cls]['methods'] as TreeMap).each {
+							findChildMethods(json, cls, it.key).each { lines.add('\t' + it) }
+						}
+					return
+				}
+
+				//Method SAS
+				lines.add(cls + ' ' + desc.replace(' ', '') + (comment == null ? '' : ' ' + comment))
+				findChildMethods(json, cls, desc).each { lines.add('\t' + it) }
+			}
+			f.text = lines.join('\n')
+		}
+	}
+
+	protected static findChildMethods(json, cls, desc)
+	{
+		return json.values().findAll{ it.methods != null && it.methods[desc] != null && it.methods[desc].override == cls}
+				.collect { it.name + ' ' + desc.replace(' ', '') } as TreeSet
+	}
+}

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

@@ -0,0 +1,31 @@
+package net.minecraftforge.forge.tasks
+
+import java.util.function.BiConsumer
+
+public class ClosureHelper {
+    BiConsumer<String, Closure> callback
+    
+    public ClosureHelper(Closure cl, BiConsumer<String, Closure> callback) {
+        this.callback = callback
+        apply(this, cl)
+    }
+    
+    
+    def methodMissing(String name, Object args) {
+        if (!args.class.isArray()) return
+        Object[] aargs = (Object[])args
+        
+        if (aargs.length == 1 && aargs[0] instanceof Closure) {
+            this.callback.accept(name, (Closure)aargs[0])
+        } else {
+            throw new IllegalArgumentException('Unknown method: "' + name + '" with arguments ' + args + ' for ' + this)
+        }
+    }
+    
+    static <T> T apply(T obj, Closure cl) {
+        cl.delegate = obj
+        cl.resolveStrategy = Closure.DELEGATE_FIRST
+        cl()
+        return obj
+    }
+}

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

@@ -0,0 +1,73 @@
+package net.minecraftforge.forge.tasks
+
+import org.gradle.api.DefaultTask
+import org.gradle.api.file.RegularFileProperty
+import org.gradle.api.provider.Property
+import org.gradle.api.tasks.Input
+import org.gradle.api.tasks.Optional
+import org.gradle.api.tasks.OutputFile
+import org.gradle.api.tasks.TaskAction
+
+import java.util.zip.ZipEntry
+import java.util.zip.ZipInputStream
+import java.util.zip.ZipOutputStream
+
+abstract class Crowdin extends DefaultTask {
+    @Input abstract Property<String> getId()
+	@Input @Optional abstract Property<String> getKey()
+	@Input boolean json = true
+	@OutputFile abstract RegularFileProperty getOutput()
+	@OutputFile abstract RegularFileProperty getExport()
+
+    Crowdin() {
+		outputs.upToDateWhen{ false }
+		id.convention('minecraft-forge')
+		output.convention(project.layout.buildDirectory.dir(name).map {it.file("output.zip") })
+		export.convention(project.layout.buildDirectory.dir(name).map {it.file("export.json") })
+	}
+
+    @TaskAction
+    def run() {
+		File outputFile = output.get().asFile
+		File exportFile = export.get().asFile
+		if (outputFile.exists())
+			outputFile.delete()
+		
+		if (!key.isPresent())
+			return
+		String key = this.key.get()
+		String id = this.id.get()
+		
+		// Force an export
+		new URL("https://api.crowdin.com/api/project/${id}/export?key=${key}").withInputStream { i ->
+			exportFile.withOutputStream { it << i }
+		}
+		
+		if (!exportFile.text.contains('success')) {
+			throw new RuntimeException("Crowdin export failed, see ${exportFile} for more info")
+		}
+
+		new URL("https://api.crowdin.com/api/project/${id}/download/all.zip?key=${key}").withInputStream { i -> 
+			new ZipInputStream(i).withCloseable { zin ->
+				outputFile.withOutputStream { out ->
+					new ZipOutputStream(out).withCloseable { zout -> 
+						ZipEntry zein
+						while ((zein = zin.nextEntry) != null) {
+							if (zein.isDirectory()) {
+								zout.putNextEntry(new ZipEntry(zein.name))
+							} else {
+								// 1.13+ uses json
+								if (zein.name.endsWith('.json') == json) {
+									ZipEntry zeout = new ZipEntry(json ? zein.name.toLowerCase() : zein.name)
+									zeout.time = 1
+									zout.putNextEntry(zeout)
+									zout << zin
+								}
+							}
+						}
+					}
+				}
+			}
+		}
+    }
+}

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

@@ -0,0 +1,54 @@
+package net.minecraftforge.forge.tasks
+
+import org.gradle.api.DefaultTask
+import org.gradle.api.file.ConfigurableFileCollection
+import org.gradle.api.file.DirectoryProperty
+import org.gradle.api.file.RegularFileProperty
+import org.gradle.api.tasks.InputFile
+import org.gradle.api.tasks.Internal
+import org.gradle.api.tasks.OutputFile
+import org.gradle.api.tasks.OutputFiles
+import org.gradle.api.tasks.TaskAction
+import org.gradle.api.tasks.OutputDirectory
+
+import java.nio.file.Files
+
+abstract class DownloadLibraries extends DefaultTask {
+	@InputFile abstract RegularFileProperty getInput()
+	@OutputDirectory abstract DirectoryProperty getOutput()
+	@OutputFile abstract RegularFileProperty getLibrariesOutput()
+
+    DownloadLibraries() {
+		output.convention(project.layout.buildDirectory.dir(name))
+        librariesOutput.convention(project.layout.buildDirectory.dir(name).map(d -> d.file('libraries.txt')))
+	}
+
+    @TaskAction
+    def run() {
+		Util.init()
+		File outputDir = output.get().asFile
+        def libraries = new ArrayList()
+
+		def json = input.get().asFile.json().libraries.each { lib ->
+		    //TODO: Thread?
+			def artifacts = [lib.downloads.artifact] + lib.downloads.get('classifiers', [:]).values()
+			artifacts.each{ art -> 
+				def target = new File(outputDir, art.path)
+				libraries.add(target.absolutePath)
+				if (!target.exists() || !art.sha1.equals(target.sha1())) {
+					project.logger.lifecycle("Downloading ${art.url}")
+					if (!target.parentFile.exists()) {
+						target.parentFile.mkdirs()
+					}
+					new URL(art.url).withInputStream { i ->
+						target.withOutputStream { it << i }
+					}
+					if (!art.sha1.equals(target.sha1())) {
+						throw new IllegalStateException("Failed to download ${art.url} to ${target.canonicalPath} SHA Mismatch")
+					}
+				}
+			}
+		}
+        Files.write(librariesOutput.get().asFile.toPath(), libraries)
+    }
+}

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

@@ -0,0 +1,109 @@
+package net.minecraftforge.forge.tasks
+
+import groovy.transform.EqualsAndHashCode
+
+import java.util.ArrayList
+import java.util.HashMap
+import java.util.TreeMap
+import java.util.TreeSet
+import java.util.function.BiConsumer
+
+import org.gradle.api.DefaultTask
+import org.gradle.api.tasks.*
+
+import org.objectweb.asm.Opcodes
+import org.objectweb.asm.Type
+import org.objectweb.asm.tree.ClassNode
+import org.objectweb.asm.tree.FieldNode
+import org.objectweb.asm.tree.MethodNode
+
+import static org.objectweb.asm.Opcodes.*
+
+abstract class FieldCompareFinder extends BytecodeFinder {
+    @Nested
+    Map<String, Search> fields = [:] as HashMap
+    @Internal
+    Map<Search, String> fieldsReverse = [:] as HashMap
+    @Internal
+    Map<String, Set<ObjectTarget>> targets = [:] as TreeMap
+    
+    @Override
+    protected pre() {
+        //fields.each{ k,v -> logger.lifecycle("Fields: " + k + ' ' + v) }
+    }
+    
+    @Override
+    protected process(ClassNode parent, MethodNode node) {
+        def last = null
+        def parentInstance = new ObjectTarget(owner: parent.name, name: '', desc: '')
+        for (int x = 0; x < node.instructions.size(); x++) {
+            def current = node.instructions.get(x)
+            if (current.opcode == IF_ACMPEQ || current.opcode == IF_ACMPNE) {
+                if (last != null && (last.opcode == GETSTATIC || last.opcode == GETFIELD)) {
+                    def target = new Search(cls: last.owner, name: last.name)
+                    def wanted = fieldsReverse.get(target)
+                    def original = fields.get(wanted)
+                    def instance = new ObjectTarget(owner: parent.name, name: node.name, desc: node.desc)
+                    if (wanted != null && (original.blacklist == null || (!original.blacklist.contains(instance) && !original.blacklist.contains(parentInstance)))) {
+                        targets.computeIfAbsent(wanted, { k -> new TreeSet() }).add(instance)
+                    }
+                }
+            }
+            last = current
+        }
+    }
+    
+    @Internal
+    @Override
+    protected Object getData() {
+		def ret = [:] as HashMap
+		targets.forEach{ k, v -> 
+			def e = fields.get(k)
+			ret[k] = [
+				cls: e.cls, 
+				name: e.name, 
+				replacement: e.replacement, 
+				targets: v
+			]
+		}
+        return ret
+    }
+    
+    @EqualsAndHashCode(excludes = ['replacement', 'blacklist'])
+    public static class Search {
+        @Input
+        String cls
+        
+        @Input
+        String name
+		
+		@Input
+		String replacement
+    
+        @Nested
+        @Optional
+        Set<ObjectTarget> blacklist
+        
+        @Override
+        String toString() {
+            return cls + '.' + name
+        }
+        
+        def blacklist(def owner, def name, def desc) {
+            if (blacklist == null)
+                blacklist = new HashSet()
+            blacklist.add(new ObjectTarget(owner: owner, name: name, desc: desc))
+        }
+        def blacklist(def owner) {
+            blacklist(owner, '', '')
+        }
+    }
+    
+    def fields(Closure cl) {
+        new ClosureHelper(cl, {name, ccl ->
+            def search = ClosureHelper.apply(new Search(), ccl)
+            this.fields.put(name, search)
+            this.fieldsReverse.put(search, name)
+        })
+    }
+}

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

@@ -0,0 +1,44 @@
+package net.minecraftforge.forge.tasks
+
+import org.gradle.api.tasks.bundling.Zip
+import org.gradle.api.tasks.*
+import org.gradle.api.provider.SetProperty
+
+abstract class InstallerJar extends Zip {
+    @Input @Optional abstract SetProperty<String> getPackedDependencies()
+    
+    InstallerJar() {
+        archiveClassifier.set('installer')
+        archiveExtension.set('jar') // Needs to be Zip task to not override Manifest, so set extension
+        destinationDirectory.set(project.layout.buildDirectory.dir('libs'))
+
+        def installerJson = project.tasks.installerJson
+        def launcherJson = project.tasks.launcherJson
+        def downloadInstaller = project.tasks.downloadInstaller
+        
+        dependsOn(installerJson, launcherJson, downloadInstaller)
+        from(installerJson, launcherJson)
+
+        from(project.rootProject.file('/src/main/resources/url.png'))
+        project.afterEvaluate {
+            from(project.zipTree(downloadInstaller.output)) {
+                duplicatesStrategy = 'exclude'
+            }
+            
+            if (!System.env.MAVEN_USER) {
+                dependsOn(project.universalJar)
+                from(project.universalJar) {
+                    into '/maven/' + project.group.replace('.', '/') + '/' + project.universalJar.archiveBaseName.get() + '/' + project.version + '/'
+                }
+    
+                packedDependencies.get().forEach {
+                    def jarTask = project.rootProject.getTasks().findByPath(it)
+                    dependsOn(jarTask)
+                    from(jarTask) {
+                        into '/maven/' + jarTask.project.group.replace('.', '/') + '/' + jarTask.archiveBaseName.get() + '/' + jarTask.project.version + '/'
+                    }
+                }
+            }
+        }
+    }
+}

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

@@ -0,0 +1,81 @@
+package net.minecraftforge.forge.tasks
+
+import groovy.json.JsonBuilder
+import org.gradle.api.DefaultTask
+import org.gradle.api.file.ConfigurableFileCollection
+import org.gradle.api.file.RegularFileProperty
+import org.gradle.api.provider.Property
+import org.gradle.api.provider.SetProperty
+import org.gradle.api.tasks.*
+
+import java.nio.file.Files
+
+abstract class InstallerJson extends DefaultTask {
+    @OutputFile abstract RegularFileProperty getOutput()
+    @InputFiles abstract ConfigurableFileCollection getInput()
+    @Input @Optional abstract SetProperty<String> getPackedDependencies()
+    @Input @Optional final Map<String, Object> libraries = new LinkedHashMap<>()
+    @Input Map<String, Object> json = new LinkedHashMap<>()
+    @InputFile abstract RegularFileProperty getIcon()
+    @Input abstract Property<String> getLauncherJsonName()
+    @Input abstract Property<String> getLogo()
+    @Input abstract Property<String> getMirrors()
+    @Input abstract Property<String> getWelcome()
+
+    InstallerJson() {
+        getLauncherJsonName().convention('/version.json')
+        getLogo().convention('/big_logo.png')
+        getMirrors().convention('https://files.minecraftforge.net/mirrors-2.0.json')
+        getWelcome().convention("Welcome to the simple ${project.name.capitalize()} installer.")
+                
+        getOutput().convention(project.layout.buildDirectory.file('install_profile.json'))
+
+        ['client', 'server'].each { side ->
+            ['slim', 'extra'].each { type ->
+                def tsk = project.tasks.getByName("download${side.capitalize()}${type.capitalize()}")
+                dependsOn(tsk)
+                input.from(tsk.output)
+            }
+            def tsk = project.tasks.getByName("create${side.capitalize()}SRG")
+            dependsOn(tsk)
+            input.from(tsk.output)
+        }
+
+        
+        project.afterEvaluate {
+            (packedDependencies.get().collect{ project.rootProject.tasks.findByPath(it) } + [project.universalJar]).forEach {
+                dependsOn(it)
+                input.from it.archiveFile
+            }
+        }
+    }
+
+    @TaskAction
+    protected void exec() {
+        def libs = libraries
+        for (def child : packedDependencies.get().collect{ project.rootProject.tasks.findByPath(it) } + [project.universalJar]) {
+            def dep = Util.getMavenDep(child)
+            def path = Util.getMavenPath(child)
+            libs.put(dep.toString(), [
+                name: dep,
+                downloads: [
+                    artifact: [
+                        path: path,
+                        url: "https://maven.minecraftforge.net/${path}",
+                        sha1: child.archiveFile.get().asFile.sha1(),
+                        size: child.archiveFile.get().asFile.length()
+                    ]
+                ]
+            ])
+        }
+        json.libraries = libs.values().sort{a,b -> a.name.compareTo(b.name)}
+        json.icon = "data:image/png;base64," + new String(Base64.getEncoder().encode(Files.readAllBytes(icon.get().asFile.toPath())))
+        json.json = launcherJsonName.get()
+        json.logo = logo.get()
+        if (!mirrors.get().isEmpty())
+            json.mirrorList = mirrors.get()
+        json.welcome = welcome.get()
+
+        Files.writeString(output.get().getAsFile().toPath(), new JsonBuilder(json).toPrettyString())
+    }
+}

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

@@ -0,0 +1,71 @@
+package net.minecraftforge.forge.tasks
+
+import groovy.json.JsonBuilder
+import org.gradle.api.DefaultTask
+import org.gradle.api.file.ConfigurableFileCollection
+import org.gradle.api.file.RegularFileProperty
+import org.gradle.api.provider.SetProperty
+import org.gradle.api.tasks.*
+
+import java.nio.file.Files
+
+import static net.minecraftforge.forge.tasks.Util.getArtifacts
+import static net.minecraftforge.forge.tasks.Util.iso8601Now
+
+abstract class LauncherJson extends DefaultTask {
+    @OutputFile abstract RegularFileProperty getOutput()
+    @InputFiles abstract ConfigurableFileCollection getInput()
+    @Input Map<String, Object> json = new LinkedHashMap<>()
+    @Input @Optional abstract SetProperty<String> getPackedDependencies()
+    
+    @Internal final vanilla = project.project(':mcp').file('build/mcp/downloadJson/version.json')
+    @Internal final timestamp = iso8601Now()
+    @Internal final comment = [
+        "Please do not automate the download and installation of Forge.",
+        "Our efforts are supported by ads from the download page.",
+        "If you MUST automate this, please consider supporting the project through https://www.patreon.com/LexManos/"
+    ]
+    @Internal final id = "${project.rootProject.ext.MC_VERSION}-${project.name}${project.version.substring(project.rootProject.ext.MC_VERSION.length())}"
+
+    LauncherJson() {
+        getOutput().convention(project.layout.buildDirectory.file('version.json'))
+
+        dependsOn(':fmlloader:jar', 'universalJar')
+        getInput().from(project.tasks.universalJar.archiveFile,
+                project.project(':fmlloader').jar.archiveFile,
+                vanilla)
+                
+        project.afterEvaluate {
+            packedDependencies.get().forEach {
+                def jarTask = project.rootProject.tasks.findByPath(it)
+                dependsOn(jarTask)
+                input.from jarTask.archiveFile
+            }
+        }
+    }
+
+    @TaskAction
+    protected void exec() {
+        if (!json.libraries)
+            json.libraries = []
+        getArtifacts(project, project.configurations.installer, false).each { key, lib -> json.libraries.add(lib) }
+        getArtifacts(project, project.configurations.moduleonly, false).each { key, lib -> json.libraries.add(lib) }
+
+        packedDependencies.get().collect{ project.rootProject.tasks.findByPath(it) }.forEach {
+            def path = Util.getMavenPath(it)
+            
+            json.libraries.add([
+                name: Util.getMavenDep(it),
+                downloads: [
+                    artifact: [
+                        path: path,
+                        url: "https://maven.minecraftforge.net/${path}",
+                        sha1: it.archiveFile.get().asFile.sha1(),
+                        size: it.archiveFile.get().asFile.length()
+                    ]
+                ]
+            ])
+        }
+        Files.writeString(output.get().asFile.toPath(), new JsonBuilder(json).toPrettyString())
+    }
+}

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

@@ -0,0 +1,32 @@
+package net.minecraftforge.forge.tasks
+
+import groovy.transform.EqualsAndHashCode
+
+import org.gradle.api.tasks.Input
+import org.gradle.api.tasks.Nested
+import org.gradle.api.tasks.Optional
+
+@EqualsAndHashCode
+public class ObjectTarget implements Comparable<ObjectTarget> {
+    @Input
+    String owner
+    
+    @Input
+    String name
+    
+    @Input
+    @Optional
+    String desc
+    
+    @Override
+    String toString() {
+        if (desc == null)
+            return owner + '.' + name
+        return owner + '.' + name + desc
+    }
+    
+    @Override
+    int compareTo(ObjectTarget o) {
+        return toString().compareTo(o.toString())
+    }
+}

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

@@ -0,0 +1,141 @@
+package net.minecraftforge.forge.tasks
+
+import groovy.json.JsonSlurper
+
+import java.io.File
+import java.security.MessageDigest
+import java.text.SimpleDateFormat
+import java.util.Date
+
+public class Util {
+	static void init() {
+		File.metaClass.sha1 = { ->
+			MessageDigest md = MessageDigest.getInstance('SHA-1')
+			delegate.eachByte 4096, {bytes, size ->
+				md.update(bytes, 0, size)
+			}
+			return md.digest().collect {String.format "%02x", it}.join()
+		}
+	
+		File.metaClass.json = { -> new JsonSlurper().parseText(delegate.text) }
+		
+		Date.metaClass.iso8601 = { ->
+			def format = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssZ")
+			def result = format.format(delegate)
+			return result[0..21] + ':' + result[22..-1]
+		}
+        
+        String.metaClass.rsplit = { String del, int limit = -1 ->
+            def lst = new ArrayList()
+            def x = 0, idx
+            def tmp = delegate
+            while ((idx = tmp.lastIndexOf(del)) != -1 && (limit == -1 || x++ < limit)) {
+                lst.add(0, tmp.substring(idx + del.length(), tmp.length()))
+                tmp = tmp.substring(0, idx)
+            }
+            lst.add(0, tmp)
+            return lst
+        }
+	}
+	
+	public static String[] getClasspath(project, libs, artifact) {
+		def ret = []
+		artifactTree(project, artifact).each { key, lib ->
+			libs[lib.name] = lib
+			if (lib.name != artifact)
+				ret.add(lib.name)
+		}
+		return ret
+	}
+	
+	public static def getArtifacts(project, config, classifiers) {
+		def ret = [:]
+		config.resolvedConfiguration.resolvedArtifacts.each {
+			def art = [
+				group: it.moduleVersion.id.group,
+				name: it.moduleVersion.id.name,
+				version: it.moduleVersion.id.version,
+				classifier: it.classifier,
+				extension: it.extension,
+				file: it.file
+			]
+			def key = art.group + ':' + art.name
+			def folder = "${art.group.replace('.', '/')}/${art.name}/${art.version}/"
+			def filename = "${art.name}-${art.version}"
+			if (art.classifier != null)
+				filename += "-${art.classifier}"
+			filename += ".${art.extension}"
+			def path = "${folder}${filename}"
+			def url = "https://libraries.minecraft.net/${path}"
+			if (!checkExists(url)) {
+				url = "https://maven.minecraftforge.net/${path}"
+			}
+			//TODO remove when Mojang launcher is updated
+			if (!classifiers && art.classifier != null) { 
+				//Mojang launcher doesn't currently support classifiers, so... move it to part of the version, and force the extension to 'jar'
+				// However, keep the path normal so that our mirror system works.
+				art.version = "${art.version}-${art.classifier}"
+				art.classifier = null
+				art.extension = 'jar'
+			}
+			ret[key] = [
+				name: "${art.group}:${art.name}:${art.version}" + (art.classifier == null ? '' : ":${art.classifier}") + (art.extension == 'jar' ? '' : "@${art.extension}"),
+				downloads: [
+					artifact: [
+						path: path,
+						url: url,
+						sha1: sha1(art.file),
+						size: art.file.length()
+					]
+				]
+			]
+		}
+		return ret
+	}
+    
+    public static def getMavenPath(task) {        
+        def classifier = task.archiveClassifier.get()
+        def dep = "${task.project.group}:${task.project.name}:${task.project.version}" + (classifier == '' ? '' : ':' + classifier)
+        return "${task.project.group.replace('.', '/')}/${task.project.name}/${task.project.version}/${task.project.name}-${task.project.version}".toString() + (classifier == '' ? '' : '-' + classifier) + '.jar'
+    }
+    
+    public static def getMavenDep(task) {        
+        def classifier = task.archiveClassifier.get()
+        return "${task.project.group}:${task.project.name}:${task.project.version}" + (classifier == '' ? '' : ':' + classifier)
+    }
+
+	public static def iso8601Now() { new Date().iso8601() }
+
+	public static def sha1(file) {
+		MessageDigest md = MessageDigest.getInstance('SHA-1')
+		file.eachByte 4096, {bytes, size ->
+			md.update(bytes, 0, size)
+		}
+		return md.digest().collect {String.format "%02x", it}.join()
+	}
+
+	private static def artifactTree(project, artifact) {
+		if (!project.ext.has('tree_resolver'))
+			project.ext.tree_resolver = 1
+		def cfg = project.configurations.create('tree_resolver_' + project.ext.tree_resolver++)
+		def dep = project.dependencies.create(artifact)
+		cfg.dependencies.add(dep)
+		def files = cfg.resolve()
+		return getArtifacts(project, cfg, true)
+	}
+	
+	private static boolean checkExists(url) {
+		try {
+			def code = new URL(url).openConnection().with {
+				requestMethod = 'HEAD'
+				connect()
+				responseCode
+			}
+			return code == 200
+		} catch (Exception e) {
+			if (e.toString().contains('unable to find valid certification path to requested target'))
+				throw new RuntimeException('Failed to connect to ' + url + ': Missing certificate root authority, try updating java')
+			throw e
+		}
+	}
+}

docs/README.md

@@ -1,17 +1,17 @@
-<img src="assets/Forge_logo.svg">
+![Forge Logo](assets/Forge_logo.svg)
 
 MinecraftForge
 =============
-[![Stable Release](https://img.shields.io/badge/dynamic/json?url=https://files.minecraftforge.net/net/minecraftforge/forge/promotions_slim.json&label=Stable&prefix=1.14.4-&query=$.promos["1.14.4-recommended"]&color=brightgreen&logo=data:image/svg+xml;base64,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)](https://files.minecraftforge.net)
-[![Latest Release](https://img.shields.io/badge/dynamic/json?url=https://files.minecraftforge.net/net/minecraftforge/forge/promotions_slim.json&label=Latest&prefix=1.14.4-&query=$.promos["1.14.4-latest"]&color=blue&logo=data:image/svg+xml;base64,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
-)](https://files.minecraftforge.net) [![Discord](https://img.shields.io/discord/313125603924639766.svg?color=%237289da&label=Discord&logo=discord&logoColor=%237289da)](https://discord.gg/UvedJ9m) [![Support](https://img.shields.io/badge/Patreon-Support-orange.svg?logo=Patreon)](https://www.patreon.com/LexManos) [![Merch](https://img.shields.io/badge/Flocker-Merch-blueviolet.svg)](https://forgedev.flocker.tv/)
+[![Stable Release](https://img.shields.io/badge/dynamic/json?url=https://files.minecraftforge.net/net/minecraftforge/forge/promotions_slim.json&label=Stable&prefix=1.16.5-&query=$.promos["1.16.5-recommended"]&color=brightgreen&logo=data:image/svg+xml;base64,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)](https://files.minecraftforge.net)
+[![Latest Release](https://img.shields.io/badge/dynamic/json?url=https://files.minecraftforge.net/net/minecraftforge/forge/promotions_slim.json&label=Latest&prefix=1.16.5-&query=$.promos["1.16.5-latest"]&color=blue&logo=data:image/svg+xml;base64,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
+)](https://files.minecraftforge.net) [![Discord](https://img.shields.io/discord/313125603924639766.svg?color=%237289da&label=Discord&logo=discord&logoColor=%237289da)](https://discord.gg/UvedJ9m) [![Support](https://img.shields.io/badge/Patreon-Support-orange.svg?logo=Patreon)](https://www.patreon.com/LexManos)
 
 Forge is a free, open-source modding API all of your favourite mods use!
 
 | Version  | Support |
 | ------------- | ------------- |
-| 1.14.x  | Active  |
-| 1.12.x  | Legacy  |
+| 1.16.x  | Active  |
+| 1.15.x  | LTS  |
 
 * [Download]
 * [Forum]
@@ -60,7 +60,7 @@ We require all contributors to acknowledge the [Forge Contributor
  signed it, you should be OK.
 
 #### Donate
-*Forge is a large project with many collaborators working on it around the clock. Forge is and will always remain free to use and modify. However, it costs money to run such a large project as this, so please consider [becoming a patron](https://www.patreon.com/LexManos) or buying some [cool merch](https://forgedev.flocker.tv/).*
+*Forge is a large project with many collaborators working on it around the clock. Forge is and will always remain free to use and modify. However, it costs money to run such a large project as this, so please consider [becoming a patron](https://www.patreon.com/LexManos).*
 
 [Download]: https://files.minecraftforge.net/
 [Forum]: https://www.minecraftforge.net/forum/

fmlcore/build.gradle

@@ -0,0 +1,64 @@
+plugins {
+    id 'com.github.ben-manes.versions'
+    id 'org.javamodularity.moduleplugin' version '1.8.3' apply false
+}
+apply plugin: 'java-library'
+apply plugin: 'jacoco'
+apply plugin: 'org.javamodularity.moduleplugin'
+
+dependencyUpdates.rejectVersionIf { isNonStable(it.candidate.version) }
+
+dependencies {
+    compileOnly('org.jetbrains:annotations:21.0.1')
+    implementation(project(':fmlloader'))
+    api('net.minecraftforge:eventbus:5.0.+')
+    implementation('commons-io:commons-io:2.5')
+}
+
+task sourcesJar(type: Jar) {
+    archiveClassifier = 'sources'
+    from sourceSets.main.allSource
+}
+
+ext {
+    MANIFESTS = [
+        '': [
+            'FMLModType': 'LIBRARY',
+            'Timestamp': new Date().format("yyyy-MM-dd'T'HH:mm:ssZ"),
+            'Git-Commit': GIT_INFO.abbreviatedId,
+            'Git-Branch': GIT_INFO.branch,
+            'Build-Number': "${System.getenv('BUILD_NUMBER')?:0}"
+        ] as LinkedHashMap,
+        'net/minecraftforge/fml/loading/': [
+            'Specification-Title':      'FMLLoader',
+            'Specification-Vendor':     'Forge Development LLC',
+            'Specification-Version':    '1',
+            'Implementation-Title':     'FML Loader',
+            'Implementation-Version':   '1.0',
+            'Implementation-Vendor':    'Forge'
+        ] as LinkedHashMap
+    ]
+}
+
+jar.doFirst {
+    MANIFESTS.each { pkg, values ->
+        if (pkg == '')
+            manifest.attributes(values)
+        else
+            manifest.attributes(values, pkg)
+    }
+}
+
+tasks.withType(JavaCompile) {
+    options.compilerArgs << '-Xlint:unchecked'
+}
+
+artifacts {
+    archives jar
+    archives sourcesJar
+}
+
+publishing.publications.mavenJava(MavenPublication) {
+    from components.java
+    artifact sourcesJar
+}

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

@@ -0,0 +1,36 @@
+package net.minecraftforge.fml;
+
+import cpw.mods.modlauncher.util.ServiceLoaderUtils;
+import net.minecraftforge.eventbus.api.BusBuilder;
+import net.minecraftforge.eventbus.api.IEventBus;
+import net.minecraftforge.fml.config.IConfigEvent;
+import net.minecraftforge.fml.loading.FMLLoader;
+
+import java.util.ServiceLoader;
+import java.util.function.Supplier;
+
+public class Bindings {
+    private static final Bindings INSTANCE = new Bindings();
+
+    private final IBindingsProvider provider;
+
+    private Bindings() {
+        final var providers = ServiceLoaderUtils.streamServiceLoader(()->ServiceLoader.load(FMLLoader.getGameLayer(), IBindingsProvider.class), sce->{}).toList();
+        if (providers.size() != 1) {
+            throw new IllegalStateException("Could not find bindings provider");
+        }
+        this.provider = providers.get(0);
+    }
+
+    public static Supplier<IEventBus> getForgeBus() {
+        return INSTANCE.provider.getForgeBusSupplier();
+    }
+
+    public static Supplier<I18NParser> getMessageParser() {
+        return INSTANCE.provider.getMessageParser();
+    }
+
+    public static Supplier<IConfigEvent.ConfigConfig> getConfigConfiguration() {
+        return INSTANCE.provider.getConfigConfiguration();
+    }
+}

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

@@ -0,0 +1,32 @@
+package net.minecraftforge.fml;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.function.Supplier;
+
+public class CrashReportCallables {
+    private static final List<ISystemReportExtender> crashCallables = Collections.synchronizedList(new ArrayList<>());
+
+    public static void registerCrashCallable(ISystemReportExtender callable)
+    {
+        crashCallables.add(callable);
+    }
+
+    public static void registerCrashCallable(String headerName, Supplier<String> reportGenerator) {
+        registerCrashCallable(new ISystemReportExtender() {
+            @Override
+            public String getLabel() {
+                return headerName;
+            }
+            @Override
+            public String get() {
+                return reportGenerator.get();
+            }
+        });
+    }
+
+    public static List<ISystemReportExtender> allCrashCallables() {
+        return List.copyOf(crashCallables);
+    }
+}

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

@@ -0,0 +1,98 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml;
+
+import static net.minecraftforge.fml.Logging.LOADING;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ConcurrentLinkedDeque;
+import java.util.concurrent.Executor;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Supplier;
+
+import com.google.common.base.Stopwatch;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import net.minecraftforge.forgespi.language.IModInfo;
+
+/**
+ * Utility for running code on the main launch thread at the next available
+ * opportunity. There is no guaranteed order that work from various mods will be
+ * run, but your own work will be run sequentially.
+ * <p>
+ * <strong>Use of this class after startup is not possible.</strong> At that
+ * point, {@link IThreadListener} should be used instead.
+ * <p>
+ * Exceptions from tasks will be handled gracefully, causing a mod loading
+ * error. Tasks that take egregiously long times to run will be logged.
+ */
+public class DeferredWorkQueue
+{
+    private static final Logger LOGGER = LogManager.getLogger();
+
+    private static final Map<ModLoadingStage, DeferredWorkQueue> workQueues = new HashMap<>();
+
+    private final ConcurrentLinkedDeque<TaskInfo> tasks = new ConcurrentLinkedDeque<>();
+    private final ModLoadingStage modLoadingStage;
+
+    public DeferredWorkQueue(ModLoadingStage modLoadingStage) {
+        this.modLoadingStage = modLoadingStage;
+        workQueues.put(modLoadingStage, this);
+    }
+
+    @SuppressWarnings("OptionalUsedAsFieldOrParameterType")
+    public static Optional<DeferredWorkQueue> lookup(Optional<ModLoadingStage> parallelClass) {
+        return Optional.ofNullable(workQueues.get(parallelClass.orElse(null)));
+    }
+
+    public void runTasks() {
+        if (tasks.isEmpty()) return;
+        LOGGER.debug(LOADING, "Dispatching synchronous work for work queue {}: {} jobs", modLoadingStage, tasks.size());
+        Stopwatch timer = Stopwatch.createStarted();
+        tasks.forEach(t->makeRunnable(t, Runnable::run));
+        timer.stop();
+        LOGGER.debug(LOADING, "Synchronous work queue completed in {}", timer);
+    }
+
+    private static void makeRunnable(TaskInfo ti, Executor executor) {
+        executor.execute(() -> {
+            Stopwatch timer = Stopwatch.createStarted();
+            ti.task.run();
+            timer.stop();
+            if (timer.elapsed(TimeUnit.SECONDS) >= 1) {
+                LOGGER.warn(LOADING, "Mod '{}' took {} to run a deferred task.", ti.owner.getModId(), timer);
+            }
+        });
+    }
+
+    public CompletableFuture<Void> enqueueWork(final IModInfo modInfo, final Runnable work) {
+        return CompletableFuture.runAsync(work, r->tasks.add(new TaskInfo(modInfo, r)));
+    }
+
+    public <T> CompletableFuture<T> enqueueWork(final IModInfo modInfo, final Supplier<T> work) {
+        return CompletableFuture.supplyAsync(work, r->tasks.add(new TaskInfo(modInfo, r)));
+    }
+
+    record TaskInfo(IModInfo owner, Runnable task) {}
+}

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

@@ -0,0 +1,276 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml;
+
+import net.minecraftforge.api.distmarker.Dist;
+import net.minecraftforge.fml.loading.FMLEnvironment;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import java.io.Serializable;
+import java.lang.invoke.SerializedLambda;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.Objects;
+import java.util.concurrent.Callable;
+import java.util.function.Supplier;
+
+/**
+ * Use to execute code conditionally based on sidedness.
+ * <ul>
+ * <li>When you want to call something on one side and return a result {@link #safeCallWhenOn(Dist, Supplier)}</li>
+ * <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>
+ */
+public final class DistExecutor
+{
+    private static final Logger LOGGER = LogManager.getLogger();
+    private DistExecutor() {}
+
+    /**
+     * Run the callable in the supplier only on the specified {@link Side}.
+     * This method is NOT sided-safe and special care needs to be taken in code using this method that implicit class
+     * loading is not triggered by the Callable.
+     *
+     * This method can cause unexpected ClassNotFound exceptions.
+     *
+     * Use {@link #safeCallWhenOn(Dist, Supplier)} where possible.
+     *
+     * @param dist The dist to run on
+     * @param toRun A supplier of the callable to run (Supplier wrapper to ensure classloading only on the appropriate dist)
+     * @param <T> The return type from the callable
+     * @return The callable's result
+     * @deprecated use {@link #safeCallWhenOn(Dist, Supplier)} instead. This remains for advanced use cases.
+     */
+    @Deprecated
+    public static <T> T callWhenOn(Dist dist, Supplier<Callable<T>> toRun) {
+        return unsafeCallWhenOn(dist, toRun);
+    }
+
+    public static <T> T unsafeCallWhenOn(Dist dist, Supplier<Callable<T>> toRun) {
+        if (dist == FMLEnvironment.dist) {
+            try
+            {
+                return toRun.get().call();
+            }
+            catch (Exception e)
+            {
+                throw new RuntimeException(e);
+            }
+        }
+        return null;
+    }
+
+    /**
+     * Call the SafeCallable when on the correct {@link Dist}.
+     *
+     * <strong>The lambda supplied here is required to be a method reference to a method defined in
+     * another class, otherwise an invalid SafeReferent error will be thrown</strong>
+     * @param dist the dist which this will run on
+     * @param toRun the SafeCallable to run and return the result from
+     * @param <T> The type of the SafeCallable
+     * @return the result of the SafeCallable or null if on the wrong side
+     */
+    public static <T> T safeCallWhenOn(Dist dist, Supplier<SafeCallable<T>> toRun) {
+        validateSafeReferent(toRun);
+        return callWhenOn(dist, toRun::get);
+    }
+
+    /**
+     * Runs the supplied Runnable on the speicified side. Same warnings apply as {@link #callWhenOn(Dist, Supplier)}.
+     *
+     * This method can cause unexpected ClassNotFound exceptions.
+     *
+     * @see #callWhenOn(Dist, Supplier)
+     * @param dist Dist to run this code on
+     * @param toRun The code to run
+     * @deprecated use {@link #safeRunWhenOn(Dist, Supplier)} where possible. Advanced uses only.
+     */
+    @Deprecated
+    public static void runWhenOn(Dist dist, Supplier<Runnable> toRun) {
+        unsafeRunWhenOn(dist, toRun);
+    }
+    /**
+     * Runs the supplied Runnable on the speicified side. Same warnings apply as {@link #unsafeCallWhenOn(Dist, Supplier)}.
+     *
+     * This method can cause unexpected ClassNotFoundException problems in common scenarios. Understand the pitfalls of
+     * the way the class verifier works to load classes before using this.
+     *
+     * Use {@link #safeRunWhenOn(Dist, Supplier)} if you can.
+     *
+     * @see #unsafeCallWhenOn(Dist, Supplier)
+     * @param dist Dist to run this code on
+     * @param toRun The code to run
+     */
+    public static void unsafeRunWhenOn(Dist dist, Supplier<Runnable> toRun) {
+        if (dist == FMLEnvironment.dist) {
+            toRun.get().run();
+        }
+    }
+
+    /**
+     * Call the supplied SafeRunnable when on the correct Dist.
+     * @param dist The dist to run on
+     * @param toRun The code to run
+     */
+    public static void safeRunWhenOn(Dist dist, Supplier<SafeRunnable> toRun) {
+        validateSafeReferent(toRun);
+        if (dist == FMLEnvironment.dist)  {
+            toRun.get().run();
+        }
+    }
+    /**
+     * Executes one of the two suppliers, based on which side is active.
+     *
+     * <p>
+     *     Example (replacement for old SidedProxy):<br/>
+     * {@code Proxy p = DistExecutor.runForDist(()->ClientProxy::new, ()->ServerProxy::new);}
+     *
+     * NOTE: the double supplier is required to avoid classloading the secondary target.
+     *
+     * @param clientTarget The supplier supplier to run when on the {@link Dist#CLIENT}
+     * @param serverTarget The supplier supplier to run when on the {@link Dist#DEDICATED_SERVER}
+     * @param <T> The common type to return
+     * @return The returned instance
+     * @deprecated Use {@link #safeRunForDist(Supplier, Supplier)}
+     */
+    @Deprecated
+    public static <T> T runForDist(Supplier<Supplier<T>> clientTarget, Supplier<Supplier<T>> serverTarget) {
+        return unsafeRunForDist(clientTarget, serverTarget);
+    }
+
+    /**
+     * Unsafe version of {@link #safeRunForDist(Supplier, Supplier)}. Use only when you know what you're doing
+     * and understand why the verifier can cause unexpected ClassNotFoundException crashes even when code is apparently
+     * not sided. Ensure you test both sides fully to be confident in using this.
+     *
+     * @param clientTarget The supplier supplier to run when on the {@link Dist#CLIENT}
+     * @param serverTarget The supplier supplier to run when on the {@link Dist#DEDICATED_SERVER}
+     * @param <T> The common type to return
+     * @return The returned instance
+     */
+    public static <T> T unsafeRunForDist(Supplier<Supplier<T>> clientTarget, Supplier<Supplier<T>> serverTarget) {
+        switch (FMLEnvironment.dist)
+        {
+            case CLIENT:
+                return clientTarget.get().get();
+            case DEDICATED_SERVER:
+                return serverTarget.get().get();
+            default:
+                throw new IllegalArgumentException("UNSIDED?");
+        }
+    }
+    /**
+     * Executes one of the two suppliers, based on which side is active.
+     *
+     * <p>
+     *     Example (replacement for old SidedProxy):<br/>
+     * {@code Proxy p = DistExecutor.safeRunForDist(()->ClientProxy::new, ()->ServerProxy::new);}
+     *
+     * NOTE: the double supplier is required to avoid classloading the secondary target.
+     *
+     * @param clientTarget The supplier supplier to run when on the {@link Dist#CLIENT}
+     * @param serverTarget The supplier supplier to run when on the {@link Dist#DEDICATED_SERVER}
+     * @param <T> The common type to return
+     * @return The returned instance
+     */
+    public static <T> T safeRunForDist(Supplier<SafeSupplier<T>> clientTarget, Supplier<SafeSupplier<T>> serverTarget) {
+        validateSafeReferent(clientTarget);
+        validateSafeReferent(serverTarget);
+        switch (FMLEnvironment.dist)
+        {
+            case CLIENT:
+                return clientTarget.get().get();
+            case DEDICATED_SERVER:
+                return serverTarget.get().get();
+            default:
+                throw new IllegalArgumentException("UNSIDED?");
+        }
+    }
+
+    /**
+     * A safe referent. This will assert that it is being called via a separated class method reference. This will
+     * avoid the common pitfalls of {@link #callWhenOn(Dist, Supplier)} above.
+     *
+     * SafeReferents assert that they are defined as a separate method outside the scope of the calling class.
+     *
+     * <strong>Implementations need to be defined in a separate class to the referring site, with appropriate
+     * visibility to be accessible at the callsite (generally, avoid private methods).</strong>
+     *
+     * <p>
+     * Valid:<br/>
+     *
+     * {@code DistExecutor.safeCallWhenOn(Dist.CLIENT, ()->AnotherClass::clientOnlyMethod);}
+     *
+     * <p>
+     * Invalid:<br/>
+     *
+     * {@code DistExecutor.safeCallWhenOn(Dist.CLIENT, ()->()->Minecraft.getInstance().world);}
+     */
+    public interface SafeReferent {}
+
+    /**
+     * SafeCallable version of {@link SafeReferent}.
+     * @see SafeReferent
+     * @param <T> The return type of the Callable
+     */
+    public interface SafeCallable<T> extends SafeReferent, Callable<T>, Serializable {}
+
+    /**
+     * SafeSupplier version of {@link SafeReferent}
+     * @param <T> The return type of the Supplier
+     */
+    public interface SafeSupplier<T> extends SafeReferent, Supplier<T>, Serializable {}
+
+    /**
+     * SafeRunnable version of {@link SafeReferent}
+     */
+    public interface SafeRunnable extends SafeReferent, Runnable, Serializable {}
+
+    private static final void validateSafeReferent(Supplier<? extends SafeReferent> safeReferentSupplier) {
+        if (FMLEnvironment.production) return;
+        final SafeReferent setter;
+        try {
+            setter = safeReferentSupplier.get();
+        } catch (Exception e) {
+            // Typically a class cast exception, just return out, expected.
+            return;
+        }
+
+        for (Class<?> cl = setter.getClass(); cl != null; cl = cl.getSuperclass()) {
+            try {
+                Method m = cl.getDeclaredMethod("writeReplace");
+                m.setAccessible(true);
+                Object replacement = m.invoke(setter);
+                if (!(replacement instanceof SerializedLambda))
+                    break;// custom interface implementation
+                SerializedLambda l = (SerializedLambda) replacement;
+                if (Objects.equals(l.getCapturingClass(), l.getImplClass())) {
+                    LOGGER.fatal("Detected unsafe referent usage, please view the code at {}",Thread.currentThread().getStackTrace()[3]);
+                    throw new RuntimeException("Unsafe Referent usage found in safe referent method");
+                }
+            } catch (NoSuchMethodException e) {
+            } catch (IllegalAccessException | InvocationTargetException e) {
+                break;
+            }
+        }
+    }
+}

fmlcore/src/main/java/net/minecraftforge/fml/I18NParser.java

@@ -0,0 +1,6 @@
+package net.minecraftforge.fml;
+
+public interface I18NParser {
+    String parseMessage(String i18nMessage, Object... args);
+    String stripControlCodes(String toStrip);
+}

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

@@ -0,0 +1,12 @@
+package net.minecraftforge.fml;
+
+import net.minecraftforge.eventbus.api.IEventBus;
+import net.minecraftforge.fml.config.IConfigEvent;
+
+import java.util.function.Supplier;
+
+public interface IBindingsProvider {
+    Supplier<IEventBus> getForgeBusSupplier();
+    Supplier<I18NParser> getMessageParser();
+    Supplier<IConfigEvent.ConfigConfig> getConfigConfiguration();
+}

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

@@ -0,0 +1,62 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml;
+
+import java.util.function.BiPredicate;
+import java.util.function.Supplier;
+
+public interface IExtensionPoint<T extends Record>
+{
+    /**
+     * Compatibility display test for the mod.
+     * Used for displaying compatibility with remote servers with the same mod, and on disk saves.
+     *
+     * The supplier provides my "local" version for sending across the network or writing to disk
+     * The predicate tests the version from a remote instance or save for acceptability (Boolean is true for network, false for local save)
+     * and returns true if the version is compatible.
+     *
+     * <p>Return {@link net.minecraftforge.fml.network.FMLNetworkConstants#IGNORESERVERONLY} in the supplier, if you wish to be ignored
+     * as a server side only mod.</p>
+     * <p>Return true in the predicate for all values of the input string (when network boolean is true) if you are client side,
+     * and don't care about matching any potential server version.</p>
+     *
+     * <p>
+     * Examples: A server only mod
+     *
+     * <code><pre>
+     *     registerExtensionPoint(DISPLAYTEST, ()->Pair.of(
+     *      ()->FMLNetworkConstants.IGNORESERVERONLY, // ignore me, I'm a server only mod
+     *      (s,b)->true // i accept anything from the server or the save, if I'm asked
+     *     )
+     * </pre></code>
+     * </p>
+     * <p>
+     * Examples: A client only mod
+     * <code><pre>
+     *     registerExtensionPoint(DISPLAYTEST, ()->Pair.of(
+     *      ()->"anything. i don't care", // if i'm actually on the server, this string is sent but i'm a client only mod, so it won't be
+     *      (remoteversionstring,networkbool)->networkbool // i accept anything from the server, by returning true if it's asking about the server
+     *     )
+     * </pre></code>
+     * </p>
+     *
+     */
+    record DisplayTest(Supplier<String> suppliedVersion, BiPredicate<String, Boolean> remoteVersionTest) implements IExtensionPoint<DisplayTest> {}
+}

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

@@ -0,0 +1,25 @@
+package net.minecraftforge.fml;
+
+import net.minecraftforge.eventbus.api.Event;
+import net.minecraftforge.fml.event.IModBusEvent;
+
+import java.util.List;
+import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executor;
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+public interface IModLoadingState {
+    String name();
+    String previous();
+    ModLoadingPhase phase();
+    Function<ModList, String> message();
+    Optional<Consumer<ModList>> inlineRunnable();
+
+    default <T extends Event & IModBusEvent> Optional<CompletableFuture<List<Throwable>>> buildTransition(final Executor syncExecutor, final Executor parallelExecutor) {
+        return buildTransition(syncExecutor, parallelExecutor, e->CompletableFuture.runAsync(()->{}, e), e->CompletableFuture.runAsync(()->{}, e));
+    }
+
+    <T extends Event & IModBusEvent> Optional<CompletableFuture<List<Throwable>>> buildTransition(Executor syncExecutor, Executor parallelExecutor, Function<Executor, CompletableFuture<Void>> preSyncTask, Function<Executor, CompletableFuture<Void>> postSyncTask);
+}

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

@@ -0,0 +1,7 @@
+package net.minecraftforge.fml;
+
+import java.util.List;
+
+public interface IModStateProvider {
+    List<IModLoadingState> getAllStates();
+}

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

@@ -0,0 +1,87 @@
+package net.minecraftforge.fml;
+
+import net.minecraftforge.eventbus.api.Event;
+import net.minecraftforge.fml.event.IModBusEvent;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executor;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+import java.util.function.Supplier;
+import java.util.stream.Stream;
+
+@SuppressWarnings("unchecked")
+public interface IModStateTransition {
+    static IModStateTransition buildNoopTransition() {
+        return new NoopTransition();
+    }
+
+    default <T extends Event & IModBusEvent> CompletableFuture<List<Throwable>> build(Executor syncExecutor, Executor parallelExecutor, Function<Executor, CompletableFuture<Void>> preSyncTask, Function<Executor, CompletableFuture<Void>> postSyncTask) {
+        List<CompletableFuture<List<Throwable>>> cfs = new ArrayList<>();
+        this.eventFunctionStream().get()
+                .map(f->(EventGenerator<T>)f)
+                .reduce((head, tail)-> addCompletableFutureTaskForModDispatch(syncExecutor, parallelExecutor, cfs, head, ModLoadingStage::currentState, tail))
+                .ifPresent(last-> addCompletableFutureTaskForModDispatch(syncExecutor, parallelExecutor, cfs, last, nextModLoadingStage(), null));
+        final CompletableFuture<Void> preSyncTaskCF = preSyncTask.apply(syncExecutor);
+        final CompletableFuture<List<Throwable>> eventDispatchCF = ModList.gather(cfs).thenCompose(ModList::completableFutureFromExceptionList);
+        final CompletableFuture<List<Throwable>> postEventDispatchCF = preSyncTaskCF.thenComposeAsync(n -> eventDispatchCF, parallelExecutor).thenApply(r -> {
+            postSyncTask.apply(syncExecutor);
+            return r;
+        });
+        return this.finalActivityGenerator().apply(syncExecutor, postEventDispatchCF);
+    }
+
+    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<List<Throwable>>> completeableFutures, final EventGenerator<T> eventGenerator, BiFunction<ModLoadingStage, Throwable, ModLoadingStage> nextState, final EventGenerator<T> nextGenerator) {
+        completeableFutures.add(((BiFunction<Executor, EventGenerator<T>, CompletableFuture<List<Throwable>>>)preDispatchHook()).apply(threadSelector().apply(syncExecutor, parallelExecutor), eventGenerator));
+        completeableFutures.add(ModList.get().futureVisitor(eventGenerator, nextState).apply(threadSelector().apply(syncExecutor, parallelExecutor)));
+        completeableFutures.add(((BiFunction<Executor, EventGenerator<T>, CompletableFuture<List<Throwable>>>)postDispatchHook()).apply(threadSelector().apply(syncExecutor, parallelExecutor), eventGenerator));
+        return nextGenerator;
+    }
+
+    Supplier<Stream<EventGenerator<?>>> eventFunctionStream();
+    ThreadSelector threadSelector();
+    BiFunction<Executor, CompletableFuture<List<Throwable>>, CompletableFuture<List<Throwable>>> finalActivityGenerator();
+    BiFunction<Executor, ? extends EventGenerator<?>, CompletableFuture<List<Throwable>>> preDispatchHook();
+    BiFunction<Executor, ? extends EventGenerator<?>, CompletableFuture<List<Throwable>>> postDispatchHook();
+
+    interface EventGenerator<T extends Event & IModBusEvent> extends Function<ModContainer, T> {
+        static <FN extends Event & 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<List<Throwable>>, CompletableFuture<List<Throwable>>> finalActivityGenerator() {
+        return (e, t) -> t.thenApplyAsync(Function.identity(), e);
+    }
+
+    @Override
+    public BiFunction<Executor, ? extends EventGenerator<?>, CompletableFuture<List<Throwable>>> preDispatchHook() {
+        return (t, f)-> CompletableFuture.completedFuture(Collections.emptyList());
+    }
+
+    @Override
+    public BiFunction<Executor, ? extends EventGenerator<?>, CompletableFuture<List<Throwable>>> postDispatchHook() {
+        return (t, f)-> CompletableFuture.completedFuture(Collections.emptyList());
+    }
+}

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

@@ -0,0 +1,27 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml;
+
+import java.util.function.Supplier;
+
+public interface ISystemReportExtender extends Supplier<String>
+{
+    String getLabel();
+}

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

@@ -1,6 +1,20 @@
 /*
- * Copyright (c) Forge Development LLC and contributors
- * SPDX-License-Identifier: LGPL-2.1-only
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
 package net.minecraftforge.fml;
@@ -19,38 +33,32 @@ import java.util.stream.StreamSupport;
 
 public class InterModComms
 {
-    public static final class IMCMessage {
-        private final String modId;
-        private final String method;
-        private final String senderModId;
-        private final Supplier<?> thing;
-
-        IMCMessage(String senderModId, String modId, String method, Supplier<?> thing)
-        {
-            this.senderModId = senderModId;
-            this.modId = modId;
-            this.method = method;
-            this.thing = thing;
-        }
+    public record IMCMessage(String senderModId, String modId, String method, Supplier<?> messageSupplier) {
 
         /**
+         * Deprecated: use {@link #senderModId()}
          * @return The modid of the sender. This is supplied by the caller, or by the active mod container context.
          * Consider it unreliable.
          */
+        @Deprecated
         public final String getSenderModId() {
             return this.senderModId;
         }
 
         /**
+         * Deprecated: use {@link #modId()}
          * @return The modid being sent to.
          */
+        @Deprecated
         public final String getModId() {
             return this.modId;
         }
 
         /**
+         * Deprecated: use {@link #method()}
          * @return The method being sent to.
          */
+        @Deprecated
         public final String getMethod() {
             return this.method;
         }
@@ -58,10 +66,12 @@ public class InterModComms
         /**
          * @param <T> The type of the message.
          * @return A {@link Supplier} of the message.
+         * Use {@link #messageSupplier()}
          */
         @SuppressWarnings("unchecked")
+        @Deprecated
         public final <T> Supplier<T> getMessageSupplier() {
-            return (Supplier<T>)this.thing;
+            return (Supplier<T>) this.messageSupplier;
         }
     }
 

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

@@ -0,0 +1,40 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class LoadingFailedException extends RuntimeException {
+    private final List<ModLoadingException> loadingExceptions;
+
+    public LoadingFailedException(final List<ModLoadingException> loadingExceptions) {
+        this.loadingExceptions = loadingExceptions;
+    }
+
+    public List<ModLoadingException> getErrors() {
+        return this.loadingExceptions;
+    }
+
+    @Override
+    public String getMessage() {
+        return "Loading errors encountered: " + this.loadingExceptions.stream().map(ModLoadingException::getMessage).collect(Collectors.joining(",\n\t", "[\n\t", "\n]"));
+    }
+}

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

@@ -0,0 +1,39 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml;
+
+import org.apache.logging.log4j.Marker;
+import org.apache.logging.log4j.MarkerManager;
+
+public class Logging
+{
+    // Lots of markers
+    public static final Marker CORE = MarkerManager.getMarker("CORE");
+    public static final Marker LOADING = MarkerManager.getMarker("LOADING");
+    public static final Marker SCAN = MarkerManager.getMarker("SCAN");
+    public static final Marker SPLASH = MarkerManager.getMarker("SPLASH");
+    public static final Marker CAPABILITIES = MarkerManager.getMarker("CAPABILITIES");
+    public static final Marker MODELLOADING = MarkerManager.getMarker("MODELLOADING");
+    public static final Marker FORGEMOD = MarkerManager.getMarker("FORGEMOD").addParents(LOADING);
+
+    // --log CORE:+DEBUG,SCAN:-OFF
+    // forge log debug 5
+
+}

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

@@ -0,0 +1,41 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml;
+
+public enum LogicalSide
+{
+    CLIENT, SERVER;
+
+    /**
+     * @return if the logical side is a server.
+     */
+    public boolean isServer()
+    {
+        return !isClient();
+    }
+
+    /**
+     * @return if the logical side is a client.
+     */
+    public boolean isClient()
+    {
+        return this == CLIENT;
+    }
+}

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

@@ -0,0 +1,170 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml;
+
+import net.minecraftforge.eventbus.api.Event;
+import net.minecraftforge.fml.config.IConfigEvent;
+import net.minecraftforge.fml.config.ModConfig;
+import net.minecraftforge.fml.event.IModBusEvent;
+import net.minecraftforge.forgespi.language.IModInfo;
+
+import java.util.EnumMap;
+import java.util.HashMap;
+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.function.Consumer;
+import java.util.function.Supplier;
+
+/**
+ * The container that wraps around mods in the system.
+ * <p>
+ * The philosophy is that individual mod implementation technologies should not
+ * impact the actual loading and management of mod code. This class provides
+ * 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
+{
+    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<Class<? extends IExtensionPoint<?>>, Supplier<?>> extensionPoints = new IdentityHashMap<>();
+    protected final EnumMap<ModConfig.Type, ModConfig> configs = new EnumMap<>(ModConfig.Type.class);
+    @SuppressWarnings("OptionalUsedAsFieldOrParameterType")
+    protected Optional<Consumer<IConfigEvent>> configHandler = Optional.empty();
+
+    public ModContainer(IModInfo info)
+    {
+        this.modId = info.getModId();
+        // TODO: Currently not reading namespace from configuration..
+        this.namespace = this.modId;
+        this.modInfo = info;
+        this.modLoadingStage = ModLoadingStage.CONSTRUCT;
+        // default displaytest extension checks for version string match
+        registerExtensionPoint(IExtensionPoint.DisplayTest.class, () -> new IExtensionPoint.DisplayTest(()->this.modInfo.getVersion().toString(),
+                (incoming, isNetwork)->Objects.equals(incoming, this.modInfo.getVersion().toString())));
+    }
+
+    /**
+     * Errored container state, used for filtering. Does nothing.
+     */
+    ModContainer()
+    {
+        this.modLoadingStage = ModLoadingStage.ERROR;
+        modId = "BROKEN";
+        namespace = "BROKEN";
+        modInfo = null;
+    }
+    /**
+     * @return the modid for this mod
+     */
+    public final String getModId()
+    {
+        return modId;
+    }
+
+    /**
+     * @return the resource prefix for the mod
+     */
+    public final String getNamespace()
+    {
+        return namespace;
+    }
+
+    /**
+     * @return The current loading stage for this mod
+     */
+    public ModLoadingStage getCurrentState()
+    {
+        return modLoadingStage;
+    }
+
+    public static <T extends Event & IModBusEvent> CompletableFuture<Void> buildTransitionHandler(
+            final ModContainer target,
+            final IModStateTransition.EventGenerator<T> eventGenerator,
+            final BiFunction<ModLoadingStage, Throwable, ModLoadingStage> stateChangeHandler,
+            final Executor executor) {
+        return CompletableFuture
+                .runAsync(() -> {
+                    ModLoadingContext.get().setActiveContainer(target, target.contextExtension.get());
+                    target.activityMap.getOrDefault(target.modLoadingStage, ()->{}).run();
+                    target.acceptEvent(eventGenerator.apply(target));
+                }, executor)
+                .whenComplete((mc, exception) -> {
+                    target.modLoadingStage = stateChangeHandler.apply(target.modLoadingStage, exception);
+                    ModLoadingContext.get().setActiveContainer(null, null);
+                });
+    }
+
+    public IModInfo getModInfo()
+    {
+        return modInfo;
+    }
+
+    @SuppressWarnings("unchecked")
+    public <T extends Record> Optional<T> getCustomExtension(Class<? extends IExtensionPoint<T>> point) {
+        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)
+    {
+        extensionPoints.put(point, extension);
+    }
+
+    public void addConfig(final ModConfig modConfig) {
+       configs.put(modConfig.getType(), modConfig);
+    }
+
+    public void dispatchConfigEvent(IConfigEvent event) {
+        configHandler.ifPresent(configHandler->configHandler.accept(event));
+    }
+
+    /**
+     * Does this mod match the supplied mod?
+     *
+     * @param mod to compare
+     * @return if the mod matches
+     */
+    public abstract boolean matches(Object mod);
+
+    /**
+     * @return the mod object instance
+     */
+    public abstract Object getMod();
+
+    /**
+     * 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) {}
+}

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

@@ -0,0 +1,244 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml;
+
+import net.minecraftforge.eventbus.api.Event;
+import net.minecraftforge.fml.event.IModBusEvent;
+import net.minecraftforge.forgespi.language.IModFileInfo;
+import net.minecraftforge.forgespi.language.IModInfo;
+import net.minecraftforge.forgespi.language.ModFileScanData;
+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.List;
+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;
+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 Logger LOGGER = LogManager.getLogger();
+    private static ModList INSTANCE;
+    private final List<IModFileInfo> modFiles;
+    private final List<IModInfo> sortedList;
+    private final Map<String, ModFileInfo> fileById;
+    private List<ModContainer> mods;
+    private Map<String, ModContainer> indexedMods;
+    private List<ModFileScanData> modFileScanData;
+
+    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));
+        CrashReportCallables.registerCrashCallable("Mod List", this::crashReport);
+    }
+
+    private String getModContainerState(String modId) {
+        return getModContainerById(modId).map(ModContainer::getCurrentState).map(Object::toString).orElse("NONE");
+    }
+
+    private String fileToLine(IModFile mf) {
+        return String.format("%-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()),
+                ((ModFileInfo)mf.getModFileInfo()).getCodeSigningFingerprint().orElse("NOSIGNATURE"));
+    }
+    private String crashReport() {
+        return "\n"+applyForEachModFile(this::fileToLine).collect(Collectors.joining("\n\t\t", "\t\t", ""));
+    }
+
+    public static ModList of(List<ModFile> modFiles, List<ModInfo> sortedList)
+    {
+        INSTANCE = new ModList(modFiles, sortedList);
+        return INSTANCE;
+    }
+
+    public static ModList get() {
+        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()
+    {
+        return modFiles;
+    }
+
+    public IModFileInfo getModFileById(String modid)
+    {
+        return this.fileById.get(modid);
+    }
+
+    <T extends Event & IModBusEvent> Function<Executor, CompletableFuture<List<Throwable>>> futureVisitor(
+            final IModStateTransition.EventGenerator<T> eventGenerator,
+            final BiFunction<ModLoadingStage, Throwable, ModLoadingStage> stateChange) {
+        return executor -> gather(
+                this.mods.stream()
+                .map(mod -> ModContainer.buildTransitionHandler(mod, eventGenerator, stateChange, executor))
+                .collect(Collectors.toList()))
+            .thenComposeAsync(ModList::completableFutureFromExceptionList, executor);
+    }
+    static CompletionStage<List<Throwable>> completableFutureFromExceptionList(List<? extends Map.Entry<?, Throwable>> t) {
+        if (t.stream().noneMatch(e->e.getValue()!=null)) {
+            return CompletableFuture.completedFuture(Collections.emptyList());
+        } else {
+            final List<Throwable> throwables = t.stream().filter(e -> e.getValue() != null).map(Map.Entry::getValue).collect(Collectors.toList());
+            CompletableFuture<List<Throwable>> 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)
+    {
+        this.mods = modContainers;
+        this.indexedMods = modContainers.stream().collect(Collectors.toMap(ModContainer::getModId, Function.identity()));
+    }
+
+    @SuppressWarnings("unchecked")
+    public <T> Optional<T> getModObjectById(String modId)
+    {
+        return getModContainerById(modId).map(ModContainer::getMod).map(o -> (T) o);
+    }
+
+    public Optional<? extends ModContainer> getModContainerById(String modId)
+    {
+        return Optional.ofNullable(this.indexedMods.get(modId));
+    }
+
+    public Optional<? extends ModContainer> getModContainerByObject(Object obj)
+    {
+        return mods.stream().filter(mc -> mc.getMod() == obj).findFirst();
+    }
+
+    public List<IModInfo> getMods()
+    {
+        return this.sortedList;
+    }
+
+    public boolean isLoaded(String modTarget)
+    {
+        return this.indexedMods.containsKey(modTarget);
+    }
+
+    public int size()
+    {
+        return mods.size();
+    }
+
+    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());
+        }
+        return modFileScanData;
+
+    }
+
+    public void forEachModFile(Consumer<IModFile> fileConsumer)
+    {
+        modFiles.stream().map(IModFileInfo::getFile).forEach(fileConsumer);
+    }
+
+    public <T> Stream<T> applyForEachModFile(Function<IModFile, T> function) {
+        return modFiles.stream().map(IModFileInfo::getFile).map(function);
+    }
+
+    public void forEachModContainer(BiConsumer<String, ModContainer> modContainerConsumer) {
+        indexedMods.forEach(modContainerConsumer);
+    }
+
+    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

@@ -0,0 +1,333 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml;
+
+import com.google.common.collect.ImmutableList;
+import net.minecraftforge.eventbus.api.Event;
+import net.minecraftforge.fml.event.IModBusEvent;
+import net.minecraftforge.fml.loading.FMLLoader;
+import net.minecraftforge.fml.loading.LoadingModList;
+import net.minecraftforge.fml.loading.moddiscovery.InvalidModIdentifier;
+import net.minecraftforge.fml.loading.moddiscovery.ModFile;
+import net.minecraftforge.fml.loading.moddiscovery.ModFileInfo;
+import net.minecraftforge.fml.loading.progress.StartupMessageManager;
+import net.minecraftforge.forgespi.language.IModInfo;
+import net.minecraftforge.forgespi.language.IModLanguageProvider;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import java.util.Arrays;
+import java.util.Collection;
+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.CompletionException;
+import java.util.concurrent.Executor;
+import java.util.function.Consumer;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+import static net.minecraftforge.fml.Logging.CORE;
+import static net.minecraftforge.fml.Logging.LOADING;
+
+/**
+ * Loads mods.
+ *
+ * Dispatch cycle is seen in {@link #loadMods()} and {@link #finishMods()}
+ *
+ * Overall sequence for loadMods is:
+ * <dl>
+ *     <dt>CONSTRUCT</dt>
+ *     <dd>Constructs the mod instance. Mods can typically setup basic environment such as Event listeners
+ *     and Configuration specifications here.</dd>
+ *     <dt>Automated dispatches</dt>
+ *     <dd>Dispatches automated elements : {@link net.minecraftforge.fml.common.Mod.EventBusSubscriber},
+ *     {@link net.minecraftforge.event.RegistryEvent}, {@link net.minecraftforge.common.capabilities.CapabilityInject}
+ *     and others</dd>
+ *     <dt>CONFIG_LOAD</dt>
+ *     <dd>Dispatches ConfigLoadEvent to mods</dd>
+ *     <dt>COMMON_SETUP</dt>
+ *     <dd>Dispatches {@link net.minecraftforge.fml.event.lifecycle.FMLCommonSetupEvent} to mods</dd>
+ *     <dt>SIDED_SETUP</dt>
+ *     <dd>Dispatches {@link net.minecraftforge.fml.event.lifecycle.FMLClientSetupEvent} or
+ *     {@link net.minecraftforge.fml.event.lifecycle.FMLDedicatedServerSetupEvent} to mods</dd>
+ * </dl>
+ *
+ * Overall sequence for finishMods is:
+ * <dl>
+ *     <dt>ENQUEUE_IMC</dt>
+ *     <dd>Dispatches {@link net.minecraftforge.fml.event.lifecycle.InterModEnqueueEvent} to mods,
+ *     for enqueuing {@link InterModComms} messages for other mods to receive subsequently</dd>
+ *     <dt>PROCESS_IMC</dt>
+ *     <dd>Dispatches {@link net.minecraftforge.fml.event.lifecycle.InterModProcessEvent} to mods,
+ *     for processing {@link InterModComms} messages received from other mods prior to this event</dd>
+ *     <dt>COMPLETE</dt>
+ *     <dd>Dispatches {@link net.minecraftforge.fml.event.lifecycle.FMLLoadCompleteEvent} to mods,
+ *     and completes the mod loading sequence.</dd>
+ * </dl>
+ */
+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 List<ModLoadingWarning> loadingWarnings;
+    private final ModStateManager stateManager;
+    private boolean loadingStateValid;
+    @SuppressWarnings("OptionalUsedAsFieldOrParameterType")
+    private final Optional<Consumer<String>> statusConsumer = StartupMessageManager.modLoaderConsumer();
+    private ModList modList;
+
+    private ModLoader()
+    {
+        INSTANCE = this;
+        this.loadingModList = FMLLoader.getLoadingModList();
+        this.loadingExceptions = FMLLoader.getLoadingModList().getErrors().stream()
+                .flatMap(ModLoadingException::fromEarlyException)
+                .collect(Collectors.toList());
+        this.loadingWarnings = FMLLoader.getLoadingModList().getBrokenFiles().stream()
+                .map(file -> new ModLoadingWarning(null, ModLoadingStage.VALIDATE, InvalidModIdentifier.identifyJarProblem(file.getFilePath()).orElse("fml.modloading.brokenfile"), file.getFileName()))
+                .collect(Collectors.toList());
+        FMLLoader.getLoadingModList().getModFiles().stream()
+                .filter(ModFileInfo::missingLicense) //Search for files with missing licenses
+                .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
+                .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);
+    }
+
+    private 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() {
+        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", "")).
+                collect(Collectors.joining("\n\t\t","\t\t",""));
+    }
+
+    public static ModLoader get()
+    {
+        return INSTANCE == null ? INSTANCE = new ModLoader() : INSTANCE;
+    }
+
+    /**
+     * Run on the primary starting thread by ClientModLoader and ServerModLoader
+     * @param syncExecutor An executor to run tasks on the main thread
+     * @param parallelExecutor An executor to run tasks on a parallel loading thread pool
+     * @param periodicTask Optional periodic task to perform on the main thread while other activities run
+     */
+    public void gatherAndInitializeMods(final ModWorkManager.DrivenExecutor syncExecutor, final Executor parallelExecutor, final Runnable periodicTask) {
+        loadingStateValid = true;
+        statusConsumer.ifPresent(c->c.accept("Waiting for scan to complete"));
+        FMLLoader.backgroundScanHandler.waitForScanToComplete(periodicTask);
+        statusConsumer.ifPresent(c->c.accept("Loading mods"));
+        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));
+            modList.setLoadedMods(Collections.emptyList());
+            loadingStateValid = false;
+            throw new LoadingFailedException(loadingExceptions);
+        }
+        statusConsumer.ifPresent(c->c.accept("Building Mod List"));
+        final List<ModContainer> modContainers = loadingModList.getModFiles().stream()
+                .map(ModFileInfo::getFile)
+                .map(this::buildMods)
+                .<ModContainer>mapMulti(Iterable::forEach)
+                .toList();
+        if (!loadingExceptions.isEmpty()) {
+            LOGGER.fatal(CORE, "Failed to initialize mod containers", loadingExceptions.get(0));
+            modList.setLoadedMods(Collections.emptyList());
+            loadingStateValid = false;
+            throw new LoadingFailedException(loadingExceptions);
+        }
+        modList.setLoadedMods(modContainers);
+        this.modList = modList;
+        statusConsumer.ifPresent(c->c.accept("Dispatching gathering events"));
+        stateManager.getStates(ModLoadingPhase.GATHER).forEach(mls->dispatchAndHandleError(mls, syncExecutor, parallelExecutor, periodicTask));
+        statusConsumer.ifPresent(c->c.accept("Gathering phase complete"));
+    }
+
+    public void loadMods(final ModWorkManager.DrivenExecutor syncExecutor, final Executor parallelExecutor, final Runnable periodicTask) {
+        statusConsumer.ifPresent(c->c.accept("Performing load phase"));
+        stateManager.getStates(ModLoadingPhase.LOAD).forEach(mls->dispatchAndHandleError(mls, syncExecutor, parallelExecutor, periodicTask));
+        statusConsumer.ifPresent(c->c.accept("Mod setup complete"));
+    }
+
+    public void finishMods(final ModWorkManager.DrivenExecutor syncExecutor, final Executor parallelExecutor, final Runnable periodicTask) {
+        statusConsumer.ifPresent(c->c.accept("Performing completion phase"));
+        stateManager.getStates(ModLoadingPhase.COMPLETE).forEach(mls->dispatchAndHandleError(mls, syncExecutor, parallelExecutor, periodicTask));
+        statusConsumer.ifPresent(c->c.accept(String.format("Mod loading complete - %d mods loaded", this.modList.size())));
+    }
+
+    private void dispatchAndHandleError(IModLoadingState state, ModWorkManager.DrivenExecutor syncExecutor, Executor parallelExecutor, final Runnable ticker) {
+        if (!isLoadingStateValid()) {
+            LOGGER.error("Cowardly refusing to process mod state change request from {}", state);
+            return;
+        }
+        statusConsumer.ifPresent(c->c.accept(state.message().apply(this.modList)));
+        state.inlineRunnable().ifPresent(a->a.accept(this.modList));
+        state.buildTransition(syncExecutor, parallelExecutor).ifPresent(t->waitForTransition(state, syncExecutor, ticker, t));
+    }
+
+    private void dispatchAndHandleError(IModLoadingState state, ModWorkManager.DrivenExecutor syncExecutor, Executor parallelExecutor, final Runnable ticker, Function<Executor, CompletableFuture<Void>> preSyncTask, Function<Executor, CompletableFuture<Void>> postSyncTask) {
+        if (!isLoadingStateValid()) {
+            LOGGER.error("Cowardly refusing to process mod state change request from {}", state);
+            return;
+        }
+        statusConsumer.ifPresent(c->c.accept(state.message().apply(this.modList)));
+        state.inlineRunnable().ifPresent(a->a.accept(this.modList));
+        state.buildTransition(syncExecutor, parallelExecutor, preSyncTask, postSyncTask).ifPresent(t->waitForTransition(state, syncExecutor, ticker, t));
+    }
+
+    private void waitForTransition(final IModLoadingState state, final ModWorkManager.DrivenExecutor syncExecutor, final Runnable ticker, final CompletableFuture<List<Throwable>> transition) {
+        while (!transition.isDone()) {
+            syncExecutor.drive(ticker);
+        }
+        try {
+            transition.join();
+        } catch (CompletionException e) {
+            loadingStateValid = false;
+            Throwable t = e.getCause();
+            final List<Throwable> notModLoading = Arrays.stream(t.getSuppressed())
+                    .filter(obj -> !(obj instanceof ModLoadingException))
+                    .collect(Collectors.toList());
+            if (!notModLoading.isEmpty()) {
+                LOGGER.fatal("Encountered non-modloading exceptions!", e);
+                throw e;
+            }
+
+            final List<ModLoadingException> modLoadingExceptions = Arrays.stream(t.getSuppressed())
+                    .filter(ModLoadingException.class::isInstance)
+                    .map(ModLoadingException.class::cast)
+                    .collect(Collectors.toList());
+            LOGGER.fatal(LOADING,"Failed to complete lifecycle event {}, {} errors found", state.name(), modLoadingExceptions.size());
+            throw new LoadingFailedException(modLoadingExceptions);
+        }
+    }
+
+    private List<ModContainer> buildMods(final ModFile modFile)
+    {
+        final Map<String, IModInfo> modInfoMap = modFile.getModFileInfo().getMods().stream().collect(Collectors.toMap(IModInfo::getModId, Function.identity()));
+
+        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)
+                .collect(Collectors.toList());
+        if (containers.size() != modInfoMap.size()) {
+            LOGGER.fatal(LOADING,"File {} constructed {} mods: {}, but had {} mods specified: {}",
+                    modFile.getFilePath(),
+                    containers.size(), containers.stream().map(c -> c != null ? c.getModId() : "(null)").sorted().collect(Collectors.toList()),
+                    modInfoMap.size(), modInfoMap.values().stream().map(IModInfo::getModId).sorted().collect(Collectors.toList()));
+            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).collect(Collectors.toList());
+    }
+
+    private ModContainer buildModContainerFromTOML(final ModFile modFile, final Map<String, IModInfo> modInfoMap, final Map.Entry<String, ? extends IModLanguageProvider.IModLanguageLoader> idToProviderEntry) {
+        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));
+            return languageLoader.loadMod(info, modFile.getScanResult(), FMLLoader.getGameLayer());
+        } catch (ModLoadingException mle) {
+            // exceptions are caught and added to the error list for later handling
+            loadingExceptions.add(mle);
+            // return an errored container instance here, because we tried and failed building a container.
+            return new ErroredModContainer();
+        }
+    }
+
+    /**
+     * @return If the current mod loading state is valid. Use if you interact with vanilla systems directly during loading
+     * 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;
+    }
+
+    public <T extends Event & 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().forEachModContainer((id, mc) -> mc.acceptEvent(generator.apply(mc)));
+    }
+
+    public <T extends Event & 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().forEachModContainer((id, mc) -> mc.acceptEvent(e));
+    }
+
+    public List<ModLoadingWarning> getWarnings()
+    {
+        return ImmutableList.copyOf(this.loadingWarnings);
+    }
+
+    public void addWarning(ModLoadingWarning warning)
+    {
+        this.loadingWarnings.add(warning);
+    }
+
+    private static boolean runningDataGen = false;
+
+    public static boolean isDataGenRunning () {
+        return runningDataGen;
+    }
+
+    private static class ErroredModContainer extends ModContainer {
+        public ErroredModContainer() {
+            super();
+        }
+
+        @Override
+        public boolean matches(final Object mod) {
+            return false;
+        }
+
+        @Override
+        public Object getMod() {
+            return null;
+        }
+    }
+}

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

@@ -0,0 +1,75 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml;
+
+import net.minecraftforge.fml.config.IConfigSpec;
+import net.minecraftforge.fml.config.ModConfig;
+
+import java.util.function.Supplier;
+
+public class ModLoadingContext
+{
+    private static final ThreadLocal<ModLoadingContext> context = ThreadLocal.withInitial(ModLoadingContext::new);
+    private Object languageExtension;
+    private ModLoadingStage stage;
+
+    public static ModLoadingContext get() {
+        return context.get();
+    }
+
+    private ModContainer activeContainer;
+
+    public void setActiveContainer(final ModContainer container, final Object languageExtension) {
+        this.activeContainer = container;
+        this.languageExtension = languageExtension;
+    }
+
+    public ModContainer getActiveContainer() {
+        return activeContainer == null ? ModList.get().getModContainerById("minecraft").orElseThrow(()->new RuntimeException("Where is minecraft???!")) : activeContainer;
+    }
+
+    public String getActiveNamespace() {
+        return activeContainer == null ? "minecraft" : activeContainer.getNamespace();
+    }
+
+    /**
+     * Register an {@link IExtensionPoint} with the mod container.
+     * @param point The extension point to register
+     * @param extension An extension operator
+     * @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);
+    }
+
+    public void registerConfig(ModConfig.Type type, IConfigSpec<?> spec) {
+        getActiveContainer().addConfig(new ModConfig(type, spec, getActiveContainer()));
+    }
+
+    public void registerConfig(ModConfig.Type type, IConfigSpec<?> spec, String fileName) {
+        getActiveContainer().addConfig(new ModConfig(type, spec, getActiveContainer(), fileName));
+    }
+
+
+    @SuppressWarnings("unchecked")
+    public <T> T extension() {
+        return (T)languageExtension;
+    }
+}

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

@@ -0,0 +1,90 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml;
+
+import com.google.common.collect.Streams;
+import net.minecraftforge.fml.loading.EarlyLoadingException;
+import net.minecraftforge.forgespi.language.IModInfo;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Stream;
+
+/**
+ * General purpose mod loading error message
+ */
+public class ModLoadingException extends RuntimeException
+{
+    private static final long serialVersionUID = 2048947398536935507L;
+    /**
+     * Mod Info for mod with issue
+     */
+    private final IModInfo modInfo;
+    /**
+     * The stage where this error was encountered
+     */
+    private final ModLoadingStage errorStage;
+
+    /**
+     * I18N message to use for display
+     */
+    private final String i18nMessage;
+
+    /**
+     * Context for message display
+     */
+    private final List<Object> context;
+
+    public ModLoadingException(final IModInfo modInfo, final ModLoadingStage errorStage, final String i18nMessage, final Throwable originalException, Object... context) {
+        super("Mod Loading Exception", originalException);
+        this.modInfo = modInfo;
+        this.errorStage = errorStage;
+        this.i18nMessage = i18nMessage;
+        this.context = Arrays.asList(context);
+    }
+
+    static Stream<ModLoadingException> fromEarlyException(final EarlyLoadingException e) {
+        return e.getAllData().stream().map(ed->new ModLoadingException(ed.getModInfo(), ModLoadingStage.VALIDATE, ed.getI18message(), e.getCause(), ed.getArgs()));
+    }
+
+    public String getI18NMessage() {
+        return i18nMessage;
+    }
+
+    public Object[] getContext() {
+        return context.toArray();
+    }
+
+    public String formatToString() {
+        return Bindings.getMessageParser().get().parseMessage(i18nMessage, Streams.concat(Stream.of(modInfo, errorStage, getCause()), context.stream()).toArray());
+    }
+
+    @Override
+    public String getMessage() {
+        return formatToString();
+    }
+
+    public IModInfo getModInfo() {
+        return modInfo;
+    }
+    public String getCleanMessage() {
+        return Bindings.getMessageParser().get().stripControlCodes(formatToString());
+    }
+}

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

@@ -0,0 +1,9 @@
+package net.minecraftforge.fml;
+
+public enum ModLoadingPhase {
+    ERROR, // Special state for error handling
+    GATHER,
+    LOAD,
+    COMPLETE,
+    DONE;
+}

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

@@ -0,0 +1,51 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml;
+
+public enum ModLoadingStage
+{
+    ERROR,
+    VALIDATE,
+    CONSTRUCT,
+    COMMON_SETUP,
+    SIDED_SETUP,
+    ENQUEUE_IMC,
+    PROCESS_IMC,
+    COMPLETE,
+    DONE;
+
+    private final DeferredWorkQueue deferredWorkQueue;
+
+    ModLoadingStage() {
+        deferredWorkQueue = new DeferredWorkQueue(this);
+    }
+
+    ModLoadingStage nextState(Throwable exception) {
+        return exception != null ? ERROR : values()[this.ordinal()+1];
+    }
+
+    public ModLoadingStage currentState(Throwable exception) {
+        return exception != null ? ERROR : this;
+    }
+
+    public DeferredWorkQueue getDeferredWorkQueue() {
+        return deferredWorkQueue;
+    }
+}

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

@@ -0,0 +1,33 @@
+package net.minecraftforge.fml;
+
+import net.minecraftforge.eventbus.api.Event;
+import net.minecraftforge.fml.event.IModBusEvent;
+
+import java.util.List;
+import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executor;
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+public record ModLoadingState(String name, String previous, Function<ModList, String> message, ModLoadingPhase phase, Optional<Consumer<ModList>> inlineRunnable, Optional<IModStateTransition> transition) implements IModLoadingState {
+    @Override
+    public <T extends Event & IModBusEvent> Optional<CompletableFuture<List<Throwable>>> buildTransition(final Executor syncExecutor, final Executor parallelExecutor, Function<Executor, CompletableFuture<Void>> preSyncTask, Function<Executor, CompletableFuture<Void>> postSyncTask) {
+        return transition.map(t->t.build(syncExecutor, parallelExecutor, preSyncTask, postSyncTask));
+    }
+
+    public static ModLoadingState empty(final String name, final String previous, final ModLoadingPhase phase) {
+        return new ModLoadingState(name, previous, ml->"", phase, Optional.empty(), Optional.empty());
+    }
+
+    public static ModLoadingState withTransition(final String name, final String previous, final ModLoadingPhase phase, IModStateTransition transition) {
+        return new ModLoadingState(name, previous, ml->"Processing transition "+name, phase, Optional.empty(), Optional.of(transition));
+    }
+
+    public static ModLoadingState withTransition(final String name, final String previous, final Function<ModList, String> message, final ModLoadingPhase phase, IModStateTransition transition) {
+        return new ModLoadingState(name, previous, message, phase, Optional.empty(), Optional.of(transition));
+    }
+    public static ModLoadingState withInline(final String name, final String previous, final ModLoadingPhase phase, Consumer<ModList> inline) {
+        return new ModLoadingState(name, previous, ml->"Processing work "+name, phase, Optional.of(inline), Optional.empty());
+    }
+}

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

@@ -0,0 +1,60 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml;
+
+import com.google.common.collect.Streams;
+import net.minecraftforge.forgespi.language.IModInfo;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Stream;
+
+public class ModLoadingWarning
+{
+    /**
+     * Mod Info for mod with warning
+     */
+    private final IModInfo modInfo;
+    /**
+     * The stage where this warning was encountered
+     */
+    private final ModLoadingStage warningStage;
+
+    /**
+     * I18N message to use for display
+     */
+    private final String i18nMessage;
+
+    /**
+     * Context for message display
+     */
+    private final List<Object> context;
+
+    public ModLoadingWarning(final IModInfo modInfo, final ModLoadingStage warningStage, final String i18nMessage, Object... context) {
+        this.modInfo = modInfo;
+        this.warningStage = warningStage;
+        this.i18nMessage = i18nMessage;
+        this.context = Arrays.asList(context);
+    }
+
+    public String formatToString() {
+        return Bindings.getMessageParser().get().parseMessage(i18nMessage, Streams.concat(Stream.of(modInfo, warningStage), context.stream()).toArray());
+    }
+}

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

@@ -0,0 +1,38 @@
+package net.minecraftforge.fml;
+
+import com.google.common.graph.GraphBuilder;
+import com.google.common.graph.MutableGraph;
+import cpw.mods.modlauncher.util.ServiceLoaderUtils;
+import net.minecraftforge.fml.loading.FMLLoader;
+import net.minecraftforge.fml.loading.toposort.TopologicalSort;
+
+import java.util.*;
+import java.util.function.Function;
+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)
+                .collect(Collectors.groupingBy(IModLoadingState::phase, ()->new EnumMap<>(ModLoadingPhase.class), Collectors.toUnmodifiableList()));
+    }
+
+    public List<IModLoadingState> getStates(final ModLoadingPhase phase) {
+        var nodes = stateMap.get(phase);
+        var lookup = nodes.stream().collect(Collectors.toMap(IModLoadingState::name, Function.identity()));
+
+        var graph = GraphBuilder.directed().allowsSelfLoops(false).<IModLoadingState>build();
+        var dummy = ModLoadingState.empty("", "", phase);
+        nodes.forEach(graph::addNode);
+        graph.addNode(dummy);
+        nodes.forEach(n->graph.putEdge(lookup.getOrDefault(n.previous(), dummy), n));
+        return TopologicalSort.topologicalSort(graph, Comparator.comparingInt(nodes::indexOf)).stream().filter(st->st!=dummy).toList();
+    }
+}

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

@@ -0,0 +1,125 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml;
+
+import net.minecraftforge.fml.loading.FMLConfig;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import java.util.concurrent.*;
+import java.util.concurrent.locks.LockSupport;
+
+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();
+
+        default void drive(Runnable ticker) {
+            if (!selfDriven()) {
+                while (driveOne()) {
+                    ticker.run();
+                }
+            } else {
+                // park for a bit so other threads can schedule
+                LockSupport.parkNanos(PARK_TIME);
+            }
+        }
+    }
+    private static class SyncExecutor implements DrivenExecutor {
+        private ConcurrentLinkedDeque<Runnable> tasks = new ConcurrentLinkedDeque<>();
+
+        @Override
+        public boolean driveOne() {
+            final Runnable task = tasks.pollFirst();
+            if (task != null) {
+                task.run();
+            }
+            return task != null;
+        }
+
+        @Override
+        public boolean selfDriven() {
+            return false;
+        }
+
+        @Override
+        public void execute(final Runnable command) {
+            tasks.addLast(command);
+        }
+    }
+
+    private static class WrappingExecutor implements DrivenExecutor {
+        private final Executor wrapped;
+
+        public WrappingExecutor(final Executor executor) {
+            this.wrapped = executor;
+        }
+
+        @Override
+        public boolean selfDriven() {
+            return true;
+        }
+
+        @Override
+        public boolean driveOne() {
+            return false;
+        }
+
+        @Override
+        public void execute(final Runnable command) {
+            wrapped.execute(command);
+        }
+    }
+
+    private static SyncExecutor syncExecutor;
+
+    public static DrivenExecutor syncExecutor() {
+        if (syncExecutor == null)
+            syncExecutor = new SyncExecutor();
+        return syncExecutor;
+    }
+
+    public static DrivenExecutor wrappedExecutor(Executor executor) {
+        return new WrappingExecutor(executor);
+    }
+
+    private static ForkJoinPool parallelThreadPool;
+    public static Executor parallelExecutor() {
+        if (parallelThreadPool == null) {
+            final int loadingThreadCount = FMLConfig.loadingThreadCount();
+            LOGGER.debug(LOADING, "Using {} threads for parallel mod-loading", loadingThreadCount);
+            parallelThreadPool = new ForkJoinPool(loadingThreadCount, ModWorkManager::newForkJoinWorkerThread, null, false);
+        }
+        return parallelThreadPool;
+    }
+
+    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;
+    }
+
+}

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

@@ -1,6 +1,20 @@
 /*
- * Copyright (c) Forge Development LLC and contributors
- * SPDX-License-Identifier: LGPL-2.1-only
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
 package net.minecraftforge.fml;

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

@@ -0,0 +1,37 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml;
+
+import java.util.Optional;
+import java.util.function.Consumer;
+
+public class StartupMessageManager {
+    public static void addModMessage(final String message) {
+        net.minecraftforge.fml.loading.progress.StartupMessageManager.addModMessage(message);
+    }
+
+    public static Optional<Consumer<String>> modLoaderConsumer() {
+        return net.minecraftforge.fml.loading.progress.StartupMessageManager.modLoaderConsumer();
+    }
+
+    public static Optional<Consumer<String>> mcLoaderConsumer() {
+        return net.minecraftforge.fml.loading.progress.StartupMessageManager.mcLoaderConsumer();
+    }
+}

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

@@ -0,0 +1,20 @@
+package net.minecraftforge.fml;
+
+import java.util.concurrent.Executor;
+import java.util.function.BinaryOperator;
+
+public enum ThreadSelector implements BinaryOperator<Executor> {
+    SYNC((sync, parallel) -> sync),
+    PARALLEL((sync, parallel) -> parallel);
+
+    private final BinaryOperator<Executor> selector;
+
+    ThreadSelector(final BinaryOperator<Executor> selector) {
+        this.selector = selector;
+    }
+
+    @Override
+    public Executor apply(final Executor sync, final Executor parallel) {
+        return this.selector.apply(sync, parallel);
+    }
+}

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

@@ -1,44 +1,39 @@
 /*
- * Copyright (c) Forge Development LLC and contributors
- * SPDX-License-Identifier: LGPL-2.1-only
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
 package net.minecraftforge.fml;
 
 import com.google.common.io.ByteStreams;
 import com.google.gson.Gson;
-import net.minecraftforge.common.ForgeConfig;
 import net.minecraftforge.fml.loading.FMLConfig;
 import net.minecraftforge.fml.loading.moddiscovery.ModInfo;
 import net.minecraftforge.forgespi.language.IModInfo;
-import net.minecraftforge.versions.mcp.MCPVersion;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.apache.maven.artifact.versioning.ComparableVersion;
+
 import java.io.IOException;
 import java.io.InputStream;
 import java.net.HttpURLConnection;
 import java.net.URL;
 import java.net.URLConnection;
-import java.nio.charset.StandardCharsets;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.LinkedHashMap;
-import java.util.LinkedList;
-import java.util.List;
-import java.util.Map;
-import java.util.concurrent.ConcurrentHashMap;
-import javax.annotation.Nonnull;
-import javax.annotation.Nullable;
-
-
-import javax.annotation.Nonnull;
-import javax.annotation.Nullable;
-import java.io.IOException;
-import java.io.InputStream;
-import java.net.HttpURLConnection;
-import java.net.URL;
-import java.net.URLConnection;
+import java.net.http.HttpClient;
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -107,25 +102,7 @@ public class VersionChecker
 
     }
 
-    public static class CheckResult
-    {
-        @Nonnull
-        public final Status status;
-        @Nullable
-        public final ComparableVersion target;
-        @Nullable
-        public final Map<ComparableVersion, String> changes;
-        @Nullable
-        public final String url;
-
-        private CheckResult(@Nonnull Status status, @Nullable ComparableVersion target, @Nullable Map<ComparableVersion, String> changes, @Nullable String url)
-        {
-            this.status = status;
-            this.target = target;
-            this.changes = changes == null ? Collections.<ComparableVersion, String>emptyMap() : Collections.unmodifiableMap(changes);
-            this.url = url;
-        }
-    }
+    public record CheckResult(VersionChecker.Status status, ComparableVersion target, Map<ComparableVersion, String> changes, String url) {}
 
     public static void startVersionCheck()
     {
@@ -177,16 +154,17 @@ public class VersionChecker
                 throw new IOException("Too many redirects while trying to fetch " + url);
             }
 
-            @SuppressWarnings("UnstableApiUsage")
             private void process(IModInfo mod)
             {
+//                HttpClient.newBuilder().build();
                 Status status = PENDING;
                 ComparableVersion target = null;
                 Map<ComparableVersion, String> changes = null;
                 String display_url = null;
                 try
                 {
-                    URL url = mod.getUpdateURL();
+                    if (mod.getUpdateURL().isEmpty()) return;
+                    URL url = mod.getUpdateURL().get();
                     LOGGER.info("[{}] Starting version check at {}", mod.getModId(), url.toString());
 
                     InputStream con = openUrlStream(url);
@@ -202,7 +180,8 @@ public class VersionChecker
                     Map<String, String> promos = (Map<String, String>)json.get("promos");
                     display_url = (String)json.get("homepage");
 
-                    String mcVersion = MCPVersion.getMCVersion();
+//                    String mcVersion = MCPVersion.getMCVersion();
+                    var mcVersion = "1.17";
                     String rec = promos.get(mcVersion + "-recommended");
                     String lat = promos.get(mcVersion + "-latest");
                     ComparableVersion current = new ComparableVersion(mod.getVersion().toString());
@@ -283,9 +262,8 @@ public class VersionChecker
     private static List<IModInfo> gatherMods()
     {
         List<IModInfo> ret = new LinkedList<>();
-        for (ModInfo info : ModList.get().getMods()) {
-            URL url = info.getUpdateURL();
-            if (url != null)
+        for (IModInfo info : ModList.get().getMods()) {
+            if (info.getUpdateURL().isPresent())
                 ret.add(info);
         }
         return ret;

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

@@ -0,0 +1,172 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.config;
+
+import com.electronwill.nightconfig.core.ConfigFormat;
+import com.electronwill.nightconfig.core.file.CommentedFileConfig;
+import com.electronwill.nightconfig.core.file.FileWatcher;
+import com.electronwill.nightconfig.core.io.ParsingException;
+import com.electronwill.nightconfig.core.io.WritingMode;
+import net.minecraftforge.fml.loading.FMLConfig;
+import net.minecraftforge.fml.loading.FMLPaths;
+import org.apache.commons.io.FilenameUtils;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.function.Function;
+
+import static net.minecraftforge.fml.config.ConfigTracker.CONFIG;
+
+public class ConfigFileTypeHandler {
+    private static final Logger LOGGER = LogManager.getLogger();
+    static ConfigFileTypeHandler TOML = new ConfigFileTypeHandler();
+    private static final Path defaultConfigPath = FMLPaths.GAMEDIR.get().resolve(FMLConfig.defaultConfigPath());
+
+    public Function<ModConfig, CommentedFileConfig> reader(Path configBasePath) {
+        return (c) -> {
+            final Path configPath = configBasePath.resolve(c.getFileName());
+            final CommentedFileConfig configData = CommentedFileConfig.builder(configPath).sync().
+                    preserveInsertionOrder().
+                    autosave().
+                    onFileNotFound((newfile, configFormat)-> setupConfigFile(c, newfile, configFormat)).
+                    writingMode(WritingMode.REPLACE).
+                    build();
+            LOGGER.debug(CONFIG, "Built TOML config for {}", configPath.toString());
+            try
+            {
+                configData.load();
+            }
+            catch (ParsingException ex)
+            {
+                throw new ConfigLoadingException(c, ex);
+            }
+            LOGGER.debug(CONFIG, "Loaded TOML config file {}", configPath.toString());
+            try {
+                FileWatcher.defaultInstance().addWatch(configPath, new ConfigWatcher(c, configData, Thread.currentThread().getContextClassLoader()));
+                LOGGER.debug(CONFIG, "Watching TOML config file {} for changes", configPath.toString());
+            } catch (IOException e) {
+                throw new RuntimeException("Couldn't watch config file", e);
+            }
+            return configData;
+        };
+    }
+
+    public void unload(Path configBasePath, ModConfig config) {
+        Path configPath = configBasePath.resolve(config.getFileName());
+        try {
+            FileWatcher.defaultInstance().removeWatch(configBasePath.resolve(config.getFileName()));
+        } catch (RuntimeException e) {
+            LOGGER.error("Failed to remove config {} from tracker!", configPath.toString(), e);
+        }
+    }
+
+    private boolean setupConfigFile(final ModConfig modConfig, final Path file, final ConfigFormat<?> conf) throws IOException {
+        Path p = defaultConfigPath.resolve(modConfig.getFileName());
+        if (Files.exists(p)) {
+            LOGGER.info(CONFIG, "Loading default config file from path {}", p);
+            Files.copy(p, file);
+        } else {
+            Files.createFile(file);
+            conf.initEmptyFile(file);
+        }
+        return true;
+    }
+
+    public static void backUpConfig(final CommentedFileConfig commentedFileConfig)
+    {
+        backUpConfig(commentedFileConfig, 5); //TODO: Think of a way for mods to set their own preference (include a sanity check as well, no disk stuffing)
+    }
+
+    public static void backUpConfig(final CommentedFileConfig commentedFileConfig, final int maxBackups)
+    {
+        Path bakFileLocation = commentedFileConfig.getNioPath().getParent();
+        String bakFileName = FilenameUtils.removeExtension(commentedFileConfig.getFile().getName());
+        String bakFileExtension = FilenameUtils.getExtension(commentedFileConfig.getFile().getName()) + ".bak";
+        Path bakFile = bakFileLocation.resolve(bakFileName + "-1" + "." + bakFileExtension);
+        try
+        {
+            for(int i = maxBackups; i > 0; i--)
+            {
+                Path oldBak = bakFileLocation.resolve(bakFileName + "-" + i + "." + bakFileExtension);
+                if(Files.exists(oldBak))
+                {
+                    if(i >= maxBackups)
+                        Files.delete(oldBak);
+                    else
+                        Files.move(oldBak, bakFileLocation.resolve(bakFileName + "-" + (i + 1) + "." + bakFileExtension));
+                }
+            }
+            Files.copy(commentedFileConfig.getNioPath(), bakFile);
+        }
+        catch (IOException exception)
+        {
+            LOGGER.warn(CONFIG, "Failed to back up config file {}", commentedFileConfig.getNioPath(), exception);
+        }
+    }
+
+    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 void run() {
+            // Force the regular classloader onto the special thread
+            Thread.currentThread().setContextClassLoader(realClassLoader);
+            if (!this.modConfig.getSpec().isCorrecting()) {
+                try
+                {
+                    this.commentedFileConfig.load();
+                    if(!this.modConfig.getSpec().isCorrect(commentedFileConfig))
+                    {
+                        LOGGER.warn(CONFIG, "Configuration file {} is not correct. Correcting", commentedFileConfig.getFile().getAbsolutePath());
+                        ConfigFileTypeHandler.backUpConfig(commentedFileConfig);
+                        this.modConfig.getSpec().correct(commentedFileConfig);
+                        commentedFileConfig.save();
+                    }
+                }
+                catch (ParsingException ex)
+                {
+                    throw new ConfigLoadingException(modConfig, ex);
+                }
+                LOGGER.debug(CONFIG, "Config file {} changed, sending notifies", this.modConfig.getFileName());
+                this.modConfig.getSpec().afterReload();
+                this.modConfig.fireEvent(IConfigEvent.reloading(this.modConfig));
+            }
+        }
+    }
+
+    private static class ConfigLoadingException extends RuntimeException
+    {
+        public ConfigLoadingException(ModConfig config, Exception cause)
+        {
+            super("Failed loading config file " + config.getFileName() + " of type " + config.getType() + " for modid " + config.getModId(), cause);
+        }
+    }
+}

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

@@ -0,0 +1,110 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.config;
+
+import com.electronwill.nightconfig.core.CommentedConfig;
+import com.electronwill.nightconfig.core.file.CommentedFileConfig;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.apache.logging.log4j.Marker;
+import org.apache.logging.log4j.MarkerManager;
+
+import java.nio.file.Path;
+import java.util.*;
+import java.util.concurrent.ConcurrentHashMap;
+
+public class ConfigTracker {
+    private static final Logger LOGGER = LogManager.getLogger();
+    static final Marker CONFIG = MarkerManager.getMarker("CONFIG");
+    public static final ConfigTracker INSTANCE = new ConfigTracker();
+    private final ConcurrentHashMap<String, ModConfig> fileMap;
+    private final EnumMap<ModConfig.Type, Set<ModConfig>> configSets;
+    private final ConcurrentHashMap<String, Map<ModConfig.Type, ModConfig>> configsByMod;
+
+    private ConfigTracker() {
+        this.fileMap = new ConcurrentHashMap<>();
+        this.configSets = new EnumMap<>(ModConfig.Type.class);
+        this.configsByMod = new ConcurrentHashMap<>();
+        this.configSets.put(ModConfig.Type.CLIENT, Collections.synchronizedSet(new LinkedHashSet<>()));
+        this.configSets.put(ModConfig.Type.COMMON, Collections.synchronizedSet(new LinkedHashSet<>()));
+//        this.configSets.put(ModConfig.Type.PLAYER, new ConcurrentSkipListSet<>());
+        this.configSets.put(ModConfig.Type.SERVER, Collections.synchronizedSet(new LinkedHashSet<>()));
+    }
+
+    void trackConfig(final ModConfig config) {
+        if (this.fileMap.containsKey(config.getFileName())) {
+            LOGGER.error(CONFIG,"Detected config file conflict {} between {} and {}", config.getFileName(), this.fileMap.get(config.getFileName()).getModId(), config.getModId());
+            throw new RuntimeException("Config conflict detected!");
+        }
+        this.fileMap.put(config.getFileName(), config);
+        this.configSets.get(config.getType()).add(config);
+        this.configsByMod.computeIfAbsent(config.getModId(), (k)->new EnumMap<>(ModConfig.Type.class)).put(config.getType(), config);
+        LOGGER.debug(CONFIG, "Config file {} for {} tracking", config.getFileName(), config.getModId());
+    }
+
+    public void loadConfigs(ModConfig.Type type, Path configBasePath) {
+        LOGGER.debug(CONFIG, "Loading configs type {}", type);
+        this.configSets.get(type).forEach(config -> openConfig(config, configBasePath));
+    }
+
+    public void unloadConfigs(ModConfig.Type type, Path configBasePath) {
+        LOGGER.debug(CONFIG, "Unloading configs type {}", type);
+        this.configSets.get(type).forEach(config -> closeConfig(config, configBasePath));
+    }
+
+    private 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);
+        config.fireEvent(IConfigEvent.loading(config));
+        config.save();
+    }
+
+    private 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());
+            config.save();
+            config.getHandler().unload(configBasePath, config);
+            config.setConfigData(null);
+        }
+    }
+
+    public void loadDefaultServerConfigs() {
+        configSets.get(ModConfig.Type.SERVER).forEach(modConfig -> {
+            final CommentedConfig commentedConfig = CommentedConfig.inMemory();
+            modConfig.getSpec().correct(commentedConfig);
+            modConfig.setConfigData(commentedConfig);
+            modConfig.fireEvent(IConfigEvent.loading(modConfig));
+        });
+    }
+
+    public String getConfigFileName(String modId, ModConfig.Type type) {
+        return Optional.ofNullable(configsByMod.getOrDefault(modId, Collections.emptyMap()).getOrDefault(type, null)).
+                map(ModConfig::getFullPath).map(Object::toString).orElse(null);
+    }
+
+    public Map<ModConfig.Type, Set<ModConfig>> configSets() {
+        return configSets;
+    }
+
+    public ConcurrentHashMap<String, ModConfig> fileMap() {
+        return fileMap;
+    }
+}

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

@@ -0,0 +1,24 @@
+package net.minecraftforge.fml.config;
+
+import net.minecraftforge.eventbus.api.Event;
+import net.minecraftforge.fml.Bindings;
+
+import java.util.function.Function;
+
+public interface IConfigEvent {
+    record ConfigConfig(Function<ModConfig, IConfigEvent> loading, Function<ModConfig, IConfigEvent> reloading) {}
+    ConfigConfig CONFIGCONFIG = Bindings.getConfigConfiguration().get();
+
+    static IConfigEvent reloading(ModConfig modConfig) {
+        return CONFIGCONFIG.reloading().apply(modConfig);
+    }
+    static IConfigEvent loading(ModConfig modConfig) {
+        return CONFIGCONFIG.loading().apply(modConfig);
+    }
+    ModConfig getConfig();
+
+    @SuppressWarnings("unchecked")
+    default <T extends Event & IConfigEvent> T self() {
+        return (T) this;
+    }
+}

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

@@ -0,0 +1,21 @@
+package net.minecraftforge.fml.config;
+
+import com.electronwill.nightconfig.core.CommentedConfig;
+import com.electronwill.nightconfig.core.UnmodifiableConfig;
+
+public interface IConfigSpec<T extends IConfigSpec<T>> extends UnmodifiableConfig {
+    @SuppressWarnings("unchecked")
+    default T self() {
+        return (T) this;
+    }
+
+    void acceptConfig(CommentedConfig data);
+
+    boolean isCorrecting();
+
+    boolean isCorrect(CommentedConfig commentedFileConfig);
+
+    int correct(CommentedConfig commentedFileConfig);
+
+    void afterReload();
+}

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

@@ -0,0 +1,141 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.config;
+
+import com.electronwill.nightconfig.core.CommentedConfig;
+import com.electronwill.nightconfig.core.file.CommentedFileConfig;
+import com.electronwill.nightconfig.toml.TomlFormat;
+import net.minecraftforge.fml.ModContainer;
+import net.minecraftforge.fml.loading.StringUtils;
+
+import java.io.ByteArrayInputStream;
+import java.nio.file.Path;
+import java.util.concurrent.Callable;
+
+public class ModConfig
+{
+    private final Type type;
+    private final IConfigSpec<?> spec;
+    private final String fileName;
+    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;
+        ConfigTracker.INSTANCE.trackConfig(this);
+    }
+
+    public ModConfig(final Type type, final IConfigSpec<?> spec, final ModContainer activeContainer) {
+        this(type, spec, activeContainer, defaultConfigName(type, activeContainer.getModId()));
+    }
+
+    private static String defaultConfigName(Type type, String modId) {
+        // config file name would be "forge-client.toml" and "forge-server.toml"
+        return String.format("%s-%s.toml", modId, type.extension());
+    }
+    public Type getType() {
+        return type;
+    }
+
+    public String getFileName() {
+        return fileName;
+    }
+
+    public ConfigFileTypeHandler getHandler() {
+        return configHandler;
+    }
+
+    @SuppressWarnings("unchecked")
+    public <T extends IConfigSpec<T>> IConfigSpec<T> getSpec() {
+        return (IConfigSpec<T>) spec;
+    }
+
+    public String getModId() {
+        return container.getModId();
+    }
+
+    public CommentedConfig getConfigData() {
+        return this.configData;
+    }
+
+    void setConfigData(final CommentedConfig configData) {
+        this.configData = configData;
+        this.spec.acceptConfig(this.configData);
+    }
+
+    void fireEvent(final IConfigEvent configEvent) {
+        this.container.dispatchConfigEvent(configEvent);
+    }
+
+    public void save() {
+        ((CommentedFileConfig)this.configData).save();
+    }
+
+    public Path getFullPath() {
+        return ((CommentedFileConfig)this.configData).getNioPath();
+    }
+
+    public void acceptSyncedConfig(byte[] bytes) {
+        setConfigData(TomlFormat.instance().createParser().parse(new ByteArrayInputStream(bytes)));
+        fireEvent(IConfigEvent.reloading(this));
+    }
+
+    public enum Type {
+        /**
+         * Common mod config for configuration that needs to be loaded on both environments.
+         * Loaded on both servers and clients.
+         * Stored in the global config directory.
+         * Not synced.
+         * Suffix is "-common" by default.
+         */
+        COMMON,
+        /**
+         * Client config is for configuration affecting the ONLY client state such as graphical options.
+         * Only loaded on the client side.
+         * Stored in the global config directory.
+         * Not synced.
+         * Suffix is "-client" by default.
+         */
+        CLIENT,
+//        /**
+//         * Player type config is configuration that is associated with a player.
+//         * Preferences around machine states, for example.
+//         */
+//        PLAYER,
+        /**
+         * Server type config is configuration that is associated with a server instance.
+         * Only loaded during server startup.
+         * Stored in a server/save specific "serverconfig" directory.
+         * Synced to clients during connection.
+         * Suffix is "-server" by default.
+         */
+        SERVER;
+
+        public String extension() {
+            return StringUtils.toLowerCase(name());
+        }
+    }
+}

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

@@ -0,0 +1,26 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.event;
+
+/**
+ * Marker interface for events dispatched on the ModLifecycle event bus instead of the primary event bus
+ */
+public interface IModBusEvent {
+}

fmlcore/src/main/java/net/minecraftforge/fml/util/CertificateHelper.java

@@ -0,0 +1,92 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.util;
+
+import com.google.common.collect.ImmutableList;
+
+import java.nio.ByteBuffer;
+import java.security.MessageDigest;
+import java.security.cert.Certificate;
+
+public class CertificateHelper {
+
+    private static final String HEXES = "0123456789abcdef";
+
+    public static ImmutableList<String> getFingerprints(Certificate[] certificates)
+    {
+        int len = 0;
+        if (certificates != null)
+        {
+            len = certificates.length;
+        }
+        ImmutableList.Builder<String> certBuilder = ImmutableList.builder();
+        for (int i = 0; i < len; i++)
+        {
+            certBuilder.add(CertificateHelper.getFingerprint(certificates[i]));
+        }
+        return certBuilder.build();
+    }
+
+    public static String getFingerprint(Certificate certificate)
+    {
+        if (certificate == null)
+        {
+            return "NO VALID CERTIFICATE FOUND";
+        }
+        try
+        {
+            MessageDigest md = MessageDigest.getInstance("SHA-1");
+            byte[] der = certificate.getEncoded();
+            md.update(der);
+            byte[] digest = md.digest();
+            return hexify(digest);
+        }
+        catch (Exception e)
+        {
+            return "CERTIFICATE FINGERPRINT EXCEPTION";
+        }
+    }
+
+    public static String getFingerprint(ByteBuffer buffer)
+    {
+        try
+        {
+            MessageDigest digest = MessageDigest.getInstance("SHA-1");
+            digest.update(buffer);
+            byte[] chksum = digest.digest();
+            return hexify(chksum);
+        }
+        catch (Exception e)
+        {
+            return "CERTIFICATE FINGERPRINT EXCEPTION";
+        }
+    }
+
+    private static String hexify(byte[] chksum)
+    {
+        final StringBuilder hex = new StringBuilder( 2 * chksum.length );
+        for ( final byte b : chksum ) {
+          hex.append(HEXES.charAt((b & 0xF0) >> 4))
+             .append(HEXES.charAt((b & 0x0F)));
+        }
+        return hex.toString();
+    }
+
+}

fmlcore/src/main/java/net/minecraftforge/fml/util/EnhancedRuntimeException.java

@@ -1,9 +1,23 @@
 /*
- * Copyright (c) Forge Development LLC and contributors
- * SPDX-License-Identifier: LGPL-2.1-only
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
-package net.minecraftforge.fml.common;
+package net.minecraftforge.fml.util;
 
 import java.io.PrintStream;
 import java.io.PrintWriter;

fmlcore/src/main/java/net/minecraftforge/fml/util/LoaderException.java

@@ -0,0 +1,48 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.util;
+
+
+public class LoaderException extends EnhancedRuntimeException
+{
+    /**
+     *
+     */
+    private static final long serialVersionUID = -5675297950958861378L;
+
+    public LoaderException(Throwable wrapped)
+    {
+        super(wrapped);
+    }
+
+    public LoaderException()
+    {
+    }
+    public LoaderException(String message)
+    {
+        super(message);
+    }
+    public LoaderException(String message, Throwable cause)
+    {
+        super(message, cause);
+    }
+
+    @Override protected void printStackTrace(WrappedPrintStream stream){}
+}

fmlcore/src/main/java/net/minecraftforge/fml/util/LoaderExceptionModCrash.java

@@ -0,0 +1,39 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.util;
+
+/**
+ * Prevent LoaderException from adding its own stack trace to the wrapped throwable's stack trace.
+ */
+public class LoaderExceptionModCrash extends LoaderException
+{
+    private static final long serialVersionUID = 1L;
+
+    public LoaderExceptionModCrash(String message, Throwable cause)
+    {
+        super(message, cause);
+    }
+
+    @Override
+    public synchronized Throwable fillInStackTrace()
+    {
+        return this;
+    }
+}

fmlcore/src/main/java/net/minecraftforge/fml/util/ObfuscationReflectionHelper.java

@@ -0,0 +1,276 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.util;
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+import java.util.StringJoiner;
+
+import cpw.mods.modlauncher.api.INameMappingService;
+import net.minecraftforge.fml.loading.FMLLoader;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.apache.logging.log4j.Marker;
+import org.apache.logging.log4j.MarkerManager;
+
+import com.google.common.base.Preconditions;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * Some reflection helper code.
+ * This may not work properly in Java 9 with its new, more restrictive, reflection management.
+ * As such, if issues are encountered, please report them and we can see what we can do to expand
+ * the compatibility.
+ *
+ * In other cases, AccessTransformers may be used.
+ *
+ * All field and method names should be passed in as SRG names, and this will automatically resolve if MCP mappings are detected.
+ *
+ */
+@SuppressWarnings({"serial", "unchecked", "unused", "WeakerAccess"})
+public class ObfuscationReflectionHelper
+{
+    private static final Logger LOGGER = LogManager.getLogger();
+    private static final Marker REFLECTION = MarkerManager.getMarker("REFLECTION");
+
+    /**
+     * Remaps a name using the SRG naming function
+     * @param domain The {@link INameMappingService.Domain} to use to remap the name.
+     * @param name   The name to try and remap.
+     * @return The remapped name, or the original name if it couldn't be remapped.
+     */
+    @NotNull
+    public static String remapName(INameMappingService.Domain domain, String name)
+    {
+        return FMLLoader.getNameFunction("srg").map(f->f.apply(domain, name)).orElse(name);
+    }
+
+    /**
+     * Gets the value a field with the specified name in the given class.
+     * Note: For performance, use {@link #findField(Class, String)} if you are getting the value more than once.
+     * <p>
+     * Throws an exception if the field is not found or the value of the field cannot be gotten.
+     *
+     * @param classToAccess The class to find the field on.
+     * @param instance      The instance of the {@code classToAccess}.
+     * @param fieldName     The SRG (unmapped) name of the field to find (e.g. "f_46443_").
+     * @param <T>           The type of the value.
+     * @param <E>           The type of the {@code classToAccess}.
+     * @return The value of the field with the specified name in the {@code classToAccess}.
+     * @throws UnableToAccessFieldException If there was a problem getting the field.
+     * @throws UnableToAccessFieldException If there was a problem getting the value.
+     */
+    @Nullable
+    public static <T, E> T getPrivateValue(Class<? super E> classToAccess, E instance, String fieldName)
+    {
+        try
+        {
+            return (T) findField(classToAccess, fieldName).get(instance);
+        }
+        catch (UnableToFindFieldException e)
+        {
+            LOGGER.error(REFLECTION,"Unable to locate field {} ({}) on type {}", fieldName, remapName(INameMappingService.Domain.FIELD, fieldName), classToAccess.getName(), e);
+            throw e;
+        }
+        catch (IllegalAccessException e)
+        {
+            LOGGER.error(REFLECTION,"Unable to access field {} ({}) on type {}", fieldName, remapName(INameMappingService.Domain.FIELD, fieldName), classToAccess.getName(), e);
+            throw new UnableToAccessFieldException(e);
+        }
+    }
+
+    /**
+     * Sets the value a field with the specified name in the given class.
+     * Note: For performance, use {@link #findField(Class, String)} if you are setting the value more than once.
+     * <p>
+     * Throws an exception if the field is not found or the value of the field cannot be set.
+     *
+     * @param classToAccess The class to find the field on.
+     * @param instance      The instance of the {@code classToAccess}.
+     * @param value         The new value for the field
+     * @param fieldName     The name of the field in the {@code classToAccess}.
+     * @param <T>           The type of the value.
+     * @param <E>           The type of the {@code classToAccess}.
+     * @throws UnableToFindFieldException   If there was a problem getting the field.
+     * @throws UnableToAccessFieldException If there was a problem setting the value of the field.
+     */
+    public static <T, E> void setPrivateValue(@NotNull final Class<? super T> classToAccess, @NotNull final T instance, @Nullable final E value, @NotNull final String fieldName)
+    {
+        try
+        {
+            findField(classToAccess, fieldName).set(instance, value);
+        }
+        catch (UnableToFindFieldException e)
+        {
+            LOGGER.error("Unable to locate any field {} on type {}", fieldName, classToAccess.getName(), e);
+            throw e;
+        }
+        catch (IllegalAccessException e)
+        {
+            LOGGER.error("Unable to set any field {} on type {}", fieldName, classToAccess.getName(), e);
+            throw new UnableToAccessFieldException(e);
+        }
+    }
+
+    /**
+     * Finds a method with the specified name and parameters in the given class and makes it accessible.
+     * Note: For performance, store the returned value and avoid calling this repeatedly.
+     * <p>
+     * Throws an exception if the method is not found.
+     *
+     * @param clazz          The class to find the method on.
+     * @param methodName     The SRG (unmapped) name of the method to find (e.g. "m_5776_").
+     * @param parameterTypes The parameter types of the method to find.
+     * @return The method with the specified name and parameters in the given class.
+     * @throws NullPointerException        If {@code clazz} is null.
+     * @throws NullPointerException        If {@code methodName} is null.
+     * @throws IllegalArgumentException    If {@code methodName} is empty.
+     * @throws NullPointerException        If {@code parameterTypes} is null.
+     * @throws UnableToFindMethodException If the method could not be found.
+     */
+    @NotNull
+    public static Method findMethod(@NotNull final Class<?> clazz, @NotNull final String methodName, @NotNull final Class<?>... parameterTypes)
+    {
+        Preconditions.checkNotNull(clazz, "Class to find method on cannot be null.");
+        Preconditions.checkNotNull(methodName, "Name of method to find cannot be null.");
+        Preconditions.checkArgument(!methodName.isEmpty(), "Name of method to find cannot be empty.");
+        Preconditions.checkNotNull(parameterTypes, "Parameter types of method to find cannot be null.");
+
+        try
+        {
+            Method m = clazz.getDeclaredMethod(remapName(INameMappingService.Domain.METHOD, methodName), parameterTypes);
+            m.setAccessible(true);
+            return m;
+        }
+        catch (Exception e)
+        {
+            throw new UnableToFindMethodException(e);
+        }
+    }
+
+    /**
+     * Finds a constructor with the specified parameter types in the given class and makes it accessible.
+     * Note: For performance, store the returned value and avoid calling this repeatedly.
+     * <p>
+     * Throws an exception if the constructor is not found.
+     *
+     * @param clazz          The class to find the constructor in.
+     * @param parameterTypes The parameter types of the constructor.
+     * @param <T>            The type.
+     * @return The constructor with the specified parameters in the given class.
+     * @throws NullPointerException        If {@code clazz} is null.
+     * @throws NullPointerException        If {@code parameterTypes} is null.
+     * @throws UnknownConstructorException If the constructor could not be found.
+     */
+    @NotNull
+    public static <T> Constructor<T> findConstructor(@NotNull final Class<T> clazz, @NotNull final Class<?>... parameterTypes)
+    {
+        Preconditions.checkNotNull(clazz, "Class to find constructor on cannot be null.");
+        Preconditions.checkNotNull(parameterTypes, "Parameter types of constructor to find cannot be null.");
+
+        try
+        {
+            Constructor<T> constructor = clazz.getDeclaredConstructor(parameterTypes);
+            constructor.setAccessible(true);
+            return constructor;
+        }
+        catch (final NoSuchMethodException e)
+        {
+            final StringBuilder desc = new StringBuilder();
+            desc.append(clazz.getSimpleName());
+
+            StringJoiner joiner = new StringJoiner(", ", "(", ")");
+            for (Class<?> type : parameterTypes)
+            {
+                joiner.add(type.getSimpleName());
+            }
+            desc.append(joiner);
+
+            throw new UnknownConstructorException("Could not find constructor '" + desc.toString() + "' in " + clazz);
+        }
+    }
+
+    /**
+     * Finds a field with the specified name in the given class and makes it accessible.
+     * Note: For performance, store the returned value and avoid calling this repeatedly.
+     * <p>
+     * Throws an exception if the field is not found.
+     *
+     * @param clazz     The class to find the field on.
+     * @param fieldName The SRG (unmapped) name of the field to find (e.g. "f_46443_").
+     * @param <T>       The type.
+     * @return The constructor with the specified parameters in the given class.
+     * @throws NullPointerException       If {@code clazz} is null.
+     * @throws NullPointerException       If {@code fieldName} is null.
+     * @throws IllegalArgumentException   If {@code fieldName} is empty.
+     * @throws UnableToFindFieldException If the field could not be found.
+     */
+    @NotNull
+    public static <T> Field findField(@NotNull final Class<? super T> clazz, @NotNull final String fieldName)
+    {
+        Preconditions.checkNotNull(clazz, "Class to find field on cannot be null.");
+        Preconditions.checkNotNull(fieldName, "Name of field to find cannot be null.");
+        Preconditions.checkArgument(!fieldName.isEmpty(), "Name of field to find cannot be empty.");
+
+        try
+        {
+            Field f = clazz.getDeclaredField(remapName(INameMappingService.Domain.FIELD, fieldName));
+            f.setAccessible(true);
+            return f;
+        }
+        catch (Exception e)
+        {
+            throw new UnableToFindFieldException(e);
+        }
+    }
+
+    public static class UnableToAccessFieldException extends RuntimeException
+    {
+        private UnableToAccessFieldException(Exception e)
+        {
+            super(e);
+        }
+    }
+
+    public static class UnableToFindFieldException extends RuntimeException
+    {
+        private UnableToFindFieldException(Exception e)
+        {
+            super(e);
+        }
+    }
+
+    public static class UnableToFindMethodException extends RuntimeException
+    {
+        public UnableToFindMethodException(Throwable failed)
+        {
+            super(failed);
+        }
+    }
+
+    public static class UnknownConstructorException extends RuntimeException
+    {
+        public UnknownConstructorException(final String message)
+        {
+            super(message);
+        }
+    }
+}

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

@@ -0,0 +1,30 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.util.thread;
+
+import net.minecraftforge.fml.LogicalSide;
+
+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/SidedThreadGroup.java

@@ -0,0 +1,55 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.util.thread;
+
+import net.minecraftforge.fml.LogicalSide;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.concurrent.ThreadFactory;
+
+/**
+ * A thread group and factory combination which belongs to a {@link LogicalSide}.
+ */
+public final class SidedThreadGroup extends ThreadGroup implements ThreadFactory
+{
+    private final LogicalSide side;
+
+    SidedThreadGroup(final LogicalSide side)
+    {
+        super(side.name());
+        this.side = side;
+    }
+
+    /**
+     * Gets the side this sided thread group belongs to.
+     *
+     * @return the side
+     */
+    public LogicalSide getSide()
+    {
+        return this.side;
+    }
+
+    @Override
+    public Thread newThread(@NotNull final Runnable runnable)
+    {
+        return new Thread(this, runnable);
+    }
+}

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

@@ -0,0 +1,31 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.util.thread;
+
+import net.minecraftforge.fml.LogicalSide;
+
+public final class SidedThreadGroups
+{
+    public static final SidedThreadGroup CLIENT = new SidedThreadGroup(LogicalSide.CLIENT);
+    public static final SidedThreadGroup SERVER = new SidedThreadGroup(LogicalSide.SERVER);
+
+    private SidedThreadGroups() {
+    }
+}

fmlloader/build.gradle

@@ -0,0 +1,80 @@
+plugins {
+    id 'com.github.ben-manes.versions'
+    id 'org.javamodularity.moduleplugin' version '1.8.3' apply false
+}
+apply plugin: 'java-library'
+apply plugin: 'jacoco'
+apply plugin: 'org.javamodularity.moduleplugin'
+
+dependencyUpdates.rejectVersionIf { isNonStable(it.candidate.version) }
+configurations.forEach{ it.transitive = false }
+
+dependencies {
+    implementation('net.sf.jopt-simple:jopt-simple:5.0.4')
+    compileOnly('org.jetbrains:annotations:21.0.0')
+    api("org.ow2.asm:asm:${ASM_VERSION}")
+    api("org.ow2.asm:asm-tree:${ASM_VERSION}")
+    api("org.ow2.asm:asm-commons:${ASM_VERSION}")
+    api('net.minecraftforge:forgespi:4.0.+')
+    api('org.apache.logging.log4j:log4j-api:2.14.1')
+    api('com.google.guava:guava:21.0')
+    api('com.google.code.gson:gson:2.8.0')
+    api('org.apache.maven:maven-artifact:3.8.1')
+    api('org.apache.commons:commons-lang3:3.8.1')
+    api('com.electronwill.night-config:core:3.6.3')
+    api('com.electronwill.night-config:toml:3.6.3')
+    api('cpw.mods:modlauncher:9.0.+')
+    api('net.minecraftforge:coremods:5.0.+')
+    implementation("cpw.mods:securejarhandler:${SECUREJARHANDLER_VERSION}")
+    implementation('org.apache.logging.log4j:log4j-core:2.14.1')
+    annotationProcessor('org.apache.logging.log4j:log4j-core:2.14.1')
+    implementation('net.minecraftforge:accesstransformers:8.0.4')
+    implementation('net.minecrell:terminalconsoleappender:1.2.0')
+//    implementation('org.jline:jline:3.12.+')
+    testCompileOnly('org.jetbrains:annotations:21.0.0')
+    testRuntimeOnly("cpw.mods:bootstraplauncher:${BOOTSTRAPLAUNCHER_VERSION}")
+}
+
+task sourcesJar(type: Jar) {
+    archiveClassifier = 'sources'
+    from sourceSets.main.allSource
+}
+
+ext {
+    MANIFESTS = [
+        '/': [
+            'Timestamp': new Date().format("yyyy-MM-dd'T'HH:mm:ssZ"),
+            'Git-Commit': GIT_INFO.abbreviatedId,
+            'Git-Branch': GIT_INFO.branch,
+            'Build-Number': "${System.getenv('BUILD_NUMBER')?:0}",
+        ] as LinkedHashMap,
+        'net/minecraftforge/fml/loading/': [
+            'Specification-Title':      'FMLLoader',
+            'Specification-Vendor':     'Forge Development LLC',
+            'Specification-Version':    '1',
+            'Implementation-Title':     'FML Loader',
+            'Implementation-Version':   '1.0',
+            'Implementation-Vendor':    'Forge'
+        ] as LinkedHashMap
+    ]
+}
+
+jar.doFirst {
+    MANIFESTS.each { pkg, values ->
+        manifest.attributes(values, pkg)
+    }
+}
+
+tasks.withType(JavaCompile) {
+    options.compilerArgs << '-Xlint:unchecked'
+}
+
+artifacts {
+    archives jar
+    archives sourcesJar
+}
+
+publishing.publications.mavenJava(MavenPublication) {
+    from components.java
+    artifact sourcesJar
+}

fmlloader/src/main/java/net/minecraftforge/common/asm/CapabilityInjectDefinalize.java

@@ -0,0 +1,76 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.common.asm;
+
+import java.nio.file.Path;
+import java.util.EnumSet;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+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 @CapabilityInject annotation, prevents the JITer from in lining them so our runtime replacements can work.
+ */
+public class CapabilityInjectDefinalize implements ILaunchPluginService {
+
+    private final String CAP        = "Lnet/minecraftforge/common/capabilities/Capability;";       //Don't directly reference this to prevent class loading.
+    private final String CAP_INJECT = "Lnet/minecraftforge/common/capabilities/CapabilityInject;"; //Don't directly reference this to prevent class loading.
+
+    @Override
+    public String name() {
+        return "capability_inject_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(CAP_INJECT));
+    }
+
+    @Override
+    public int processClassWithFlags(final Phase phase, final ClassNode classNode, final Type classType, final String reason)
+    {
+        final int flags = Opcodes.ACC_PUBLIC | Opcodes.ACC_STATIC | Opcodes.ACC_FINAL;
+        final AtomicBoolean changed = new AtomicBoolean();
+        classNode.fields.stream().filter(f -> ((f.access & flags) == flags) && f.desc.equals(CAP) && 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.
+            changed.compareAndSet(false, prev != f.access);
+        });
+
+        return changed.get() ? ComputeFlags.SIMPLE_REWRITE : ComputeFlags.NO_REWRITE;
+    }
+
+}

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

@@ -1,6 +1,20 @@
 /*
- * Copyright (c) Forge Development LLC and contributors
- * SPDX-License-Identifier: LGPL-2.1-only
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
 package net.minecraftforge.common.asm;
@@ -59,9 +73,9 @@ public class ObjectHolderDefinalize implements ILaunchPluginService {
     }
 
     @Override
-    public boolean processClass(Phase phase, ClassNode classNode, Type classType)
+    public int processClassWithFlags(final Phase phase, final ClassNode classNode, final Type classType, final String reason)
     {
-        AtomicBoolean changes = new AtomicBoolean();
+        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;
 
@@ -93,7 +107,7 @@ public class ObjectHolderDefinalize implements ILaunchPluginService {
                 changes.compareAndSet(false, prev != f.access);
             });
         }
-        return changes.get();
+        return changes.get() ? ComputeFlags.SIMPLE_REWRITE : ComputeFlags.NO_REWRITE;
     }
 
 }

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

@@ -1,6 +1,20 @@
 /*
- * Copyright (c) Forge Development LLC and contributors
- * SPDX-License-Identifier: LGPL-2.1-only
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
 package net.minecraftforge.common.asm;
@@ -55,10 +69,10 @@ public class RuntimeEnumExtender implements ILaunchPluginService {
     }
 
     @Override
-    public boolean processClass(Phase phase, ClassNode classNode, Type classType)
+    public int processClassWithFlags(final Phase phase, final ClassNode classNode, final Type classType, final String reason)
     {
         if ((classNode.access & Opcodes.ACC_ENUM) == 0)
-            return false;
+            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;
@@ -66,7 +80,7 @@ public class RuntimeEnumExtender implements ILaunchPluginService {
         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())) {
-            return false;
+            return ComputeFlags.NO_REWRITE;
         }
         
         //Static methods named "create" with first argument as a string
@@ -84,8 +98,8 @@ public class RuntimeEnumExtender implements ILaunchPluginService {
             if (args.length == 0 || !args[0].equals(STRING)) {
                 LOGGER.fatal(()->new AdvancedLogMessageAdapter(sb-> {
                     sb.append("Enum has create method without String as first parameter:\n");
-                    sb.append("  Enum: " + classType.getDescriptor()).append("\n");
-                    sb.append("  Target: ").append(mtd.name + mtd.desc).append("\n");
+                    sb.append("  Enum: ").append(classType.getDescriptor()).append("\n");
+                    sb.append("  Target: ").append(mtd.name).append(mtd.desc).append("\n");
                 }));
                 throw new IllegalStateException("Enum has create method without String as first parameter: " + mtd.name + mtd.desc);
             }
@@ -94,8 +108,8 @@ public class RuntimeEnumExtender implements ILaunchPluginService {
             if (!ret.equals(classType)) {
                 LOGGER.fatal(()->new AdvancedLogMessageAdapter(sb-> {
                     sb.append("Enum has create method with incorrect return type:\n");
-                    sb.append("  Enum: " + classType.getDescriptor()).append("\n");
-                    sb.append("  Target: ").append(mtd.name + mtd.desc).append("\n");
+                    sb.append("  Enum: ").append(classType.getDescriptor()).append("\n");
+                    sb.append("  Target: ").append(mtd.name).append(mtd.desc).append("\n");
                     sb.append("  Found: ").append(ret.getClassName()).append(", Expected: ").append(classType.getClassName());
                 }));
                 throw new IllegalStateException("Enum has create method with incorrect return type: " + mtd.name + mtd.desc);
@@ -209,7 +223,7 @@ public class RuntimeEnumExtender implements ILaunchPluginService {
                 ins.areturn(classType);
             }
         });
-        return true;
+        return ComputeFlags.COMPUTE_FRAMES;
     }
 
 }

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

@@ -0,0 +1,62 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading;
+
+import org.apache.logging.log4j.message.Message;
+import org.apache.logging.log4j.util.StringBuilderFormattable;
+
+import java.util.function.Consumer;
+
+public class AdvancedLogMessageAdapter implements Message, StringBuilderFormattable {
+    private static final long serialVersionUID = -8291754833965087436L;
+
+    private static final Object[] EMPTY = new Object[0];
+
+    private final Consumer<StringBuilder> logMessageBuilder;
+
+    public AdvancedLogMessageAdapter(final Consumer<StringBuilder> logMessageBuilder) {
+        this.logMessageBuilder = logMessageBuilder;
+    }
+
+    @Override
+    public String getFormattedMessage() {
+        return "";
+    }
+
+    @Override
+    public String getFormat() {
+        return "";
+    }
+
+    @Override
+    public Object[] getParameters() {
+        return EMPTY;
+    }
+
+    @Override
+    public Throwable getThrowable() {
+        return null;
+    }
+
+    @Override
+    public void formatTo(final StringBuilder buffer) {
+        logMessageBuilder.accept(buffer);
+    }
+}

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

@@ -0,0 +1,48 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+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 ExecutorService runner = Executors.newSingleThreadExecutor();
+
+    public static void runAndTick(Runnable r, Runnable tick) {
+        final Future<?> work = runner.submit(r);
+        do {
+            tick.run();
+            try {
+                Thread.sleep(50);
+            } catch (InterruptedException ignored) {
+            }
+        } while (!work.isDone());
+        try {
+            runner.shutdown();
+            work.get();
+        } catch (ExecutionException ee) {
+            throw new RuntimeException(ee.getCause());
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+    }
+}

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

@@ -0,0 +1,70 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading;
+
+import net.minecraftforge.forgespi.language.IModInfo;
+
+import java.util.List;
+
+/**
+ * Thrown during early loading phase, and collected by the LoadingModList for handoff to the client
+ * or server.
+ */
+public class EarlyLoadingException extends RuntimeException {
+    public static class ExceptionData {
+        private final IModInfo modInfo;
+        private final String i18message;
+        private final Object[] args;
+
+        public ExceptionData(final String message, Object... args) {
+            this(message, null, args);
+        }
+
+        public ExceptionData(final String message, final IModInfo modInfo, Object... args) {
+            this.i18message = message;
+            this.modInfo = modInfo;
+            this.args = args;
+        }
+
+        public String getI18message() {
+            return i18message;
+        }
+
+        public Object[] getArgs() {
+            return args;
+        }
+
+        public IModInfo getModInfo() {
+            return modInfo;
+        }
+    }
+    private final List<ExceptionData> errorMessages;
+
+    public List<ExceptionData> getAllData() {
+        return errorMessages;
+    }
+
+    EarlyLoadingException(final String message, final Throwable originalException, List<ExceptionData> errorMessages) {
+        super(message, originalException);
+        this.errorMessages = errorMessages;
+    }
+
+
+}

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

@@ -0,0 +1,105 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading;
+
+import com.electronwill.nightconfig.core.ConfigSpec;
+import com.electronwill.nightconfig.core.file.CommentedFileConfig;
+import com.electronwill.nightconfig.core.file.FileNotFoundAction;
+import com.electronwill.nightconfig.core.io.ParsingException;
+import com.electronwill.nightconfig.core.io.WritingMode;
+import net.minecraftforge.api.distmarker.Dist;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Arrays;
+import java.util.Objects;
+import java.util.stream.Collectors;
+
+import static net.minecraftforge.fml.loading.LogMarkers.CORE;
+
+public class FMLConfig
+{
+    private static final Logger LOGGER = LogManager.getLogger();
+    private static FMLConfig INSTANCE = new FMLConfig();
+    private static ConfigSpec configSpec = new ConfigSpec();
+    static {
+        configSpec.define("splashscreen", Boolean.TRUE);
+        configSpec.define("maxThreads", -1);
+        configSpec.define("versionCheck", Boolean.TRUE);
+        configSpec.define("defaultConfigPath",  "defaultconfigs");
+    }
+
+    private CommentedFileConfig configData;
+
+    private void loadFrom(final Path configFile)
+    {
+        configData = CommentedFileConfig.builder(configFile).sync()
+                .onFileNotFound(FileNotFoundAction.copyData(Objects.requireNonNull(getClass().getResourceAsStream("/META-INF/defaultfmlconfig.toml"))))
+                .autosave().autoreload()
+                .writingMode(WritingMode.REPLACE)
+                .build();
+        try
+        {
+            configData.load();
+        }
+        catch (ParsingException e)
+        {
+            throw new RuntimeException("Failed to load FML config from " + configFile.toString(), e);
+        }
+        if (!configSpec.isCorrect(configData)) {
+            LOGGER.warn(CORE, "Configuration file {} is not correct. Correcting", configFile);
+            configSpec.correct(configData, (action, path, incorrectValue, correctedValue) ->
+                    LOGGER.warn(CORE, "Incorrect key {} was corrected from {} to {}", path, incorrectValue, correctedValue));
+        }
+        configData.save();
+    }
+
+    public static void load()
+    {
+        final Path configFile = FMLPaths.FMLCONFIG.get();
+        INSTANCE.loadFrom(configFile);
+        LOGGER.trace(CORE, "Loaded FML config from {}", FMLPaths.FMLCONFIG.get());
+        LOGGER.trace(CORE, "Splash screen is {}", FMLConfig::splashScreenEnabled);
+        LOGGER.trace(CORE, "Max threads for mod loading computed at {}", FMLConfig::loadingThreadCount);
+        LOGGER.trace(CORE, "Version check is {}", FMLConfig::runVersionCheck);
+        LOGGER.trace(CORE, "Default config paths at {}", FMLConfig::defaultConfigPath);
+        FMLPaths.getOrCreateGameRelativePath(Paths.get(FMLConfig.defaultConfigPath()), "default config directory");
+    }
+
+    public static boolean splashScreenEnabled() {
+        return INSTANCE.configData.<Boolean>getOptional("splashscreen").orElse(Boolean.FALSE);
+    }
+
+    public static int loadingThreadCount() {
+        int val = INSTANCE.configData.<Integer>getOptional("maxThreads").orElse(-1);
+        if (val <= 0) return Runtime.getRuntime().availableProcessors();
+        return val;
+    }
+
+    public static boolean runVersionCheck() {
+        return INSTANCE.configData.<Boolean>getOptional("versionCheck").orElse(Boolean.TRUE);
+    }
+
+    public static String defaultConfigPath() {
+        return INSTANCE.configData.<String>getOptional("defaultConfigPath").orElse("defaultconfigs");
+    }
+}

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

@@ -0,0 +1,44 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading;
+
+import cpw.mods.modlauncher.api.IEnvironment;
+import cpw.mods.modlauncher.api.TypesafeMap;
+import net.minecraftforge.api.distmarker.Dist;
+import net.minecraftforge.forgespi.Environment;
+
+import java.util.function.Supplier;
+
+public class FMLEnvironment
+{
+    public static final Dist dist = FMLLoader.getDist();
+    public static final String naming = FMLLoader.getNaming();
+    public static final boolean production = FMLLoader.isProduction() || System.getProperties().containsKey("production");
+    public static final boolean secureJarsEnabled = FMLLoader.isSecureJarEnabled();
+
+    static void setupInteropEnvironment(IEnvironment environment) {
+        environment.computePropertyIfAbsent(IEnvironment.Keys.NAMING.get(), v->naming);
+        environment.computePropertyIfAbsent(Environment.Keys.DIST.get(), v->dist);
+    }
+
+    public static class Keys {
+        public static final Supplier<TypesafeMap.Key<ClassLoader>> LOCATORCLASSLOADER = IEnvironment.buildKey("LOCATORCLASSLOADER",ClassLoader.class);
+    }
+}

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

@@ -0,0 +1,269 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading;
+
+import cpw.mods.modlauncher.Launcher;
+import cpw.mods.modlauncher.api.*;
+import cpw.mods.modlauncher.serviceapi.ILaunchPluginService;
+import cpw.mods.modlauncher.util.ServiceLoaderUtils;
+import net.minecraftforge.accesstransformer.service.AccessTransformerService;
+import net.minecraftforge.api.distmarker.Dist;
+import net.minecraftforge.fml.loading.moddiscovery.*;
+import net.minecraftforge.fml.loading.progress.EarlyProgressVisualization;
+import net.minecraftforge.fml.loading.progress.StartupMessageManager;
+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.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.*;
+import java.util.function.BiFunction;
+import java.util.stream.Collectors;
+
+import static net.minecraftforge.fml.loading.LogMarkers.CORE;
+import static net.minecraftforge.fml.loading.LogMarkers.SCAN;
+
+public class FMLLoader
+{
+    private static final Logger LOGGER = LogManager.getLogger();
+    private static AccessTransformerService accessTransformer;
+    private static ModDiscoverer modDiscoverer;
+    private static ICoreModProvider coreModProvider;
+    private static ILaunchPluginService eventBus;
+    private static LanguageLoadingProvider languageLoadingProvider;
+    private static Dist dist;
+    private static String naming;
+    private static LoadingModList loadingModList;
+    private static RuntimeDistCleaner runtimeDistCleaner;
+    private static Path gamePath;
+    private static VersionInfo versionInfo;
+    private static String launchHandlerName;
+    private static CommonLaunchHandler commonLaunchHandler;
+    public static Runnable progressWindowTick;
+    private static ModValidator modValidator;
+    public static BackgroundScanHandler backgroundScanHandler;
+    private static boolean production;
+    private static IModuleLayerManager moduleLayerManager;
+
+    static void onInitialLoad(IEnvironment environment, Set<String> otherServices) throws IncompatibleEnvironmentException
+    {
+        final String version = LauncherVersion.getVersion();
+        LOGGER.debug(CORE,"FML {} loading", version);
+        final Package modLauncherPackage = ITransformationService.class.getPackage();
+        LOGGER.debug(CORE,"FML found ModLauncher version : {}", modLauncherPackage.getImplementationVersion());
+        if (!modLauncherPackage.isCompatibleWith("4.0")) {
+            LOGGER.fatal(CORE,"Found incompatible ModLauncher specification : {}, version {} from {}", modLauncherPackage.getSpecificationVersion(), modLauncherPackage.getImplementationVersion(), modLauncherPackage.getImplementationVendor());
+            throw new IncompatibleEnvironmentException("Incompatible modlauncher found "+modLauncherPackage.getSpecificationVersion());
+        }
+
+        accessTransformer = (AccessTransformerService) environment.findLaunchPlugin("accesstransformer").orElseThrow(()-> {
+            LOGGER.fatal(CORE,"Access Transformer library is missing, we need this to run");
+            return new IncompatibleEnvironmentException("Missing AccessTransformer, cannot run");
+        });
+
+        final Package atPackage = accessTransformer.getClass().getPackage();
+        LOGGER.debug(CORE,"FML found AccessTransformer version : {}", atPackage.getImplementationVersion());
+        if (!atPackage.isCompatibleWith("1.0")) {
+            LOGGER.fatal(CORE,"Found incompatible AccessTransformer specification : {}, version {} from {}", atPackage.getSpecificationVersion(), atPackage.getImplementationVersion(), atPackage.getImplementationVendor());
+            throw new IncompatibleEnvironmentException("Incompatible accesstransformer found "+atPackage.getSpecificationVersion());
+        }
+
+        eventBus = environment.findLaunchPlugin("eventbus").orElseThrow(()-> {
+            LOGGER.fatal(CORE,"Event Bus library is missing, we need this to run");
+            return new IncompatibleEnvironmentException("Missing EventBus, cannot run");
+        });
+
+        final Package eventBusPackage = eventBus.getClass().getPackage();
+        LOGGER.debug(CORE,"FML found EventBus version : {}", eventBusPackage.getImplementationVersion());
+        if (!eventBusPackage.isCompatibleWith("1.0")) {
+            LOGGER.fatal(CORE,"Found incompatible EventBus specification : {}, version {} from {}", eventBusPackage.getSpecificationVersion(), eventBusPackage.getImplementationVersion(), eventBusPackage.getImplementationVendor());
+            throw new IncompatibleEnvironmentException("Incompatible eventbus found "+eventBusPackage.getSpecificationVersion());
+        }
+
+        runtimeDistCleaner = (RuntimeDistCleaner)environment.findLaunchPlugin("runtimedistcleaner").orElseThrow(()-> {
+            LOGGER.fatal(CORE,"Dist Cleaner is missing, we need this to run");
+            return new IncompatibleEnvironmentException("Missing DistCleaner, cannot run!");
+        });
+        LOGGER.debug(CORE, "Found Runtime Dist Cleaner");
+
+        var coreModProviders = ServiceLoaderUtils.streamWithErrorHandling(ServiceLoader.load(FMLLoader.class.getModule().getLayer(), ICoreModProvider.class), sce -> LOGGER.fatal(CORE, "Failed to load a coremod library, expect problems", sce)).toList();
+
+        if (coreModProviders.isEmpty()) {
+            LOGGER.fatal(CORE, "Found no coremod provider. Cannot run");
+            throw new IncompatibleEnvironmentException("No coremod library found");
+        } else if (coreModProviders.size() > 1) {
+            LOGGER.fatal(CORE, "Found multiple coremod providers : {}. Cannot run", coreModProviders.stream().map(p -> p.getClass().getName()).collect(Collectors.toList()));
+            throw new IncompatibleEnvironmentException("Multiple coremod libraries found");
+        }
+
+        coreModProvider = coreModProviders.get(0);
+        final Package coremodPackage = coreModProvider.getClass().getPackage();
+        LOGGER.debug(CORE,"FML found CoreMod version : {}", coremodPackage.getImplementationVersion());
+
+
+        LOGGER.debug(CORE, "Found ForgeSPI package implementation version {}", Environment.class.getPackage().getImplementationVersion());
+        LOGGER.debug(CORE, "Found ForgeSPI package specification {}", Environment.class.getPackage().getSpecificationVersion());
+        if (Integer.parseInt(Environment.class.getPackage().getSpecificationVersion()) < 2) {
+            LOGGER.fatal(CORE, "Found an out of date ForgeSPI implementation: {}, loading cannot continue", Environment.class.getPackage().getSpecificationVersion());
+            throw new IncompatibleEnvironmentException("ForgeSPI is out of date, we cannot continue");
+        }
+
+        try {
+            Class.forName("com.electronwill.nightconfig.core.Config", false, environment.getClass().getClassLoader());
+            Class.forName("com.electronwill.nightconfig.toml.TomlFormat", false, environment.getClass().getClassLoader());
+        } catch (ClassNotFoundException e) {
+            LOGGER.fatal(CORE, "Failed to load NightConfig");
+            throw new IncompatibleEnvironmentException("Missing NightConfig");
+        }
+    }
+
+    static void setupLaunchHandler(final IEnvironment environment, final Map<String, ?> arguments)
+    {
+        final String launchTarget = environment.getProperty(IEnvironment.Keys.LAUNCHTARGET.get()).orElse("MISSING");
+        final Optional<ILaunchHandlerService> launchHandler = environment.findLaunchHandler(launchTarget);
+        LOGGER.debug(CORE, "Using {} as launch service", launchTarget);
+        if (launchHandler.isEmpty()) {
+            LOGGER.fatal(CORE,"Missing LaunchHandler {}, cannot continue", launchTarget);
+            throw new RuntimeException("Missing launch handler: " + launchTarget);
+        }
+
+        if (!(launchHandler.get() instanceof CommonLaunchHandler)) {
+            LOGGER.fatal(CORE, "Incompatible Launch handler found - type {}, cannot continue", launchHandler.get().getClass().getName());
+            throw new RuntimeException("Incompatible launch handler found");
+        }
+        commonLaunchHandler = (CommonLaunchHandler)launchHandler.get();
+        launchHandlerName = launchHandler.get().name();
+        gamePath = environment.getProperty(IEnvironment.Keys.GAMEDIR.get()).orElse(Paths.get(".").toAbsolutePath());
+
+        naming = commonLaunchHandler.getNaming();
+        dist = commonLaunchHandler.getDist();
+        production = commonLaunchHandler.isProduction();
+
+        versionInfo = new VersionInfo(arguments);
+
+        StartupMessageManager.modLoaderConsumer().ifPresent(c->c.accept("Early Loading!"));
+        accessTransformer.getExtension().accept(Pair.of(naming, "srg"));
+
+        LOGGER.debug(CORE,"Received command line version data  : {}", versionInfo);
+
+        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();
+        var pluginResources = modValidator.getPluginResources();
+        return List.of(pluginResources);
+    }
+
+    public static List<ITransformationService.Resource> completeScan(IModuleLayerManager layerManager) {
+        progressWindowTick = EarlyProgressVisualization.INSTANCE.accept(dist, commonLaunchHandler.isData(), versionInfo.mcVersion());
+        moduleLayerManager = layerManager;
+        languageLoadingProvider = new LanguageLoadingProvider();
+        backgroundScanHandler = modValidator.stage2Validation();
+        loadingModList = backgroundScanHandler.getLoadingModList();
+        return List.of(modValidator.getModResources());
+    }
+
+    public static ICoreModProvider getCoreModProvider() {
+        return coreModProvider;
+    }
+
+    public static LanguageLoadingProvider getLanguageLoadingProvider()
+    {
+        return languageLoadingProvider;
+    }
+
+    static ModDiscoverer getModDiscoverer() {
+        return modDiscoverer;
+    }
+
+    public static CommonLaunchHandler getLaunchHandler() {
+        return commonLaunchHandler;
+    }
+
+    public static void addAccessTransformer(Path atPath, ModFile modName)
+    {
+        LOGGER.debug(SCAN, "Adding Access Transformer in {}", modName.getFilePath());
+        accessTransformer.offerResource(atPath, modName.getFileName());
+    }
+
+    public static Dist getDist()
+    {
+        return dist;
+    }
+
+    public static void beforeStart(ClassLoader launchClassLoader)
+    {
+        StartupMessageManager.modLoaderConsumer().ifPresent(c->c.accept("Launching minecraft"));
+        progressWindowTick.run();
+    }
+
+    public static LoadingModList getLoadingModList()
+    {
+        return loadingModList;
+    }
+
+    public static Path getGamePath()
+    {
+        return gamePath;
+    }
+
+    public static String getNaming() {
+        return naming;
+    }
+
+    public static Optional<BiFunction<INameMappingService.Domain, String, String>> getNameFunction(final String naming) {
+        return Launcher.INSTANCE.environment().findNameMapping(naming);
+    }
+
+    public static String getLauncherInfo() {
+        return Launcher.INSTANCE.environment().getProperty(IEnvironment.Keys.MLIMPL_VERSION.get()).orElse("MISSING");
+    }
+
+    public static List<Map<String, String>> modLauncherModList() {
+        return Launcher.INSTANCE.environment().getProperty(IEnvironment.Keys.MODLIST.get()).orElseGet(Collections::emptyList);
+    }
+
+    public static String launcherHandlerName() {
+        return launchHandlerName;
+    }
+
+    public static boolean isProduction() {
+        return production;
+    }
+
+    public static boolean isSecureJarEnabled() {
+        return true;
+    }
+
+    public static ModuleLayer getGameLayer() {
+        return moduleLayerManager.getLayer(IModuleLayerManager.Layer.GAME).orElseThrow();
+    }
+
+    public static VersionInfo versionInfo() {
+        return versionInfo;
+    }
+}

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

@@ -0,0 +1,93 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading;
+
+import cpw.mods.modlauncher.api.IEnvironment;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Arrays;
+
+import static net.minecraftforge.fml.loading.LogMarkers.CORE;
+
+public enum FMLPaths
+{
+    GAMEDIR(),
+    MODSDIR("mods"),
+    CONFIGDIR("config"),
+    FMLCONFIG(false, CONFIGDIR, "fml.toml");
+
+    private static final Logger LOGGER = LogManager.getLogger();
+    private final Path relativePath;
+    private final boolean isDirectory;
+    private Path absolutePath;
+
+    FMLPaths() {
+        this("");
+    }
+
+    FMLPaths(String... path) {
+        relativePath = computePath(path);
+        this.isDirectory = true;
+    }
+
+    FMLPaths(boolean isDir, FMLPaths parent, String... path) {
+        this.relativePath = parent.relativePath.resolve(computePath(path));
+        this.isDirectory = isDir;
+    }
+
+    private Path computePath(String... path)
+    {
+        return Paths.get(path[0], Arrays.copyOfRange(path, 1, path.length));
+    }
+
+    public static void setup(IEnvironment env) {
+        final Path rootPath = env.getProperty(IEnvironment.Keys.GAMEDIR.get()).orElseThrow(() -> new RuntimeException("No game path found"));
+
+        loadAbsolutePaths(rootPath);
+    }
+
+    public static void loadAbsolutePaths(Path rootPath)
+    {
+        for (FMLPaths path : FMLPaths.values())
+        {
+            path.absolutePath = rootPath.resolve(path.relativePath).toAbsolutePath().normalize();
+            if (path.isDirectory)
+            {
+                FileUtils.getOrCreateDirectory(path.absolutePath, path.name());
+            }
+            LOGGER.debug(CORE,"Path {} is {}", ()-> path, ()-> path.absolutePath);
+        }
+    }
+
+    public static Path getOrCreateGameRelativePath(Path path, String name) {
+        return FileUtils.getOrCreateDirectory(FMLPaths.GAMEDIR.get().resolve(path), name);
+    }
+
+    public Path relative() {
+        return relativePath;
+    }
+
+    public Path get() {
+        return absolutePath;
+    }
+}

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

@@ -0,0 +1,157 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading;
+
+import cpw.mods.jarhandling.SecureJar;
+import cpw.mods.modlauncher.api.*;
+import joptsimple.ArgumentAcceptingOptionSpec;
+import joptsimple.OptionSpecBuilder;
+import net.minecraftforge.fml.loading.moddiscovery.ModFile;
+import net.minecraftforge.forgespi.Environment;
+import net.minecraftforge.forgespi.locating.IModFile;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.jetbrains.annotations.NotNull;
+
+import java.nio.file.Path;
+import java.util.AbstractMap;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Set;
+import java.util.function.BiFunction;
+import java.util.stream.Collectors;
+
+import static net.minecraftforge.fml.loading.LogMarkers.CORE;
+
+public class FMLServiceProvider implements ITransformationService
+{
+    private static final Logger LOGGER = LogManager.getLogger();
+    private ArgumentAcceptingOptionSpec<String> modsOption;
+    private ArgumentAcceptingOptionSpec<String> modListsOption;
+    private ArgumentAcceptingOptionSpec<String> mavenRootsOption;
+    private ArgumentAcceptingOptionSpec<String> forgeOption;
+    private ArgumentAcceptingOptionSpec<String> mcOption;
+    private ArgumentAcceptingOptionSpec<String> forgeGroupOption;
+    private ArgumentAcceptingOptionSpec<String> mcpOption;
+    private ArgumentAcceptingOptionSpec<String> mappingsOption;
+    private List<String> modsArgumentList;
+    private List<String> modListsArgumentList;
+    private List<String> mavenRootsArgumentList;
+    private String targetForgeVersion;
+    private String targetMcVersion;
+    private String targetMcpVersion;
+    private String targetMcpMappings;
+    private String targetForgeGroup;
+    private Map<String, Object> arguments;
+
+    public FMLServiceProvider()
+    {
+        final String markerselection = System.getProperty("forge.logging.markers", "");
+        Arrays.stream(markerselection.split(",")).forEach(marker -> System.setProperty("forge.logging.marker." + marker.toLowerCase(Locale.ROOT), "ACCEPT"));
+    }
+
+    @Override
+    public String name()
+    {
+        return "fml";
+    }
+
+    @Override
+    public void initialize(IEnvironment environment) {
+        LOGGER.debug(CORE, "Setting up basic FML game directories");
+        FMLPaths.setup(environment);
+        LOGGER.debug(CORE, "Loading configuration");
+        FMLConfig.load();
+        LOGGER.debug(CORE, "Preparing ModFile");
+        environment.computePropertyIfAbsent(Environment.Keys.MODFILEFACTORY.get(), k->ModFile.buildFactory());
+        arguments = new HashMap<>();
+        arguments.put("modLists", modListsArgumentList);
+        arguments.put("mods", modsArgumentList);
+        arguments.put("mavenRoots", mavenRootsArgumentList);
+        arguments.put("forgeVersion", targetForgeVersion);
+        arguments.put("forgeGroup", targetForgeGroup);
+        arguments.put("mcVersion", targetMcVersion);
+        arguments.put("mcpVersion", targetMcpVersion);
+        arguments.put("mcpMappings", targetMcpMappings);
+        LOGGER.debug(CORE, "Preparing launch handler");
+        FMLLoader.setupLaunchHandler(environment, arguments);
+        FMLEnvironment.setupInteropEnvironment(environment);
+        Environment.build(environment);
+    }
+
+    @Override
+    public List<Resource> beginScanning(final IEnvironment environment) {
+        LOGGER.debug(CORE,"Initiating mod scan");
+        return FMLLoader.beginModScan(arguments);
+    }
+
+    @Override
+    public List<Resource> completeScan(final IModuleLayerManager layerManager) {
+        return FMLLoader.completeScan(layerManager);
+    }
+
+    @Override
+    public void onLoad(IEnvironment environment, Set<String> otherServices) throws IncompatibleEnvironmentException
+    {
+//        LOGGER.debug("Injecting tracing printstreams for STDOUT/STDERR.");
+//        System.setOut(new TracingPrintStream(LogManager.getLogger("STDOUT"), System.out));
+//        System.setErr(new TracingPrintStream(LogManager.getLogger("STDERR"), System.err));
+        FMLLoader.onInitialLoad(environment, otherServices);
+    }
+
+    @Override
+    public void arguments(BiFunction<String, String, OptionSpecBuilder> argumentBuilder)
+    {
+        forgeOption = argumentBuilder.apply("forgeVersion", "Forge Version number").withRequiredArg().ofType(String.class).required();
+        forgeGroupOption = argumentBuilder.apply("forgeGroup", "Forge Group (for testing)").withRequiredArg().ofType(String.class).defaultsTo("net.minecraftforge");
+        mcOption = argumentBuilder.apply("mcVersion", "Minecraft Version number").withRequiredArg().ofType(String.class).required();
+        mcpOption = argumentBuilder.apply("mcpVersion", "MCP Version number").withRequiredArg().ofType(String.class).required();
+        mappingsOption = argumentBuilder.apply("mcpMappings", "MCP Mappings Channel and Version").withRequiredArg().ofType(String.class);
+        modsOption = argumentBuilder.apply("mods", "List of mods to add").withRequiredArg().ofType(String.class).withValuesSeparatedBy(",");
+        modListsOption = argumentBuilder.apply("modLists", "JSON modlists").withRequiredArg().ofType(String.class).withValuesSeparatedBy(",");
+        mavenRootsOption = argumentBuilder.apply("mavenRoots", "Maven root directories").withRequiredArg().ofType(String.class).withValuesSeparatedBy(",");
+    }
+
+    @Override
+    public void argumentValues(OptionResult option)
+    {
+        modsArgumentList = option.values(modsOption);
+        modListsArgumentList = option.values(modListsOption);
+        mavenRootsArgumentList = option.values(mavenRootsOption);
+        targetForgeVersion = option.value(forgeOption);
+        targetForgeGroup = option.value(forgeGroupOption);
+        targetMcVersion = option.value(mcOption);
+        targetMcpVersion = option.value(mcpOption);
+        targetMcpMappings = option.value(mappingsOption);
+    }
+
+    @Override
+    public @NotNull List<ITransformer> transformers()
+    {
+        LOGGER.debug(CORE, "Loading coremod transformers");
+        return new ArrayList<>(FMLLoader.getCoreModProvider().getCoreModTransformers());
+    }
+
+}

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

@@ -0,0 +1,70 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import java.io.IOException;
+import java.nio.file.FileAlreadyExistsException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import static net.minecraftforge.fml.loading.LogMarkers.CORE;
+
+public class FileUtils
+{
+    private static final Logger LOGGER = LogManager.getLogger();
+
+    public static Path getOrCreateDirectory(Path dirPath, String dirLabel) {
+        if (!Files.isDirectory(dirPath.getParent())) {
+            getOrCreateDirectory(dirPath.getParent(), "parent of "+dirLabel);
+        }
+        if (!Files.isDirectory(dirPath))
+        {
+            LOGGER.debug(CORE,"Making {} directory : {}", dirLabel, dirPath);
+            try {
+                Files.createDirectory(dirPath);
+            } catch (IOException e) {
+                if (e instanceof FileAlreadyExistsException) {
+                    LOGGER.fatal(CORE,"Failed to create {} directory - there is a file in the way", dirLabel);
+                } else {
+                    LOGGER.fatal(CORE,"Problem with creating {} directory (Permissions?)", dirLabel, e);
+                }
+                throw new RuntimeException("Problem creating directory", e);
+            }
+            LOGGER.debug(CORE,"Created {} directory : {}", dirLabel, dirPath);
+        } else {
+            LOGGER.debug(CORE,"Found existing {} directory : {}", dirLabel, dirPath);
+        }
+        return dirPath;
+    }
+
+
+    public static String fileExtension(final Path path) {
+        String fileName = path.getFileName().toString();
+        int idx = fileName.lastIndexOf('.');
+        if (idx > -1) {
+            return fileName.substring(idx+1);
+        } else {
+            return "";
+        }
+    }
+}

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

@@ -0,0 +1,58 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading;
+
+import java.util.Optional;
+
+/**
+ * Finds Version data from a package, with possible default values
+ */
+public class JarVersionLookupHandler {
+    public static Optional<String> getImplementationVersion(final String pkgName) {
+        // Note that with Java 9, you'll probably want the module's version data, hence pulling this out
+        final String pkgVersion = Package.getPackage(pkgName).getImplementationVersion();
+        return Optional.ofNullable(pkgVersion);
+    }
+
+    public static Optional<String> getSpecificationVersion(final String pkgName) {
+        // Note that with Java 9, you'll probably want the module's version data, hence pulling this out
+        final String pkgVersion = Package.getPackage(pkgName).getSpecificationVersion();
+        return Optional.ofNullable(pkgVersion);
+    }
+
+    public static Optional<String> getImplementationVersion(final Class<?> clazz) {
+        // With java 9 we'll use the module's version if it exists in preference.
+        final String pkgVersion = clazz.getPackage().getImplementationVersion();
+        return Optional.ofNullable(pkgVersion);
+    }
+
+    public static Optional<String> getImplementationTitle(final Class<?> clazz) {
+        // With java 9 we'll use the module's version if it exists in preference.
+        final String pkgVersion = clazz.getPackage().getImplementationTitle();
+        return Optional.ofNullable(pkgVersion);
+    }
+
+
+    public static Optional<String> getSpecificationVersion(final Class<?> clazz) {
+        // With java 9 we'll use the module's version if it exists in preference.
+        final String pkgVersion = clazz.getPackage().getSpecificationVersion();
+        return Optional.ofNullable(pkgVersion);
+    }
+}

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

@@ -0,0 +1,168 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading;
+
+import cpw.mods.modlauncher.Launcher;
+import cpw.mods.modlauncher.api.IModuleLayerManager;
+import cpw.mods.modlauncher.util.ServiceLoaderUtils;
+import net.minecraftforge.fml.loading.progress.StartupMessageManager;
+import net.minecraftforge.forgespi.language.IModLanguageProvider;
+import net.minecraftforge.fml.loading.moddiscovery.ExplodedDirectoryLocator;
+import net.minecraftforge.fml.loading.moddiscovery.ModFile;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.apache.maven.artifact.versioning.ArtifactVersion;
+import org.apache.maven.artifact.versioning.DefaultArtifactVersion;
+import org.apache.maven.artifact.versioning.VersionRange;
+
+import java.io.File;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.ServiceLoader;
+import java.util.function.Consumer;
+import java.util.function.Function;
+import java.util.stream.Stream;
+
+import static net.minecraftforge.fml.loading.LogMarkers.CORE;
+import static net.minecraftforge.fml.loading.LogMarkers.LOADING;
+
+public class LanguageLoadingProvider
+{
+    private static final Logger LOGGER = LogManager.getLogger();
+    private final List<IModLanguageProvider> languageProviders = new ArrayList<>();
+    private final ServiceLoader<IModLanguageProvider> serviceLoader;
+    private final Map<String, ModLanguageWrapper> languageProviderMap = new HashMap<>();
+    private List<Path> languagePaths = new ArrayList<>();
+
+    public void forEach(final Consumer<IModLanguageProvider> consumer)
+    {
+        languageProviders.forEach(consumer);
+    }
+
+    public <T> Stream<T> applyForEach(final Function<IModLanguageProvider, T> function) {
+        return languageProviders.stream().map(function);
+    }
+
+    private static class ModLanguageWrapper {
+        private final IModLanguageProvider modLanguageProvider;
+
+        private final ArtifactVersion version;
+        public ModLanguageWrapper(IModLanguageProvider modLanguageProvider, ArtifactVersion version)
+        {
+            this.modLanguageProvider = modLanguageProvider;
+            this.version = version;
+        }
+        public ArtifactVersion getVersion()
+        {
+            return version;
+        }
+
+        public IModLanguageProvider getModLanguageProvider()
+        {
+            return modLanguageProvider;
+        }
+
+
+    }
+
+    LanguageLoadingProvider() {
+        var sl = Launcher.INSTANCE.environment().findModuleLayerManager().flatMap(lm->lm.getLayer(IModuleLayerManager.Layer.PLUGIN)).orElseThrow();
+        serviceLoader = ServiceLoader.load(sl, IModLanguageProvider.class);
+        loadLanguageProviders();
+    }
+    private void loadLanguageProviders() {
+        LOGGER.debug(CORE, "Found {} language providers", ServiceLoaderUtils.streamServiceLoader(()->serviceLoader, sce->LOGGER.fatal("Problem with language loaders")).count());
+        serviceLoader.forEach(languageProviders::add);
+
+        languageProviders.forEach(lp -> {
+            final Path lpPath;
+            try {
+                lpPath = Paths.get(lp.getClass().getProtectionDomain().getCodeSource().getLocation().toURI());
+            } catch (URISyntaxException e) {
+                throw new RuntimeException("Huh?", e);
+            }
+            Optional<String> implementationVersion = JarVersionLookupHandler.getImplementationVersion(lp.getClass());
+            String impl = implementationVersion.orElse(Files.isDirectory(lpPath) ? FMLLoader.versionInfo().forgeVersion().split("\\.")[0] : null);
+            if (impl == null) {
+                LOGGER.fatal(CORE, "Found unversioned language provider {}", lp.name());
+                throw new RuntimeException("Failed to find implementation version for language provider "+ lp.name());
+            }
+            LOGGER.debug(CORE, "Found language provider {}, version {}", lp.name(), impl);
+            StartupMessageManager.modLoaderConsumer().ifPresent(c->c.accept("Loaded language provider "+lp.name()+ " " + impl));
+            languageProviderMap.put(lp.name(), new ModLanguageWrapper(lp, new DefaultArtifactVersion(impl)));
+        });
+    }
+
+    void addForgeLanguage(final Path forgePath) {
+        if (!languageProviderMap.containsKey("javafml")) {
+            LOGGER.debug(CORE,"Adding forge as a language from {}", forgePath.toString());
+            addLanguagePaths(Stream.of(forgePath));
+            serviceLoader.reload();
+            loadLanguageProviders();
+        } else {
+            LOGGER.debug(CORE, "Skipping adding forge jar - javafml is already present");
+        }
+    }
+
+    private void addLanguagePaths(final Stream<Path> langPaths) {
+        languageProviders.clear();
+        languageProviderMap.clear();
+//        langPaths.peek(languagePaths::add).map(Path::toFile).map(File::toURI).map(rethrowFunction(URI::toURL)).forEach(languageClassLoader::addURL);
+    }
+
+    public void addAdditionalLanguages(List<ModFile> modFiles)
+    {
+        if (modFiles==null) return;
+        Stream<Path> langPaths = modFiles.stream().map(ModFile::getFilePath);
+        addLanguagePaths(langPaths);
+        serviceLoader.reload();
+        loadLanguageProviders();
+    }
+
+    Stream<Path> getLibraries() {
+        return languagePaths.stream();
+    }
+
+    public IModLanguageProvider findLanguage(ModFile mf, String modLoader, VersionRange modLoaderVersion) {
+        final String languageFileName = mf.getLocator() instanceof ExplodedDirectoryLocator ? "in-development" : mf.getFileName();
+        final ModLanguageWrapper mlw = languageProviderMap.get(modLoader);
+        if (mlw == null) {
+            LOGGER.error(LOADING,"Missing language {} version {} wanted by {}", modLoader, modLoaderVersion, languageFileName);
+            throw new EarlyLoadingException("Missing language "+modLoader, null, Collections.singletonList(new EarlyLoadingException.ExceptionData("fml.language.missingversion", modLoader, modLoaderVersion, languageFileName, "null")));
+        }
+        if (!VersionSupportMatrix.testVersionSupportMatrix(modLoaderVersion, modLoader, "languageloader", (llid, range) -> range.containsVersion(mlw.getVersion()))) {
+            LOGGER.error(LOADING,"Missing language {} version {} wanted by {}, found {}", modLoader, modLoaderVersion, languageFileName, mlw.getVersion());
+            throw new EarlyLoadingException("Missing language "+ modLoader + " matching range "+modLoaderVersion + " found "+mlw.getVersion(), null, Collections.singletonList(new EarlyLoadingException.ExceptionData("fml.language.missingversion", modLoader, modLoaderVersion, languageFileName, mlw.getVersion())));
+        }
+
+        return mlw.getModLanguageProvider();
+    }
+}

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

@@ -0,0 +1,42 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import static net.minecraftforge.fml.loading.LogMarkers.CORE;
+
+public class LauncherVersion {
+    private static final Logger LOGGER = LogManager.getLogger();
+    private static final String launcherVersion;
+
+    static {
+        String vers = JarVersionLookupHandler.getImplementationVersion(LauncherVersion.class).orElse(System.getenv("LAUNCHER_VERSION"));
+        if (vers == null) throw new RuntimeException("Missing FMLLauncher version, cannot continue");
+        launcherVersion = vers;
+        LOGGER.debug(CORE, "Found FMLLauncher version {}", launcherVersion);
+    }
+
+    public static String getVersion()
+    {
+        return launcherVersion;
+    }
+}

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

@@ -0,0 +1,99 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+import static net.minecraftforge.fml.loading.LogMarkers.CORE;
+
+public class LibraryFinder {
+    private static final Logger LOGGER = LogManager.getLogger();
+    private static Path libsPath;
+    static Path findLibsPath() {
+        if (libsPath == null) {
+            libsPath = Path.of(System.getProperty("libraryDirectory","crazysnowmannonsense/cheezwhizz"));
+            if (!Files.isDirectory(libsPath)) {
+                throw new IllegalStateException("Missing libraryDirectory system property, cannot continue");
+            }
+        }
+        return libsPath;
+    }
+
+    public static Path findJarPathFor(final String className, final String jarName) {
+        final URL resource = LibraryFinder.class.getClassLoader().getResource(className);
+        return findJarPathFor(className, jarName, resource);
+    }
+
+    public static Path findJarPathFor(final String resourceName, final String jarName, final URL resource) {
+        try {
+            Path path;
+            final URI uri = resource.toURI();
+            if (uri.getScheme().equals("jar") && uri.getRawSchemeSpecificPart().contains("!/")) {
+                int lastExcl = uri.getRawSchemeSpecificPart().lastIndexOf("!/");
+                path = Paths.get(new URI(uri.getRawSchemeSpecificPart().substring(0, lastExcl)));
+            } else {
+                path = Paths.get(new URI("file://"+uri.getRawSchemeSpecificPart().substring(0, uri.getRawSchemeSpecificPart().length()-resourceName.length())));
+            }
+            LOGGER.debug(CORE, "Found JAR {} at path {}", jarName, path.toString());
+            return path;
+        } catch (NullPointerException | URISyntaxException e) {
+            LOGGER.fatal(CORE, "Failed to find JAR for class {} - {}", resourceName, jarName);
+            throw new RuntimeException("Unable to locate "+resourceName+" - "+jarName, e);
+        }
+    }
+
+    static Path getForgeLibraryPath(final String mcVersion, final String forgeVersion, final String forgeGroup) {
+        Path forgePath = findLibsPath().resolve(MavenCoordinateResolver.get(forgeGroup, "forge", "", "universal", mcVersion+"-"+forgeVersion));
+        LOGGER.debug(CORE, "Found forge path {} is {}", forgePath, pathStatus(forgePath));
+        return forgePath;
+    }
+
+    static String pathStatus(final Path path) {
+        return Files.exists(path) ? "present" : "missing";
+    }
+
+    static Path[] getMCPaths(final String mcVersion, final String mcpVersion, final String forgeVersion, final String forgeGroup, final String type) {
+        Path srgMcPath = findLibsPath().resolve(MavenCoordinateResolver.get("net.minecraft", type, "", "srg", mcVersion+"-"+mcpVersion));
+        Path mcExtrasPath = findLibsPath().resolve(MavenCoordinateResolver.get("net.minecraft", type, "", "extra", mcVersion+"-"+mcpVersion));
+        Path patchedBinariesPath = findLibsPath().resolve(MavenCoordinateResolver.get(forgeGroup, "forge", "", type, mcVersion+"-"+forgeVersion));
+        LOGGER.debug(CORE,"SRG MC at {} is {}", srgMcPath.toString(), pathStatus(srgMcPath));
+        LOGGER.debug(CORE,"MC Extras at {} is {}", mcExtrasPath.toString(), pathStatus(mcExtrasPath));
+        LOGGER.debug(CORE,"Forge patches at {} is {}", patchedBinariesPath.toString(), pathStatus(patchedBinariesPath));
+        return new Path[] { patchedBinariesPath, mcExtrasPath, srgMcPath };
+    }
+
+    public static Path findPathForMaven(final String group, final String artifact, final String extension, final String classifier, final String version) {
+        return findLibsPath().resolve(MavenCoordinateResolver.get(group, artifact, extension, classifier, version));
+    }
+    public static Path findPathForMaven(final String maven) {
+        return findLibsPath().resolve(MavenCoordinateResolver.get(maven));
+    }
+    public static Path getFMLCorePath() {
+        return findLibsPath().resolve(MavenCoordinateResolver.get("net.minecraftforge:fmlcore:1.0"));
+    }
+}

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

@@ -0,0 +1,178 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+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 java.net.URL;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.*;
+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
+{
+    private static LoadingModList INSTANCE;
+    private final List<ModFileInfo> modFiles;
+    private final List<ModInfo> sortedList;
+    private final Map<String, ModFileInfo> fileById;
+    private final List<EarlyLoadingException> preLoadErrors;
+    private List<ModFile> brokenFiles;
+
+    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());
+        this.fileById = this.modFiles.stream()
+                .map(ModFileInfo::getMods)
+                .flatMap(Collection::stream)
+                .map(ModInfo.class::cast)
+                .collect(Collectors.toMap(ModInfo::getModId, ModInfo::getOwningFile));
+        this.preLoadErrors = new ArrayList<>();
+    }
+
+    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()
+    {
+        modFiles.stream()
+                .map(ModFileInfo::getFile)
+                .map(ModFile::getCoreMods)
+                .flatMap(List::stream)
+                .forEach(FMLLoader.getCoreModProvider()::addCoreMod);
+    }
+
+    public void addAccessTransformers()
+    {
+        modFiles.stream()
+                .map(ModFileInfo::getFile)
+                .forEach(mod -> mod.getAccessTransformer().ifPresent(path -> FMLLoader.addAccessTransformer(path, mod)));
+    }
+
+    public void addForScanning(BackgroundScanHandler backgroundScanHandler)
+    {
+        backgroundScanHandler.setLoadingModList(this);
+        modFiles.stream()
+                .map(ModFileInfo::getFile)
+                .forEach(backgroundScanHandler::submitForScanning);
+    }
+
+    public List<ModFileInfo> getModFiles()
+    {
+        return modFiles;
+    }
+
+    public Path findResource(final String className)
+    {
+        for (ModFileInfo mf : modFiles) {
+            final Path resource = mf.getFile().findResource(className);
+            if (Files.exists(resource)) return resource;
+        }
+        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)
+    {
+        return this.fileById.get(modid);
+    }
+
+    public List<ModInfo> getMods()
+    {
+        return this.sortedList;
+    }
+
+    public List<EarlyLoadingException> getErrors() {
+        return preLoadErrors;
+    }
+
+    public void setBrokenFiles(final List<ModFile> brokenFiles) {
+        this.brokenFiles = brokenFiles;
+    }
+
+    public List<ModFile> getBrokenFiles() {
+        return this.brokenFiles;
+    }
+}

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

@@ -0,0 +1,30 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading;
+
+import org.apache.logging.log4j.Marker;
+import org.apache.logging.log4j.MarkerManager;
+
+public class LogMarkers {
+    public static final Marker CORE = MarkerManager.getMarker("CORE");
+    public static final Marker LOADING = MarkerManager.getMarker("LOADING");
+    public static final Marker SCAN = MarkerManager.getMarker("SCAN");
+    public static final Marker SPLASH = MarkerManager.getMarker("SPLASH");
+}

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

@@ -1,9 +1,4 @@
-/*
- * Copyright (c) Forge Development LLC and contributors
- * SPDX-License-Identifier: LGPL-2.1-only
- */
-
-package net.minecraftforge.userdev;
+package net.minecraftforge.fml.loading;
 
 import cpw.mods.modlauncher.api.INameMappingService;
 import org.apache.commons.lang3.tuple.Pair;
@@ -33,7 +28,7 @@ public class MCPNamingService implements INameMappingService {
 
     @Override
     public String mappingVersion() {
-        return "1234";
+        return "1234"; //TODO: Minecraft Version?
     }
 
     @Override
@@ -78,19 +73,14 @@ public class MCPNamingService implements INameMappingService {
         return fields.getOrDefault(origin, origin);
     }
 
-
-    private static void loadMappings(final String mappingFileName, BiConsumer<String, String> mapStore)
-    {
-        URL path = ClassLoader.getSystemResource(mappingFileName); //We EXPLICITLY go throught the SystemClassLoader here because this is dev-time only. And will be on the root classpath.
+    private static void loadMappings(final String mappingFileName, BiConsumer<String, String> mapStore) {
+        URL path = ClassLoader.getSystemResource(mappingFileName); //We EXPLICITLY go through the SystemClassLoader here because this is dev-time only. And will be on the root classpath.
         if (path == null)
             return;
 
-        try (BufferedReader reader = new BufferedReader(new InputStreamReader(path.openStream())))
-        {
+        try (BufferedReader reader = new BufferedReader(new InputStreamReader(path.openStream()))) {
             reader.lines().skip(1).map(e -> e.split(",")).forEach(e -> mapStore.accept(e[0], e[1]));
-        }
-        catch (IOException e1)
-        {
+        } catch (IOException e1) {
             LOGGER.error(CORE, "Error reading mappings", e1);
         }
     }

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

@@ -0,0 +1,58 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading;
+
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+/**
+ * Convert a maven coordinate into a Path.
+ *
+ * This is gradle standard not maven standard coordinate formatting
+ * {@code <groupId>:<artifactId>[:<classifier>]:<version>[@extension]}, must not be {@code null}.
+ */
+
+public class MavenCoordinateResolver {
+    public static Path get(final String coordinate) {
+        final String[] parts = coordinate.split(":");
+        final String groupId = parts[0];
+        final String artifactId = parts[1];
+        final String classifier = parts.length > 3 ? parts[2] : "";
+        final String[] versext = parts[parts.length-1].split("@");
+        final String version = versext[0];
+        final String extension = versext.length > 1 ? versext[1] : "";
+        return get(groupId, artifactId, extension, classifier, version);
+    }
+
+    public static Path get(final String groupId, final String artifactId, final String extension, final String classifier, final String version)
+    {
+        final String fileName = artifactId + "-" + version +
+                (!classifier.isEmpty() ? "-"+ classifier : "") +
+                (!extension.isEmpty() ? "." + extension : ".jar");
+
+        String[] groups = groupId.split("\\.");
+        Path result = Paths.get(groups[0]);
+        for (int i = 1; i < groups.length; i++) {
+            result = result.resolve(groups[i]);
+        }
+
+        return result.resolve(artifactId).resolve(version).resolve(fileName);
+    }
+}

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

@@ -0,0 +1,76 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading;
+
+import cpw.mods.modlauncher.api.LamdbaExceptionUtils;
+import cpw.mods.modlauncher.api.NamedPath;
+import cpw.mods.modlauncher.serviceapi.ITransformerDiscoveryService;
+import org.apache.logging.log4j.LogManager;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Stream;
+import java.util.zip.ZipFile;
+
+public class ModDirTransformerDiscoverer implements ITransformerDiscoveryService {
+    @Override
+    public List<NamedPath> candidates(final Path gameDirectory) {
+        ModDirTransformerDiscoverer.scan(gameDirectory);
+        return List.copyOf(found);
+    }
+
+    private final static List<NamedPath> found = new ArrayList<>();
+
+    public static List<Path> allExcluded() {
+        return found.stream().map(np->np.paths()[0]).toList();
+    }
+
+    private static void scan(final Path gameDirectory) {
+        final Path modsDir = gameDirectory.resolve(FMLPaths.MODSDIR.relative()).toAbsolutePath().normalize();
+        if (!Files.exists(modsDir)) {
+            // Skip if the mods dir doesn't exist yet.
+            return;
+        }
+        try (var walk = Files.walk(modsDir, 1)){
+            walk.forEach(ModDirTransformerDiscoverer::visitFile);
+        } catch (IOException | IllegalStateException ioe) {
+            LogManager.getLogger().error("Error during early discovery", ioe);
+        }
+    }
+
+    private static void visitFile(Path path) {
+        if (!Files.isRegularFile(path)) return;
+        if (!path.toString().endsWith(".jar")) return;
+        if (LamdbaExceptionUtils.uncheck(() -> Files.size(path)) == 0) return;
+        try (ZipFile zf = new ZipFile(new File(path.toUri()))) {
+            if (zf.getEntry("META-INF/services/cpw.mods.modlauncher.api.ITransformationService") != null) {
+                found.add(new NamedPath(zf.getName(), path));
+            } else if (zf.getEntry("META-INF/services/net.minecraftforge.forgespi.locating.IModLocator") != null) {
+                found.add(new NamedPath(zf.getName(), path));
+            }
+        } catch (IOException ioe) {
+            LogManager.getLogger().error("Zip Error when loading jar file {}", path, ioe);
+        }
+    }
+}

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

@@ -0,0 +1,110 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading;
+
+import cpw.mods.modlauncher.api.LamdbaExceptionUtils;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URL;
+import java.net.URLConnection;
+import java.net.URLStreamHandler;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.jar.Manifest;
+
+import static net.minecraftforge.fml.loading.LogMarkers.CORE;
+
+public class ModJarURLHandler extends URLStreamHandler
+{
+    private static final Logger LOGGER = LogManager.getLogger();
+    // modjar://modid/path/to/file
+    @Override
+    protected URLConnection openConnection(URL url) {
+        return new ModJarURLConnection(url);
+    }
+
+    @Override
+    protected int hashCode(final URL u) {
+        return Objects.hash(u.getHost(), u.getFile());
+    }
+
+    @Override
+    protected boolean equals(final URL u1, final URL u2) {
+        return Objects.equals(u1.getProtocol(), u2.getProtocol())
+                && Objects.equals(u1.getHost(), u2.getHost())
+                && Objects.equals(u1.getFile(), u2.getFile());
+    }
+
+    static class ModJarURLConnection extends URLConnection {
+        private Path resource;
+        private String modpath;
+        private String modid;
+        private Optional<Manifest> manifest;
+
+        public ModJarURLConnection(final URL url) {
+            super(url);
+        }
+
+        @Override
+        public void connect()
+        {
+//            if (resource == null) {
+//                modid = url.getHost();
+//                // trim first char
+//                modpath = url.getPath().substring(1);
+//                resource = FMLLoader.getLoadingModList().getModFileById(modid).getFile().findResource(modpath);
+//                manifest = FMLLoader.getLoadingModList().getModFileById(modid).getManifest();
+//            }
+        }
+
+        @Override
+        public InputStream getInputStream() throws IOException
+        {
+            connect();
+            LOGGER.trace(CORE, "Loading modjar URL {} got resource {} {}", url, resource, resource != null ? Files.exists(resource) : "missing");
+            return Files.newInputStream(resource);
+        }
+
+        @Override
+        public long getContentLengthLong() {
+            try {
+                connect();
+                return Files.size(resource);
+            } catch (IOException e) {
+                return -1L;
+            }
+        }
+
+        // Used to cache protectiondomains by "top level object" aka the modid
+        @Override
+        public URL getURL() {
+            return LamdbaExceptionUtils.uncheck(()->new URL("modjar://"+modid));
+        }
+
+        public Optional<Manifest> getManifest() {
+            return manifest;
+        }
+    }
+}

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

@@ -0,0 +1,247 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading;
+
+import com.google.common.graph.GraphBuilder;
+import com.google.common.graph.MutableGraph;
+import net.minecraftforge.forgespi.language.IModFileInfo;
+import net.minecraftforge.forgespi.language.IModInfo;
+import net.minecraftforge.fml.loading.EarlyLoadingException.ExceptionData;
+import net.minecraftforge.fml.loading.moddiscovery.ModFile;
+import net.minecraftforge.fml.loading.moddiscovery.ModFileInfo;
+import net.minecraftforge.fml.loading.moddiscovery.ModInfo;
+import net.minecraftforge.fml.loading.toposort.CyclePresentException;
+import net.minecraftforge.fml.loading.toposort.TopologicalSort;
+import net.minecraftforge.forgespi.locating.IModFile;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.apache.logging.log4j.util.StringBuilderFormattable;
+import org.apache.maven.artifact.versioning.ArtifactVersion;
+import org.apache.maven.artifact.versioning.DefaultArtifactVersion;
+
+import java.util.*;
+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
+{
+    private static final Logger LOGGER = LogManager.getLogger();
+    private List<ModFile> modFiles;
+    private List<ModInfo> sortedList;
+    private Map<String, ModInfo> modIdNameLookup;
+    private List<ModFile> forgeAndMC;
+
+    private ModSorter(final List<ModFile> modFiles)
+    {
+        this.modFiles = modFiles;
+    }
+
+    public static LoadingModList sort(List<ModFile> mods, final List<ExceptionData> errors)
+    {
+        final ModSorter ms = new ModSorter(mods);
+        try {
+            ms.buildUniqueList();
+        } catch (EarlyLoadingException e) {
+            // We cannot build any list with duped mods. We have to abort immediately and report it
+            return LoadingModList.of(ms.forgeAndMC, ms.forgeAndMC.stream().map(mf->(ModInfo)mf.getModInfos().get(0)).collect(toList()), e);
+        }
+        // try and validate dependencies
+        final List<ExceptionData> failedList = Stream.concat(ms.verifyDependencyVersions().stream(), errors.stream()).toList();
+        // if we miss one or the other, we abort now
+        if (!failedList.isEmpty()) {
+            return LoadingModList.of(ms.forgeAndMC, ms.forgeAndMC.stream().map(mf->(ModInfo)mf.getModInfos().get(0)).collect(toList()), 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();
+            } catch (EarlyLoadingException e) {
+                earlyLoadingException = e;
+            }
+            return LoadingModList.of(ms.modFiles, ms.sortedList, earlyLoadingException);
+        }
+    }
+
+    @SuppressWarnings("UnstableApiUsage")
+    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<IModFileInfo, Integer> infos = modFiles.stream()
+                .map(ModFile::getModFileInfo)
+                .collect(toMap(Function.identity(), e -> counter.incrementAndGet()));
+        infos.keySet().forEach(i -> graph.addNode((ModFileInfo) i));
+        modFiles.stream()
+                .map(ModFile::getModInfos)
+                .<IModInfo>mapMulti(Iterable::forEach)
+                .map(IModInfo::getDependencies)
+                .<IModInfo.ModVersion>mapMulti(Iterable::forEach)
+                .forEach(dep -> addDependency(graph, dep));
+
+        final List<ModFileInfo> sorted;
+        try
+        {
+            sorted = TopologicalSort.topologicalSort(graph, Comparator.comparing(infos::get));
+        }
+        catch (CyclePresentException e)
+        {
+            Set<Set<ModFileInfo>> cycles = e.getCycles();
+            LOGGER.error(LOADING, () -> new AdvancedLogMessageAdapter(buffer ->
+                    buffer.append("Mod Sorting failed.\n")
+                    .append("Detected Cycles: ")
+                    .append(cycles)
+                    .append('\n')));
+            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();
+            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());
+    }
+
+    @SuppressWarnings("UnstableApiUsage")
+    private void addDependency(MutableGraph<ModFileInfo> topoGraph, IModInfo.ModVersion dep)
+    {
+        final ModFileInfo self = (ModFileInfo)dep.getOwner().getOwningFile();
+        final ModInfo targetModInfo = modIdNameLookup.get(dep.getModId());
+        // soft dep that doesn't exist. Just return. No edge required.
+        if (targetModInfo == null) return;
+        final ModFileInfo target = targetModInfo.getOwningFile();
+        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);
+        }
+    }
+
+    private void buildUniqueList()
+    {
+        // Collect mod files by first modid in the file. This will be used for deduping purposes
+        final Map<String, List<IModFile>> modFilesByFirstId = modFiles.stream()
+                .collect(groupingBy(mf -> mf.getModInfos().get(0).getModId()));
+
+        // Capture forge and MC here, so we can keep them for later
+        forgeAndMC = new ArrayList<>();
+        var mc = modFilesByFirstId.get("minecraft");
+        if (mc != null && !mc.isEmpty())
+            forgeAndMC.add((ModFile) mc.get(0));
+        else
+            throw new IllegalStateException("Failed to find minecraft somehow?");
+
+        // Select the newest by artifact version sorting of non-unique files thus identified
+        this.modFiles = modFilesByFirstId.entrySet().stream()
+                .map(this::selectNewestModInfo)
+                .map(Map.Entry::getValue)
+                .map(ModFile.class::cast)
+                .collect(toList());
+
+        // Transform to the full mod id list
+        final Map<String, List<ModInfo>> modIds = modFiles.stream()
+                .map(ModFile::getModInfos)
+                .flatMap(Collection::stream)
+                .map(ModInfo.class::cast)
+                .collect(groupingBy(IModInfo::getModId));
+
+        // 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<ModInfo> dupedMods = modIds.values().stream()
+                .filter(modInfos -> modInfos.size() > 1)
+                .map(modInfos -> modInfos.get(0))
+                .toList();
+
+        if (!dupedMods.isEmpty()) {
+            final List<EarlyLoadingException.ExceptionData> duplicateModErrors = dupedMods.stream()
+                    .map(dm -> new EarlyLoadingException.ExceptionData("fml.modloading.dupedmod",
+                            dm, Objects.toString(dm))).toList();
+            throw new EarlyLoadingException("Duplicate mods found", null,  duplicateModErrors);
+        }
+
+        modIdNameLookup = modIds.entrySet().stream()
+                .collect(toMap(Map.Entry::getKey, e -> e.getValue().get(0)));
+    }
+
+    private Map.Entry<String, IModFile> selectNewestModInfo(Map.Entry<String, List<IModFile>> fullList) {
+        List<IModFile> 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.<IModFile, ArtifactVersion>comparing(mf -> mf.getModInfos().get(0).getVersion()).reversed());
+            LOGGER.debug("Selected file {} for modid {} with version {}", modInfoList.get(0).getFileName(), fullList.getKey(), modInfoList.get(0).getModInfos().get(0).getVersion());
+        }
+        return Map.entry(fullList.getKey(), modInfoList.get(0));
+    }
+
+    private List<EarlyLoadingException.ExceptionData> verifyDependencyVersions()
+    {
+        final var modVersions = modFiles.stream()
+                .map(ModFile::getModInfos)
+                .<IModInfo>mapMulti(Iterable::forEach)
+                .collect(toMap(IModInfo::getModId, IModInfo::getVersion));
+
+        final var modVersionDependencies = modFiles.stream()
+                .map(ModFile::getModInfos)
+                .<IModInfo>mapMulti(Iterable::forEach)
+                .collect(groupingBy(Function.identity(), flatMapping(e -> e.getDependencies().stream(), toList())));
+
+        final var modRequirements = modVersionDependencies.values().stream()
+                .<IModInfo.ModVersion>mapMulti(Iterable::forEach)
+                .filter(mv -> mv.getSide().isCorrectSide())
+                .collect(toSet());
+
+        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()) {
+            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();
+        }
+        return Collections.emptyList();
+    }
+
+    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("NONE"))));
+    }
+}

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

@@ -1,6 +1,20 @@
 /*
- * Copyright (c) Forge Development LLC and contributors
- * SPDX-License-Identifier: LGPL-2.1-only
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
 package net.minecraftforge.fml.loading;
@@ -48,7 +62,7 @@ public class RuntimeDistCleaner implements ILaunchPluginService
     }
 
     @Override
-    public boolean processClass(Phase phase, ClassNode classNode, Type classType)
+    public int processClassWithFlags(final Phase phase, final ClassNode classNode, final Type classType, final String reason)
     {
         AtomicBoolean changes = new AtomicBoolean();
         if (remove(classNode.visibleAnnotations, DIST))
@@ -133,7 +147,7 @@ public class RuntimeDistCleaner implements ILaunchPluginService
                 }
             }
         }
-        return changes.get();
+        return changes.get() ? ComputeFlags.SIMPLE_REWRITE : ComputeFlags.NO_REWRITE;
     }
 
     @SuppressWarnings("unchecked")
@@ -182,7 +196,7 @@ public class RuntimeDistCleaner implements ILaunchPluginService
         private final List<Handle> dynamicLambdaHandles = new ArrayList<>();
 
         public LambdaGatherer() {
-            super(Opcodes.ASM5);
+            super(Opcodes.ASM9);
         }
 
         public void accept(MethodNode method) {

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

@@ -0,0 +1,62 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading;
+
+import com.google.common.collect.ImmutableMap;
+import net.minecraftforge.fml.loading.moddiscovery.ModFile;
+import org.apache.commons.lang3.text.StrLookup;
+import org.apache.commons.lang3.text.StrSubstitutor;
+
+import java.util.Map;
+
+@SuppressWarnings("deprecation")
+public class StringSubstitutor
+{
+    private static final Map<String,String> globals = ImmutableMap.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) {
+        return new StrLookup<String>()
+        {
+            @Override
+            public String lookup(String key)
+            {
+                final String[] parts = key.split("\\.");
+                if (parts.length == 1) return key;
+                final String pfx = parts[0];
+                if ("global".equals(pfx))
+                {
+                    return globals.get(parts[1]);
+                }
+                else if ("file".equals(pfx) && file != null)
+                {
+                    return String.valueOf(file.getSubstitutionMap().get().get(parts[1]));
+                }
+                return key;
+            }
+        };
+    }
+}

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

@@ -0,0 +1,66 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading;
+
+import org.apache.commons.lang3.text.StrSubstitutor;
+
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.util.Locale;
+import java.util.Map;
+
+public class StringUtils {
+    public static String toLowerCase(final String str) {
+        return str.toLowerCase(Locale.ROOT);
+    }
+
+    public static String toUpperCase(final String str) {
+        return str.toUpperCase(Locale.ROOT);
+    }
+
+    public static boolean endsWith(final String search, final String... endings) {
+        String lowerSearch = toLowerCase(search);
+        return java.util.stream.Stream.of(endings).anyMatch(lowerSearch::endsWith);
+    }
+
+    public static URL toURL(final String string) {
+        if (string == null || string.trim().isEmpty() || string.contains("myurl.me") || string.contains("example.invalid"))
+            return null;
+
+        try {
+            return new URL(string); }
+        catch (MalformedURLException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public static String parseStringFormat(final String input, final Map<String, String> properties) {
+        return StrSubstitutor.replace(input, properties);
+    }
+
+    public static String binToHex(final byte[] bytes) {
+        StringBuilder sb = new StringBuilder();
+        for (int i = 0; i < bytes.length; i++) {
+            sb.append(Integer.toHexString((bytes[i]&0xf0) >>4));
+            sb.append(Integer.toHexString(bytes[i]&0x0f));
+        }
+        return sb.toString();
+    }
+}

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

@@ -0,0 +1,115 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading;
+
+import org.apache.logging.log4j.Logger;
+
+import java.io.PrintStream;
+
+/**
+ * PrintStream which redirects it's output to a given logger.
+ *
+ */
+public class TracingPrintStream extends PrintStream
+{
+
+    private static final int BASE_DEPTH = 4;
+    private final Logger logger;
+
+    public TracingPrintStream(Logger logger, PrintStream original)
+    {
+        super(original);
+        this.logger = logger;
+    }
+
+    private void log(String s)
+    {
+        logger.info("{}{}", getPrefix(), s);
+    }
+
+    private static String getPrefix()
+    {
+        StackTraceElement[] elems = Thread.currentThread().getStackTrace();
+        StackTraceElement elem = elems[Math.min(BASE_DEPTH, elems.length - 1)]; // The caller is always at BASE_DEPTH, including this call.
+        if (elem.getClassName().startsWith("kotlin.io."))
+        {
+            elem = elems[Math.min(BASE_DEPTH + 2, elems.length - 1)]; // Kotlins IoPackage masks origins 2 deeper in the stack.
+        }
+        else if (elem.getClassName().startsWith("java.lang.Throwable"))
+        {
+            elem = elems[Math.min(BASE_DEPTH + 4, elems.length - 1)];
+        }
+        return "[" + elem.getClassName() + ":" + elem.getMethodName() + ":" + elem.getLineNumber() + "]: ";
+    }
+
+    @Override
+    public void println(Object o)
+    {
+        log(String.valueOf(o));
+    }
+
+    @Override
+    public void println(String s)
+    {
+        log(s);
+    }
+
+    @Override
+    public void println(boolean x)
+    {
+        log(String.valueOf(x));
+    }
+
+    @Override
+    public void println(char x)
+    {
+        log(String.valueOf(x));
+    }
+
+    @Override
+    public void println(int x)
+    {
+        log(String.valueOf(x));
+    }
+
+    @Override
+    public void println(long x)
+    {
+        log(String.valueOf(x));
+    }
+
+    @Override
+    public void println(float x)
+    {
+        log(String.valueOf(x));
+    }
+
+    @Override
+    public void println(double x)
+    {
+        log(String.valueOf(x));
+    }
+
+    @Override
+    public void println(char[] x)
+    {
+        log(String.valueOf(x));
+    }
+}

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

@@ -0,0 +1,17 @@
+package net.minecraftforge.fml.loading;
+
+import java.util.Map;
+
+public record VersionInfo(String forgeVersion, String mcVersion, String mcpVersion, String forgeGroup) {
+    VersionInfo(Map<String, ?> arguments) {
+        this((String) arguments.get("forgeVersion"), (String) arguments.get("mcVersion"), (String) arguments.get("mcpVersion"), (String) arguments.get("forgeGroup"));
+    }
+
+    public String mcAndForgeVersion() {
+        return mcVersion+"-"+forgeVersion;
+    }
+
+    public String mcAndMCPVersion() {
+        return mcVersion + "-" + mcpVersion;
+    }
+}

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

@@ -0,0 +1,55 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+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 java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.function.BiPredicate;
+
+public class VersionSupportMatrix {
+    private static final HashMap<String, List<ArtifactVersion>> overrideVersions = new HashMap<>();
+    static {
+        final ArtifactVersion version = new DefaultArtifactVersion(FMLLoader.versionInfo().mcVersion());
+        // if (MavenVersionAdapter.createFromVersionSpec("[1.16.4,1.16.5]").containsVersion(version)) {
+        //     // 1.16.4 is Compatible with 1.16.3
+        //     add("languageloader.javafml", "34");
+        //     add("mod.minecraft",          "1.16.3");
+        //     add("mod.forge",              "34.1.42");
+        //     // 1.16.5 is Compatible with 1.16.4, and thus 1.16.3
+        //     add("languageloader.javafml", "35");
+        //     add("mod.minecraft",          "1.16.4");
+        //     add("mod.forge",              "35.1.37");
+        // }
+    }
+    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) {
+        if (standardLookup.test(lookupId, declaredRange)) return true;
+        List<ArtifactVersion> custom = overrideVersions.get(type +"." +lookupId);
+        return custom == null ? false  : custom.stream().anyMatch(declaredRange::containsVersion);
+    }
+}

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

@@ -0,0 +1,73 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading.log4j;
+
+import net.minecrell.terminalconsole.HighlightErrorConverter;
+import net.minecrell.terminalconsole.TerminalConsoleAppender;
+import org.apache.logging.log4j.Logger;
+import org.apache.logging.log4j.core.config.Configuration;
+import org.apache.logging.log4j.core.config.plugins.Plugin;
+import org.apache.logging.log4j.core.pattern.ConverterKeys;
+import org.apache.logging.log4j.core.pattern.HighlightConverter;
+import org.apache.logging.log4j.core.pattern.PatternConverter;
+import org.apache.logging.log4j.status.StatusLogger;
+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.
+ * Ansi support is determined by TerminalConsoleAppender
+ */
+@Plugin(name = "highlightForge", category = PatternConverter.CATEGORY)
+@ConverterKeys("highlightForge")
+@PerformanceSensitive("allocation")
+public class ForgeHighlight {
+    protected static final Logger LOGGER = StatusLogger.getLogger();
+
+    /**
+     * Gets a new instance of the {@link HighlightErrorConverter} with the
+     * specified options.
+     *
+     * @param config The current configuration
+     * @param options The pattern options
+     * @return The new instance
+     */
+    public static @Nullable HighlightConverter newInstance(Configuration config, String[] options) {
+        try {
+            Method method = TerminalConsoleAppender.class.getDeclaredMethod("initializeTerminal");
+            method.setAccessible(true);
+            method.invoke(null);
+        } catch (ReflectiveOperationException e) {
+            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]);
+        }
+        return HighlightConverter.newInstance(config, options);
+    }
+}