Fix BusGroup.DEFAULT not being trimmed after mod loading completes, also trim mod BusGroups now too (#10721)

Saves some memory by trimming various backing collections of loaded EventBuses on the default BusGroup

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

@@ -5,6 +5,7 @@
 
 package net.minecraftforge.fml;
 
+import net.minecraftforge.eventbus.api.bus.BusGroup;
 import net.minecraftforge.fml.config.IConfigEvent;
 import net.minecraftforge.fml.config.ModConfig;
 import net.minecraftforge.fml.event.IModBusEvent;
@@ -157,6 +158,14 @@ public abstract class ModContainer {
      */
     public abstract Object getMod();
 
+    /**
+     * @return the mod bus group for this specific mod, or null if there is none.
+     *         Leave null if you use {@link BusGroup#DEFAULT} for your mod lifecycle events.
+     */
+    public BusGroup getModBusGroup() {
+        return null;
+    }
+
     /**
      * Accept an arbitrary event for processing by the mod. Probably posted to an event bus in the lower level container.
      * @param e Event to accept

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

@@ -6,6 +6,7 @@
 package net.minecraftforge.fml;
 
 import com.google.common.collect.ImmutableList;
+import net.minecraftforge.eventbus.api.bus.BusGroup;
 import net.minecraftforge.fml.event.IModBusEvent;
 import net.minecraftforge.fml.loading.FMLEnvironment;
 import net.minecraftforge.fml.loading.FMLLoader;
@@ -232,7 +233,19 @@ public class ModLoader {
         for (IModLoadingState mls : stateList) {
             dispatchAndHandleError(mls, syncExecutor, parallelExecutor, periodicTask, progress);
         }
-        statusConsumer.accept(String.format("Mod loading complete - %d mods loaded", this.modList.size()));
+
+        var modBusGroups = Set.of(
+                modList.getLoadedMods().stream()
+                        .map(ModContainer::getModBusGroup)
+                        .filter(Objects::nonNull)
+                        .toArray(BusGroup[]::new)
+        );
+        for (var modBusGroup : modBusGroups) {
+            parallelExecutor.execute(modBusGroup::trim);
+        }
+        parallelExecutor.execute(BusGroup.DEFAULT::trim);
+
+        statusConsumer.accept("Mod loading complete - %d mods loaded".formatted(this.modList.size()));
         progress.complete();
     }
 

javafmllanguage/src/main/java/net/minecraftforge/fml/javafmlmod/FMLModContainer.java

@@ -47,8 +47,9 @@ public class FMLModContainer extends ModContainer {
         this.contextExtension = () -> context;
         try {
             var moduleName = info.getOwningFile().moduleName();
-            var module = gameLayer.findModule(moduleName)
-                .orElseThrow(() -> new IllegalStateException("Failed to find " + moduleName + " in " + gameLayer));
+            var module = gameLayer.findModule(moduleName).orElse(null);
+            if (module == null)
+                throw new IllegalStateException("Failed to find " + moduleName + " in " + gameLayer);
 
             openModules(gameLayer, module, info.getOwningFile().getFile().getSecureJar());
 
@@ -166,6 +167,7 @@ public class FMLModContainer extends ModContainer {
         return modInstance;
     }
 
+    @Override
     public BusGroup getModBusGroup() {
         return this.eventBusGroup;
     }

src/main/java/net/minecraftforge/fml/core/ModStateProvider.java

@@ -136,8 +136,7 @@ public class ModStateProvider implements IModStateProvider {
      *
      * @see ModLoadingStage#DONE
      */
-    public static final ModLoadingState DONE = ModLoadingState.of("DONE", ModLoadingPhase.DONE)
-            .withInline(ml -> BusGroup.DEFAULT.trim());
+    public static final ModLoadingState DONE = ModLoadingState.of("DONE", ModLoadingPhase.DONE).empty();
 
     @Override
     public List<IModLoadingState> getAllStates() {