Add support for referencing forge's resources and specifying existing mods to data generators (#7456)

src/main/java/net/minecraftforge/client/model/generators/ModelProvider.java

@@ -47,7 +47,7 @@ public abstract class ModelProvider<T extends ModelBuilder<T>> implements IDataP
         private final ExistingFileHelper delegate;
 
         public ExistingFileHelperIncludingGenerated(ExistingFileHelper delegate) {
-            super(Collections.emptyList(), true);
+            super(Collections.emptyList(), Collections.emptySet(), true);
             this.delegate = delegate;
         }
 

src/main/java/net/minecraftforge/common/data/ExistingFileHelper.java

@@ -26,6 +26,8 @@ import java.util.Collection;
 
 import com.google.common.annotations.VisibleForTesting;
 
+import java.util.Collections;
+import java.util.Set;
 import net.minecraft.resources.FilePack;
 import net.minecraft.resources.FolderPack;
 import net.minecraft.resources.IResource;
@@ -35,20 +37,29 @@ import net.minecraft.resources.ResourcePackType;
 import net.minecraft.resources.SimpleReloadableResourceManager;
 import net.minecraft.resources.VanillaPack;
 import net.minecraft.util.ResourceLocation;
+import net.minecraftforge.fml.ModList;
 import net.minecraftforge.fml.event.lifecycle.GatherDataEvent;
+import net.minecraftforge.fml.loading.moddiscovery.ModFileInfo;
+import net.minecraftforge.fml.packs.ModFileResourcePack;
 
 /**
  * Enables data providers to check if other data files currently exist. The
  * instance provided in the {@link GatherDataEvent} utilizes the standard
- * resources (via {@link VanillaPack}), as well as any extra resource packs
- * passed in via the {@code --existing} argument.
+ * resources (via {@link VanillaPack}), forge's resources, as well as any
+ * extra resource packs passed in via the {@code --existing} argument,
+ * or mod resources via the {@code --existing-mod} argument.
  */
 public class ExistingFileHelper {
 
     private final SimpleReloadableResourceManager clientResources, serverData;
     private final boolean enable;
 
+    @Deprecated//TODO: Remove in 1.17
     public ExistingFileHelper(Collection<Path> existingPacks, boolean enable) {
+        this(existingPacks, Collections.emptySet(), enable);
+    }
+
+    public ExistingFileHelper(Collection<Path> existingPacks, Set<String> existingMods, boolean enable) {
         this.clientResources = new SimpleReloadableResourceManager(ResourcePackType.CLIENT_RESOURCES);
         this.serverData = new SimpleReloadableResourceManager(ResourcePackType.SERVER_DATA);
         this.clientResources.addResourcePack(new VanillaPack("minecraft", "realms"));
@@ -58,7 +69,15 @@ public class ExistingFileHelper {
             IResourcePack pack = file.isDirectory() ? new FolderPack(file) : new FilePack(file);
             this.clientResources.addResourcePack(pack);
             this.serverData.addResourcePack(pack);
-        };
+        }
+        for (String existingMod : existingMods) {
+            ModFileInfo modFileInfo = ModList.get().getModFileById(existingMod);
+            if (modFileInfo != null) {
+                IResourcePack pack = new ModFileResourcePack(modFileInfo.getFile());
+                this.clientResources.addResourcePack(pack);
+                this.serverData.addResourcePack(pack);
+            }
+        }
         this.enable = enable;
     }
 

src/main/java/net/minecraftforge/fml/DatagenModLoader.java

@@ -19,6 +19,7 @@
 
 package net.minecraftforge.fml;
 
+import java.util.Collections;
 import net.minecraft.util.registry.Bootstrap;
 import net.minecraftforge.common.data.ExistingFileHelper;
 import net.minecraftforge.fml.event.lifecycle.GatherDataEvent;
@@ -39,14 +40,23 @@ public class DatagenModLoader {
         return runningDataGen;
     }
 
-    public static void begin(final Set<String> mods, final Path path, final java.util.Collection<Path> inputs, Collection<Path> existingPacks, final boolean serverGenerators, final boolean clientGenerators, final boolean devToolGenerators, final boolean reportsGenerator, final boolean structureValidator, final boolean flat) {
+    @Deprecated //TODO: Remove in 1.17
+    public static void begin(final Set<String> mods, final Path path, final Collection<Path> inputs, Collection<Path> existingPacks, final boolean serverGenerators, final boolean clientGenerators, final boolean devToolGenerators, final boolean reportsGenerator, final boolean structureValidator, final boolean flat) {
+        begin(mods, path, inputs, existingPacks, Collections.emptySet(), serverGenerators, clientGenerators, devToolGenerators, reportsGenerator, structureValidator, flat);
+    }
+
+    public static void begin(final Set<String> mods, final Path path, final Collection<Path> inputs, Collection<Path> existingPacks, Set<String> existingMods, final boolean serverGenerators, final boolean clientGenerators, final boolean devToolGenerators, final boolean reportsGenerator, final boolean structureValidator, final boolean flat) {
         if (mods.contains("minecraft") && mods.size() == 1) return;
         LOGGER.info("Initializing Data Gatherer for mods {}", mods);
         runningDataGen = true;
         Bootstrap.register();
         dataGeneratorConfig = new GatherDataEvent.DataGeneratorConfig(mods, path, inputs, serverGenerators, clientGenerators, devToolGenerators, reportsGenerator, structureValidator, flat);
-        existingFileHelper = new ExistingFileHelper(existingPacks, structureValidator);
         ModLoader.get().gatherAndInitializeMods(ModWorkManager.syncExecutor(), ModWorkManager.parallelExecutor(), ()->{});
+        if (!mods.contains("forge")) {
+            //If we aren't generating data for forge, automatically add forge as an existing so mods can access forge's data
+            existingMods.add("forge");
+        }
+        existingFileHelper = new ExistingFileHelper(existingPacks, existingMods, structureValidator);
         ModLoader.get().runEventGenerator(mc->new GatherDataEvent(mc, dataGeneratorConfig.makeGenerator(p->dataGeneratorConfig.isFlat() ? p : p.resolve(mc.getModId()), dataGeneratorConfig.getMods().contains(mc.getModId())), dataGeneratorConfig, existingFileHelper));
         dataGeneratorConfig.runAll();
     }