tweak datapack loading

src/main/java/net/fabricmc/fabric/mixin/resources/MixinMinecraftServer.java

@@ -16,7 +16,11 @@
 
 package net.fabricmc.fabric.mixin.resources;
 
+import net.fabricmc.fabric.resources.ModDataPackSupplier;
+import net.fabricmc.fabric.resources.ModResourcePack;
 import net.fabricmc.fabric.resources.ModResourcePackUtil;
+import net.minecraft.class_3283;
+import net.minecraft.class_3288;
 import net.minecraft.client.MinecraftGame;
 import net.minecraft.resource.ReloadableResourceManager;
 import net.minecraft.resource.ResourcePack;
@@ -30,15 +34,26 @@ import org.spongepowered.asm.mixin.injection.Inject;
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
 import org.spongepowered.asm.mixin.injection.callback.LocalCapture;
 
+import java.io.File;
+import java.util.ArrayList;
 import java.util.List;
 
 @Mixin(MinecraftServer.class)
 public class MixinMinecraftServer {
     @Shadow
-    private ReloadableResourceManager dataManager;
+    private class_3283<class_3288> field_4595;
 
-    @Inject(method = "reloadDataPacks", at = @At(value = "INVOKE", target = "Lnet/minecraft/resource/ReloadableResourceManager;reload(Ljava/util/List;)V", ordinal = 0), locals = LocalCapture.CAPTURE_FAILHARD)
-    public void reloadDataPacks(LevelProperties properties, CallbackInfo info, List<ResourcePack> list) {
-        ModResourcePackUtil.appendModResourcePacks(list, ResourceType.DATA);
+    @Inject(method = "method_3800", at = @At(value = "INVOKE", target = "Lnet/minecraft/class_3283;method_14443(Lnet/minecraft/class_3285;)V", ordinal = 1))
+    public void method_3800(File file, LevelProperties properties, CallbackInfo info) {
+    	// TODO: "vanilla" does not emit a message; neither should a modded datapack
+    	List<ResourcePack> packs = new ArrayList<>();
+        ModResourcePackUtil.appendModResourcePacks(packs, ResourceType.DATA);
+        for (ResourcePack pack : packs) {
+        	if (!(pack instanceof ModResourcePack)) {
+        		throw new RuntimeException("Not a ModResourcePack!");
+	        }
+
+			field_4595.method_14443(new ModDataPackSupplier((ModResourcePack) pack));
+        }
     }
 }

src/main/java/net/fabricmc/fabric/resources/ModDataPackSupplier.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2016, 2017, 2018 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.fabric.resources;
+
+import net.minecraft.class_3285;
+import net.minecraft.class_3288;
+
+import java.util.Map;
+
+public class ModDataPackSupplier implements class_3285 {
+	private final ModResourcePack pack;
+
+	public ModDataPackSupplier(ModResourcePack pack) {
+		this.pack = pack;
+	}
+
+	@Override
+	public <T extends class_3288> void method_14453(Map<String, T> map, class_3288.class_3290<T> class_3290) {
+		T var3 = class_3288.method_14456("fabric:" + pack.getModInfo().getId(),
+			false, () -> this.pack, class_3290, class_3288.class_3289.BOTTOM);
+
+		if (var3 != null) {
+			map.put(var3.method_14463(), var3);
+		}
+	}
+}

src/main/java/net/fabricmc/fabric/resources/ModDirectoryResourcePack.java

@@ -22,7 +22,7 @@ import net.minecraft.resource.ResourceNotFoundException;
 
 import java.io.*;
 
-public class ModDirectoryResourcePack extends DirectoryResourcePack {
+public class ModDirectoryResourcePack extends DirectoryResourcePack implements ModResourcePack {
     private final ModInfo info;
 
     public ModDirectoryResourcePack(ModInfo info, File file) {
@@ -52,4 +52,9 @@ public class ModDirectoryResourcePack extends DirectoryResourcePack {
     protected boolean containsFilename(String filename) {
         return super.containsFilename(filename) || ModResourcePackUtil.containsDefault(info, filename);
     }
+
+	@Override
+	public ModInfo getModInfo() {
+		return info;
+	}
 }

src/main/java/net/fabricmc/fabric/resources/ModResourcePack.java

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2016, 2017, 2018 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.fabric.resources;
+
+import net.fabricmc.loader.ModInfo;
+import net.minecraft.resource.ResourcePack;
+
+public interface ModResourcePack extends ResourcePack {
+	ModInfo getModInfo();
+}

src/main/java/net/fabricmc/fabric/resources/ModZipResourcePack.java

@@ -26,7 +26,7 @@ import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
 
-public class ModZipResourcePack extends ZipResourcePack {
+public class ModZipResourcePack extends ZipResourcePack implements ModResourcePack {
     private final ModInfo info;
 
     public ModZipResourcePack(ModInfo info, File file) {
@@ -56,4 +56,9 @@ public class ModZipResourcePack extends ZipResourcePack {
     public boolean containsFilename(String filename) {
         return super.containsFilename(filename) || ModResourcePackUtil.containsDefault(info, filename);
     }
+
+	@Override
+	public ModInfo getModInfo() {
+		return info;
+	}
 }