Use knownPackInfo on mod data packs to avoid registry syncing (#3726)

* use knownPack to avoid syncing mod data packs.

* remove empty class

* checkstyle and licenses

* move debug logging from testmod into main module

* fix knownPackInfo not working for build-in data packs.

* make bundled data packs not required for client, and don't auto enable

* improve testmod with added builtin data pack + better error message

* Increase max known packs in C2S packet

* validate size before sending
* changeable with system property

* change mixin from ModifyConstant to ModifyArg to be more clear.

* Apply suggestions from code review

Co-authored-by: modmuss <modmuss50@gmail.com>

* store list of knownPacks as server start

avoids desync on pack change (since registries aren't reloaded)

* be extra safe: only request knownPacks that were enabled at server start and still are.

Doesn't rely on the fact that registries aren't synced anymore.

---------

Co-authored-by: modmuss <modmuss50@gmail.com>
(cherry picked from commit c0e5481f61)

fabric-resource-loader-v0/src/client/java/net/fabricmc/fabric/mixin/resource/loader/client/ClientDataPackManagerMixin.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 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.mixin.resource.loader.client;
+
+import java.util.List;
+
+import com.llamalad7.mixinextras.injector.ModifyReturnValue;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Unique;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Redirect;
+
+import net.minecraft.client.resource.ClientDataPackManager;
+import net.minecraft.registry.VersionedIdentifier;
+import net.minecraft.resource.ResourcePackManager;
+
+import net.fabricmc.fabric.impl.resource.loader.ModResourcePackCreator;
+import net.fabricmc.fabric.impl.resource.loader.ModResourcePackUtil;
+
+@Mixin(ClientDataPackManager.class)
+public class ClientDataPackManagerMixin {
+	@Unique
+	private static final Logger LOGGER = LoggerFactory.getLogger("ClientDataPackManagerMixin");
+
+	@Redirect(method = "<init>", at = @At(value = "INVOKE", target = "Lnet/minecraft/resource/VanillaDataPackProvider;createClientManager()Lnet/minecraft/resource/ResourcePackManager;"))
+	public ResourcePackManager createClientManager() {
+		return ModResourcePackUtil.createClientManager();
+	}
+
+	@ModifyReturnValue(method = "getCommonKnownPacks", at = @At("RETURN"))
+	List<VersionedIdentifier> getCommonKnownPacksReturn(List<VersionedIdentifier> original) {
+		if (original.size() > ModResourcePackCreator.MAX_KNOWN_PACKS) {
+			LOGGER.warn("Too many knownPacks: Found {}; max {}", original.size(), ModResourcePackCreator.MAX_KNOWN_PACKS);
+			return original.subList(0, ModResourcePackCreator.MAX_KNOWN_PACKS);
+		}
+
+		return original;
+	}
+}

fabric-resource-loader-v0/src/client/resources/fabric-resource-loader-v0.client.mixins.json

@@ -9,7 +9,8 @@
     "KeyedResourceReloadListenerClientMixin",
     "ResourcePackOrganizerMixin",
     "VanillaResourcePackProviderMixin",
-    "GameOptionsWriteVisitorMixin"
+    "GameOptionsWriteVisitorMixin",
+    "ClientDataPackManagerMixin"
   ],
   "injectors": {
     "defaultRequire": 1

fabric-resource-loader-v0/src/main/java/net/fabricmc/fabric/impl/resource/loader/FabricOriginalKnownPacksGetter.java

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 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.impl.resource.loader;
+
+import java.util.List;
+
+import net.minecraft.registry.VersionedIdentifier;
+
+public interface FabricOriginalKnownPacksGetter {
+	/**
+	 * @return the data packs known at server start
+	 */
+	List<VersionedIdentifier> fabric_getOriginalKnownPacks();
+}

fabric-resource-loader-v0/src/main/java/net/fabricmc/fabric/impl/resource/loader/ModNioResourcePack.java

@@ -42,6 +42,7 @@ import org.jetbrains.annotations.Nullable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import net.minecraft.registry.VersionedIdentifier;
 import net.minecraft.resource.AbstractFileResourcePack;
 import net.minecraft.resource.InputSupplier;
 import net.minecraft.resource.ResourcePack;
@@ -106,7 +107,7 @@ public class ModNioResourcePack implements ResourcePack, ModResourcePack {
 				packId,
 				displayName,
 				ModResourcePackCreator.RESOURCE_PACK_SOURCE,
-				Optional.empty()
+				Optional.of(new VersionedIdentifier(ModResourcePackCreator.FABRIC, packId, mod.getMetadata().getVersion().getFriendlyString()))
 		);
 		ModNioResourcePack ret = new ModNioResourcePack(packId, mod, paths, type, activationType, modBundled, metadata);
 

fabric-resource-loader-v0/src/main/java/net/fabricmc/fabric/impl/resource/loader/ModResourcePackCreator.java

@@ -68,12 +68,23 @@ public class ModResourcePackCreator implements ResourcePackProvider {
 		}
 	};
 	public static final ModResourcePackCreator CLIENT_RESOURCE_PACK_PROVIDER = new ModResourcePackCreator(ResourceType.CLIENT_RESOURCES);
-	private static final ResourcePackPosition ACTIVATION_INFO = new ResourcePackPosition(true, ResourcePackProfile.InsertionPosition.TOP, false);
+	/**
+	 * The maximum ammount of known data packs requested from the client, including vanilla data packs.
+	 */
+	public static final int MAX_KNOWN_PACKS = Integer.getInteger("fabric-resource-loader-v0:maxKnownPacks", 1024);
 
 	private final ResourceType type;
+	private final ResourcePackPosition activationInfo;
+	private final boolean forClientDataPackManager;
 
 	public ModResourcePackCreator(ResourceType type) {
+		this(type, false);
+	}
+
+	protected ModResourcePackCreator(ResourceType type, boolean forClientDataPackManager) {
 		this.type = type;
+		this.activationInfo = new ResourcePackPosition(!forClientDataPackManager, ResourcePackProfile.InsertionPosition.TOP, false);
+		this.forClientDataPackManager = forClientDataPackManager;
 	}
 
 	/**
@@ -106,7 +117,7 @@ public class ModResourcePackCreator implements ResourcePackProvider {
 				metadata,
 				new PlaceholderResourcePack.Factory(this.type, metadata),
 				this.type,
-				ACTIVATION_INFO
+				this.activationInfo
 		));
 
 		// Build a list of mod resource packs.
@@ -131,11 +142,14 @@ public class ModResourcePackCreator implements ResourcePackProvider {
 					pack.getInfo(),
 					new ModResourcePackFactory(pack),
 					this.type,
-					ACTIVATION_INFO
+					this.activationInfo
 			);
 
 			if (profile != null) {
-				((FabricResourcePackProfile) profile).fabric_setParentsPredicate(parents);
+				if (!forClientDataPackManager) {
+					((FabricResourcePackProfile) profile).fabric_setParentsPredicate(parents);
+				}
+
 				consumer.accept(profile);
 			}
 		}

fabric-resource-loader-v0/src/main/java/net/fabricmc/fabric/impl/resource/loader/ModResourcePackUtil.java

@@ -43,11 +43,14 @@ import net.minecraft.SharedConstants;
 import net.minecraft.resource.DataConfiguration;
 import net.minecraft.resource.DataPackSettings;
 import net.minecraft.resource.ResourcePack;
+import net.minecraft.resource.ResourcePackManager;
 import net.minecraft.resource.ResourcePackProfile;
 import net.minecraft.resource.ResourceType;
+import net.minecraft.resource.VanillaDataPackProvider;
 import net.minecraft.resource.featuretoggle.FeatureFlags;
 import net.minecraft.resource.metadata.PackResourceMetadata;
 import net.minecraft.text.Text;
+import net.minecraft.util.path.SymlinkFinder;
 
 import net.fabricmc.fabric.api.resource.ModResourcePack;
 import net.fabricmc.fabric.api.resource.ResourcePackActivationType;
@@ -233,4 +236,12 @@ public final class ModResourcePackUtil {
 
 		return new DataPackSettings(enabled, disabled);
 	}
+
+	/**
+	 * Creates the ResousePackManager used by the ClientDataPackManager and replaces
+	 * {@code VanillaDataPackProvider.createClientManager} used by vanilla.
+	 */
+	public static ResourcePackManager createClientManager() {
+		return new ResourcePackManager(new VanillaDataPackProvider(new SymlinkFinder((path) -> true)), new ModResourcePackCreator(ResourceType.SERVER_DATA, true));
+	}
 }

fabric-resource-loader-v0/src/main/java/net/fabricmc/fabric/impl/resource/loader/ResourceManagerHelperImpl.java

@@ -25,7 +25,6 @@ import java.util.Iterator;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
-import java.util.Optional;
 import java.util.Set;
 import java.util.function.Consumer;
 
@@ -119,7 +118,7 @@ public class ResourceManagerHelperImpl implements ResourceManagerHelper {
 						entry.getRight().getId(),
 						entry.getLeft(),
 						new BuiltinModResourcePackSource(pack.getFabricModMetadata().getName()),
-						Optional.empty()
+						entry.getRight().getKnownPackInfo()
 				);
 				ResourcePackPosition info2 = new ResourcePackPosition(
 						pack.getActivationType() == ResourcePackActivationType.ALWAYS_ENABLED,

fabric-resource-loader-v0/src/main/java/net/fabricmc/fabric/mixin/resource/loader/MinecraftServerMixin.java

@@ -16,22 +16,41 @@
 
 package net.fabricmc.fabric.mixin.resource.loader;
 
+import java.net.Proxy;
 import java.util.List;
 
+import com.mojang.datafixers.DataFixer;
 import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Unique;
 import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
 import org.spongepowered.asm.mixin.injection.Redirect;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
 
+import net.minecraft.registry.VersionedIdentifier;
 import net.minecraft.resource.ResourcePack;
 import net.minecraft.resource.ResourcePackManager;
 import net.minecraft.resource.ResourcePackProfile;
 import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.SaveLoader;
+import net.minecraft.server.WorldGenerationProgressListenerFactory;
+import net.minecraft.util.ApiServices;
+import net.minecraft.world.level.storage.LevelStorage;
 
 import net.fabricmc.fabric.impl.resource.loader.BuiltinModResourcePackSource;
+import net.fabricmc.fabric.impl.resource.loader.FabricOriginalKnownPacksGetter;
 import net.fabricmc.fabric.impl.resource.loader.ModNioResourcePack;
 
 @Mixin(MinecraftServer.class)
-public class MinecraftServerMixin {
+public class MinecraftServerMixin implements FabricOriginalKnownPacksGetter {
+	@Unique
+	private List<VersionedIdentifier> fabric_originalKnownPacks;
+
+	@Inject(method = "<init>", at = @At("TAIL"))
+	private void init(Thread serverThread, LevelStorage.Session session, ResourcePackManager dataPackManager, SaveLoader saveLoader, Proxy proxy, DataFixer dataFixer, ApiServices apiServices, WorldGenerationProgressListenerFactory worldGenerationProgressListenerFactory, CallbackInfo ci) {
+		this.fabric_originalKnownPacks = saveLoader.resourceManager().streamResourcePacks().flatMap(pack -> pack.getInfo().knownPackInfo().stream()).toList();
+	}
+
 	@Redirect(method = "loadDataPacks(Lnet/minecraft/resource/ResourcePackManager;Lnet/minecraft/resource/DataConfiguration;ZZ)Lnet/minecraft/resource/DataConfiguration;", at = @At(value = "INVOKE", target = "Ljava/util/List;contains(Ljava/lang/Object;)Z"))
 	private static boolean onCheckDisabled(List<String> list, Object o, ResourcePackManager resourcePackManager) {
 		String profileId = (String) o;
@@ -52,4 +71,9 @@ public class MinecraftServerMixin {
 
 		return false;
 	}
+
+	@Override
+	public List<VersionedIdentifier> fabric_getOriginalKnownPacks() {
+		return this.fabric_originalKnownPacks;
+	}
 }

fabric-resource-loader-v0/src/main/java/net/fabricmc/fabric/mixin/resource/loader/RegistryLoaderMixin.java

@@ -1,51 +0,0 @@
-/*
- * Copyright (c) 2016, 2017, 2018, 2019 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.mixin.resource.loader;
-
-import java.util.Optional;
-
-import com.llamalad7.mixinextras.injector.ModifyExpressionValue;
-import com.llamalad7.mixinextras.sugar.Local;
-import com.mojang.serialization.Lifecycle;
-import org.spongepowered.asm.mixin.Mixin;
-import org.spongepowered.asm.mixin.Unique;
-import org.spongepowered.asm.mixin.injection.At;
-
-import net.minecraft.registry.RegistryLoader;
-import net.minecraft.registry.entry.RegistryEntryInfo;
-import net.minecraft.resource.Resource;
-
-import net.fabricmc.fabric.api.resource.ModResourcePack;
-
-@Mixin(RegistryLoader.class)
-public class RegistryLoaderMixin {
-	@Unique
-	private static final RegistryEntryInfo MOD_PROVIDED_INFO = new RegistryEntryInfo(Optional.empty(), Lifecycle.stable());
-
-	// On the server side, loading mod-provided DRM entries should not show experiments screen.
-	// While the lifecycle is set to experimental on the client side (a de-sync),
-	// there is no good way to fix this without breaking protocol; the lifecycle seems to be unused on
-	// the client side anyway.
-	@ModifyExpressionValue(method = "loadFromResource(Lnet/minecraft/resource/ResourceManager;Lnet/minecraft/registry/RegistryOps$RegistryInfoGetter;Lnet/minecraft/registry/MutableRegistry;Lcom/mojang/serialization/Decoder;Ljava/util/Map;)V", at = @At(value = "INVOKE", target = "Ljava/util/function/Function;apply(Ljava/lang/Object;)Ljava/lang/Object;"))
-	private static Object markModProvidedAsStable(Object original, @Local Resource resource) {
-		if (original instanceof RegistryEntryInfo info && info.knownPackInfo().isEmpty() && resource.getPack() instanceof ModResourcePack) {
-			return MOD_PROVIDED_INFO;
-		}
-
-		return original;
-	}
-}

fabric-resource-loader-v0/src/main/java/net/fabricmc/fabric/mixin/resource/loader/SelectKnownPacksC2SPacketMixin.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 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.mixin.resource.loader;
+
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.ModifyArg;
+
+import net.minecraft.network.packet.c2s.config.SelectKnownPacksC2SPacket;
+
+import net.fabricmc.fabric.impl.resource.loader.ModResourcePackCreator;
+
+@Mixin(SelectKnownPacksC2SPacket.class)
+public class SelectKnownPacksC2SPacketMixin {
+	@ModifyArg(method = "<clinit>", at = @At(value = "INVOKE", target = "Lnet/minecraft/network/codec/PacketCodecs;toList(I)Lnet/minecraft/network/codec/PacketCodec$ResultFunction;"))
+	private static int setMaxKnownPacks(int constant) {
+		return ModResourcePackCreator.MAX_KNOWN_PACKS;
+	}
+}

fabric-resource-loader-v0/src/main/java/net/fabricmc/fabric/mixin/resource/loader/ServerConfigurationNetworkHandlerMixin.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 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.mixin.resource.loader;
+
+import java.util.List;
+
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.ModifyArg;
+
+import net.minecraft.network.ClientConnection;
+import net.minecraft.registry.VersionedIdentifier;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.network.ConnectedClientData;
+import net.minecraft.server.network.ServerCommonNetworkHandler;
+import net.minecraft.server.network.ServerConfigurationNetworkHandler;
+
+import net.fabricmc.fabric.impl.resource.loader.FabricOriginalKnownPacksGetter;
+
+@Mixin(ServerConfigurationNetworkHandler.class)
+public abstract class ServerConfigurationNetworkHandlerMixin extends ServerCommonNetworkHandler {
+	public ServerConfigurationNetworkHandlerMixin(MinecraftServer server, ClientConnection connection, ConnectedClientData clientData) {
+		super(server, connection, clientData);
+	}
+
+	/**
+	 * Only use packs that were enabled at server start and are enabled now. This avoids a descync when packs have been
+	 * enabled or disabled before the client joins. Since the server registry contents aren't reloaded, we don't want
+	 * the client to use the new data pack data.
+	 */
+	@ModifyArg(method = "sendConfigurations", at = @At(value = "INVOKE", target = "Lnet/minecraft/server/network/SynchronizeRegistriesTask;<init>(Ljava/util/List;Lnet/minecraft/registry/CombinedDynamicRegistries;)V", ordinal = 0))
+	public List<VersionedIdentifier> filterKnownPacks(List<VersionedIdentifier> currentKnownPacks) {
+		return ((FabricOriginalKnownPacksGetter) this.server).fabric_getOriginalKnownPacks().stream().filter(currentKnownPacks::contains).toList();
+	}
+}

fabric-resource-loader-v0/src/main/java/net/fabricmc/fabric/mixin/resource/loader/SynchronizeRegistriesTaskMixin.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 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.mixin.resource.loader;
+
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.function.Consumer;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.spongepowered.asm.mixin.Final;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.Unique;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+import net.minecraft.network.packet.Packet;
+import net.minecraft.network.packet.s2c.config.SelectKnownPacksS2CPacket;
+import net.minecraft.registry.VersionedIdentifier;
+import net.minecraft.server.network.SynchronizeRegistriesTask;
+
+import net.fabricmc.fabric.impl.resource.loader.ModResourcePackCreator;
+
+@Mixin(SynchronizeRegistriesTask.class)
+public abstract class SynchronizeRegistriesTaskMixin {
+	@Unique
+	private static final Logger LOGGER = LoggerFactory.getLogger("SynchronizeRegistriesTaskMixin");
+	@Shadow
+	@Final
+	private List<VersionedIdentifier> knownPacks;
+
+	@Shadow
+	protected abstract void syncRegistryAndTags(Consumer<Packet<?>> sender, Set<VersionedIdentifier> commonKnownPacks);
+
+	@Inject(method = "onSelectKnownPacks", at = @At("HEAD"), cancellable = true)
+	public void onSelectKnownPacks(List<VersionedIdentifier> clientKnownPacks, Consumer<Packet<?>> sender, CallbackInfo ci) {
+		if (new HashSet<>(this.knownPacks).containsAll(clientKnownPacks)) {
+			this.syncRegistryAndTags(sender, Set.copyOf(clientKnownPacks));
+			ci.cancel();
+		}
+	}
+
+	@Inject(method = "syncRegistryAndTags", at = @At("HEAD"))
+	public void syncRegistryAndTags(Consumer<Packet<?>> sender, Set<VersionedIdentifier> commonKnownPacks, CallbackInfo ci) {
+		LOGGER.debug("Syncronizing registries with common known packs: {}", commonKnownPacks);
+	}
+
+	@Inject(method = "sendPacket", at = @At("HEAD"), cancellable = true)
+	private void sendPacket(Consumer<Packet<?>> sender, CallbackInfo ci) {
+		if (this.knownPacks.size() > ModResourcePackCreator.MAX_KNOWN_PACKS) {
+			LOGGER.warn("Too many knownPacks: Found {}; max {}", this.knownPacks.size(), ModResourcePackCreator.MAX_KNOWN_PACKS);
+			sender.accept(new SelectKnownPacksS2CPacket(this.knownPacks.subList(0, ModResourcePackCreator.MAX_KNOWN_PACKS)));
+			ci.cancel();
+		}
+	}
+}

fabric-resource-loader-v0/src/main/resources/fabric-resource-loader-v0.mixins.json

@@ -7,12 +7,14 @@
     "KeyedResourceReloadListenerMixin",
     "LifecycledResourceManagerImplMixin",
     "MinecraftServerMixin",
-    "RegistryLoaderMixin",
     "ResourceMixin",
     "ResourcePackManagerMixin",
     "ResourcePackProfileMixin",
+    "SelectKnownPacksC2SPacketMixin",
+    "ServerConfigurationNetworkHandlerMixin",
     "ServerPropertiesHandlerMixin",
     "SimpleResourceReloadMixin",
+    "SynchronizeRegistriesTaskMixin",
     "TestServerMixin"
   ],
   "server": [

fabric-resource-loader-v0/src/testmod/java/net/fabricmc/fabric/test/mixin/resource/loader/SynchronizeRegistriesTaskMixin.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 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.test.mixin.resource.loader;
+
+import java.util.List;
+import java.util.Set;
+import java.util.function.Consumer;
+
+import org.spongepowered.asm.mixin.Final;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+import net.minecraft.network.packet.Packet;
+import net.minecraft.registry.VersionedIdentifier;
+import net.minecraft.server.network.SynchronizeRegistriesTask;
+
+import net.fabricmc.fabric.test.resource.loader.BuiltinResourcePackTestMod;
+
+@Mixin(SynchronizeRegistriesTask.class)
+public class SynchronizeRegistriesTaskMixin {
+	@Shadow
+	@Final
+	private List<VersionedIdentifier> knownPacks;
+
+	@Inject(method = "syncRegistryAndTags", at = @At("HEAD"))
+	public void syncRegistryAndTags(Consumer<Packet<?>> sender, Set<VersionedIdentifier> commonKnownPacks, CallbackInfo ci) {
+		BuiltinResourcePackTestMod.LOGGER.info("Syncronizing registries with common known packs: {}", commonKnownPacks);
+
+		if (!commonKnownPacks.containsAll(this.knownPacks)) {
+			BuiltinResourcePackTestMod.LOGGER.error("(Ignore when not local client) Not all server mod data packs known to client. Missing: {}", this.knownPacks.stream().filter(knownPack -> !commonKnownPacks.contains(knownPack)).toList());
+		}
+	}
+}

fabric-resource-loader-v0/src/testmod/java/net/fabricmc/fabric/test/resource/loader/BuiltinResourcePackTestMod.java

@@ -30,7 +30,7 @@ import net.fabricmc.loader.api.FabricLoader;
 public class BuiltinResourcePackTestMod implements ModInitializer {
 	public static final String MODID = "fabric-resource-loader-v0-testmod";
 
-	private static final Logger LOGGER = LoggerFactory.getLogger(BuiltinResourcePackTestMod.class);
+	public static final Logger LOGGER = LoggerFactory.getLogger(BuiltinResourcePackTestMod.class);
 
 	@Override
 	public void onInitialize() {

fabric-resource-loader-v0/src/testmod/resources/data/minecraft/wolf_variant/woods.json

@@ -0,0 +1,6 @@
+{
+  "wild_texture": "fabric-resource-loader-v0-testmod:entity/wolf/green",
+  "angry_texture": "fabric-resource-loader-v0-testmod:entity/wolf/green",
+  "tame_texture": "fabric-resource-loader-v0-testmod:entity/wolf/green",
+  "biomes": "minecraft:forest"
+}

fabric-resource-loader-v0/src/testmod/resources/fabric-resource-loader-v0-testmod.mixins.json

@@ -0,0 +1,13 @@
+{
+  "required": true,
+  "package": "net.fabricmc.fabric.test.mixin.resource.loader",
+  "compatibilityLevel": "JAVA_17",
+  "mixins": [
+    "SynchronizeRegistriesTaskMixin"
+  ],
+  "server": [
+  ],
+  "injectors": {
+    "defaultRequire": 1
+  }
+}

fabric-resource-loader-v0/src/testmod/resources/fabric.mod.json

@@ -17,5 +17,8 @@
     "server": [
       "net.fabricmc.fabric.test.resource.loader.LanguageTestMod"
     ]
-  }
+  },
+  "mixins": [
+    "fabric-resource-loader-v0-testmod.mixins.json"
+  ]
 }

fabric-resource-loader-v0/src/testmod/resources/resourcepacks/test2/data/minecraft/wolf_variant/woods.json

@@ -0,0 +1,6 @@
+{
+  "wild_texture": "fabric-resource-loader-v0-testmod:entity/wolf/pink",
+  "angry_texture": "fabric-resource-loader-v0-testmod:entity/wolf/pink",
+  "tame_texture": "fabric-resource-loader-v0-testmod:entity/wolf/pink",
+  "biomes": "minecraft:forest"
+}