Split client only code into its own sourceset. (#2179)

A common source of crashes on modded Minecraft servers comes from modders accidently calling client only code from the client, this PR is another large step towards elimitating that.

This PR has been months in the making and years in the planning, requiring major changes to Loom & Loader. In recent Minecraft versions Mojang has made it easier than ever to cleanly split the jar, going against the status-quo of merging the client and server into one jar.

From the start we have designed Fabric to have a very clear split between client and common (client & server) code. Fabric has always encoraged keeping client only code seprate from the server, this can be seen at a fundamental level with the entrypoints in Loader. Fabric API's have all been designed with this mind.

This PR provides a compile safety net around Fabric API using client only code on the server. Even though there are almost 400 changed files, minimal changes beyond moving the files were required to achieve this in Fabric API, thanks to the effort of all contributors in the past.

These changes should not affect modders or players in anyway, a single "universal" jar is still produced. Im happy to awnswer any questions.

build.gradle

@@ -9,7 +9,7 @@ plugins {
 	id "eclipse"
 	id "idea"
 	id "maven-publish"
-	id "fabric-loom" version "0.12.27" apply false
+	id "fabric-loom" version "0.12.38" apply false
 	id "com.diffplug.spotless" version "6.5.1"
 	id "org.ajoberstar.grgit" version "3.1.0"
 	id "com.matthewprenger.cursegradle" version "1.4.0"
@@ -63,10 +63,16 @@ def getBranch() {
 
 def moduleDependencies(project, List<String> depNames) {
 	def deps = depNames.iterator().collect { project.dependencies.project(path: ":$it", configuration: 'namedElements') }
+	def clientOutputs = depNames.iterator().collect { findProject(":$it").sourceSets.client.output }
+
 	project.dependencies {
 		deps.each {
 			api it
 		}
+
+		clientOutputs.each {
+			clientImplementation it
+		}
 	}
 
 	// As we manually handle the maven artifacts, we need to also manually specify the deps.
@@ -88,6 +94,21 @@ def moduleDependencies(project, List<String> depNames) {
 	}
 }
 
+def testDependencies(project, List<String> depNames) {
+	def deps = depNames.iterator().collect { project.dependencies.project(path: ":$it", configuration: 'namedElements') }
+	def clientOutputs = depNames.iterator().collect { findProject(":$it").sourceSets.client.output }
+
+	project.dependencies {
+		deps.each {
+			testmodImplementation it
+		}
+
+		clientOutputs.each {
+			testmodImplementation it
+		}
+	}
+}
+
 allprojects {
 	group = "net.fabricmc.fabric-api"
 
@@ -126,10 +147,22 @@ allprojects {
 		it.options.release = 17
 	}
 
+	java {
+		// Must be added before the split source sets are setup.
+		withSourcesJar()
+	}
+
+	loom {
+		splitEnvironmentSourceSets()
+	}
+
 	sourceSets {
 		testmod {
 			compileClasspath += main.compileClasspath
 			runtimeClasspath += main.runtimeClasspath
+
+			compileClasspath += client.compileClasspath
+			runtimeClasspath += client.runtimeClasspath
 		}
 	}
 
@@ -152,10 +185,26 @@ allprojects {
 		}
 	}
 
+	allprojects.each { p ->
+		if (project.name == "deprecated") return
+
+		loom.mods.register(p.name) {
+			sourceSet p.sourceSets.main
+			sourceSet p.sourceSets.client
+		}
+
+		loom.mods.register(p.name + "-testmod") {
+			sourceSet p.sourceSets.testmod
+		}
+	}
+
 	dependencies {
 		minecraft "com.mojang:minecraft:$rootProject.minecraft_version"
 		mappings "net.fabricmc:yarn:${rootProject.minecraft_version}${project.yarn_version}:v2"
 		modApi "net.fabricmc:fabric-loader:${project.loader_version}"
+
+		testmodImplementation sourceSets.main.output
+		testmodImplementation sourceSets.client.output
 	}
 
 	loom {
@@ -176,10 +225,6 @@ allprojects {
 		}
 	}
 
-	java {
-		withSourcesJar()
-	}
-
 	checkstyle {
 		configFile = rootProject.file("checkstyle.xml")
 		toolVersion = "9.1"
@@ -200,6 +245,19 @@ allprojects {
 	task generateResources {
 		group = "fabric"
 	}
+
+	task testmodJar(type: Jar) {
+		from sourceSets.testmod.output
+		destinationDirectory = new File(project.buildDir, "devlibs")
+		archiveClassifier = "testmod"
+	}
+
+	task remapTestmodJar(type: net.fabricmc.loom.task.RemapJarTask, dependsOn: testmodJar) {
+		input = testmodJar.archiveFile
+		archiveClassifier = "testmod"
+		addNestedDependencies = false
+	}
+	build.dependsOn remapTestmodJar
 }
 
 // Apply auxiliary buildscripts to submodules
@@ -226,10 +284,13 @@ javadoc {
 	}
 
 	allprojects.each {
+		if (it.name == "deprecated") return
+
 		source(it.sourceSets.main.allJava.srcDirs)
+		source(it.sourceSets.client.allJava.srcDirs)
 	}
 
-	classpath = sourceSets.main.compileClasspath
+	classpath = files(sourceSets.main.compileClasspath, sourceSets.client.compileClasspath)
 	include("**/api/**")
 	failOnError false
 }
@@ -305,9 +366,12 @@ subprojects {
 
 	afterEvaluate {
 		// Disable the gen sources task on sub projects
-		genSourcesWithFernFlower.enabled = false
-		genSourcesWithCfr.enabled = false
-		unpickJar.enabled = false
+		genClientOnlySourcesWithFernFlower.enabled = false
+		genClientOnlySourcesWithCfr.enabled = false
+		genCommonSourcesWithCfr.enabled = false
+		genCommonSourcesWithFernFlower.enabled = false
+		unpickClientOnlyJar.enabled = false
+		unpickCommonJar.enabled = false
 	}
 }
 
@@ -395,6 +459,7 @@ dependencies {
 			if (it.name == "deprecated") return
 
 			api project(path: "${it.path}", configuration: "namedElements")
+			clientImplementation project("${it.path}:").sourceSets.client.output
 
 			testmodImplementation project("${it.path}:").sourceSets.testmod.output
 		}

deprecated/fabric-containers-v0/src/main/java/net/fabricmc/fabric/api/container/ContainerProviderRegistry.java

@@ -24,7 +24,6 @@ import net.minecraft.server.network.ServerPlayerEntity;
 import net.minecraft.util.Identifier;
 import net.minecraft.network.PacketByteBuf;
 
-import net.fabricmc.fabric.api.client.screen.ScreenProviderRegistry;
 import net.fabricmc.fabric.impl.container.ContainerProviderImpl;
 
 /**
@@ -37,7 +36,7 @@ public interface ContainerProviderRegistry {
 	/**
 	 * Register a "packet buffer -> container" factory. This is used both on the client and server side.
 	 *
-	 * @param identifier a shared identifier, this identifier should also be used to register a container using {@link ScreenProviderRegistry}
+	 * @param identifier a shared identifier, this identifier should also be used to register a container using {@link net.fabricmc.fabric.api.client.screen.ScreenProviderRegistry}
 	 * @param factory    the ContainerFactory that should return a new {@link ScreenHandler}
 	 */
 	void registerFactory(Identifier identifier, ContainerFactory<ScreenHandler> factory);

deprecated/fabric-events-lifecycle-v0/src/main/java/net/fabricmc/fabric/api/event/world/WorldTickCallback.java

@@ -18,7 +18,6 @@ package net.fabricmc.fabric.api.event.world;
 
 import net.minecraft.world.World;
 
-import net.fabricmc.fabric.api.client.event.lifecycle.v1.ClientTickEvents;
 import net.fabricmc.fabric.api.event.Event;
 import net.fabricmc.fabric.api.event.EventFactory;
 import net.fabricmc.fabric.api.event.lifecycle.v1.ServerTickEvents;
@@ -27,7 +26,7 @@ import net.fabricmc.fabric.api.event.lifecycle.v1.ServerTickEvents;
 public interface WorldTickCallback {
 	/**
 	 * @deprecated The new WorldTickCallback has been split into a client and server callback.
-	 * Please use the {@link ServerTickEvents#END_WORLD_TICK server} or {@link ClientTickEvents#END_WORLD_TICK client} callbacks.
+	 * Please use the {@link ServerTickEvents#END_WORLD_TICK server} or {@link net.fabricmc.fabric.api.client.event.lifecycle.v1.ClientTickEvents#END_WORLD_TICK client} callbacks.
 	 */
 	@Deprecated
 	Event<WorldTickCallback> EVENT = EventFactory.createArrayBacked(WorldTickCallback.class,

deprecated/fabric-networking-v0/src/client/java/net/fabricmc/fabric/api/network/ClientSidePacketRegistry.java

@@ -23,7 +23,6 @@ import net.minecraft.network.Packet;
 import net.minecraft.util.Identifier;
 import net.minecraft.network.PacketByteBuf;
 
-import net.fabricmc.fabric.api.client.networking.v1.ClientPlayNetworking;
 import net.fabricmc.fabric.impl.networking.ClientSidePacketRegistryImpl;
 
 /**
@@ -34,7 +33,7 @@ import net.fabricmc.fabric.impl.networking.ClientSidePacketRegistryImpl;
  * <ul><li>registering client-side packet receivers (server -&gt; client packets)
  * <li>sending packets to the server (client -&gt; server packets).</ul>
  *
- * @deprecated Please migrate to {@link ClientPlayNetworking}.
+ * @deprecated Please migrate to {@link net.fabricmc.fabric.api.client.networking.v1.ClientPlayNetworking}.
  */
 @Deprecated
 public interface ClientSidePacketRegistry extends PacketRegistry {

deprecated/fabric-networking-v0/src/main/java/net/fabricmc/fabric/api/event/network/C2SPacketTypeCallback.java

@@ -21,7 +21,6 @@ import java.util.Collection;
 import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.util.Identifier;
 
-import net.fabricmc.fabric.api.client.networking.v1.C2SPlayChannelEvents;
 import net.fabricmc.fabric.api.event.Event;
 import net.fabricmc.fabric.api.event.EventFactory;
 import net.fabricmc.fabric.api.networking.v1.S2CPlayChannelEvents;
@@ -38,7 +37,7 @@ import net.fabricmc.fabric.api.networking.v1.S2CPlayChannelEvents;
 @Deprecated
 public interface C2SPacketTypeCallback {
 	/**
-	 * @deprecated Please migrate to {@link C2SPlayChannelEvents#REGISTER}.
+	 * @deprecated Please migrate to {@link net.fabricmc.fabric.api.client.networking.v1.C2SPlayChannelEvents#REGISTER}.
 	 */
 	@Deprecated
 	Event<C2SPacketTypeCallback> REGISTERED = EventFactory.createArrayBacked(
@@ -51,7 +50,7 @@ public interface C2SPacketTypeCallback {
 	);
 
 	/**
-	 * @deprecated Please migrate to {@link C2SPlayChannelEvents#UNREGISTER}.
+	 * @deprecated Please migrate to {@link net.fabricmc.fabric.api.client.networking.v1.C2SPlayChannelEvents#UNREGISTER}.
 	 */
 	@Deprecated
 	Event<C2SPacketTypeCallback> UNREGISTERED = EventFactory.createArrayBacked(

deprecated/fabric-networking-v0/src/main/java/net/fabricmc/fabric/api/event/network/S2CPacketTypeCallback.java

@@ -20,7 +20,6 @@ import java.util.Collection;
 
 import net.minecraft.util.Identifier;
 
-import net.fabricmc.fabric.api.client.networking.v1.C2SPlayChannelEvents;
 import net.fabricmc.fabric.api.event.Event;
 import net.fabricmc.fabric.api.event.EventFactory;
 import net.fabricmc.fabric.api.networking.v1.S2CPlayChannelEvents;
@@ -32,7 +31,7 @@ import net.fabricmc.fabric.api.networking.v1.S2CPlayChannelEvents;
  * <p>Registrations received will be for <em>client -&gt; server</em> packets
  * that the sending server can understand.
  *
- * @deprecated Please migrate to {@link C2SPlayChannelEvents} since this was incorrectly named.
+ * @deprecated Please migrate to {@link net.fabricmc.fabric.api.client.networking.v1.C2SPlayChannelEvents} since this was incorrectly named.
  */
 @Deprecated
 public interface S2CPacketTypeCallback {

deprecated/fabric-networking-v0/src/main/java/net/fabricmc/fabric/api/network/PacketConsumer.java

@@ -18,13 +18,12 @@ package net.fabricmc.fabric.api.network;
 
 import net.minecraft.network.PacketByteBuf;
 
-import net.fabricmc.fabric.api.client.networking.v1.ClientPlayNetworking;
 import net.fabricmc.fabric.api.networking.v1.ServerPlayNetworking;
 
 /**
  * Interface for receiving CustomPayload-based packets.
  *
- * @deprecated See the corresponding play packet handler in {@link ClientPlayNetworking} or {@link ServerPlayNetworking}
+ * @deprecated See the corresponding play packet handler in {@link net.fabricmc.fabric.api.client.networking.v1.ClientPlayNetworking} or {@link ServerPlayNetworking}
  */
 @Deprecated
 @FunctionalInterface

fabric-api-base/build.gradle

@@ -1,7 +1,7 @@
 archivesBaseName = "fabric-api-base"
 version = getSubprojectVersion(project)
 
-dependencies {
-	testmodImplementation project(path: ':fabric-command-api-v2', configuration: 'namedElements')
-	testmodImplementation project(path: ':fabric-lifecycle-events-v1', configuration: 'namedElements')
-}
+testDependencies(project, [
+	':fabric-command-api-v2',
+	':fabric-lifecycle-events-v1'
+])

fabric-api-lookup-api-v1/build.gradle

@@ -6,7 +6,7 @@ moduleDependencies(project, [
 	'fabric-lifecycle-events-v1'
 ])
 
-dependencies {
-	testmodImplementation project(path: ':fabric-rendering-v1', configuration: 'namedElements')
-	testmodImplementation project(path: ':fabric-object-builder-api-v1', configuration: 'namedElements')
-}
+testDependencies(project, [
+	':fabric-rendering-v1',
+	':fabric-object-builder-api-v1'
+])

fabric-biome-api-v1/build.gradle

@@ -5,7 +5,7 @@ loom {
     accessWidenerPath = file("src/main/resources/fabric-biome-api-v1.accesswidener")
 }
 
-dependencies {
-	testmodImplementation project(path: ':fabric-api-base', configuration: 'namedElements')
-	testmodImplementation project(path: ':fabric-resource-loader-v0', configuration: 'namedElements')
-}
+testDependencies(project, [
+	':fabric-api-base',
+	':fabric-resource-loader-v0'
+])

fabric-command-api-v2/build.gradle

@@ -1,14 +1,14 @@
 archivesBaseName = "fabric-command-api-v2"
 version = getSubprojectVersion(project)
 
-dependencies {
-	testmodImplementation project(path: ':fabric-lifecycle-events-v1', configuration: 'namedElements')
-}
-
 moduleDependencies(project, [
 		'fabric-api-base'
 ])
 
+testDependencies(project, [
+		':fabric-lifecycle-events-v1',
+])
+
 loom {
 	accessWidenerPath = file('src/main/resources/fabric-command-api-v2.accesswidener')
 }

fabric-command-api-v2/src/client/resources/fabric-command-api-v2.client.mixins.json

@@ -0,0 +1,14 @@
+{
+  "required": true,
+  "package": "net.fabricmc.fabric.mixin.command.client",
+  "compatibilityLevel": "JAVA_16",
+  "client": [
+    "ClientCommandSourceMixin",
+    "ClientPlayerEntityMixin",
+    "ClientPlayNetworkHandlerMixin",
+    "MinecraftClientMixin"
+  ],
+  "injectors": {
+    "defaultRequire": 1
+  }
+}

fabric-command-api-v2/src/main/resources/fabric-command-api-v2.mixins.json

@@ -6,12 +6,6 @@
     "CommandManagerMixin",
     "HelpCommandAccessor"
   ],
-  "client": [
-    "client.ClientCommandSourceMixin",
-    "client.ClientPlayerEntityMixin",
-    "client.ClientPlayNetworkHandlerMixin",
-    "client.MinecraftClientMixin"
-  ],
   "injectors": {
     "defaultRequire": 1
   }

fabric-command-api-v2/src/main/resources/fabric.mod.json

@@ -23,7 +23,11 @@
   "description": "Adds command-related hooks.",
   "accessWidener": "fabric-command-api-v2.accesswidener",
   "mixins": [
-    "fabric-command-api-v2.mixins.json"
+    "fabric-command-api-v2.mixins.json",
+    {
+      "config": "fabric-command-api-v2.client.mixins.json",
+      "environment": "client"
+    }
   ],
   "custom": {
     "fabric-api:module-lifecycle": "stable"

fabric-content-registries-v0/src/client/resources/fabric-content-registries-v0.client.mixins.json

@@ -0,0 +1,11 @@
+{
+  "required": true,
+  "package": "net.fabricmc.fabric.mixin.content.registry.client",
+  "compatibilityLevel": "JAVA_16",
+  "client": [
+    "MixinClientPlayNetworkHandler"
+  ],
+  "injectors": {
+    "defaultRequire": 1
+  }
+}

fabric-content-registries-v0/src/main/resources/fabric-content-registries-v0.mixins.json

@@ -11,9 +11,6 @@
     "OxidizableMixin",
     "ShovelItemAccessor"
   ],
-  "client": [
-    "client.MixinClientPlayNetworkHandler"
-  ],
   "injectors": {
     "defaultRequire": 1
   }

fabric-content-registries-v0/src/main/resources/fabric.mod.json

@@ -23,7 +23,11 @@
   },
   "description": "Adds registries for vanilla mechanics that are missing them.",
   "mixins": [
-    "fabric-content-registries-v0.mixins.json"
+    "fabric-content-registries-v0.mixins.json",
+    {
+      "config": "fabric-content-registries-v0.client.mixins.json",
+      "environment": "client"
+    }
   ],
   "accessWidener" : "fabric-content-registries-v0.accesswidener",
   "custom": {

fabric-data-generation-api-v1/src/client/resources/fabric-data-generation-api-v1.client.mixins.json

@@ -0,0 +1,11 @@
+{
+  "required": true,
+  "package": "net.fabricmc.fabric.mixin.datagen.client",
+  "compatibilityLevel": "JAVA_16",
+  "client": [
+    "MinecraftClientMixin"
+  ],
+  "injectors": {
+    "defaultRequire": 1
+  }
+}

fabric-data-generation-api-v1/src/main/resources/fabric-data-generation-api-v1.mixins.json

@@ -8,9 +8,6 @@
     "DynamicRegistryManagerAccessor",
     "TagBuilderMixin"
   ],
-  "client": [
-    "client.MinecraftClientMixin"
-  ],
   "server": [
     "server.MainMixin"
   ],

fabric-data-generation-api-v1/src/main/resources/fabric.mod.json

@@ -20,7 +20,11 @@
   },
   "description": "Allows for automatic data generation.",
   "mixins": [
-    "fabric-data-generation-api-v1.mixins.json"
+    "fabric-data-generation-api-v1.mixins.json",
+    {
+      "config": "fabric-data-generation-api-v1.client.mixins.json",
+      "environment": "client"
+    }
   ],
   "accessWidener" : "fabric-data-generation-api-v1.accesswidener",
   "custom": {

fabric-dimensions-v1/build.gradle

@@ -1,12 +1,12 @@
 archivesBaseName = "fabric-dimensions-v1"
 version = getSubprojectVersion(project)
 
-dependencies {
-	testmodImplementation project(path: ':fabric-command-api-v2', configuration: 'namedElements')
-	testmodImplementation project(path: ':fabric-resource-loader-v0', configuration: 'namedElements')
-	testmodImplementation project(path: ':fabric-lifecycle-events-v1', configuration: 'namedElements')
-}
-
 moduleDependencies(project, [
 		'fabric-api-base'
 ])
+
+testDependencies(project, [
+	':fabric-command-api-v2',
+	':fabric-resource-loader-v0',
+	':fabric-lifecycle-events-v1'
+])

fabric-entity-events-v1/build.gradle

@@ -5,9 +5,9 @@ moduleDependencies(project, [
 		'fabric-api-base'
 ])
 
-dependencies {
-	testmodImplementation project(path: ':fabric-command-api-v2', configuration: 'namedElements')
-	testmodImplementation project(path: ':fabric-networking-api-v1', configuration: 'namedElements')
-	testmodImplementation project(path: ':fabric-registry-sync-v0', configuration: 'namedElements')
-	testmodImplementation project(path: ':fabric-rendering-v1', configuration: 'namedElements')
-}
+testDependencies(project, [
+	':fabric-command-api-v2',
+	':fabric-networking-api-v1',
+	':fabric-registry-sync-v0',
+	':fabric-rendering-v1'
+])

fabric-entity-events-v1/src/client/resources/fabric-entity-events-v1.client.mixins.json

@@ -0,0 +1,12 @@
+{
+  "required": true,
+  "package": "net.fabricmc.fabric.mixin.entity.event",
+  "compatibilityLevel": "JAVA_16",
+  "client": [
+    "elytra.ClientPlayerEntityMixin"
+  ],
+  "injectors": {
+    "defaultRequire": 1,
+    "maxShiftBy": 3
+  }
+}

fabric-entity-events-v1/src/main/resources/fabric-entity-events-v1.mixins.json

@@ -12,9 +12,6 @@
     "ServerPlayerEntityMixin",
     "TeleportCommandMixin"
   ],
-  "client": [
-    "elytra.ClientPlayerEntityMixin"
-  ],
   "injectors": {
     "defaultRequire": 1,
     "maxShiftBy": 3

fabric-entity-events-v1/src/main/resources/fabric.mod.json

@@ -20,7 +20,11 @@
   },
   "description": "Events to hook into entities.",
   "mixins": [
-    "fabric-entity-events-v1.mixins.json"
+    "fabric-entity-events-v1.mixins.json",
+    {
+      "config": "fabric-entity-events-v1.client.mixins.json",
+      "environment": "client"
+    }
   ],
   "custom": {
     "fabric-api:module-lifecycle": "stable"

fabric-events-interaction-v0/src/client/java/net/fabricmc/fabric/mixin/event/interaction/client/MixinClientPlayerInteractionManager.java

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package net.fabricmc.fabric.mixin.event.interaction;
+package net.fabricmc.fabric.mixin.event.interaction.client;
 
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.Shadow;

fabric-events-interaction-v0/src/client/java/net/fabricmc/fabric/mixin/event/interaction/client/MixinMinecraftClient.java

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package net.fabricmc.fabric.mixin.event.interaction;
+package net.fabricmc.fabric.mixin.event.interaction.client;
 
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.Shadow;

fabric-events-interaction-v0/src/client/resources/fabric-events-interaction-v0.client.mixins.json

@@ -0,0 +1,12 @@
+{
+  "required": true,
+  "package": "net.fabricmc.fabric.mixin.event.interaction.client",
+  "compatibilityLevel": "JAVA_16",
+  "client": [
+    "MixinClientPlayerInteractionManager",
+    "MixinMinecraftClient"
+  ],
+  "injectors": {
+    "defaultRequire": 1
+  }
+}

fabric-events-interaction-v0/src/main/resources/fabric-events-interaction-v0.mixins.json

@@ -7,10 +7,6 @@
     "MixinServerPlayerInteractionManager",
     "MixinServerPlayNetworkHandler"
   ],
-  "client": [
-    "MixinClientPlayerInteractionManager",
-    "MixinMinecraftClient"
-  ],
   "injectors": {
     "defaultRequire": 1
   }

fabric-events-interaction-v0/src/main/resources/fabric.mod.json

@@ -30,7 +30,11 @@
   },
   "description": "Events for player interaction with blocks and entities.",
   "mixins": [
-    "fabric-events-interaction-v0.mixins.json"
+    "fabric-events-interaction-v0.mixins.json",
+    {
+      "config": "fabric-events-interaction-v0.client.mixins.json",
+      "environment": "client"
+    }
   ],
   "custom": {
     "fabric-api:module-lifecycle": "stable"

fabric-game-rule-api-v1/build.gradle

@@ -5,8 +5,8 @@ loom {
 	accessWidenerPath = file("src/main/resources/fabric-game-rule-api-v1.accesswidener")
 }
 
-dependencies {
-	testmodImplementation project(path: ':fabric-api-base', configuration: 'namedElements')
-	testmodImplementation project(path: ':fabric-lifecycle-events-v1', configuration: 'namedElements')
-	testmodImplementation project(path: ':fabric-resource-loader-v0', configuration: 'namedElements')
-}
+testDependencies(project, [
+	':fabric-api-base',
+	':fabric-lifecycle-events-v1',
+	':fabric-resource-loader-v0'
+])

fabric-game-rule-api-v1/src/client/resources/fabric-game-rule-api-v1.client.mixins.json

@@ -0,0 +1,13 @@
+{
+  "required": true,
+  "package": "net.fabricmc.fabric.mixin.gamerule.client",
+  "compatibilityLevel": "JAVA_16",
+  "client": [
+    "EditGameRulesScreenAccessor",
+    "RuleListWidgetMixin",
+    "RuleListWidgetVisitorMixin"
+  ],
+  "injectors": {
+    "defaultRequire": 1
+  }
+}

fabric-game-rule-api-v1/src/main/resources/fabric-game-rule-api-v1.mixins.json

@@ -10,11 +10,6 @@
     "IntRuleAccessor",
     "RuleKeyMixin"
   ],
-  "client": [
-    "client.EditGameRulesScreenAccessor",
-    "client.RuleListWidgetMixin",
-    "client.RuleListWidgetVisitorMixin"
-  ],
   "injectors": {
     "defaultRequire": 1
   }

fabric-game-rule-api-v1/src/main/resources/fabric.mod.json

@@ -20,7 +20,11 @@
   },
   "description": "Allows registration of custom game rules.",
   "mixins": [
-    "fabric-game-rule-api-v1.mixins.json"
+    "fabric-game-rule-api-v1.mixins.json",
+    {
+      "config": "fabric-game-rule-api-v1.client.mixins.json",
+      "environment": "client"
+    }
   ],
   "accessWidener" : "fabric-game-rule-api-v1.accesswidener",
   "custom": {

fabric-item-api-v1/src/client/resources/fabric-item-api-v1.client.mixins.json

@@ -0,0 +1,13 @@
+{
+  "required": true,
+  "package": "net.fabricmc.fabric.mixin.item.client",
+  "compatibilityLevel": "JAVA_16",
+  "client": [
+    "ClientPlayerInteractionManagerMixin",
+    "HeldItemRendererMixin",
+    "ItemStackMixin"
+  ],
+  "injectors": {
+    "defaultRequire": 1
+  }
+}

fabric-item-api-v1/src/main/java/net/fabricmc/fabric/api/item/v1/FabricItem.java

@@ -19,7 +19,6 @@ package net.fabricmc.fabric.api.item.v1;
 import com.google.common.collect.Multimap;
 
 import net.minecraft.block.BlockState;
-import net.minecraft.client.network.ClientPlayerEntity;
 import net.minecraft.entity.EquipmentSlot;
 import net.minecraft.entity.attribute.EntityAttribute;
 import net.minecraft.entity.attribute.EntityAttributeModifier;
@@ -42,7 +41,7 @@ public interface FabricItem {
 	 * This function is called on the client side when the NBT or count of the stack has changed, but not the item,
 	 * and returning false cancels this animation.
 	 *
-	 * @param player   the current player; this may be safely cast to {@link ClientPlayerEntity} in client-only code
+	 * @param player   the current player; this may be safely cast to {@link net.minecraft.client.network.ClientPlayerEntity} in client-only code
 	 * @param hand     the hand; this function applies both to the main hand and the off hand
 	 * @param oldStack the previous stack, of this item
 	 * @param newStack the new stack, also of this item

fabric-item-api-v1/src/main/resources/fabric-item-api-v1.mixins.json

@@ -7,11 +7,6 @@
     "ItemMixin",
     "LivingEntityMixin"
   ],
-  "client": [
-    "client.ClientPlayerInteractionManagerMixin",
-    "client.HeldItemRendererMixin",
-    "client.ItemStackMixin"
-  ],
   "injectors": {
     "defaultRequire": 1
   }

fabric-item-api-v1/src/main/resources/fabric.mod.json

@@ -16,7 +16,11 @@
     "FabricMC"
   ],
   "mixins": [
-    "fabric-item-api-v1.mixins.json"
+    "fabric-item-api-v1.mixins.json",
+    {
+      "config": "fabric-item-api-v1.client.mixins.json",
+      "environment": "client"
+    }
   ],
   "depends": {
     "fabricloader": ">=0.4.0",

fabric-item-groups-v0/src/client/resources/fabric-item-groups-v0.client.mixins.json

@@ -0,0 +1,12 @@
+{
+  "required": true,
+  "package": "net.fabricmc.fabric.mixin.item.group.client",
+  "compatibilityLevel": "JAVA_16",
+  "client": [
+    "MixinItemGroup",
+    "MixinCreativePlayerInventoryGui"
+  ],
+  "injectors": {
+    "defaultRequire": 1
+  }
+}

fabric-item-groups-v0/src/main/resources/fabric-item-groups-v0.mixins.json

@@ -5,10 +5,6 @@
   "mixins": [
     "MixinItemGroup"
   ],
-  "client": [
-    "client.MixinItemGroup",
-    "client.MixinCreativePlayerInventoryGui"
-  ],
   "injectors": {
     "defaultRequire": 1
   }

fabric-item-groups-v0/src/main/resources/fabric.mod.json

@@ -23,7 +23,11 @@
   },
   "description": "An API for adding custom item groups.",
   "mixins": [
-    "fabric-item-groups-v0.mixins.json"
+    "fabric-item-groups-v0.mixins.json",
+    {
+      "config": "fabric-item-groups-v0.client.mixins.json",
+      "environment": "client"
+    }
   ],
   "custom": {
     "fabric-api:module-lifecycle": "stable"

fabric-key-binding-api-v1/build.gradle

@@ -1,8 +1,8 @@
 archivesBaseName = "fabric-key-binding-api-v1"
 version = getSubprojectVersion(project)
 
-dependencies {
-	testmodImplementation project(path: ':fabric-api-base', configuration: 'namedElements')
-	testmodImplementation project(path: ':fabric-lifecycle-events-v1', configuration: 'namedElements')
-	testmodImplementation project(path: ':fabric-resource-loader-v0', configuration: 'namedElements')
-}
+testDependencies(project, [
+	':fabric-api-base',
+	':fabric-lifecycle-events-v1',
+	':fabric-resource-loader-v0'
+])