Add Forge dependencies using the userdev jar

src/main/java/net/fabricmc/loom/AbstractPlugin.java

@@ -51,6 +51,7 @@ import org.gradle.plugins.ide.idea.model.IdeaModel;
 
 import net.fabricmc.loom.providers.ForgeProvider;
 import net.fabricmc.loom.providers.ForgeUniversalProvider;
+import net.fabricmc.loom.providers.ForgeUserdevProvider;
 import net.fabricmc.loom.providers.LaunchProvider;
 import net.fabricmc.loom.providers.MappingsCache;
 import net.fabricmc.loom.providers.MappingsProvider;
@@ -128,12 +129,18 @@ public class AbstractPlugin implements Plugin<Project> {
 		if (project.getExtensions().getByType(LoomGradleExtension.class).isForge()) {
 			Configuration forgeConfig = project.getConfigurations().maybeCreate(Constants.FORGE);
 			forgeConfig.setTransitive(false);
+			Configuration forgeUserdevConfig = project.getConfigurations().maybeCreate(Constants.FORGE_USERDEV);
+			forgeUserdevConfig.setTransitive(false);
 			Configuration forgeInstallerConfig = project.getConfigurations().maybeCreate(Constants.FORGE_INSTALLER);
 			forgeInstallerConfig.setTransitive(false);
 			Configuration forgeUniversalConfig = project.getConfigurations().maybeCreate(Constants.FORGE_UNIVERSAL);
 			forgeUniversalConfig.setTransitive(false);
+			Configuration forgeDependencies = project.getConfigurations().maybeCreate(Constants.FORGE_DEPENDENCIES);
+			forgeDependencies.setTransitive(false);
 			Configuration mcpConfig = project.getConfigurations().maybeCreate(Constants.MCP_CONFIG);
 			mcpConfig.setTransitive(false);
+
+			extendsFrom(Constants.MINECRAFT_DEPENDENCIES, Constants.FORGE_DEPENDENCIES);
 		}
 
 		Configuration includeConfig = project.getConfigurations().maybeCreate(Constants.INCLUDE);
@@ -248,8 +255,9 @@ public class AbstractPlugin implements Plugin<Project> {
 			extension.setDependencyManager(dependencyManager);
 
 			if (extension.isForge()) {
-				dependencyManager.addProvider(new McpConfigProvider(getProject()));
 				dependencyManager.addProvider(new ForgeProvider(getProject()));
+				dependencyManager.addProvider(new ForgeUserdevProvider(getProject()));
+				dependencyManager.addProvider(new McpConfigProvider(getProject()));
 				dependencyManager.addProvider(new PatchProvider(getProject()));
 				dependencyManager.addProvider(new ForgeUniversalProvider(getProject()));
 			}

src/main/java/net/fabricmc/loom/providers/ForgeProvider.java

@@ -38,12 +38,8 @@ public class ForgeProvider extends DependencyProvider {
 
 	@Override
 	public void provide(DependencyInfo dependency, Consumer<Runnable> postPopulationScheduler) throws Exception {
-		addDependency(dependency.getDepString() + ":universal", Constants.FORGE_UNIVERSAL);
-		addDependency(dependency.getDepString() + ":launcher", Constants.MINECRAFT_DEPENDENCIES);
+		addDependency(dependency.getDepString() + ":userdev", Constants.FORGE_USERDEV);
 		addDependency(dependency.getDepString() + ":installer", Constants.FORGE_INSTALLER);
-
-		addDependency("net.minecraftforge:eventbus:3.0.2", Constants.MINECRAFT_DEPENDENCIES);
-		addDependency("net.minecraftforge:forgespi:3.0.0", Constants.MINECRAFT_DEPENDENCIES);
 	}
 
 	@Override

src/main/java/net/fabricmc/loom/providers/ForgeUniversalProvider.java

@@ -45,7 +45,7 @@ public class ForgeUniversalProvider extends DependencyProvider {
 		forge = new File(getExtension().getProjectPersistentCache(), "forge-" + dependency.getDependency().getVersion() + ".jar");
 
 		if (!forge.exists() || isRefreshDeps()) {
-			File dep = dependency.resolveFile().orElseThrow(() -> new IllegalStateException("Could not resolve Forge"));
+			File dep = dependency.resolveFile().orElseThrow(() -> new RuntimeException("Could not resolve Forge"));
 			Files.copy(dep, forge);
 		}
 	}

src/main/java/net/fabricmc/loom/providers/ForgeUserdevProvider.java

@@ -0,0 +1,80 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2016, 2017, 2018 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.providers;
+
+import java.io.File;
+import java.io.Reader;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.function.Consumer;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import org.gradle.api.Project;
+
+import net.fabricmc.loom.util.Constants;
+import net.fabricmc.loom.util.DependencyProvider;
+
+public class ForgeUserdevProvider extends DependencyProvider {
+	public ForgeUserdevProvider(Project project) {
+		super(project);
+	}
+
+	@Override
+	public void provide(DependencyInfo dependency, Consumer<Runnable> postPopulationScheduler) throws Exception {
+		Path configJson = getExtension()
+				.getProjectPersistentCache()
+				.toPath()
+				.resolve("forge-config-" + dependency.getDependency().getVersion() + ".json");
+
+		if (Files.notExists(configJson) || isRefreshDeps()) {
+			File resolved = dependency.resolveFile().orElseThrow(() -> new RuntimeException("Could not resolve Forge userdev"));
+			Files.copy(resolved.toPath(), configJson);
+		}
+
+		JsonObject json;
+
+		try (Reader reader = Files.newBufferedReader(configJson)) {
+			json = new Gson().fromJson(reader, JsonObject.class);
+		}
+
+		addDependency(json.get("mcp").getAsString(), Constants.MCP_CONFIG);
+		addDependency(json.get("universal").getAsString(), Constants.FORGE_UNIVERSAL);
+
+		for (JsonElement lib : json.get("libraries").getAsJsonArray()) {
+			addDependency(lib.getAsString(), Constants.FORGE_DEPENDENCIES);
+		}
+
+		// TODO: Read launch configs from the JSON too
+		// TODO: Should I copy the patches from here as well?
+		//       That'd require me to run the "MCP environment" fully up to merging.
+	}
+
+	@Override
+	public String getTargetConfig() {
+		return Constants.FORGE_USERDEV;
+	}
+}

src/main/java/net/fabricmc/loom/providers/McpConfigProvider.java

@@ -55,7 +55,7 @@ public class McpConfigProvider extends DependencyProvider {
 			return; // No work for us to do here
 		}
 
-		Path mcpZip = dependency.resolveFile().orElseThrow(() -> new IllegalStateException("Could not resolve MCPConfig")).toPath();
+		Path mcpZip = dependency.resolveFile().orElseThrow(() -> new RuntimeException("Could not resolve MCPConfig")).toPath();
 
 		if (!mcp.exists() || isRefreshDeps()) {
 			Files.copy(mcpZip, mcp.toPath(), StandardCopyOption.REPLACE_EXISTING);

src/main/java/net/fabricmc/loom/providers/PatchProvider.java

@@ -54,7 +54,7 @@ public class PatchProvider extends DependencyProvider {
 		if (Files.notExists(clientPatches) || Files.notExists(serverPatches) || isRefreshDeps()) {
 			getProject().getLogger().info(":extracting forge patches");
 
-			Path installerJar = dependency.resolveFile().orElseThrow(() -> new IllegalStateException("Could not resolve Forge installer")).toPath();
+			Path installerJar = dependency.resolveFile().orElseThrow(() -> new RuntimeException("Could not resolve Forge installer")).toPath();
 
 			try (FileSystem fs = FileSystems.newFileSystem(new URI("jar:" + installerJar.toUri()), ImmutableMap.of("create", false))) {
 				Files.copy(fs.getPath("data", "client.lzma"), clientPatches, StandardCopyOption.REPLACE_EXISTING);

src/main/java/net/fabricmc/loom/util/Constants.java

@@ -55,8 +55,10 @@ public class Constants {
 	public static final String MAPPINGS_FINAL = "mappingsFinal";
 	public static final String MCP_CONFIG = "mcp";
 	public static final String FORGE = "forge";
+	public static final String FORGE_USERDEV = "forgeUserdev";
 	public static final String FORGE_INSTALLER = "forgeInstaller";
 	public static final String FORGE_UNIVERSAL = "forgeUniversal";
+	public static final String FORGE_DEPENDENCIES = "forgeDependencies";
 
 	public static final String MIXIN_COMPILE_EXTENSIONS_VERSION = "0.3.1.5";
 	public static final String DEV_LAUNCH_INJECTOR_VERSION = "0.2.1+build.8";