Support for FG2-era Forge

build.gradle

@@ -126,6 +126,7 @@ dependencies {
 	}
 	testImplementation 'io.javalin:javalin:3.13.11'
 	testImplementation 'net.fabricmc:fabric-installer:0.9.0'
+	runtimeOnly 'dev.architectury.architectury-pack200:dev.architectury.architectury-pack200.gradle.plugin:0.1.3'
 
 	compileOnly 'org.jetbrains:annotations:22.0.0'
 }

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

@@ -139,6 +139,14 @@ default boolean isForgeAndNotOfficial() {
 		return isForge() && !getMcpConfigProvider().isOfficial();
 	}
 
+	default boolean isLegacyForge() {
+		return isForge() && getForgeUserdevProvider().isLegacyForge();
+	}
+
+	default boolean isModernForge() {
+		return isForge() && !isLegacyForge();
+	}
+
 	boolean supportsInclude();
 
 	default SrgProvider getSrgProvider() {

src/main/java/net/fabricmc/loom/api/ForgeExtensionAPI.java

@@ -33,6 +33,8 @@
 import org.gradle.api.provider.SetProperty;
 import org.jetbrains.annotations.ApiStatus;
 
+import net.fabricmc.loom.configuration.providers.forge.fg2.Pack200Provider;
+
 /**
  * This is the forge extension api available exposed to build scripts.
  */
@@ -148,4 +150,6 @@ interface DataGenConsumer {
 	 * @see ForgeLocalMod
 	 */
 	NamedDomainObjectContainer<ForgeLocalMod> getLocalMods();
+
+	Property<Pack200Provider> getPack200Provider();
 }

src/main/java/net/fabricmc/loom/build/ModCompileRemapper.java

@@ -181,7 +181,7 @@ private static boolean shouldRemapMod(Logger logger, File artifact, Object id, b
 			}
 
 			if (forge) {
-				if (zipFile.getEntry("META-INF/mods.toml") != null) {
+				if (zipFile.getEntry("META-INF/mods.toml") != null || zipFile.getEntry("mcmod.info") != null) {
 					logger.info("Found Forge mod in " + config + ": {}", id);
 					return true;
 				}

src/main/java/net/fabricmc/loom/configuration/CompileConfiguration.java

@@ -198,9 +198,9 @@ public static void configureCompile(Project p) {
 			}
 
 			if (extension.isForge()) {
+				dependencyManager.addProvider(new ForgeUniversalProvider(project));
 				dependencyManager.addProvider(new McpConfigProvider(project));
 				dependencyManager.addProvider(new PatchProvider(project));
-				dependencyManager.addProvider(new ForgeUniversalProvider(project));
 			}
 
 			dependencyManager.addProvider(extension.isForge() ? new FieldMigratedMappingsProvider(project) : new MappingsProviderImpl(project));

src/main/java/net/fabricmc/loom/configuration/providers/LaunchProvider.java

@@ -31,7 +31,7 @@
 import java.nio.file.Files;
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.HashMap;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -66,15 +66,15 @@ public void provide(DependencyInfo dependency, Consumer<Runnable> postPopulation
 				.property("client", "java.library.path", getExtension().getMinecraftProvider().nativesDir().getAbsolutePath())
 				.property("client", "org.lwjgl.librarypath", getExtension().getMinecraftProvider().nativesDir().getAbsolutePath());
 
-		if (!getExtension().isForge()) {
+		if (!getExtension().isModernForge()) {
 			launchConfig
 					.argument("client", "--assetIndex")
 					.argument("client", getExtension().getMinecraftProvider().getVersionInfo().assetIndex().fabricId(getExtension().getMinecraftProvider().minecraftVersion()))
 					.argument("client", "--assetsDir")
 					.argument("client", new File(getDirectories().getUserCache(), "assets").getAbsolutePath());
 		}
 
-		if (getExtension().isForge()) {
+		if (getExtension().isModernForge()) {
 			launchConfig
 					// Should match YarnNamingService.PATH_TO_MAPPINGS in forge-runtime
 					.property("fabric.yarnWithSrg.path", getExtension().getMappingsProvider().tinyMappingsWithSrg.toAbsolutePath().toString())
@@ -103,11 +103,29 @@ public void provide(DependencyInfo dependency, Consumer<Runnable> postPopulation
 			}
 		}
 
+		if (getExtension().isLegacyForge()) {
+			launchConfig
+					.argument("client", "--tweakClass")
+					.argument("client", Constants.LegacyForge.FML_TWEAKER)
+					.argument("server", "--tweakClass")
+					.argument("server", Constants.LegacyForge.FML_SERVER_TWEAKER)
+
+					.argument("--accessToken")
+					.argument("undefined")
+
+					.property("net.minecraftforge.gradle.GradleStart.srg.srg-mcp", getExtension().getMappingsProvider().srgToNamedSrg.toAbsolutePath().toString())
+					.property("mixin.env.remapRefMap", "true");
+
+			for (String config : PropertyUtil.getAndFinalize(getExtension().getForge().getMixinConfigs())) {
+				launchConfig.argument("--mixin").argument(config);
+			}
+		}
+
 		addDependency(Constants.Dependencies.DEV_LAUNCH_INJECTOR + Constants.Dependencies.Versions.DEV_LAUNCH_INJECTOR, Constants.Configurations.LOOM_DEVELOPMENT_DEPENDENCIES);
 		addDependency(Constants.Dependencies.TERMINAL_CONSOLE_APPENDER + Constants.Dependencies.Versions.TERMINAL_CONSOLE_APPENDER, Constants.Configurations.LOOM_DEVELOPMENT_DEPENDENCIES);
 		addDependency(Constants.Dependencies.JETBRAINS_ANNOTATIONS + Constants.Dependencies.Versions.JETBRAINS_ANNOTATIONS, JavaPlugin.COMPILE_ONLY_CONFIGURATION_NAME);
 
-		if (getExtension().isForge()) {
+		if (getExtension().isModernForge()) {
 			addDependency(Constants.Dependencies.FORGE_RUNTIME + Constants.Dependencies.Versions.FORGE_RUNTIME, Constants.Configurations.FORGE_EXTRA);
 			addDependency(Constants.Dependencies.JAVAX_ANNOTATIONS + Constants.Dependencies.Versions.JAVAX_ANNOTATIONS, JavaPlugin.COMPILE_ONLY_CONFIGURATION_NAME);
 		}
@@ -197,7 +215,7 @@ public String getTargetConfig() {
 	}
 
 	public static class LaunchConfig {
-		private final Map<String, List<String>> values = new HashMap<>();
+		private final Map<String, List<String>> values = new LinkedHashMap<>();
 
 		public LaunchConfig property(String key, String value) {
 			return property("common", key, value);

src/main/java/net/fabricmc/loom/configuration/providers/forge/FieldMigratedMappingsProvider.java

@@ -109,14 +109,21 @@ protected String createMappingsIdentifier(String mappingsName, String version, S
 	public void manipulateMappings(Path mappingsJar) throws IOException {
 		Stopwatch stopwatch = Stopwatch.createStarted();
 		LoomGradleExtension extension = getExtension();
+
+		if (extension.isLegacyForge()) {
+			// Legacy forge patches are in official namespace, so if the type of a field is changed by them, then that
+			// is effectively a new field and not traceable to any mapping. Therefore this does not apply to it.
+			return;
+		}
+
 		this.rawTinyMappings = tinyMappings;
 		this.rawTinyMappingsWithSrg = tinyMappingsWithSrg;
 		String mappingsJarName = mappingsJar.getFileName().toString();
 
 		if (getExtension().shouldGenerateSrgTiny()) {
 			if (Files.notExists(rawTinyMappingsWithSrg) || isRefreshDeps()) {
 				// Merge tiny mappings with srg
-				SrgMerger.mergeSrg(getProject().getLogger(), getExtension().getMappingsProvider()::getMojmapSrgFileIfPossible, getRawSrgFile(), rawTinyMappings, rawTinyMappingsWithSrg, true);
+				SrgMerger.mergeSrg(getProject().getLogger(), getExtension().getMappingsProvider()::getMojmapSrgFileIfPossible, getRawSrgFile(), rawTinyMappings, rawTinyMappingsWithSrg, true, false);
 			}
 		}
 

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

@@ -50,6 +50,7 @@
 import org.gradle.api.Project;
 import org.gradle.api.artifacts.Dependency;
 import org.gradle.api.artifacts.ModuleDependency;
+import org.gradle.api.artifacts.repositories.IvyArtifactRepository;
 import org.gradle.api.artifacts.transform.InputArtifact;
 import org.gradle.api.artifacts.transform.TransformAction;
 import org.gradle.api.artifacts.transform.TransformOutputs;
@@ -72,6 +73,7 @@ public class ForgeUserdevProvider extends DependencyProvider {
 	private File userdevJar;
 	private JsonObject json;
 	private Consumer<Runnable> postPopulationScheduler;
+	private boolean isLegacyForge;
 
 	public ForgeUserdevProvider(Project project) {
 		super(project);
@@ -99,19 +101,46 @@ public void provide(DependencyInfo dependency, Consumer<Runnable> postPopulation
 			Files.copy(resolved.toPath(), userdevJar.toPath(), StandardCopyOption.REPLACE_EXISTING);
 
 			try (FileSystem fs = FileSystems.newFileSystem(new URI("jar:" + resolved.toURI()), ImmutableMap.of("create", false))) {
-				Files.copy(fs.getPath("config.json"), configJson, StandardCopyOption.REPLACE_EXISTING);
+				Path configEntry = fs.getPath("config.json");
+
+				// If we cannot find a modern config json, try the legacy/FG2-era one
+				if (Files.notExists(configEntry)) {
+					configEntry = fs.getPath("dev.json");
+				}
+
+				Files.copy(configEntry, configJson, StandardCopyOption.REPLACE_EXISTING);
 			}
 		}
 
 		try (Reader reader = Files.newBufferedReader(configJson)) {
 			json = new Gson().fromJson(reader, JsonObject.class);
 		}
 
-		addDependency(json.get("mcp").getAsString(), Constants.Configurations.MCP_CONFIG);
-		addDependency(json.get("mcp").getAsString(), Constants.Configurations.SRG);
-		addDependency(json.get("universal").getAsString(), Constants.Configurations.FORGE_UNIVERSAL);
+		isLegacyForge = !json.has("mcp");
+
+		if (!isLegacyForge) {
+			addDependency(json.get("mcp").getAsString(), Constants.Configurations.MCP_CONFIG);
+			addDependency(json.get("mcp").getAsString(), Constants.Configurations.SRG);
+			addDependency(json.get("universal").getAsString(), Constants.Configurations.FORGE_UNIVERSAL);
+		} else {
+			Map<String, String> mcpDep = Map.of(
+					"group", "de.oceanlabs.mcp",
+					"name", "mcp",
+					"version", json.get("inheritsFrom").getAsString(),
+					"classifier", "srg",
+					"ext", "zip"
+			);
+			addDependency(mcpDep, Constants.Configurations.MCP_CONFIG);
+			addDependency(mcpDep, Constants.Configurations.SRG);
+			addDependency(dependency.getDepString() + ":universal", Constants.Configurations.FORGE_UNIVERSAL);
+			addLegacyMCPRepo();
+		}
 
 		for (JsonElement lib : json.get("libraries").getAsJsonArray()) {
+			if (isLegacyForge) {
+				lib = lib.getAsJsonObject().get("name");
+			}
+
 			Dependency dep = null;
 
 			if (lib.getAsString().startsWith("org.spongepowered:mixin:")) {
@@ -128,7 +157,7 @@ public void provide(DependencyInfo dependency, Consumer<Runnable> postPopulation
 				dep = addDependency(lib.getAsString(), Constants.Configurations.FORGE_DEPENDENCIES);
 			}
 
-			if (lib.getAsString().split(":").length < 4) {
+			if (!isLegacyForge && lib.getAsString().split(":").length < 4) {
 				((ModuleDependency) dep).attributes(attributes -> {
 					attributes.attribute(transformed, true);
 				});
@@ -137,7 +166,16 @@ public void provide(DependencyInfo dependency, Consumer<Runnable> postPopulation
 
 		// TODO: Should I copy the patches from here as well?
 		//       That'd require me to run the "MCP environment" fully up to merging.
-		for (Map.Entry<String, JsonElement> entry : json.getAsJsonObject("runs").entrySet()) {
+
+		if (!isLegacyForge) {
+			configureRuns(json.getAsJsonObject("runs"));
+		} else {
+			configureRunsForLegacyForge();
+		}
+	}
+
+	private void configureRuns(JsonObject runs) {
+		for (Map.Entry<String, JsonElement> entry : runs.entrySet()) {
 			LaunchProviderSettings launchSettings = getExtension().getLaunchConfigs().findByName(entry.getKey());
 			RunConfigSettings settings = getExtension().getRunConfigs().findByName(entry.getKey());
 			JsonObject value = entry.getValue().getAsJsonObject();
@@ -184,6 +222,35 @@ public void provide(DependencyInfo dependency, Consumer<Runnable> postPopulation
 		}
 	}
 
+	private void configureRunsForLegacyForge() {
+		getExtension().getRunConfigs().configureEach(config -> {
+			if (Constants.Forge.LAUNCH_TESTING.equals(config.getDefaultMainClass())) {
+				config.setDefaultMainClass(Constants.LegacyForge.LAUNCH_WRAPPER);
+			}
+		});
+	}
+
+	private void addLegacyMCPRepo() {
+		getProject().getRepositories().ivy(repo -> {
+			// Old MCP data does not have POMs
+			repo.setName("LegacyMCP");
+			repo.setUrl("https://maven.minecraftforge.net/");
+			repo.patternLayout(layout -> {
+				layout.artifact("[orgPath]/[artifact]/[revision]/[artifact]-[revision](-[classifier])(.[ext])");
+				// also check the zip so people do not have to explicitly specify the extension for older versions
+				layout.artifact("[orgPath]/[artifact]/[revision]/[artifact]-[revision](-[classifier]).zip");
+			});
+			repo.content(descriptor -> {
+				descriptor.includeGroup("de.oceanlabs.mcp");
+			});
+			repo.metadataSources(IvyArtifactRepository.MetadataSources::artifact);
+		});
+	}
+
+	public boolean isLegacyForge() {
+		return isLegacyForge;
+	}
+
 	public abstract static class RemoveNameProvider implements TransformAction<TransformParameters.None> {
 		@InputArtifact
 		public abstract Provider<FileSystemLocation> getInput();

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

@@ -64,6 +64,11 @@ public McpConfigProvider(Project project) {
 
 	@Override
 	public void provide(DependencyInfo dependency, Consumer<Runnable> postPopulationScheduler) throws Exception {
+		if (getExtension().isLegacyForge()) {
+			official = false;
+			return;
+		}
+
 		init(dependency.getDependency().getVersion());
 
 		Path mcpZip = dependency.resolveFile().orElseThrow(() -> new RuntimeException("Could not resolve MCPConfig")).toPath();