Fix dev launch issues in unobfuscated Forge

src/main/java/dev/architectury/loom/forge/dependency/ForgeLibrariesProvider.java

@@ -159,6 +159,14 @@ public static void provide(@Nullable MappingConfiguration mappingConfiguration,
 				} catch (IOException e) {
 					throw ExceptionUtil.createDescriptiveWrapper(RuntimeException::new, "Could not remap FML", e);
 				}
+			} else if (isFML) {
+				try {
+					project.getLogger().info(":remapping FML loader (non-obfuscated)");
+					// non-obfuscated FML still need to be transformed to fix UnionFS related crash in dev
+					dep = transformFmlLoader(project, artifact);
+				} catch (IOException e) {
+					throw ExceptionUtil.createDescriptiveWrapper(RuntimeException::new, "Could not remap FML", e);
+				}
 			} else {
 				dep = project.getDependencies().create(getDependencyNotation(artifact));
 
@@ -253,6 +261,39 @@ private static Object remapFmlLoader(Project project, ServiceFactory serviceFact
 		return mavenHelper.getNotation();
 	}
 
+	// Returns a Gradle dependency notation. (unobfuscated versions)
+	private static Object transformFmlLoader(Project project, ResolvedArtifact artifact) throws IOException {
+		final LoomGradleExtension extension = LoomGradleExtension.get(project);
+
+		// use the same prefix, since there is no mapping involved
+		final String postfix = "transformed" + FML_PATCH_VERSION;
+
+		// Resolve the inputs and outputs.
+		final ModuleVersionIdentifier id = artifact.getModuleVersion().getId();
+		final LocalMavenHelper mavenHelper = new LocalMavenHelper(
+				id.getGroup() + "." + postfix,
+				id.getName(),
+				id.getVersion(),
+				artifact.getClassifier(),
+				extension.getFiles().getForgeDependencyRepo().toPath()
+		);
+		final Path inputJar = artifact.getFile().toPath();
+		final Path outputJar = mavenHelper.getOutputFile(null);
+
+		// Modify jar.
+		if (!Files.exists(outputJar) || extension.refreshDeps()) {
+			mavenHelper.copyToMaven(inputJar, null);
+
+			try (FileSystemUtil.Delegate fs = FileSystemUtil.getJarFileSystem(outputJar, false)) {
+				if (Files.exists(fs.getPath(FORGE_MOD_DIR_TRANSFORMER_DISCOVERER_FILE))) {
+					ClassVisitorUtil.rewriteClassFile(fs.getPath(FORGE_MOD_DIR_TRANSFORMER_DISCOVERER_FILE), true, ModDirTransformerDiscovererPatch::new);
+				}
+			}
+		}
+
+		return mavenHelper.getNotation();
+	}
+
 	private static void remapObjectHolder(Project project, Path outputJar, MappingConfiguration mappingConfiguration) throws IOException {
 		try {
 			// Merge SRG mappings. The real SRG mapping file hasn't been created yet since the usual SRG merging

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

@@ -177,8 +177,8 @@ public void run() {
 			// TODO: Can we get rid of javax annotations on modern versions?
 			getDependencies().add(JavaPlugin.COMPILE_ONLY_CONFIGURATION_NAME, LoomVersions.JAVAX_ANNOTATIONS.mavenNotation());
 
-			// Add Forge-only dev-time dependencies
-			if (extension.isForge()) {
+			// Add Forge-only dev-time dependencies for obfuscated version
+			if (extension.isForge() && !extension.disableObfuscation()) {
 				getDependencies().add(Constants.Configurations.FORGE_EXTRA, LoomVersions.NAMING_SERVICE.mavenNotation());
 				getDependencies().add(Constants.Configurations.FORGE_EXTRA, LoomVersions.MIXIN_REMAPPER_SERVICE.mavenNotation());
 				getDependencies().add(Constants.Configurations.FORGE_EXTRA, LoomVersions.MCP_ANNOTATIONS.mavenNotation());

src/main/java/net/fabricmc/loom/task/launch/GenerateDLIConfigTask.java

@@ -59,6 +59,7 @@
 import org.gradle.api.tasks.TaskAction;
 import org.gradle.work.DisableCachingByDefault;
 import org.jetbrains.annotations.ApiStatus;
+import org.jspecify.annotations.Nullable;
 
 import net.fabricmc.loom.LoomGradleExtension;
 import net.fabricmc.loom.LoomGradlePlugin;
@@ -180,7 +181,7 @@
 						.toList();
 			}));
 
-			if (getExtension().isForge() && !getExtension().disableObfuscation()) {
+			if (getExtension().isForge()) {
 				getForgeInputs().set(getProject().provider(() -> new ForgeInputs(getProject(), getExtension())));
 			}
 		} else {
@@ -247,6 +248,10 @@
 		}
 
 		if (platform.isForgeLike()) {
+			final boolean hasPlatformMappingFile = getPlatformMappingFile().isPresent();
+			String intermediateNs = null;
+			String mappingsPath = null;
+
 			if (getPlatformMappingFile().isPresent()) {
 				// Find the mapping files for Unprotect to use for figuring out
 				// which classes are from Minecraft.
@@ -256,47 +261,49 @@
 						.map(File::getAbsolutePath)
 						.collect(Collectors.joining(File.pathSeparator));
 
-				final String intermediateNs = IntermediaryNamespaces.intermediaryNamespace(platform).toString();
-				final String mappingsPath = getPlatformMappingFile().get().getAsFile().getAbsolutePath();
+				intermediateNs = IntermediaryNamespaces.intermediaryNamespace(platform).toString();
+				mappingsPath = getPlatformMappingFile().get().getAsFile().getAbsolutePath();
 
 				launchConfig
 						.property("unprotect.mappings", unprotectMappings)
 						// See ArchitecturyNamingService in forge-runtime
 						.property("architectury.naming.sourceNamespace", intermediateNs)
 						.property("architectury.naming.mappingsPath", mappingsPath);
+			}
 
-				if (platform == ModPlatform.FORGE) {
-					final ForgeInputs forgeInputs = Objects.requireNonNull(getForgeInputs().getOrNull());
-					final List<String> dataGenMods = forgeInputs.dataGenMods();
-
-					// Only apply the hardcoded data arguments if the deprecated data generator API is being used.
-					if (!dataGenMods.isEmpty()) {
-						launchConfig
-								.argument("data", "--all")
-								.argument("data", "--mod")
-								.argument("data", String.join(",", dataGenMods))
-								.argument("data", "--output")
-								.argument("data", forgeInputs.legacyDataGenDir());
-					}
+			if (platform == ModPlatform.FORGE) {
+				final ForgeInputs forgeInputs = Objects.requireNonNull(getForgeInputs().getOrNull());
+				final List<String> dataGenMods = forgeInputs.dataGenMods();
+
+				// Only apply the hardcoded data arguments if the deprecated data generator API is being used.
+				if (!dataGenMods.isEmpty()) {
+					launchConfig
+							.argument("data", "--all")
+							.argument("data", "--mod")
+							.argument("data", String.join(",", dataGenMods))
+							.argument("data", "--output")
+							.argument("data", forgeInputs.legacyDataGenDir());
+				}
 
-					launchConfig.property("mixin.env.remapRefMap", "true");
+				launchConfig.property("mixin.env.remapRefMap", String.valueOf(hasPlatformMappingFile));
 
+				if (hasPlatformMappingFile) {
 					if (forgeInputs.useCustomMixin()) {
 						// See mixin remapper service in forge-runtime
 						launchConfig
-								.property("architectury.mixinRemapper.sourceNamespace", intermediateNs)
-								.property("architectury.mixinRemapper.mappingsPath", mappingsPath);
+								.property("architectury.mixinRemapper.sourceNamespace", Objects.requireNonNull(intermediateNs))
+								.property("architectury.mixinRemapper.mappingsPath", Objects.requireNonNull(mappingsPath));
 					} else {
-						launchConfig.property("net.minecraftforge.gradle.GradleStart.srg.srg-mcp", forgeInputs.srgToNamedSrg());
+						launchConfig.property("net.minecraftforge.gradle.GradleStart.srg.srg-mcp", Objects.requireNonNull(forgeInputs.srgToNamedSrg()));
 					}
+				}
 
-					Set<String> mixinConfigs = forgeInputs.mixinConfigs();
+				Set<String> mixinConfigs = forgeInputs.mixinConfigs();
 
-					if (!mixinConfigs.isEmpty()) {
-						for (String config : mixinConfigs) {
-							launchConfig.argument("-mixin.config");
-							launchConfig.argument(config);
-						}
+				if (!mixinConfigs.isEmpty()) {
+					for (String config : mixinConfigs) {
+						launchConfig.argument("--mixin.config");
+						launchConfig.argument(config);
 					}
 				}
 			}
@@ -392,15 +399,15 @@
 			String legacyDataGenDir,
 			Set<String> mixinConfigs,
 			boolean useCustomMixin,
-			String srgToNamedSrg
+			@Nullable String srgToNamedSrg
 	) implements Serializable {
 		public ForgeInputs(Project project, LoomGradleExtension extension) {
 			this(
 					extension.getForge().getDataGenMods(),
 					project.file("src/generated/resources").getAbsolutePath(),
 					extension.getForge().getMixinConfigs().get(),
 					extension.getForge().getUseCustomMixin().get(),
-					extension.getMappingConfiguration().srgToNamedSrg.toAbsolutePath().toString()
+					!extension.disableObfuscation() ? extension.getMappingConfiguration().srgToNamedSrg.toAbsolutePath().toString() : null
 			);
 		}
 	}