Add support for quilt.mod.json5

src/main/java/org/quiltmc/loader/impl/discovery/ClasspathModCandidateFinder.java

@@ -60,6 +60,23 @@ public static void findCandidatesStatic(ModAdder out) {
 			try {
 				Enumeration<URL> fabricMods = QuiltLauncherBase.getLauncher().getTargetClassLoader().getResources("fabric.mod.json");
 				Enumeration<URL> quiltMods = QuiltLauncherBase.getLauncher().getTargetClassLoader().getResources("quilt.mod.json");
+				Enumeration<URL> quiltQmj5Mods = QuiltLauncherBase.getLauncher().getTargetClassLoader().getResources("quilt.mod.json5");
+				while (quiltQmj5Mods.hasMoreElements()) {
+					URL url = quiltQmj5Mods.nextElement();
+
+					try {
+						Path path = LoaderUtil.normalizeExistingPath(UrlUtil.getCodeSource(url, "quilt.mod.json5"));
+						List<Path> paths = pathGroups.get(path);
+
+						if (paths == null) {
+							out.addMod(Collections.singletonList(path));
+						} else {
+							out.addMod(paths);
+						}
+					} catch (UrlConversionException e) {
+						Log.debug(LogCategory.DISCOVERY, "Error determining location for quilt.mod.json5 from %s", url, e);
+					}
+				}
 				while (quiltMods.hasMoreElements()) {
 					URL url = quiltMods.nextElement();
 

src/main/java/org/quiltmc/loader/impl/metadata/qmj/ModMetadataReader.java

@@ -71,7 +71,12 @@ public static InternalModMetadata read(InputStream json) throws IOException, Par
 	public static InternalModMetadata read(InputStream json, Path path, QuiltPluginManager manager, PluginGuiTreeNode warningNode) throws IOException, ParseException {
 		JsonLoaderValue value;
 
-		try (JsonReader reader = JsonReader.json(new InputStreamReader(json, StandardCharsets.UTF_8))) {
+		try (JsonReader reader = JsonReader.json5(new InputStreamReader(json, StandardCharsets.UTF_8))) {
+			// Only read as a JSON5 reader if it is a JSON5 file
+			if (!path.toString().endsWith(".json5")) {
+				reader.setStrictJson();
+			}
+
 			// Root must be an object
 			if (reader.peek() != JsonToken.BEGIN_OBJECT) {
 				throw new ParseException(reader, "A quilt.mod.json must have an object at the root");

src/main/java/org/quiltmc/loader/impl/plugin/quilt/StandardQuiltPlugin.java

@@ -242,12 +242,44 @@ private ModLoadOption[] scan0(Path root, QuiltLoaderIcon fileIcon, ModLocation l
 		PluginGuiTreeNode guiNode) throws IOException {
 
 		Path qmj = root.resolve("quilt.mod.json");
-		if (!FasterFiles.isRegularFile(qmj)) {
+		Path qmj5 = root.resolve("quilt.mod.json5");
+		Path usedQmj = qmj;
+
+		if (FasterFiles.exists(qmj5)) {
+			boolean enableQmj5 = QuiltLoader.isDevelopmentEnvironment() || Boolean.getBoolean(SystemProperties.ENABLE_QUILT_MOD_JSON5);
+			if (!QuiltLoader.isDevelopmentEnvironment() && !enableQmj5) {
+				QuiltLoaderText title = QuiltLoaderText.translate("gui.text.qmj5_on_production.title");
+				QuiltDisplayedError error = context().reportError(title);
+				String describedPath = context().manager().describePath(usedQmj);
+				error.appendReportText(
+						"An attempt to read a 'quilt.mod.json5' file was detected: " + describedPath,
+						"'quilt.mod.json5' files can't be used outside of a development environment without converting to a 'quilt.mod.json' file!"
+				);
+				error.appendDescription(
+						QuiltLoaderText.translate("gui.text.qmj5_on_production.desc.0"),
+						QuiltLoaderText.translate("gui.text.qmj5_on_production.desc.1"),
+						QuiltLoaderText.translate("gui.text.qmj5_on_production.desc.2", describedPath)
+				);
+				context().manager().getRealContainingFile(root).ifPresent(real ->
+						error.addFileViewButton(real)
+								.icon(QuiltLoaderGui.iconJarFile().withDecoration(QuiltLoaderGui.iconQuilt()))
+				);
+
+				guiNode.addChild(QuiltLoaderText.translate("gui.text.qmj5_on_production"));
+				return null;
+			}
+
+			if (enableQmj5) {
+				usedQmj = qmj5;
+			}
+		}
+
+		if (!FasterFiles.isRegularFile(usedQmj)) {
 			return null;
 		}
 
 		try {
-			InternalModMetadata meta = ModMetadataReader.read(qmj, context().manager(), guiNode);
+			InternalModMetadata meta = ModMetadataReader.read(usedQmj, context().manager(), guiNode);
 
 			Path from = root;
 			if (isZip) {
@@ -282,8 +314,8 @@ private ModLoadOption[] scan0(Path root, QuiltLoaderIcon fileIcon, ModLocation l
 				"gui.text.invalid_metadata.title", "quilt.mod.json", parse.getMessage()
 			);
 			QuiltDisplayedError error = context().reportError(title);
-			String describedPath = context().manager().describePath(qmj);
-			error.appendReportText("Invalid 'quilt.mod.json' metadata file:" + describedPath);
+			String describedPath = context().manager().describePath(usedQmj);
+			error.appendReportText("Invalid 'quilt.mod.json' metadata file: " + describedPath);
 			error.appendDescription(QuiltLoaderText.translate("gui.text.invalid_metadata.desc.0", describedPath));
 			error.appendThrowable(parse);
 			context().manager().getRealContainingFile(root).ifPresent(real ->

src/main/java/org/quiltmc/loader/impl/util/SystemProperties.java

@@ -75,6 +75,7 @@ public final class SystemProperties {
 	public static final String DISABLE_PRELOAD_TRANSFORM_CACHE = "loader.transform_cache.disable_preload";
 	public static final String LOG_CACHE_KEY_CHANGES = "loader.transform_cache.log_changed_keys";
 	public static final String DISABLE_BEACON = "loader.disable_beacon";
+	public static final String ENABLE_QUILT_MOD_JSON5 = "loader.debug.enable_quilt_mod_json5";
 
 	private SystemProperties() {
 	}

src/main/resources/lang/quilt_loader.properties

@@ -66,6 +66,11 @@ gui.error.ioexception.desc.0=%s
 gui.text.invalid_metadata=Invalid Metadata: %s
 gui.text.invalid_metadata.title=Unable to read %s: %s
 gui.text.invalid_metadata.desc.0=From %s
+gui.text.qmj5_on_production=Unconverted 'quilt.mod.json5' found
+gui.text.qmj5_on_production.title=Attempted to read an unconverted 'quilt.mod.json5' file
+gui.text.qmj5_on_production.desc.0=An attempt to read a 'quilt.mod.json5' file was detected!
+gui.text.qmj5_on_production.desc.1='quilt.mod.json5' files can't be used outside a development environment without converting to a 'quilt.mod.json' file!
+gui.text.qmj5_on_production.desc.2=From %s
 error.unhandled_solver=Complex solver error; see the crash report for more information
 error.unhandled_solver.desc=Please try updating quilt-loader to see if an update can describe this.\nOr report this to the quilt-loader project so this can be fixed.
 error.unhandled_solver.desc.rule_n= \n \nRule %s (%s):