Add support for quilt.mod.json5

build.gradle

@@ -133,6 +133,9 @@ dependencies {
 	// Forge mods.toml parsing
 	implementation ('com.electronwill.night-config:toml:3.6.6')
 
+	// quilt.mod.json5 parsing
+	implementation ('blue.endless:jankson:1.2.2')
+
 	// Testing
 	testImplementation(gradleTestKit())
 	testImplementation('org.spockframework:spock-core:2.3-groovy-3.0') {

src/main/java/dev/architectury/loom/metadata/ModMetadataFiles.java

@@ -2,18 +2,24 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.Map;
 import java.util.function.Function;
 import java.util.function.Supplier;
 
+import blue.endless.jankson.Jankson;
+import blue.endless.jankson.JsonElement;
+import blue.endless.jankson.JsonGrammar;
+import blue.endless.jankson.api.SyntaxError;
 import com.google.common.collect.ImmutableMap;
 import org.gradle.api.logging.Logger;
 import org.gradle.api.logging.Logging;
 import org.gradle.api.tasks.SourceSet;
 import org.jetbrains.annotations.Nullable;
 
+import net.fabricmc.loom.util.ExceptionUtil;
 import net.fabricmc.loom.util.ZipUtils;
 import net.fabricmc.loom.util.gradle.SourceSetHelper;
 
@@ -24,6 +30,7 @@ public final class ModMetadataFiles {
 	private static final Logger LOGGER = Logging.getLogger(ModMetadataFiles.class);
 	private static final Map<String, Function<byte[], ModMetadataFile>> SINGLE_FILE_METADATA_TYPES = ImmutableMap.<String, Function<byte[], ModMetadataFile>>builder()
 			.put(QuiltModJson.FILE_NAME, QuiltModJson::of)
+			.put(QuiltModJson.JSON5_FILE_NAME, convertJson5ToJson(QuiltModJson::of))
 			.put(ArchitecturyCommonJson.FILE_NAME, ArchitecturyCommonJson::of)
 			.put(ModsToml.FILE_PATH, onError(ModsToml::of, "Could not load mods.toml", () -> new ErroringModMetadataFile("mods.toml")))
 			.build();
@@ -39,6 +46,20 @@ private static <A, B> Function<A, B> onError(Function<A, B> fn, String message,
 		};
 	}
 
+	private static <R> Function<byte[], R> convertJson5ToJson(Function<byte[], R> next) {
+		return bytes -> {
+			var text = new String(bytes, StandardCharsets.UTF_8);
+			Jankson jankson = Jankson.builder().build();
+			String json;
+			try {
+				json = jankson.fromJson(text, JsonElement.class).toJson(JsonGrammar.STRICT);
+			} catch (SyntaxError e) {
+				throw ExceptionUtil.createDescriptiveWrapper(RuntimeException::new, "Could not read JSON5 file", e);
+			}
+			return next.apply(json.getBytes(StandardCharsets.UTF_8));
+		};
+	}
+
 	/**
 	 * Reads the mod metadata file from a jar.
 	 *

src/main/java/dev/architectury/loom/metadata/QuiltModJson.java

@@ -24,6 +24,8 @@
 
 public final class QuiltModJson implements JsonBackedModMetadataFile, SingleIdModMetadataFile {
 	public static final String FILE_NAME = "quilt.mod.json";
+	// See RFC 0083
+	public static final String JSON5_FILE_NAME = "quilt.mod.json5";
 	private static final Logger LOGGER = LoggerFactory.getLogger(QuiltModJson.class);
 	private static final String ACCESS_WIDENER_KEY = "access_widener";
 	private static final String MIXIN_KEY = "mixin";

src/main/java/net/fabricmc/loom/task/RemapJarTask.java

@@ -27,6 +27,7 @@
 import java.io.File;
 import java.io.IOException;
 import java.io.Serializable;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
@@ -42,8 +43,13 @@
 
 import javax.inject.Inject;
 
+import blue.endless.jankson.Jankson;
+import blue.endless.jankson.JsonElement;
+import blue.endless.jankson.JsonGrammar;
+import blue.endless.jankson.api.SyntaxError;
 import com.google.gson.JsonObject;
 import dev.architectury.loom.extensions.ModBuildExtensions;
+import dev.architectury.loom.metadata.QuiltModJson;
 import dev.architectury.tinyremapper.OutputConsumerPath;
 import dev.architectury.tinyremapper.TinyRemapper;
 import org.gradle.api.artifacts.Configuration;
@@ -79,6 +85,7 @@
 import net.fabricmc.loom.task.service.TinyRemapperService;
 import net.fabricmc.loom.util.Constants;
 import net.fabricmc.loom.util.ExceptionUtil;
+import net.fabricmc.loom.util.FileSystemUtil;
 import net.fabricmc.loom.util.ModPlatform;
 import net.fabricmc.loom.util.Pair;
 import net.fabricmc.loom.util.SidedClassVisitor;
@@ -325,6 +332,10 @@ public void execute() {
 				addNestedJars();
 				ModBuildExtensions.convertAwToAt(getParameters().getAtAccessWideners(), outputFile, getParameters().getMappingBuildServiceUuid());
 
+				if (getParameters().getPlatform().get() == ModPlatform.QUILT) {
+					convertQmj5();
+				}
+
 				if (getParameters().getPlatform().get() != ModPlatform.FORGE) {
 					modifyJarManifest();
 				}
@@ -451,6 +462,31 @@ private void addRefmaps() throws IOException {
 				})));
 			}
 		}
+
+		private void convertQmj5() throws IOException {
+			byte[] bytes = ZipUtils.unpackNullable(outputFile, QuiltModJson.JSON5_FILE_NAME);
+			if (bytes == null) return;
+
+			if (ZipUtils.contains(outputFile, QuiltModJson.FILE_NAME)) {
+				throw new IllegalStateException("Output file contains both quilt.mod.json and quilt.mod.json5");
+			}
+
+			Jankson jankson = Jankson.builder().build();
+			JsonElement json;
+
+			try {
+				json = jankson.fromJson(new String(bytes, StandardCharsets.UTF_8), JsonElement.class);
+			} catch (SyntaxError e) {
+				throw ExceptionUtil.createDescriptiveWrapper(RuntimeException::new, "Could not read quilt.mod.json5", e);
+			}
+
+			String qmj = json.toJson(JsonGrammar.STRICT);
+
+			try (FileSystemUtil.Delegate fs = FileSystemUtil.getJarFileSystem(outputFile, false)) {
+				Files.delete(fs.getPath(QuiltModJson.JSON5_FILE_NAME));
+				Files.writeString(fs.getPath(QuiltModJson.FILE_NAME), qmj, StandardCharsets.UTF_8);
+			}
+		}
 	}
 
 	@Override

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

@@ -94,7 +94,8 @@ public void run() throws IOException {
 		if (getExtension().isQuilt()) {
 			launchConfig
 					.argument("client", "--version")
-					.argument("client", "Architectury Loom");
+					.argument("client", "Architectury Loom")
+					.property("loader.enable_quilt_mod_json5_in_dev_env", "true");
 		}
 
 		if (getExtension().isForge()) {