Rewrite GenSources including full support for CFR. (#511)

* Rewrite CFR decompiler interface. Support javadoc

* CFR line numbers and fixes.

* Cleanup and fix

* Use WorkerExecutor to fork, massively cleans up the fernflower code, but does remove the fancy multithreaded logging.

* Use IPC to get logging back from the decompilers.

* Cleanup UnpickJarTask, fix leak in IPCServer

* Used published CFR build

* Handle older windows versions that do not support AF_UNIX.

* Fixes and basic unit test

* Improve memory handling of genSources

* Stop decompile worker JVM

build.gradle

@@ -88,7 +88,7 @@ dependencies {
 
 	// decompilers
 	implementation ('net.fabricmc:fabric-fernflower:1.4.1')
-	implementation ('org.benf:cfr:0.151')
+	implementation ('net.fabricmc:cfr:0.0.8')
 
 	// source code remapping
 	implementation ('net.fabricmc:mercury:0.2.4')

src/main/java/net/fabricmc/loom/api/decompilers/DecompilationMetadata.java

@@ -27,5 +27,7 @@ package net.fabricmc.loom.api.decompilers;
 import java.nio.file.Path;
 import java.util.Collection;
 
-public record DecompilationMetadata(int numberOfThreads, Path javaDocs, Collection<Path> libraries) {
+import net.fabricmc.loom.util.IOStringConsumer;
+
+public record DecompilationMetadata(int numberOfThreads, Path javaDocs, Collection<Path> libraries, IOStringConsumer logger) {
 }

src/main/java/net/fabricmc/loom/configuration/providers/minecraft/assets/MinecraftAssetsProvider.java

@@ -45,7 +45,7 @@ import net.fabricmc.loom.configuration.providers.MinecraftProviderImpl;
 import net.fabricmc.loom.configuration.providers.minecraft.MinecraftVersionMeta;
 import net.fabricmc.loom.util.MirrorUtil;
 import net.fabricmc.loom.util.HashedDownloadUtil;
-import net.fabricmc.loom.util.gradle.ProgressLogger;
+import net.fabricmc.loom.util.gradle.ProgressLoggerHelper;
 
 public class MinecraftAssetsProvider {
 	public static void provide(MinecraftProviderImpl minecraftProvider, Project project) throws IOException {
@@ -78,7 +78,7 @@ public class MinecraftAssetsProvider {
 			HashedDownloadUtil.downloadIfInvalid(new URL(assetIndex.url()), assetsInfo, assetIndex.sha1(), project.getLogger(), false);
 		}
 
-		Deque<ProgressLogger> loggers = new ConcurrentLinkedDeque<>();
+		Deque<ProgressLoggerHelper> loggers = new ConcurrentLinkedDeque<>();
 		ExecutorService executor = Executors.newFixedThreadPool(Math.min(10, Math.max(Runtime.getRuntime().availableProcessors() / 2, 1)));
 
 		AssetIndex index;
@@ -114,15 +114,15 @@ public class MinecraftAssetsProvider {
 
 					project.getLogger().debug("validating asset " + assetName[0]);
 
-					final ProgressLogger[] progressLogger = new ProgressLogger[1];
+					final ProgressLoggerHelper[] progressLogger = new ProgressLoggerHelper[1];
 
 					try {
 						HashedDownloadUtil.downloadIfInvalid(new URL(MirrorUtil.getResourcesBase(project) + sha1.substring(0, 2) + "/" + sha1), file, sha1, project.getLogger(), true, () -> {
-							ProgressLogger logger = loggers.pollFirst();
+							ProgressLoggerHelper logger = loggers.pollFirst();
 
 							if (logger == null) {
 								//Create a new logger if we need one
-								progressLogger[0] = ProgressLogger.getProgressFactory(project, MinecraftAssetsProvider.class.getName());
+								progressLogger[0] = ProgressLoggerHelper.getProgressFactory(project, MinecraftAssetsProvider.class.getName());
 								progressLogger[0].start("Downloading assets...", "assets");
 							} else {
 								// use a free logger if we can
@@ -157,6 +157,6 @@ public class MinecraftAssetsProvider {
 			throw new RuntimeException(e);
 		}
 
-		loggers.forEach(ProgressLogger::completed);
+		loggers.forEach(ProgressLoggerHelper::completed);
 	}
 }

src/main/java/net/fabricmc/loom/decompilers/DecompilerConfiguration.java

@@ -27,7 +27,7 @@ package net.fabricmc.loom.decompilers;
 import org.gradle.api.Project;
 
 import net.fabricmc.loom.LoomGradleExtension;
-import net.fabricmc.loom.decompilers.cfr.FabricCFRDecompiler;
+import net.fabricmc.loom.decompilers.cfr.LoomCFRDecompiler;
 import net.fabricmc.loom.decompilers.fernflower.FabricFernFlowerDecompiler;
 
 public final class DecompilerConfiguration {
@@ -36,7 +36,7 @@ public final class DecompilerConfiguration {
 
 	public static void setup(Project project) {
 		LoomGradleExtension extension = LoomGradleExtension.get(project);
-		extension.getGameDecompilers().add(new FabricFernFlowerDecompiler(project));
+		extension.getGameDecompilers().add(new FabricFernFlowerDecompiler());
-		extension.getGameDecompilers().add(new FabricCFRDecompiler(project));
+		extension.getGameDecompilers().add(new LoomCFRDecompiler());
 	}
 }

src/main/java/net/fabricmc/loom/decompilers/LineNumberRemapper.java

@@ -47,10 +47,9 @@ import org.objectweb.asm.Label;
 import org.objectweb.asm.MethodVisitor;
 
 import net.fabricmc.loom.util.Constants;
-import net.fabricmc.loom.util.gradle.ProgressLogger;
+import net.fabricmc.loom.util.IOStringConsumer;
 
 /**
- * TODO, Move to stitch.
  * Created by covers1624 on 18/02/19.
  */
 public class LineNumberRemapper {
@@ -88,7 +87,7 @@ public class LineNumberRemapper {
 		}
 	}
 
-	public void process(ProgressLogger logger, Path input, Path output) throws IOException {
+	public void process(IOStringConsumer logger, Path input, Path output) throws IOException {
 		Files.walkFileTree(input, new SimpleFileVisitor<>() {
 			@Override
 			public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
@@ -110,7 +109,7 @@ public class LineNumberRemapper {
 					String idx = rel.substring(0, rel.length() - 6);
 
 					if (logger != null) {
-						logger.progress("Remapping " + idx);
+						logger.accept("Remapping " + idx);
 					}
 
 					int dollarPos = idx.indexOf('$'); //This makes the assumption that only Java classes are to be remapped.

src/main/java/net/fabricmc/loom/decompilers/cfr/CFRObfuscationMapping.java

@@ -0,0 +1,230 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2021 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.decompilers.cfr;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
+
+import org.benf.cfr.reader.bytecode.analysis.types.JavaRefTypeInstance;
+import org.benf.cfr.reader.bytecode.analysis.types.JavaTypeInstance;
+import org.benf.cfr.reader.bytecode.analysis.types.MethodPrototype;
+import org.benf.cfr.reader.entities.AccessFlag;
+import org.benf.cfr.reader.entities.ClassFile;
+import org.benf.cfr.reader.entities.ClassFileField;
+import org.benf.cfr.reader.entities.Field;
+import org.benf.cfr.reader.mapping.NullMapping;
+import org.benf.cfr.reader.util.output.DelegatingDumper;
+import org.benf.cfr.reader.util.output.Dumper;
+
+import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
+import net.fabricmc.mappingio.MappingReader;
+import net.fabricmc.mappingio.adapter.MappingSourceNsSwitch;
+import net.fabricmc.mappingio.tree.MappingTree;
+import net.fabricmc.mappingio.tree.MemoryMappingTree;
+
+public class CFRObfuscationMapping extends NullMapping {
+	private final MappingTree mappingTree;
+
+	public CFRObfuscationMapping(Path mappings) {
+		mappingTree = readMappings(mappings);
+	}
+
+	@Override
+	public Dumper wrap(Dumper d) {
+		return new JavadocProvidingDumper(d);
+	}
+
+	private static MappingTree readMappings(Path input) {
+		try (BufferedReader reader = Files.newBufferedReader(input)) {
+			MemoryMappingTree mappingTree = new MemoryMappingTree();
+			MappingSourceNsSwitch nsSwitch = new MappingSourceNsSwitch(mappingTree, MappingsNamespace.NAMED.toString());
+			MappingReader.read(reader, nsSwitch);
+
+			return mappingTree;
+		} catch (IOException e) {
+			throw new RuntimeException("Failed to read mappings", e);
+		}
+	}
+
+	private class JavadocProvidingDumper extends DelegatingDumper {
+		JavadocProvidingDumper(Dumper delegate) {
+			super(delegate);
+		}
+
+		@Override
+		public Dumper dumpClassDoc(JavaTypeInstance owner) {
+			MappingTree.ClassMapping mapping = getClassMapping(owner);
+
+			if (mapping == null) {
+				return this;
+			}
+
+			List<String> recordComponentDocs = new LinkedList<>();
+
+			if (isRecord(owner)) {
+				ClassFile classFile = ((JavaRefTypeInstance) owner).getClassFile();
+
+				for (ClassFileField field : classFile.getFields()) {
+					if (field.getField().testAccessFlag(AccessFlag.ACC_STATIC)) {
+						continue;
+					}
+
+					MappingTree.FieldMapping fieldMapping = mapping.getField(field.getFieldName(), field.getField().getDescriptor());
+
+					if (fieldMapping == null) {
+						continue;
+					}
+
+					String comment = fieldMapping.getComment();
+
+					if (comment != null) {
+						recordComponentDocs.add(String.format("@param %s %s", fieldMapping.getSrcName(), comment));
+					}
+				}
+			}
+
+			String comment = mapping.getComment();
+
+			if (comment != null || !recordComponentDocs.isEmpty()) {
+				print("/**").newln();
+
+				if (comment != null) {
+					for (String line : comment.split("\\R")) {
+						print(" * ").print(line).newln();
+					}
+
+					if (!recordComponentDocs.isEmpty()) {
+						print(" * ").newln();
+					}
+				}
+
+				for (String componentDoc : recordComponentDocs) {
+					print(" * ").print(componentDoc).newln();
+				}
+
+				print(" */").newln();
+			}
+
+			return this;
+		}
+
+		@Override
+		public Dumper dumpMethodDoc(MethodPrototype method) {
+			MappingTree.ClassMapping classMapping = getClassMapping(method.getOwner());
+
+			if (classMapping == null) {
+				return this;
+			}
+
+			List<String> lines = new ArrayList<>();
+			MappingTree.MethodMapping mapping = classMapping.getMethod(method.getName(), method.getOriginalDescriptor());
+
+			if (mapping != null) {
+				String comment = mapping.getComment();
+
+				if (comment != null) {
+					lines.addAll(Arrays.asList(comment.split("\\R")));
+				}
+
+				for (MappingTree.MethodArgMapping arg : mapping.getArgs()) {
+					String argComment = arg.getComment();
+
+					if (argComment != null) {
+						lines.addAll(Arrays.asList(("@param " + arg.getSrcName() + " " + argComment).split("\\R")));
+					}
+				}
+			}
+
+			if (!lines.isEmpty()) {
+				print("/**").newln();
+
+				for (String line : lines) {
+					print(" * ").print(line).newln();
+				}
+
+				print(" */").newln();
+			}
+
+			return this;
+		}
+
+		@Override
+		public Dumper dumpFieldDoc(Field field, JavaTypeInstance owner) {
+			// None static fields in records are handled in the class javadoc.
+			if (isRecord(owner) && !isStatic(field)) {
+				return null;
+			}
+
+			MappingTree.ClassMapping classMapping = getClassMapping(owner);
+
+			if (classMapping == null) {
+				return null;
+			}
+
+			MappingTree.FieldMapping fieldMapping = classMapping.getField(field.getFieldName(), field.getDescriptor());
+			dumpComment(fieldMapping.getComment());
+
+			return this;
+		}
+
+		private MappingTree.ClassMapping getClassMapping(JavaTypeInstance type) {
+			String qualifiedName = type.getRawName().replace('.', '/');
+			return mappingTree.getClass(qualifiedName);
+		}
+
+		private boolean isRecord(JavaTypeInstance javaTypeInstance) {
+			if (javaTypeInstance instanceof JavaRefTypeInstance) {
+				ClassFile classFile = ((JavaRefTypeInstance) javaTypeInstance).getClassFile();
+				return classFile.getClassSignature().getSuperClass().getRawName().equals("java.lang.Record");
+			}
+
+			return false;
+		}
+
+		private boolean isStatic(Field field) {
+			return field.testAccessFlag(AccessFlag.ACC_STATIC);
+		}
+
+		private void dumpComment(String comment) {
+			if (comment == null || comment.isBlank()) {
+				return;
+			}
+
+			print("/**").newln();
+
+			for (String line : comment.split("\n")) {
+				print(" * ").print(line).newln();
+			}
+
+			print(" */").newln();
+		}
+	}
+}

src/main/java/net/fabricmc/loom/decompilers/cfr/CFRSinkFactory.java

@@ -0,0 +1,151 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2021 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.decompilers.cfr;
+
+import java.io.IOException;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Date;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.NavigableMap;
+import java.util.Set;
+import java.util.TreeMap;
+import java.util.jar.JarEntry;
+import java.util.jar.JarOutputStream;
+
+import com.google.common.base.Charsets;
+import org.benf.cfr.reader.api.OutputSinkFactory;
+import org.benf.cfr.reader.api.SinkReturns;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import net.fabricmc.loom.util.IOStringConsumer;
+
+public class CFRSinkFactory implements OutputSinkFactory {
+	private static final Logger ERROR_LOGGER = LoggerFactory.getLogger(CFRSinkFactory.class);
+
+	private final JarOutputStream outputStream;
+	private final IOStringConsumer logger;
+	private final Set<String> addedDirectories = new HashSet<>();
+	private final Map<String, Map<Integer, Integer>> lineMap = new TreeMap<>();
+
+	public CFRSinkFactory(JarOutputStream outputStream, IOStringConsumer logger) {
+		this.outputStream = outputStream;
+		this.logger = logger;
+	}
+
+	@Override
+	public List<SinkClass> getSupportedSinks(SinkType sinkType, Collection<SinkClass> available) {
+		return switch (sinkType) {
+		case JAVA -> Collections.singletonList(SinkClass.DECOMPILED);
+		case LINENUMBER -> Collections.singletonList(SinkClass.LINE_NUMBER_MAPPING);
+		default -> Collections.emptyList();
+		};
+	}
+
+	@Override
+	public <T> Sink<T> getSink(SinkType sinkType, SinkClass sinkClass) {
+		return switch (sinkType) {
+		case JAVA -> (Sink<T>) decompiledSink();
+		case LINENUMBER -> (Sink<T>) lineNumberMappingSink();
+		case EXCEPTION -> (e) -> ERROR_LOGGER.error((String) e);
+		default -> null;
+		};
+	}
+
+	private Sink<SinkReturns.Decompiled> decompiledSink() {
+		return sinkable -> {
+			String filename = sinkable.getPackageName().replace('.', '/');
+			if (!filename.isEmpty()) filename += "/";
+			filename += sinkable.getClassName() + ".java";
+
+			byte[] data = sinkable.getJava().getBytes(Charsets.UTF_8);
+
+			writeToJar(filename, data);
+		};
+	}
+
+	private Sink<SinkReturns.LineNumberMapping> lineNumberMappingSink() {
+		return sinkable -> {
+			final String className = sinkable.getClassName();
+			final NavigableMap<Integer, Integer> classFileMappings = sinkable.getClassFileMappings();
+			final NavigableMap<Integer, Integer> mappings = sinkable.getMappings();
+
+			if (classFileMappings == null || mappings == null) return;
+
+			for (Map.Entry<Integer, Integer> entry : mappings.entrySet()) {
+				// New line number
+				Integer dstLineNumber = entry.getValue();
+
+				// Line mapping in the original jar
+				Integer srcLineNumber = classFileMappings.get(entry.getKey());
+
+				if (srcLineNumber == null || dstLineNumber == null) continue;
+
+				lineMap.computeIfAbsent(className, (c) -> new TreeMap<>()).put(srcLineNumber, dstLineNumber);
+			}
+		};
+	}
+
+	private synchronized void writeToJar(String filename, byte[] data) {
+		String[] path = filename.split("/");
+		String pathPart = "";
+
+		for (int i = 0; i < path.length - 1; i++) {
+			pathPart += path[i] + "/";
+
+			if (addedDirectories.add(pathPart)) {
+				JarEntry entry = new JarEntry(pathPart);
+				entry.setTime(new Date().getTime());
+
+				try {
+					outputStream.putNextEntry(entry);
+					outputStream.closeEntry();
+				} catch (IOException e) {
+					throw new RuntimeException(e);
+				}
+			}
+		}
+
+		JarEntry entry = new JarEntry(filename);
+		entry.setTime(new Date().getTime());
+		entry.setSize(data.length);
+
+		try {
+			logger.accept("Writing: " + filename);
+			outputStream.putNextEntry(entry);
+			outputStream.write(data);
+			outputStream.closeEntry();
+		} catch (IOException e) {
+			throw new RuntimeException(e);
+		}
+	}
+
+	public Map<String, Map<Integer, Integer>> getLineMap() {
+		return Collections.unmodifiableMap(lineMap);
+	}
+}

src/main/java/net/fabricmc/loom/decompilers/cfr/FabricCFRDecompiler.java

@@ -1,233 +0,0 @@
-/*
- * This file is part of fabric-loom, licensed under the MIT License (MIT).
- *
- * Copyright (c) 2020-2021 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.decompilers.cfr;
-
-import java.io.FileNotFoundException;
-import java.io.IOException;
-import java.io.InputStream;
-import java.io.OutputStream;
-import java.nio.file.Files;
-import java.nio.file.Path;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.Date;
-import java.util.HashSet;
-import java.util.LinkedList;
-import java.util.List;
-import java.util.Map;
-import java.util.Set;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ExecutionException;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.Future;
-import java.util.function.Function;
-import java.util.jar.Attributes;
-import java.util.jar.JarEntry;
-import java.util.jar.JarOutputStream;
-import java.util.jar.Manifest;
-import java.util.stream.Collectors;
-import java.util.zip.ZipEntry;
-import java.util.zip.ZipFile;
-
-import com.google.common.base.Charsets;
-import com.google.common.collect.ImmutableMap;
-import org.benf.cfr.reader.api.CfrDriver;
-import org.benf.cfr.reader.api.ClassFileSource;
-import org.benf.cfr.reader.api.OutputSinkFactory;
-import org.benf.cfr.reader.api.SinkReturns;
-import org.benf.cfr.reader.bytecode.analysis.parse.utils.Pair;
-import org.gradle.api.Project;
-import org.gradle.api.internal.project.ProjectInternal;
-import org.gradle.internal.logging.progress.ProgressLogger;
-import org.gradle.internal.logging.progress.ProgressLoggerFactory;
-import org.gradle.internal.service.ServiceRegistry;
-
-import net.fabricmc.loom.api.decompilers.DecompilationMetadata;
-import net.fabricmc.loom.api.decompilers.LoomDecompiler;
-
-public class FabricCFRDecompiler implements LoomDecompiler {
-	private final Project project;
-
-	public FabricCFRDecompiler(Project project) {
-		this.project = project;
-	}
-
-	@Override
-	public String name() {
-		return "ExperimentalCfr";
-	}
-
-	@Override
-	public void decompile(Path compiledJar, Path sourcesDestination, Path linemapDestination, DecompilationMetadata metaData) {
-		project.getLogger().warn("!!!! The CFR decompiler support is currently incomplete, line numbers will not match up and there will be no javadocs in the generated source.");
-
-		// Setups the multi threaded logger, the thread id is used as the key to the ProgressLogger's
-		ServiceRegistry registry = ((ProjectInternal) project).getServices();
-		ProgressLoggerFactory factory = registry.get(ProgressLoggerFactory.class);
-		ProgressLogger progressGroup = factory.newOperation(getClass()).setDescription("Decompile");
-
-		Map<Long, ProgressLogger> loggerMap = new ConcurrentHashMap<>();
-		Function<Long, ProgressLogger> createLogger = (threadId) -> {
-			ProgressLogger pl = factory.newOperation(getClass(), progressGroup);
-			pl.setDescription("decompile worker");
-			pl.started();
-			return pl;
-		};
-
-		progressGroup.started();
-
-		Manifest manifest = new Manifest();
-		manifest.getMainAttributes().put(Attributes.Name.MANIFEST_VERSION, "1.0");
-		Set<String> addedDirectories = new HashSet<>();
-
-		try (OutputStream fos = Files.newOutputStream(sourcesDestination); JarOutputStream jos = new JarOutputStream(fos, manifest); ZipFile inputZip = new ZipFile(compiledJar.toFile())) {
-			CfrDriver driver = new CfrDriver.Builder()
-					.withOptions(ImmutableMap.of(
-							"renameillegalidents", "true",
-							"trackbytecodeloc", "true"
-					))
-					.withClassFileSource(new ClassFileSource() {
-						@Override
-						public void informAnalysisRelativePathDetail(String usePath, String classFilePath) {
-						}
-
-						@Override
-						public Collection<String> addJar(String jarPath) {
-							return null;
-						}
-
-						@Override
-						public String getPossiblyRenamedPath(String path) {
-							return path;
-						}
-
-						@Override
-						public Pair<byte[], String> getClassFileContent(String path) throws IOException {
-							ZipEntry zipEntry = inputZip.getEntry(path);
-
-							if (zipEntry == null) {
-								throw new FileNotFoundException(path);
-							}
-
-							try (InputStream inputStream = inputZip.getInputStream(zipEntry)) {
-								return Pair.make(inputStream.readAllBytes(), path);
-							}
-						}
-					})
-					.withOutputSink(new OutputSinkFactory() {
-						@Override
-						public List<SinkClass> getSupportedSinks(SinkType sinkType, Collection<SinkClass> available) {
-							return switch (sinkType) {
-								case PROGRESS -> Collections.singletonList(SinkClass.STRING);
-								case JAVA -> Collections.singletonList(SinkClass.DECOMPILED);
-								default -> Collections.emptyList();
-							};
-						}
-
-						@SuppressWarnings("unchecked")
-						@Override
-						public <T> Sink<T> getSink(SinkType sinkType, SinkClass sinkClass) {
-							return switch (sinkType) {
-								case PROGRESS -> (p) -> project.getLogger().debug((String) p);
-								case JAVA -> (Sink<T>) decompiledSink(jos, addedDirectories);
-								case EXCEPTION -> (e) -> project.getLogger().error((String) e);
-								default -> null;
-							};
-						}
-					})
-					.build();
-
-			List<String> classes = Collections.list(inputZip.entries()).stream()
-									.map(ZipEntry::getName)
-									.filter(input -> input.endsWith(".class"))
-									.collect(Collectors.toList());
-
-			ExecutorService executorService = Executors.newFixedThreadPool(metaData.numberOfThreads());
-			List<Future<?>> futures = new LinkedList<>();
-
-			for (String clazz : classes) {
-				futures.add(executorService.submit(() -> {
-					loggerMap.computeIfAbsent(Thread.currentThread().getId(), createLogger).progress(clazz);
-					driver.analyse(Collections.singletonList(clazz));
-				}));
-			}
-
-			for (Future<?> future : futures) {
-				future.get();
-			}
-		} catch (IOException | InterruptedException | ExecutionException e) {
-			throw new RuntimeException("Failed to decompile", e);
-		} finally {
-			loggerMap.forEach((threadId, progressLogger) -> progressLogger.completed());
-		}
-	}
-
-	private static OutputSinkFactory.Sink<SinkReturns.Decompiled> decompiledSink(JarOutputStream jos, Set<String> addedDirectories) {
-		return decompiled -> {
-			String filename = decompiled.getPackageName().replace('.', '/');
-			if (!filename.isEmpty()) filename += "/";
-			filename += decompiled.getClassName() + ".java";
-
-			byte[] data = decompiled.getJava().getBytes(Charsets.UTF_8);
-
-			writeToJar(filename, data, jos, addedDirectories);
-		};
-	}
-
-	// TODO move to task queue?
-	private static synchronized void writeToJar(String filename, byte[] data, JarOutputStream jos, Set<String> addedDirectories) {
-		String[] path = filename.split("/");
-		String pathPart = "";
-
-		for (int i = 0; i < path.length - 1; i++) {
-			pathPart += path[i] + "/";
-
-			if (addedDirectories.add(pathPart)) {
-				JarEntry entry = new JarEntry(pathPart);
-				entry.setTime(new Date().getTime());
-
-				try {
-					jos.putNextEntry(entry);
-					jos.closeEntry();
-				} catch (IOException e) {
-					throw new RuntimeException(e);
-				}
-			}
-		}
-
-		JarEntry entry = new JarEntry(filename);
-		entry.setTime(new Date().getTime());
-		entry.setSize(data.length);
-
-		try {
-			jos.putNextEntry(entry);
-			jos.write(data);
-			jos.closeEntry();
-		} catch (IOException e) {
-			throw new RuntimeException(e);
-		}
-	}
-}

src/main/java/net/fabricmc/loom/decompilers/cfr/LoomCFRDecompiler.java

@@ -0,0 +1,148 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2021 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.decompilers.cfr;
+
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.io.Writer;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Collections;
+import java.util.Map;
+import java.util.jar.Attributes;
+import java.util.jar.JarOutputStream;
+import java.util.jar.Manifest;
+
+import org.benf.cfr.reader.Driver;
+import org.benf.cfr.reader.state.ClassFileSourceImpl;
+import org.benf.cfr.reader.state.DCCommonState;
+import org.benf.cfr.reader.util.AnalysisType;
+import org.benf.cfr.reader.util.getopt.Options;
+import org.benf.cfr.reader.util.getopt.OptionsImpl;
+import org.benf.cfr.reader.util.output.SinkDumperFactory;
+
+import net.fabricmc.loom.api.decompilers.DecompilationMetadata;
+import net.fabricmc.loom.api.decompilers.LoomDecompiler;
+import net.fabricmc.loom.decompilers.LineNumberRemapper;
+
+public class LoomCFRDecompiler implements LoomDecompiler {
+	private static final Map<String, String> DECOMPILE_OPTIONS = Map.of(
+			"renameillegalidents", "true",
+			"trackbytecodeloc", "true",
+			"comments", "false"
+	);
+
+	@Override
+	public String name() {
+		return "Cfr";
+	}
+
+	@Override
+	public void decompile(Path compiledJar, Path sourcesDestination, Path linemapDestination, DecompilationMetadata metaData) {
+		final String path = compiledJar.toAbsolutePath().toString();
+		final Options options = OptionsImpl.getFactory().create(DECOMPILE_OPTIONS);
+
+		ClassFileSourceImpl classFileSource = new ClassFileSourceImpl(options);
+
+		for (Path library : metaData.libraries()) {
+			classFileSource.addJarContent(library.toAbsolutePath().toString(), AnalysisType.JAR);
+		}
+
+		classFileSource.informAnalysisRelativePathDetail(null, null);
+
+		DCCommonState state = new DCCommonState(options, classFileSource);
+
+		if (metaData.javaDocs() != null) {
+			state = new DCCommonState(state, new CFRObfuscationMapping(metaData.javaDocs()));
+		}
+
+		final Manifest manifest = new Manifest();
+		manifest.getMainAttributes().put(Attributes.Name.MANIFEST_VERSION, "1.0");
+
+		Map<String, Map<Integer, Integer>> lineMap;
+
+		try (JarOutputStream outputStream = new JarOutputStream(Files.newOutputStream(sourcesDestination), manifest)) {
+			CFRSinkFactory cfrSinkFactory = new CFRSinkFactory(outputStream, metaData.logger());
+			SinkDumperFactory dumperFactory = new SinkDumperFactory(cfrSinkFactory, options);
+
+			Driver.doJar(state, path, AnalysisType.JAR, dumperFactory);
+
+			lineMap = cfrSinkFactory.getLineMap();
+		} catch (IOException e) {
+			throw new UncheckedIOException("Failed to decompile", e);
+		}
+
+		writeLineMap(linemapDestination, lineMap);
+	}
+
+	private void writeLineMap(Path output, Map<String, Map<Integer, Integer>> lineMap) {
+		try (Writer writer = Files.newBufferedWriter(output, StandardCharsets.UTF_8)) {
+			for (Map.Entry<String, Map<Integer, Integer>> classEntry : lineMap.entrySet()) {
+				final String name = classEntry.getKey().replace(".", "/");
+
+				final Map<Integer, Integer> mapping = classEntry.getValue();
+
+				int maxLine = 0;
+				int maxLineDest = 0;
+				StringBuilder builder = new StringBuilder();
+
+				for (Map.Entry<Integer, Integer> mappingEntry : mapping.entrySet()) {
+					final int src = mappingEntry.getKey();
+					final int dst = mappingEntry.getValue();
+
+					maxLine = Math.max(maxLine, src);
+					maxLineDest = Math.max(maxLineDest, dst);
+
+					builder.append("\t").append(src).append("\t").append(dst).append("\n");
+				}
+
+				writer.write("%s\t%d\t%d\n".formatted(name, maxLine, maxLineDest));
+				writer.write(builder.toString());
+				writer.write("\n");
+			}
+		} catch (IOException e) {
+			throw new UncheckedIOException("Failed to write line map", e);
+		}
+	}
+
+	// A test main class to make it quicker/easier to debug with minimal jars
+	public static void main(String[] args) throws IOException {
+		LoomCFRDecompiler decompiler = new LoomCFRDecompiler();
+
+		Path lineMap = Paths.get("linemap.txt");
+
+		decompiler.decompile(Paths.get("input.jar"),
+				Paths.get("output-sources.jar"),
+				lineMap,
+				new DecompilationMetadata(4, null, Collections.emptyList(), null)
+		);
+
+		LineNumberRemapper lineNumberRemapper = new LineNumberRemapper();
+		lineNumberRemapper.readMappings(lineMap.toFile());
+		lineNumberRemapper.process(null, Paths.get("input.jar"), Paths.get("output.jar"));
+	}
+}

src/main/java/net/fabricmc/loom/decompilers/fernflower/AbstractFernFlowerDecompiler.java

@@ -1,163 +0,0 @@
-/*
- * This file is part of fabric-loom, licensed under the MIT License (MIT).
- *
- * Copyright (c) 2019-2021 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.decompilers.fernflower;
-
-import static java.text.MessageFormat.format;
-
-import java.nio.file.Path;
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.Stack;
-import java.util.function.Supplier;
-
-import org.gradle.api.Project;
-import org.gradle.api.internal.project.ProjectInternal;
-import org.gradle.api.logging.LogLevel;
-import org.gradle.internal.logging.progress.ProgressLogger;
-import org.gradle.internal.logging.progress.ProgressLoggerFactory;
-import org.gradle.internal.service.ServiceRegistry;
-import org.gradle.process.ExecResult;
-import org.jetbrains.java.decompiler.main.extern.IFernflowerPreferences;
-
-import net.fabricmc.loom.api.decompilers.DecompilationMetadata;
-import net.fabricmc.loom.api.decompilers.LoomDecompiler;
-import net.fabricmc.loom.util.ConsumingOutputStream;
-import net.fabricmc.loom.util.OperatingSystem;
-
-public abstract class AbstractFernFlowerDecompiler implements LoomDecompiler {
-	private final Project project;
-
-	protected AbstractFernFlowerDecompiler(Project project) {
-		this.project = project;
-	}
-
-	public abstract Class<? extends AbstractForkedFFExecutor> fernFlowerExecutor();
-
-	@Override
-	public void decompile(Path compiledJar, Path sourcesDestination, Path linemapDestination, DecompilationMetadata metaData) {
-		if (!OperatingSystem.is64Bit()) {
-			throw new UnsupportedOperationException("FernFlower decompiler requires a 64bit JVM to run due to the memory requirements");
-		}
-
-		project.getLogging().captureStandardOutput(LogLevel.LIFECYCLE);
-
-		Map<String, Object> options = new HashMap<>() {{
-				put(IFernflowerPreferences.DECOMPILE_GENERIC_SIGNATURES, "1");
-				put(IFernflowerPreferences.BYTECODE_SOURCE_MAPPING, "1");
-				put(IFernflowerPreferences.REMOVE_SYNTHETIC, "1");
-				put(IFernflowerPreferences.LOG_LEVEL, "trace");
-				put(IFernflowerPreferences.THREADS, metaData.numberOfThreads());
-				put(IFernflowerPreferences.INDENT_STRING, "\t");
-			}};
-
-		List<String> args = new ArrayList<>();
-
-		options.forEach((k, v) -> args.add(format("-{0}={1}", k, v)));
-		args.add(absolutePathOf(compiledJar));
-		args.add("-o=" + absolutePathOf(sourcesDestination));
-		args.add("-l=" + absolutePathOf(linemapDestination));
-		args.add("-m=" + absolutePathOf(metaData.javaDocs()));
-
-		// TODO, Decompiler breaks on jemalloc, J9 module-info.class?
-		for (Path library : metaData.libraries()) {
-			args.add("-e=" + absolutePathOf(library));
-		}
-
-		ServiceRegistry registry = ((ProjectInternal) project).getServices();
-		ProgressLoggerFactory factory = registry.get(ProgressLoggerFactory.class);
-		ProgressLogger progressGroup = factory.newOperation(getClass()).setDescription("Decompile");
-		Supplier<ProgressLogger> loggerFactory = () -> {
-			ProgressLogger pl = factory.newOperation(getClass(), progressGroup);
-			pl.setDescription("decompile worker");
-			pl.started();
-			return pl;
-		};
-		Stack<ProgressLogger> freeLoggers = new Stack<>();
-		Map<String, ProgressLogger> inUseLoggers = new HashMap<>();
-
-		progressGroup.started();
-		ExecResult result = ForkingJavaExec.javaexec(
-				project,
-				spec -> {
-					spec.getMainClass().set(fernFlowerExecutor().getName());
-					spec.jvmArgs("-Xms200m", "-Xmx3G");
-					spec.setArgs(args);
-					spec.setErrorOutput(new ConsumingOutputStream(line -> {
-						if (line.startsWith("Inconsistent inner class entries")) {
-							// Suppress this
-							return;
-						}
-
-						System.err.println(line);
-					}));
-					spec.setStandardOutput(new ConsumingOutputStream(line -> {
-						if (line.startsWith("Listening for transport") || !line.contains("::")) {
-							System.out.println(line);
-							return;
-						}
-
-						int sepIdx = line.indexOf("::");
-						String id = line.substring(0, sepIdx).trim();
-						String data = line.substring(sepIdx + 2).trim();
-
-						ProgressLogger logger = inUseLoggers.get(id);
-
-						String[] segs = data.split(" ");
-
-						if (segs[0].equals("waiting")) {
-							if (logger != null) {
-								logger.progress("Idle..");
-								inUseLoggers.remove(id);
-								freeLoggers.push(logger);
-							}
-						} else {
-							if (logger == null) {
-								if (!freeLoggers.isEmpty()) {
-									logger = freeLoggers.pop();
-								} else {
-									logger = loggerFactory.get();
-								}
-
-								inUseLoggers.put(id, logger);
-							}
-
-							logger.progress(data);
-						}
-					}));
-				});
-		inUseLoggers.values().forEach(ProgressLogger::completed);
-		freeLoggers.forEach(ProgressLogger::completed);
-		progressGroup.completed();
-
-		result.rethrowFailure();
-		result.assertNormalExitValue();
-	}
-
-	private static String absolutePathOf(Path path) {
-		return path.toAbsolutePath().toString();
-	}
-}

src/main/java/net/fabricmc/loom/decompilers/fernflower/AbstractForkedFFExecutor.java

@@ -1,107 +0,0 @@
-/*
- * This file is part of fabric-loom, licensed under the MIT License (MIT).
- *
- * Copyright (c) 2019-2020 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.decompilers.fernflower;
-
-import java.io.File;
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.Objects;
-
-/**
- * Entry point for Forked FernFlower task.
- * Takes one parameter, a single file, each line is treated as command line input.
- * Forces one input file.
- * Forces one output file using '-o=/path/to/output'
- * Created by covers1624 on 11/02/19.
- * <p>Extending classes MUST have a standard "public static void main(args)".
- * They may then call AbstractForkedFFExecutor#decompile for it to use the overridden AbstractForkedFFExecutor#runFF
- * </p>
- */
-public abstract class AbstractForkedFFExecutor {
-	public static void decompile(String[] args, AbstractForkedFFExecutor ffExecutor) {
-		Map<String, Object> options = new HashMap<>();
-		File input = null;
-		File output = null;
-		File lineMap = null;
-		File mappings = null;
-		List<File> libraries = new ArrayList<>();
-
-		boolean isOption = true;
-
-		for (String arg : args) {
-			if (isOption && arg.length() > 5 && arg.charAt(0) == '-' && arg.charAt(4) == '=') {
-				String value = arg.substring(5);
-
-				if ("true".equalsIgnoreCase(value)) {
-					value = "1";
-				} else if ("false".equalsIgnoreCase(value)) {
-					value = "0";
-				}
-
-				options.put(arg.substring(1, 4), value);
-			} else {
-				isOption = false;
-
-				if (arg.startsWith("-e=")) {
-					libraries.add(new File(arg.substring(3)));
-				} else if (arg.startsWith("-o=")) {
-					if (output != null) {
-						throw new RuntimeException("Unable to set more than one output.");
-					}
-
-					output = new File(arg.substring(3));
-				} else if (arg.startsWith("-l=")) {
-					if (lineMap != null) {
-						throw new RuntimeException("Unable to set more than one lineMap file.");
-					}
-
-					lineMap = new File(arg.substring(3));
-				} else if (arg.startsWith("-m=")) {
-					if (mappings != null) {
-						throw new RuntimeException("Unable to use more than one mappings file.");
-					}
-
-					mappings = new File(arg.substring(3));
-				} else {
-					if (input != null) {
-						throw new RuntimeException("Unable to set more than one input.");
-					}
-
-					input = new File(arg);
-				}
-			}
-		}
-
-		Objects.requireNonNull(input, "Input not set.");
-		Objects.requireNonNull(output, "Output not set.");
-		Objects.requireNonNull(mappings, "Mappings not set.");
-
-		ffExecutor.runFF(options, libraries, input, output, lineMap, mappings);
-	}
-
-	public abstract void runFF(Map<String, Object> options, List<File> libraries, File input, File output, File lineMap, File mappings);
-}

src/main/java/net/fabricmc/loom/decompilers/fernflower/FabricFernFlowerDecompiler.java

@@ -1,7 +1,7 @@
 /*
  * This file is part of fabric-loom, licensed under the MIT License (MIT).
  *
- * Copyright (c) 2018-2020 FabricMC
+ * Copyright (c) 2019-2021 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
@@ -24,20 +24,43 @@
 
 package net.fabricmc.loom.decompilers.fernflower;
 
-import org.gradle.api.Project;
+import java.nio.file.Path;
+import java.util.Map;
 
-public class FabricFernFlowerDecompiler extends AbstractFernFlowerDecompiler {
+import org.jetbrains.java.decompiler.main.Fernflower;
-	public FabricFernFlowerDecompiler(Project project) {
+import org.jetbrains.java.decompiler.main.extern.IFernflowerPreferences;
-		super(project);
+import org.jetbrains.java.decompiler.main.extern.IResultSaver;
-	}
 
+import net.fabricmc.fernflower.api.IFabricJavadocProvider;
+import net.fabricmc.loom.api.decompilers.DecompilationMetadata;
+import net.fabricmc.loom.api.decompilers.LoomDecompiler;
+
+public final class FabricFernFlowerDecompiler implements LoomDecompiler {
 	@Override
 	public String name() {
 		return "FabricFlower"; // Or something else?
 	}
 
 	@Override
-	public Class<? extends AbstractForkedFFExecutor> fernFlowerExecutor() {
+	public void decompile(Path compiledJar, Path sourcesDestination, Path linemapDestination, DecompilationMetadata metaData) {
-		return FabricForkedFFExecutor.class;
+		Map<String, Object> options = Map.of(
+				IFernflowerPreferences.DECOMPILE_GENERIC_SIGNATURES, "1",
+				IFernflowerPreferences.BYTECODE_SOURCE_MAPPING, "1",
+				IFernflowerPreferences.REMOVE_SYNTHETIC, "1",
+				IFernflowerPreferences.LOG_LEVEL, "trace",
+				IFernflowerPreferences.THREADS, String.valueOf(metaData.numberOfThreads()),
+				IFernflowerPreferences.INDENT_STRING, "\t",
+				IFabricJavadocProvider.PROPERTY_NAME, new TinyJavadocProvider(metaData.javaDocs().toFile())
+		);
+
+		IResultSaver saver = new ThreadSafeResultSaver(sourcesDestination::toFile, linemapDestination::toFile);
+		Fernflower ff = new Fernflower(FernFlowerUtils::getBytecode, saver, options, new FernflowerLogger(metaData.logger()));
+
+		for (Path library : metaData.libraries()) {
+			ff.addLibrary(library.toFile());
+		}
+
+		ff.addSource(compiledJar.toFile());
+		ff.decompileContext();
 	}
 }

src/main/java/net/fabricmc/loom/decompilers/fernflower/FernflowerLogger.java

@@ -1,7 +1,7 @@
 /*
  * This file is part of fabric-loom, licensed under the MIT License (MIT).
  *
- * Copyright (c) 2018-2020 FabricMC
+ * Copyright (c) 2021 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
@@ -24,34 +24,60 @@
 
 package net.fabricmc.loom.decompilers.fernflower;
 
-import java.io.File;
+import java.io.IOException;
-import java.util.List;
-import java.util.Map;
 
-import org.jetbrains.java.decompiler.main.Fernflower;
 import org.jetbrains.java.decompiler.main.extern.IFernflowerLogger;
-import org.jetbrains.java.decompiler.main.extern.IResultSaver;
 
-import net.fabricmc.fernflower.api.IFabricJavadocProvider;
+import net.fabricmc.loom.util.IOStringConsumer;
 
-public class FabricForkedFFExecutor extends AbstractForkedFFExecutor {
+public class FernflowerLogger extends IFernflowerLogger {
-	public static void main(String[] args) {
+	private final IOStringConsumer logger;
-		AbstractForkedFFExecutor.decompile(args, new FabricForkedFFExecutor());
+
+	public FernflowerLogger(IOStringConsumer logger) {
+		this.logger = logger;
 	}
 
 	@Override
-	public void runFF(Map<String, Object> options, List<File> libraries, File input, File output, File lineMap, File mappings) {
+	public void writeMessage(String message, Severity severity) {
-		options.put(IFabricJavadocProvider.PROPERTY_NAME, new TinyJavadocProvider(mappings));
+		if (message.contains("Inconsistent inner class entries for")) return;
-
+		System.err.println(message);
-		IResultSaver saver = new ThreadSafeResultSaver(() -> output, () -> lineMap);
-		IFernflowerLogger logger = new ThreadIDFFLogger();
-		Fernflower ff = new Fernflower(FernFlowerUtils::getBytecode, saver, options, logger);
-
-		for (File library : libraries) {
-			ff.addLibrary(library);
 	}
 
-		ff.addSource(input);
+	@Override
-		ff.decompileContext();
+	public void writeMessage(String message, Severity severity, Throwable t) {
+		writeMessage(message, severity);
+	}
+
+	private void write(String data) {
+		try {
+			logger.accept(data);
+		} catch (IOException e) {
+			throw new RuntimeException("Failed to log", e);
+		}
+	}
+
+	@Override
+	public void startReadingClass(String className) {
+		write("Decompiling " + className);
+	}
+
+	@Override
+	public void startClass(String className) {
+		write("Decompiling " + className);
+	}
+
+	@Override
+	public void startWriteClass(String className) {
+		// Nope
+	}
+
+	@Override
+	public void startMethod(String methodName) {
+		// Nope
+	}
+
+	@Override
+	public void endMethod() {
+		// Nope
 	}
 }

src/main/java/net/fabricmc/loom/decompilers/fernflower/ForkingJavaExec.java

@@ -1,70 +0,0 @@
-/*
- * This file is part of fabric-loom, licensed under the MIT License (MIT).
- *
- * Copyright (c) 2016-2021 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.decompilers.fernflower;
-
-import java.net.URL;
-import java.net.URLClassLoader;
-
-import org.gradle.api.Action;
-import org.gradle.api.Project;
-import org.gradle.api.artifacts.ConfigurationContainer;
-import org.gradle.api.artifacts.dsl.DependencyHandler;
-import org.gradle.api.file.FileCollection;
-import org.gradle.process.ExecResult;
-import org.gradle.process.JavaExecSpec;
-
-/**
- * Simple utility class for a Task that wishes to execute a java process
- * with the classpath of the gradle plugin plus groovy.
- *
- * <p>Created by covers1624 on 11/02/19.
- */
-public class ForkingJavaExec {
-	public static ExecResult javaexec(Project project, Action<? super JavaExecSpec> action) {
-		return project.javaexec(spec -> {
-			spec.classpath(getClasspath(project));
-			action.execute(spec);
-		});
-	}
-
-	private static Object getClasspath(Project project) {
-		if (System.getProperty("fabric.loom.test") != null) {
-			return getTestClasspath();
-		}
-
-		return getRuntimeClasspath(project.getRootProject().getPlugins().hasPlugin("fabric-loom") ? project.getRootProject() : project);
-	}
-
-	private static FileCollection getRuntimeClasspath(Project project) {
-		ConfigurationContainer configurations = project.getBuildscript().getConfigurations();
-		DependencyHandler handler = project.getDependencies();
-		return configurations.getByName("classpath")
-				.plus(configurations.detachedConfiguration(handler.localGroovy()));
-	}
-
-	private static URL[] getTestClasspath() {
-		return ((URLClassLoader) ForkingJavaExec.class.getClassLoader()).getURLs();
-	}
-}

src/main/java/net/fabricmc/loom/decompilers/fernflower/ThreadIDFFLogger.java

@@ -1,127 +0,0 @@
-/*
- * This file is part of fabric-loom, licensed under the MIT License (MIT).
- *
- * Copyright (c) 2019-2020 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.decompilers.fernflower;
-
-import java.io.PrintStream;
-import java.text.MessageFormat;
-import java.util.Stack;
-
-import org.jetbrains.java.decompiler.main.extern.IFernflowerLogger;
-
-/**
- * This logger simply prints what each thread is doing
- * to the console in a machine parsable way.
- *
- * <p>Created by covers1624 on 11/02/19.
- */
-public class ThreadIDFFLogger extends IFernflowerLogger {
-	public final PrintStream stdOut;
-	public final PrintStream stdErr;
-
-	private final ThreadLocal<Stack<String>> workingClass = ThreadLocal.withInitial(Stack::new);
-	private final ThreadLocal<Stack<String>> line = ThreadLocal.withInitial(Stack::new);
-
-	public ThreadIDFFLogger() {
-		this(System.err, System.out);
-	}
-
-	public ThreadIDFFLogger(PrintStream stdOut, PrintStream stdErr) {
-		this.stdOut = stdOut;
-		this.stdErr = stdErr;
-	}
-
-	@Override
-	public void writeMessage(String message, Severity severity) {
-		System.err.println(message);
-	}
-
-	@Override
-	public void writeMessage(String message, Severity severity, Throwable t) {
-		System.err.println(message);
-		t.printStackTrace(System.err);
-	}
-
-	private void print() {
-		Thread thread = Thread.currentThread();
-		long id = thread.getId();
-
-		if (line.get().isEmpty()) {
-			System.out.println(MessageFormat.format("{0} :: waiting", id));
-			return;
-		}
-
-		String line = this.line.get().peek();
-		System.out.println(MessageFormat.format("{0} :: {1}", id, line).trim());
-	}
-
-	@Override
-	public void startReadingClass(String className) {
-		workingClass.get().push(className);
-		line.get().push("Decompiling " + className);
-		print();
-	}
-
-	@Override
-	public void startClass(String className) {
-		workingClass.get().push(className);
-		line.get().push("Decompiling " + className);
-		print();
-	}
-
-	@Override
-	public void startMethod(String methodName) {
-		// No need to print out methods
-	}
-
-	@Override
-	public void endMethod() {
-	}
-
-	@Override
-	public void endClass() {
-		line.get().pop();
-		workingClass.get().pop();
-		print();
-	}
-
-	@Override
-	public void startWriteClass(String className) {
-		line.get().push("Writing " + className);
-		print();
-	}
-
-	@Override
-	public void endWriteClass() {
-		line.get().pop();
-		print();
-	}
-
-	@Override
-	public void endReadingClass() {
-		line.get().pop();
-		workingClass.get().pop();
-		print();
-	}
-}

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

@@ -26,18 +26,33 @@ package net.fabricmc.loom.task;
 
 import java.io.File;
 import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
 import java.util.Collection;
 import java.util.List;
 import java.util.Locale;
+import java.util.Objects;
+import java.util.UUID;
 import java.util.stream.Collectors;
 
 import javax.inject.Inject;
 
+import org.gradle.api.file.ConfigurableFileCollection;
+import org.gradle.api.file.RegularFileProperty;
+import org.gradle.api.provider.Property;
+import org.gradle.api.tasks.Input;
 import org.gradle.api.tasks.InputFile;
 import org.gradle.api.tasks.TaskAction;
+import org.gradle.workers.WorkAction;
+import org.gradle.workers.WorkParameters;
+import org.gradle.workers.WorkQueue;
+import org.gradle.workers.WorkerExecutor;
+import org.gradle.workers.internal.WorkerDaemonClientsManager;
+import org.jetbrains.annotations.Nullable;
 
 import net.fabricmc.loom.LoomGradleExtension;
 import net.fabricmc.loom.api.decompilers.DecompilationMetadata;
@@ -47,58 +62,216 @@ import net.fabricmc.loom.configuration.accesswidener.TransitiveAccessWidenerMapp
 import net.fabricmc.loom.configuration.providers.mappings.MappingsProviderImpl;
 import net.fabricmc.loom.decompilers.LineNumberRemapper;
 import net.fabricmc.loom.util.Constants;
-import net.fabricmc.loom.util.gradle.ProgressLogger;
+import net.fabricmc.loom.util.IOStringConsumer;
+import net.fabricmc.loom.util.OperatingSystem;
+import net.fabricmc.loom.util.gradle.ThreadedProgressLoggerConsumer;
+import net.fabricmc.loom.util.gradle.ThreadedSimpleProgressLogger;
+import net.fabricmc.loom.util.gradle.WorkerDaemonClientsManagerHelper;
+import net.fabricmc.loom.util.ipc.IPCClient;
+import net.fabricmc.loom.util.ipc.IPCServer;
 import net.fabricmc.stitch.util.StitchUtil;
 
-public class GenerateSourcesTask extends AbstractLoomTask {
+public abstract class GenerateSourcesTask extends AbstractLoomTask {
 	public final LoomDecompiler decompiler;
 
-	private File inputJar;
+	@InputFile
+	public abstract RegularFileProperty getInputJar();
+
+	/**
+	 * Max memory for forked JVM in megabytes.
+	 */
+	@Input
+	public abstract Property<Long> getMaxMemory();
+
+	@Inject
+	public abstract WorkerExecutor getWorkerExecutor();
+
+	@Inject
+	public abstract WorkerDaemonClientsManager getWorkerDaemonClientsManager();
 
 	@Inject
 	public GenerateSourcesTask(LoomDecompiler decompiler) {
 		this.decompiler = decompiler;
 
+		Objects.requireNonNull(getDecompilerConstructor(this.decompiler.getClass().getCanonicalName()),
+				"%s must have a no args constructor".formatted(this.decompiler.getClass().getCanonicalName()));
+
 		getOutputs().upToDateWhen((o) -> false);
+		getMaxMemory().convention(4096L).finalizeValueOnRead();
 	}
 
 	@TaskAction
-	public void doTask() throws Throwable {
+	public void run() throws IOException {
-		int threads = Runtime.getRuntime().availableProcessors();
+		if (!OperatingSystem.is64Bit()) {
-		Collection<Path> libraries = getProject().getConfigurations().getByName(Constants.Configurations.MINECRAFT_DEPENDENCIES).getFiles()
+			throw new UnsupportedOperationException("GenSources task requires a 64bit JVM to run due to the memory requirements.");
-				.stream().map(File::toPath).collect(Collectors.toSet());
+		}
 
-		DecompilationMetadata metadata = new DecompilationMetadata(threads, getMappings(), libraries);
+		if (!OperatingSystem.isUnixDomainSocketsSupported()) {
-		Path runtimeJar = getExtension().getMappingsProvider().mappedProvider.getMappedJar().toPath();
+			getProject().getLogger().warn("Decompile worker logging disabled as Unix Domain Sockets is not supported on your operating system.");
-		Path sourcesDestination = getMappedJarFileWithSuffix("-sources.jar").toPath();
+
-		Path linemap = getMappedJarFileWithSuffix("-sources.lmap").toPath();
+			doWork(null);
-		decompiler.decompile(inputJar.toPath(), sourcesDestination, linemap, metadata);
+			return;
+		}
+
+		// Set up the IPC path to get the log output back from the forked JVM
+		final Path ipcPath = Files.createTempFile("loom", "ipc");
+		Files.deleteIfExists(ipcPath);
+
+		try (ThreadedProgressLoggerConsumer loggerConsumer = new ThreadedProgressLoggerConsumer(getProject(), decompiler.name(), "Decompiling minecraft sources");
+				IPCServer logReceiver = new IPCServer(ipcPath, loggerConsumer)) {
+			doWork(ipcPath);
+		} catch (InterruptedException e) {
+			throw new RuntimeException("Failed to shutdown log receiver", e);
+		} finally {
+			Files.deleteIfExists(ipcPath);
+		}
+	}
+
+	private void doWork(@Nullable Path ipcPath) {
+		final String jvmMarkerValue = UUID.randomUUID().toString();
+		final WorkQueue workQueue = createWorkQueue(jvmMarkerValue);
+
+		workQueue.submit(DecompileAction.class, params -> {
+			params.getDecompilerClass().set(decompiler.getClass().getCanonicalName());
+
+			params.getInputJar().set(getInputJar());
+			params.getRuntimeJar().set(getExtension().getMappingsProvider().mappedProvider.getMappedJar());
+			params.getSourcesDestinationJar().set(getMappedJarFileWithSuffix("-sources.jar"));
+			params.getLinemap().set(getMappedJarFileWithSuffix("-sources.lmap"));
+			params.getLinemapJar().set(getMappedJarFileWithSuffix("-linemapped.jar"));
+			params.getMappings().set(getMappings().toFile());
+
+			if (ipcPath != null) {
+				params.getIPCPath().set(ipcPath.toFile());
+			}
+
+			params.getClassPath().setFrom(getProject().getConfigurations().getByName(Constants.Configurations.MINECRAFT_DEPENDENCIES));
+		});
+
+		workQueue.await();
+
+		if (useProcessIsolation()) {
+			boolean stopped = WorkerDaemonClientsManagerHelper.stopIdleJVM(getWorkerDaemonClientsManager(), jvmMarkerValue);
+
+			if (!stopped) {
+				throw new RuntimeException("Failed to stop decompile worker JVM");
+			}
+		}
+	}
+
+	private WorkQueue createWorkQueue(String jvmMarkerValue) {
+		if (!useProcessIsolation()) {
+			return getWorkerExecutor().noIsolation();
+		}
+
+		return getWorkerExecutor().processIsolation(spec -> {
+			spec.forkOptions(forkOptions -> {
+				forkOptions.setMaxHeapSize("%dm".formatted(getMaxMemory().get()));
+				forkOptions.systemProperty(WorkerDaemonClientsManagerHelper.MARKER_PROP, jvmMarkerValue);
+			});
+		});
+	}
+
+	private boolean useProcessIsolation() {
+		// Useful if you want to debug the decompiler, make sure you run gradle with enough memory.
+		return !Boolean.getBoolean("fabric.loom.genSources.debug");
+	}
+
+	public interface DecompileParams extends WorkParameters {
+		Property<String> getDecompilerClass();
+
+		RegularFileProperty getInputJar();
+		RegularFileProperty getRuntimeJar();
+		RegularFileProperty getSourcesDestinationJar();
+		RegularFileProperty getLinemap();
+		RegularFileProperty getLinemapJar();
+		RegularFileProperty getMappings();
+
+		RegularFileProperty getIPCPath();
+
+		ConfigurableFileCollection getClassPath();
+	}
+
+	public abstract static class DecompileAction implements WorkAction<DecompileParams> {
+		@Override
+		public void execute() {
+			if (!getParameters().getIPCPath().isPresent() || !OperatingSystem.isUnixDomainSocketsSupported()) {
+				// Does not support unix domain sockets, print to sout.
+				doDecompile(System.out::println);
+				return;
+			}
+
+			final Path ipcPath = getParameters().getIPCPath().get().getAsFile().toPath();
+
+			try (IPCClient ipcClient = new IPCClient(ipcPath)) {
+				doDecompile(new ThreadedSimpleProgressLogger(ipcClient));
+			} catch (Exception e) {
+				throw new RuntimeException("Failed to setup IPC Client", e);
+			}
+		}
+
+		private void doDecompile(IOStringConsumer logger) {
+			final Path inputJar = getParameters().getInputJar().get().getAsFile().toPath();
+			final Path sourcesDestinationJar = getParameters().getSourcesDestinationJar().get().getAsFile().toPath();
+			final Path linemap = getParameters().getLinemap().get().getAsFile().toPath();
+			final Path linemapJar = getParameters().getLinemapJar().get().getAsFile().toPath();
+			final Path runtimeJar = getParameters().getRuntimeJar().get().getAsFile().toPath();
+
+			final LoomDecompiler decompiler;
+
+			try {
+				decompiler = getDecompilerConstructor(getParameters().getDecompilerClass().get()).newInstance();
+			} catch (InstantiationException | IllegalAccessException | InvocationTargetException e) {
+				throw new RuntimeException("Failed to create decompiler", e);
+			}
+
+			DecompilationMetadata metadata = new DecompilationMetadata(
+					Runtime.getRuntime().availableProcessors(),
+					getParameters().getMappings().get().getAsFile().toPath(),
+					getLibraries(),
+					logger
+			);
+
+			decompiler.decompile(
+					inputJar,
+					sourcesDestinationJar,
+					linemap,
+					metadata
+			);
+
+			// Close the decompile loggers
+			try {
+				metadata.logger().accept(ThreadedProgressLoggerConsumer.CLOSE_LOGGERS);
+			} catch (IOException e) {
+				throw new UncheckedIOException("Failed to close loggers", e);
+			}
 
 			if (Files.exists(linemap)) {
-			Path linemappedJarDestination = getMappedJarFileWithSuffix("-linemapped.jar").toPath();
+				try {
-
 					// Line map the actually jar used to run the game, not the one used to decompile
-			remapLineNumbers(runtimeJar, linemap, linemappedJarDestination);
+					remapLineNumbers(metadata.logger(), runtimeJar, linemap, linemapJar);
 
-			Files.copy(linemappedJarDestination, runtimeJar, StandardCopyOption.REPLACE_EXISTING);
+					Files.copy(linemapJar, runtimeJar, StandardCopyOption.REPLACE_EXISTING);
-			Files.delete(linemappedJarDestination);
+					Files.delete(linemapJar);
+				} catch (IOException e) {
+					throw new UncheckedIOException("Failed to remap line numbers", e);
+				}
 			}
 		}
 
-	private void remapLineNumbers(Path oldCompiledJar, Path linemap, Path linemappedJarDestination) throws IOException {
+		private void remapLineNumbers(IOStringConsumer logger, Path oldCompiledJar, Path linemap, Path linemappedJarDestination) throws IOException {
-		getProject().getLogger().info(":adjusting line numbers");
 			LineNumberRemapper remapper = new LineNumberRemapper();
 			remapper.readMappings(linemap.toFile());
 
-		ProgressLogger progressLogger = ProgressLogger.getProgressFactory(getProject(), getClass().getName());
-		progressLogger.start("Adjusting line numbers", "linemap");
-
 			try (StitchUtil.FileSystemDelegate inFs = StitchUtil.getJarFileSystem(oldCompiledJar.toFile(), true);
 					StitchUtil.FileSystemDelegate outFs = StitchUtil.getJarFileSystem(linemappedJarDestination.toFile(), true)) {
-			remapper.process(progressLogger, inFs.get().getPath("/"), outFs.get().getPath("/"));
+				remapper.process(logger, inFs.get().getPath("/"), outFs.get().getPath("/"));
+			}
 		}
 
-		progressLogger.completed();
+		private Collection<Path> getLibraries() {
+			return getParameters().getClassPath().getFiles().stream().map(File::toPath).collect(Collectors.toSet());
+		}
 	}
 
 	private File getMappedJarFileWithSuffix(String suffix) {
@@ -140,13 +313,12 @@ public class GenerateSourcesTask extends AbstractLoomTask {
 		return baseMappings;
 	}
 
-	@InputFile
+	private static Constructor<LoomDecompiler> getDecompilerConstructor(String clazz) {
-	public File getInputJar() {
+		try {
-		return inputJar;
+			//noinspection unchecked
-	}
+			return (Constructor<LoomDecompiler>) Class.forName(clazz).getConstructor();
-
+		} catch (NoSuchMethodException | ClassNotFoundException e) {
-	public GenerateSourcesTask setInputJar(File inputJar) {
+			return null;
-		this.inputJar = inputJar;
+		}
-		return this;
 	}
 }

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

@@ -128,9 +128,9 @@ public final class LoomTasks {
 				File outputJar = mappingsProvider.mappedProvider.getUnpickedJar();
 
 				tasks.register("unpickJar", UnpickJarTask.class, unpickJarTask -> {
-					unpickJarTask.setUnpickDefinition(mappingsProvider.getUnpickDefinitionsFile());
+					unpickJarTask.getUnpickDefinitions().set(mappingsProvider.getUnpickDefinitionsFile());
-					unpickJarTask.setInputJar(mappingsProvider.mappedProvider.getMappedJar());
+					unpickJarTask.getInputJar().set(mappingsProvider.mappedProvider.getMappedJar());
-					unpickJarTask.setOutputJar(outputJar);
+					unpickJarTask.getOutputJar().set(outputJar);
 				});
 
 				inputJar = outputJar;
@@ -142,7 +142,7 @@ public final class LoomTasks {
 				String taskName = decompiler instanceof FabricFernFlowerDecompiler ? "genSources" : "genSourcesWith" + decompiler.name();
 				// decompiler will be passed to the constructor of GenerateSourcesTask
 				GenerateSourcesTask generateSourcesTask = tasks.register(taskName, GenerateSourcesTask.class, decompiler).get();
-				generateSourcesTask.setInputJar(inputJar);
+				generateSourcesTask.getInputJar().set(inputJar);
 
 				if (mappingsProvider.hasUnpickDefinitions()) {
 					generateSourcesTask.dependsOn(tasks.getByName("unpickJar"));

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

@@ -29,7 +29,12 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.nio.file.Files;
 
+import javax.inject.Inject;
+
+import org.gradle.api.file.ConfigurableFileCollection;
+import org.gradle.api.file.RegularFileProperty;
 import org.gradle.api.tasks.InputFile;
+import org.gradle.api.tasks.InputFiles;
 import org.gradle.api.tasks.Internal;
 import org.gradle.api.tasks.JavaExec;
 import org.gradle.api.tasks.OutputFile;
@@ -39,26 +44,43 @@ import net.fabricmc.loom.configuration.providers.LaunchProvider;
 import net.fabricmc.loom.extension.LoomFiles;
 import net.fabricmc.loom.util.Constants;
 
-public class UnpickJarTask extends JavaExec {
+public abstract class UnpickJarTask extends JavaExec {
-	File inputJar;
+	@InputFile
-	File unpickDefinition;
+	public abstract RegularFileProperty getInputJar();
 
-	File outputJar;
+	@InputFile
+	public abstract RegularFileProperty getUnpickDefinitions();
 
+	@InputFiles
+	// Only 1 file, but it comes from a configuration
+	public abstract ConfigurableFileCollection getConstantJar();
+
+	@InputFiles
+	public abstract ConfigurableFileCollection getUnpickClasspath();
+
+	@OutputFile
+	public abstract RegularFileProperty getOutputJar();
+
+	@Inject
 	public UnpickJarTask() {
-		getOutputs().upToDateWhen(e -> false);
 		classpath(getProject().getConfigurations().getByName(Constants.Configurations.UNPICK_CLASSPATH));
 		getMainClass().set("daomephsta.unpick.cli.Main");
+
+		getConstantJar().setFrom(getProject().getConfigurations().getByName(Constants.Configurations.MAPPING_CONSTANTS));
+		getUnpickClasspath().setFrom(getProject().getConfigurations().getByName(Constants.Configurations.MINECRAFT_DEPENDENCIES));
 	}
 
 	@Override
 	public void exec() {
-		fileArg(getInputJar(), getOutputJar(), getUnpickDefinition());
+		fileArg(getInputJar().get().getAsFile(), getOutputJar().get().getAsFile(), getUnpickDefinitions().get().getAsFile());
-		fileArg(getConstantJar());
+		fileArg(getConstantJar().getSingleFile());
 
 		// Classpath
 		fileArg(getExtension().getMinecraftMappedProvider().getMappedJar());
-		fileArg(getMinecraftDependencies());
+
+		for (File file : getUnpickClasspath()) {
+			fileArg(file);
+		}
 
 		writeUnpickLogConfig();
 		systemProperty("java.util.logging.config.file", getDirectories().getUnpickLoggingConfigFile().getAbsolutePath());
@@ -75,45 +97,6 @@ public class UnpickJarTask extends JavaExec {
 		}
 	}
 
-	private File[] getMinecraftDependencies() {
-		return getProject().getConfigurations().getByName(Constants.Configurations.MINECRAFT_DEPENDENCIES)
-				.resolve().toArray(new File[0]);
-	}
-
-	private File getConstantJar() {
-		return getProject().getConfigurations().getByName(Constants.Configurations.MAPPING_CONSTANTS).getSingleFile();
-	}
-
-	@InputFile
-	public File getInputJar() {
-		return inputJar;
-	}
-
-	public UnpickJarTask setInputJar(File inputJar) {
-		this.inputJar = inputJar;
-		return this;
-	}
-
-	@InputFile
-	public File getUnpickDefinition() {
-		return unpickDefinition;
-	}
-
-	public UnpickJarTask setUnpickDefinition(File unpickDefinition) {
-		this.unpickDefinition = unpickDefinition;
-		return this;
-	}
-
-	@OutputFile
-	public File getOutputJar() {
-		return outputJar;
-	}
-
-	public UnpickJarTask setOutputJar(File outputJar) {
-		this.outputJar = outputJar;
-		return this;
-	}
-
 	private void fileArg(File... files) {
 		for (File file : files) {
 			args(file.getAbsolutePath());

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

@@ -0,0 +1,31 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2021 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.util;
+
+import java.io.IOException;
+
+public interface IOStringConsumer {
+	void accept(String data) throws IOException;
+}

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

@@ -24,6 +24,11 @@
 
 package net.fabricmc.loom.util;
 
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.net.StandardProtocolFamily;
+import java.nio.channels.ServerSocketChannel;
+
 public class OperatingSystem {
 	public static String getOS() {
 		String osName = System.getProperty("os.name").toLowerCase();
@@ -63,4 +68,15 @@ public class OperatingSystem {
 		// CI seems to be set by most popular CI services
 		return System.getenv("CI") != null;
 	}
+
+	// Requires Unix, or Windows 10 17063 or later. See: https://devblogs.microsoft.com/commandline/af_unix-comes-to-windows/
+	public static boolean isUnixDomainSocketsSupported() {
+		try (ServerSocketChannel serverChannel = ServerSocketChannel.open(StandardProtocolFamily.UNIX)) {
+			return true;
+		} catch (UnsupportedOperationException e) {
+			return false;
+		} catch (IOException e) {
+			throw new UncheckedIOException(e);
+		}
+	}
 }

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

@@ -43,7 +43,7 @@ import net.fabricmc.loom.LoomGradleExtension;
 import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.loom.configuration.RemappedConfigurationEntry;
 import net.fabricmc.loom.configuration.providers.mappings.MappingsProviderImpl;
-import net.fabricmc.loom.util.gradle.ProgressLogger;
+import net.fabricmc.loom.util.gradle.ProgressLoggerHelper;
 import net.fabricmc.lorenztiny.TinyMappingsReader;
 import net.fabricmc.mappingio.tree.MemoryMappingTree;
 import net.fabricmc.stitch.util.StitchUtil;
@@ -51,7 +51,7 @@ import net.fabricmc.stitch.util.StitchUtil;
 public class SourceRemapper {
 	private final Project project;
 	private final boolean toNamed;
-	private final List<Consumer<ProgressLogger>> remapTasks = new ArrayList<>();
+	private final List<Consumer<ProgressLoggerHelper>> remapTasks = new ArrayList<>();
 
 	private Mercury mercury;
 
@@ -90,7 +90,7 @@ public class SourceRemapper {
 
 		project.getLogger().lifecycle(":remapping sources");
 
-		ProgressLogger progressLogger = ProgressLogger.getProgressFactory(project, SourceRemapper.class.getName());
+		ProgressLoggerHelper progressLogger = ProgressLoggerHelper.getProgressFactory(project, SourceRemapper.class.getName());
 		progressLogger.start("Remapping dependency sources", "sources");
 
 		remapTasks.forEach(consumer -> consumer.accept(progressLogger));

src/main/java/net/fabricmc/loom/util/gradle/ProgressLoggerHelper.java

@@ -32,11 +32,11 @@ import org.gradle.api.Project;
 /**
  * Wrapper to ProgressLogger internal API.
  */
-public class ProgressLogger {
+public class ProgressLoggerHelper {
 	private final Object logger;
 	private final Method getDescription, setDescription, getShortDescription, setShortDescription, getLoggingHeader, setLoggingHeader, start, started, startedArg, progress, completed, completedArg;
 
-	private ProgressLogger(Object logger) {
+	private ProgressLoggerHelper(Object logger) {
 		this.logger = logger;
 		this.getDescription = getMethod("getDescription");
 		this.setDescription = getMethod("setDescription", String.class);
@@ -102,17 +102,17 @@ public class ProgressLogger {
 	 * @param category The logger category
 	 * @return In any case a progress logger
 	 */
-	public static ProgressLogger getProgressFactory(Project project, String category) {
+	public static ProgressLoggerHelper getProgressFactory(Project project, String category) {
 		try {
 			Method getServices = project.getClass().getMethod("getServices");
 			Object serviceFactory = getServices.invoke(project);
 			Method get = serviceFactory.getClass().getMethod("get", Class.class);
 			Object progressLoggerFactory = get.invoke(serviceFactory, getFactoryClass());
 			Method newOperation = progressLoggerFactory.getClass().getMethod("newOperation", String.class);
-			return new ProgressLogger(newOperation.invoke(progressLoggerFactory, category));
+			return new ProgressLoggerHelper(newOperation.invoke(progressLoggerFactory, category));
 		} catch (Exception e) {
 			project.getLogger().error("Unable to get progress logger. Download progress will not be displayed.");
-			return new ProgressLogger(null);
+			return new ProgressLoggerHelper(null);
 		}
 	}
 
@@ -132,7 +132,7 @@ public class ProgressLogger {
 	 *
 	 * @param description The description.
 	 */
-	public ProgressLogger setDescription(String description) {
+	public ProgressLoggerHelper setDescription(String description) {
 		invoke(setDescription, description);
 		return this;
 	}
@@ -153,7 +153,7 @@ public class ProgressLogger {
 	 *
 	 * @param description The short description.
 	 */
-	public ProgressLogger setShortDescription(String description) {
+	public ProgressLoggerHelper setShortDescription(String description) {
 		invoke(setShortDescription, description);
 		return this;
 	}
@@ -176,7 +176,7 @@ public class ProgressLogger {
 	 *
 	 * @param header The header. May be empty or null.
 	 */
-	public ProgressLogger setLoggingHeader(String header) {
+	public ProgressLoggerHelper setLoggingHeader(String header) {
 		invoke(setLoggingHeader, header);
 		return this;
 	}
@@ -186,7 +186,7 @@ public class ProgressLogger {
 	 *
 	 * @return this logger instance
 	 */
-	public ProgressLogger start(String description, String shortDescription) {
+	public ProgressLoggerHelper start(String description, String shortDescription) {
 		invoke(start, description, shortDescription);
 		return this;
 	}

src/main/java/net/fabricmc/loom/util/gradle/ThreadedProgressLoggerConsumer.java

@@ -0,0 +1,95 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2021 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.util.gradle;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.Consumer;
+
+import org.gradle.api.Project;
+import org.gradle.api.internal.project.ProjectInternal;
+import org.gradle.internal.logging.progress.ProgressLogger;
+import org.gradle.internal.logging.progress.ProgressLoggerFactory;
+
+public class ThreadedProgressLoggerConsumer implements Consumer<String>, AutoCloseable {
+	public static final String CLOSE_LOGGERS = "LOOM_CLOSE_LOGGERS";
+
+	private final Project project;
+	private final String name;
+	private final String desc;
+
+	private final ProgressLoggerFactory progressLoggerFactory;
+	private final ProgressLogger progressGroup;
+	private final Map<String, ProgressLogger> loggers = Collections.synchronizedMap(new HashMap<>());
+
+	public ThreadedProgressLoggerConsumer(Project project, String name, String desc) {
+		this.project = project;
+		this.name = name;
+		this.desc = desc;
+
+		this.progressLoggerFactory = ((ProjectInternal) project).getServices().get(ProgressLoggerFactory.class);
+		this.progressGroup = this.progressLoggerFactory.newOperation(name).setDescription(desc);
+		progressGroup.started();
+	}
+
+	@Override
+	public void accept(String line) {
+		if (!line.contains("::")) {
+			project.getLogger().debug("Malformed threaded IPC log message: " + line);
+			return;
+		}
+
+		int idx = line.indexOf("::");
+		String id = line.substring(0, idx).trim();
+		String data = line.substring(idx + 2).trim();
+
+		if (data.equals(CLOSE_LOGGERS)) {
+			resetLoggers();
+			return;
+		}
+
+		loggers.computeIfAbsent(id, this::createLogger).progress(data);
+	}
+
+	private ProgressLogger createLogger(String id) {
+		ProgressLogger progressLogger = progressLoggerFactory.newOperation(getClass(), progressGroup);
+		progressLogger.setDescription(desc);
+		progressLogger.started();
+		return progressLogger;
+	}
+
+	private void resetLoggers() {
+		loggers.values().forEach(ProgressLogger::completed);
+		loggers.clear();
+	}
+
+	@Override
+	public void close() {
+		resetLoggers();
+
+		progressGroup.completed();
+	}
+}

src/main/java/net/fabricmc/loom/util/gradle/ThreadedSimpleProgressLogger.java

@@ -0,0 +1,36 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2021 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.util.gradle;
+
+import java.io.IOException;
+
+import net.fabricmc.loom.util.IOStringConsumer;
+
+public record ThreadedSimpleProgressLogger(IOStringConsumer parent) implements IOStringConsumer {
+	@Override
+	public void accept(String data) throws IOException {
+		parent.accept("%d::%s".formatted(Thread.currentThread().getId(), data));
+	}
+}

src/main/java/net/fabricmc/loom/util/gradle/WorkerDaemonClientsManagerHelper.java

@@ -0,0 +1,77 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2021 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.util.gradle;
+
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import org.gradle.api.Transformer;
+import org.gradle.workers.internal.DaemonForkOptions;
+import org.gradle.workers.internal.WorkerDaemonClientsManager;
+
+public class WorkerDaemonClientsManagerHelper {
+	public static final String MARKER_PROP = "fabric.loom.decompile.worker";
+
+	public static boolean stopIdleJVM(WorkerDaemonClientsManager manager, String jvmMarkerValue) {
+		AtomicBoolean stopped = new AtomicBoolean(false);
+
+		/* Transformer<List<WorkerDaemonClient>, List<WorkerDaemonClient>> */
+		Transformer<List<Object>, List<Object>> transformer = workerDaemonClients -> {
+			for (Object /* WorkerDaemonClient */ client : workerDaemonClients) {
+				DaemonForkOptions forkOptions = getForkOptions(client);
+				Map<String, Object> systemProperties = forkOptions.getJavaForkOptions().getSystemProperties();
+
+				if (systemProperties == null || !jvmMarkerValue.equals(systemProperties.get(MARKER_PROP))) {
+					// Not the JVM we are looking for
+					continue;
+				}
+
+				stopped.set(true);
+				return Collections.singletonList(client);
+			}
+
+			return Collections.emptyList();
+		};
+
+		//noinspection unchecked
+		manager.selectIdleClientsToStop((Transformer) transformer);
+
+		return stopped.get();
+	}
+
+	private static DaemonForkOptions getForkOptions(Object /* WorkerDaemonClient */ client) {
+		try {
+			Method getForkOptionsMethod = client.getClass().getDeclaredMethod("getForkOptions");
+			getForkOptionsMethod.setAccessible(true);
+			return (DaemonForkOptions) getForkOptionsMethod.invoke(client);
+		} catch (NoSuchMethodException | InvocationTargetException | IllegalAccessException e) {
+			throw new RuntimeException(e);
+		}
+	}
+}

src/main/java/net/fabricmc/loom/util/ipc/IPCClient.java

@@ -0,0 +1,67 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2021 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.util.ipc;
+
+import java.io.IOException;
+import java.net.UnixDomainSocketAddress;
+import java.nio.ByteBuffer;
+import java.nio.channels.SocketChannel;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Path;
+
+import net.fabricmc.loom.util.IOStringConsumer;
+
+public final class IPCClient implements IOStringConsumer, AutoCloseable {
+	private final Path path;
+	private final SocketChannel socketChannel;
+
+	public IPCClient(Path path) throws IOException {
+		this.path = path;
+		socketChannel = setupChannel();
+	}
+
+	private SocketChannel setupChannel() throws IOException {
+		final UnixDomainSocketAddress address = UnixDomainSocketAddress.of(path);
+		return SocketChannel.open(address);
+	}
+
+	@Override
+	public void accept(String s) throws IOException {
+		synchronized (socketChannel) {
+			ByteBuffer buf = ByteBuffer.wrap((s + "\n").getBytes(StandardCharsets.UTF_8));
+
+			while (buf.hasRemaining()) {
+				socketChannel.write(buf);
+			}
+		}
+	}
+
+	@Override
+	public void close() throws Exception {
+		synchronized (socketChannel) {
+			socketChannel.close();
+		}
+	}
+}

src/main/java/net/fabricmc/loom/util/ipc/IPCServer.java

@@ -0,0 +1,88 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2021 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.util.ipc;
+
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.net.StandardProtocolFamily;
+import java.net.UnixDomainSocketAddress;
+import java.nio.channels.ServerSocketChannel;
+import java.nio.channels.SocketChannel;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Path;
+import java.util.Scanner;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Consumer;
+
+public class IPCServer implements AutoCloseable {
+	private final ExecutorService loggerReceiverService = Executors.newSingleThreadExecutor();
+	private final Path path;
+	private final Consumer<String> consumer;
+
+	private final CountDownLatch startupLock = new CountDownLatch(1);
+
+	public IPCServer(Path path, Consumer<String> consumer) {
+		this.path = path;
+		this.consumer = consumer;
+
+		loggerReceiverService.submit(this::run);
+
+		try {
+			startupLock.await(10, TimeUnit.SECONDS);
+		} catch (InterruptedException e) {
+			throw new RuntimeException("Timed out waiting for IPC server thread to start", e);
+		}
+	}
+
+	public void run() {
+		UnixDomainSocketAddress address = UnixDomainSocketAddress.of(path);
+
+		try (ServerSocketChannel serverChannel = ServerSocketChannel.open(StandardProtocolFamily.UNIX)) {
+			serverChannel.bind(address);
+
+			startupLock.countDown();
+
+			try (SocketChannel clientChannel = serverChannel.accept();
+					Scanner scanner = new Scanner(clientChannel, StandardCharsets.UTF_8)) {
+				while (!Thread.currentThread().isInterrupted()) {
+					if (scanner.hasNextLine()) {
+						this.consumer.accept(scanner.nextLine());
+					}
+				}
+			}
+		} catch (IOException e) {
+			throw new UncheckedIOException("Failed to listen for IPC messages", e);
+		}
+	}
+
+	@Override
+	public void close() throws InterruptedException {
+		loggerReceiverService.shutdownNow();
+		loggerReceiverService.awaitTermination(10, TimeUnit.SECONDS);
+	}
+}

src/test/groovy/net/fabricmc/loom/test/integration/DecompileTest.groovy

@@ -47,6 +47,7 @@ class DecompileTest extends Specification implements GradleProjectTestTrait {
 			decompiler 		| task								| version
 			'fernflower'	| "genSources"						| DEFAULT_GRADLE
 			'fernflower'	| "genSources"						| PRE_RELEASE_GRADLE
-			'cfr' 			| "genSourcesWithExperimentalCfr"	| DEFAULT_GRADLE
+			'cfr' 			| "genSourcesWithCfr"				| DEFAULT_GRADLE
+			'cfr' 			| "genSourcesWithCfr"				| PRE_RELEASE_GRADLE
 	}
 }

src/test/groovy/net/fabricmc/loom/test/unit/IPCTest.groovy

@@ -0,0 +1,65 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2021 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.test.unit
+
+import net.fabricmc.loom.util.ipc.IPCClient
+import net.fabricmc.loom.util.ipc.IPCServer
+import spock.lang.Specification
+import spock.lang.Timeout
+
+import java.nio.file.Files
+import java.util.function.Consumer
+
+@Timeout(20)
+class IPCTest extends Specification {
+    def "ipc test"() {
+        given:
+            def path = Files.createTempFile("loom", "ipc")
+            Files.deleteIfExists(path)
+
+            def received = []
+            Consumer<String> consumer = { str ->
+                println str
+                received << str
+            }
+
+        when:
+            def ipcServer = new IPCServer(path, consumer)
+
+            new IPCClient(path).withCloseable { client ->
+               client.accept("Test")
+               client.accept("Hello")
+            }
+
+            // Allow ipcServer to finish reading, before closing.
+            while (received.size() != 2) { }
+            ipcServer.close()
+
+        then:
+            received.size() == 2
+            received[0] == "Test"
+            received[1] == "Hello"
+    }
+}

src/test/resources/projects/decompile/build.gradle

@@ -3,7 +3,7 @@ plugins {
 }
 
 dependencies {
-	minecraft "com.mojang:minecraft:1.16.5"
+	minecraft "com.mojang:minecraft:21w38a"
-	mappings "net.fabricmc:yarn:1.16.5+build.5:v2"
+	mappings "net.fabricmc:yarn:21w38a+build.11:v2"
-	modImplementation "net.fabricmc:fabric-loader:0.11.2"
+	modImplementation "net.fabricmc:fabric-loader:0.11.7"
 }