Make remapping tasks use the archive file from the Jar API (#1406)

* Make remapping tasks use the archive file from the Jar API

Other minor changes:
- Exception messages now include the absolute path of
  the jar file
- RemapSourcesJarTask now also uses descriptive wrappers
  instead of a direct new RuntimeException(...)

* Stop overriding Jar.copy with a no-op

* Add test for using Jar's API on remapJar and remapSourcesJar

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

@@ -1,7 +1,7 @@
 /*
  * This file is part of fabric-loom, licensed under the MIT License (MIT).
  *
- * Copyright (c) 2021 FabricMC
+ * Copyright (c) 2021-2025 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
@@ -27,7 +27,9 @@ package net.fabricmc.loom.task;
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
+import java.nio.file.Files;
 import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
@@ -56,6 +58,8 @@ import org.gradle.workers.WorkParameters;
 import org.gradle.workers.WorkQueue;
 import org.gradle.workers.WorkerExecutor;
 import org.jetbrains.annotations.ApiStatus;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import net.fabricmc.loom.LoomGradleExtension;
 import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
@@ -63,6 +67,7 @@ import net.fabricmc.loom.task.service.ClientEntriesService;
 import net.fabricmc.loom.task.service.JarManifestService;
 import net.fabricmc.loom.util.Check;
 import net.fabricmc.loom.util.Constants;
+import net.fabricmc.loom.util.ExceptionUtil;
 import net.fabricmc.loom.util.ZipReprocessorUtil;
 import net.fabricmc.loom.util.ZipUtils;
 import net.fabricmc.loom.util.gradle.SourceSetHelper;
@@ -115,6 +120,7 @@ public abstract class AbstractRemapJarTask extends Jar {
 
 	@Inject
 	public AbstractRemapJarTask() {
+		from(getProject().zipTree(getInputFile()));
 		getSourceNamespace().convention(MappingsNamespace.NAMED.toString()).finalizeValueOnRead();
 		getTargetNamespace().convention(MappingsNamespace.INTERMEDIARY.toString()).finalizeValueOnRead();
 		getIncludesClientOnlyClasses().convention(false).finalizeValueOnRead();
@@ -133,17 +139,11 @@ public abstract class AbstractRemapJarTask extends Jar {
 		usesService(jarManifestServiceProvider);
 	}
 
-	@Override
-	protected void copy() {
-		// Skip the default copy behaviour of AbstractCopyTask.
-	}
-
 	public final <P extends AbstractRemapParams> void submitWork(Class<? extends AbstractRemapAction<P>> workAction, Action<P> action) {
 		final WorkQueue workQueue = getWorkerExecutor().noIsolation();
 
 		workQueue.submit(workAction, params -> {
-			params.getInputFile().set(getInputFile());
+			params.getArchiveFile().set(getArchiveFile());
-			params.getOutputFile().set(getArchiveFile());
 
 			params.getSourceNamespace().set(getSourceNamespace());
 			params.getTargetNamespace().set(getTargetNamespace());
@@ -181,8 +181,7 @@ public abstract class AbstractRemapJarTask extends Jar {
 	protected abstract Provider<? extends ClientEntriesService.Options> getClientOnlyEntriesOptionsProvider(SourceSet clientSourceSet);
 
 	public interface AbstractRemapParams extends WorkParameters {
-		RegularFileProperty getInputFile();
+		RegularFileProperty getArchiveFile();
-		RegularFileProperty getOutputFile();
 
 		Property<String> getSourceNamespace();
 		Property<String> getTargetNamespace();
@@ -217,15 +216,34 @@ public abstract class AbstractRemapJarTask extends Jar {
 	}
 
 	public abstract static class AbstractRemapAction<T extends AbstractRemapParams> implements WorkAction<T> {
-		protected final Path inputFile;
+		private static final Logger LOGGER = LoggerFactory.getLogger(AbstractRemapAction.class);
 		protected final Path outputFile;
 
 		@Inject
 		public AbstractRemapAction() {
-			inputFile = getParameters().getInputFile().getAsFile().get().toPath();
+			outputFile = getParameters().getArchiveFile().getAsFile().get().toPath();
-			outputFile = getParameters().getOutputFile().getAsFile().get().toPath();
 		}
 
+		@Override
+		public final void execute() {
+			try {
+				Path tempInput = Files.createTempFile("loom-remapJar-", "-input.jar");
+				Files.copy(outputFile, tempInput, StandardCopyOption.REPLACE_EXISTING);
+				execute(tempInput);
+				Files.delete(tempInput);
+			} catch (Exception e) {
+				try {
+					Files.deleteIfExists(outputFile);
+				} catch (IOException ex) {
+					LOGGER.error("Failed to delete output file", ex);
+				}
+
+				throw ExceptionUtil.createDescriptiveWrapper(RuntimeException::new, "Failed to remap " + outputFile.toAbsolutePath(), e);
+			}
+		}
+
+		protected abstract void execute(Path inputFile) throws IOException;
+
 		protected void modifyJarManifest() throws IOException {
 			int count = ZipUtils.transform(outputFile, Map.of(Constants.Manifest.PATH, bytes -> {
 				var manifest = new Manifest(new ByteArrayInputStream(bytes));

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

@@ -1,7 +1,7 @@
 /*
  * This file is part of fabric-loom, licensed under the MIT License (MIT).
  *
- * Copyright (c) 2021-2024 FabricMC
+ * Copyright (c) 2021-2025 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
@@ -45,7 +45,6 @@ import org.gradle.api.tasks.Input;
 import org.gradle.api.tasks.InputFiles;
 import org.gradle.api.tasks.Nested;
 import org.gradle.api.tasks.SourceSet;
-import org.gradle.api.tasks.TaskAction;
 import org.gradle.api.tasks.TaskProvider;
 import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.Nullable;
@@ -64,7 +63,6 @@ import net.fabricmc.loom.task.service.ClientEntriesService;
 import net.fabricmc.loom.task.service.MixinRefmapService;
 import net.fabricmc.loom.task.service.TinyRemapperService;
 import net.fabricmc.loom.util.Constants;
-import net.fabricmc.loom.util.ExceptionUtil;
 import net.fabricmc.loom.util.Pair;
 import net.fabricmc.loom.util.SidedClassVisitor;
 import net.fabricmc.loom.util.ZipUtils;
@@ -122,8 +120,10 @@ public abstract class RemapJarTask extends AbstractRemapJarTask {
 		getMixinRefmapServiceOptions().set(MixinRefmapService.createOptions(this));
 	}
 
-	@TaskAction
+	@Override
-	public void run() {
+	protected void copy() {
+		super.copy();
+
 		submitWork(RemapAction.class, params -> {
 			if (getAddNestedDependencies().get()) {
 				params.getNestedJars().from(getNestedJars());
@@ -165,14 +165,16 @@ public abstract class RemapJarTask extends AbstractRemapJarTask {
 
 		private @Nullable TinyRemapperService tinyRemapperService;
 		private @Nullable TinyRemapper tinyRemapper;
+		private Path inputFile;
 
 		public RemapAction() {
 		}
 
 		@Override
-		public void execute() {
+		protected void execute(Path inputFile) throws IOException {
 			try (var serviceFactory = new ScopedServiceFactory()) {
 				LOGGER.info("Remapping {} to {}", inputFile, outputFile);
+				this.inputFile = inputFile;
 
 				this.tinyRemapperService = getParameters().getTinyRemapperServiceOptions().isPresent()
 						? serviceFactory.get(getParameters().getTinyRemapperServiceOptions().get())
@@ -207,20 +209,10 @@ public abstract class RemapJarTask extends AbstractRemapJarTask {
 				}
 
 				LOGGER.debug("Finished remapping {}", inputFile);
-			} catch (Exception e) {
-				try {
-					Files.deleteIfExists(outputFile);
-				} catch (IOException ex) {
-					LOGGER.error("Failed to delete output file", ex);
-				}
-
-				throw ExceptionUtil.createDescriptiveWrapper(RuntimeException::new, "Failed to remap", e);
 			}
 		}
 
 		private void prepare() {
-			final Path inputFile = getParameters().getInputFile().getAsFile().get().toPath();
-
 			if (tinyRemapperService != null) {
 				tinyRemapperService.getTinyRemapperForInputs().readInputsAsync(tinyRemapperService.getOrCreateTag(inputFile), inputFile);
 			}

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

@@ -1,7 +1,7 @@
 /*
  * This file is part of fabric-loom, licensed under the MIT License (MIT).
  *
- * Copyright (c) 2021 FabricMC
+ * Copyright (c) 2021-2025 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
@@ -26,6 +26,7 @@ package net.fabricmc.loom.task;
 
 import java.io.IOException;
 import java.nio.file.Files;
+import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
 
 import javax.inject.Inject;
@@ -35,9 +36,6 @@ import org.gradle.api.provider.Property;
 import org.gradle.api.provider.Provider;
 import org.gradle.api.tasks.Nested;
 import org.gradle.api.tasks.SourceSet;
-import org.gradle.api.tasks.TaskAction;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 import net.fabricmc.loom.task.service.ClientEntriesService;
 import net.fabricmc.loom.task.service.SourceRemapperService;
@@ -56,8 +54,10 @@ public abstract class RemapSourcesJarTask extends AbstractRemapJarTask {
 		getSourcesRemapperServiceOptions().set(SourceRemapperService.createOptions(this));
 	}
 
-	@TaskAction
+	@Override
-	public void run() {
+	protected void copy() {
+		super.copy();
+
 		submitWork(RemapSourcesAction.class, params -> {
 			if (!params.namespacesMatch()) {
 				params.getSourcesRemapperServiceOptions().set(getSourcesRemapperServiceOptions());
@@ -75,35 +75,23 @@ public abstract class RemapSourcesJarTask extends AbstractRemapJarTask {
 	}
 
 	public abstract static class RemapSourcesAction extends AbstractRemapAction<RemapSourcesParams> {
-		private static final Logger LOGGER = LoggerFactory.getLogger(RemapSourcesAction.class);
-
 		public RemapSourcesAction() {
 			super();
 		}
 
 		@Override
-		public void execute() {
+		protected void execute(Path inputFile) throws IOException {
-			try {
+			if (!getParameters().namespacesMatch()) {
-				if (!getParameters().namespacesMatch()) {
+				try (var serviceFactory = new ScopedServiceFactory()) {
-					try (var serviceFactory = new ScopedServiceFactory()) {
+					SourceRemapperService sourceRemapperService = serviceFactory.get(getParameters().getSourcesRemapperServiceOptions());
-						SourceRemapperService sourceRemapperService = serviceFactory.get(getParameters().getSourcesRemapperServiceOptions());
+					sourceRemapperService.remapSourcesJar(inputFile, outputFile);
-						sourceRemapperService.remapSourcesJar(inputFile, outputFile);
-					}
-				} else {
-					Files.copy(inputFile, outputFile, StandardCopyOption.REPLACE_EXISTING);
 				}
-
+			} else {
-				modifyJarManifest();
+				Files.copy(inputFile, outputFile, StandardCopyOption.REPLACE_EXISTING);
-				rewriteJar();
-			} catch (Exception e) {
-				try {
-					Files.deleteIfExists(outputFile);
-				} catch (IOException ex) {
-					LOGGER.error("Failed to delete output file", ex);
-				}
-
-				throw new RuntimeException("Failed to remap sources", e);
 			}
+
+			modifyJarManifest();
+			rewriteJar();
 		}
 	}
 }

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

@@ -0,0 +1,62 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 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.integration
+
+import java.util.jar.JarFile
+import java.util.jar.Manifest
+
+import spock.lang.Specification
+import spock.lang.Unroll
+
+import net.fabricmc.loom.test.util.GradleProjectTestTrait
+import net.fabricmc.loom.util.ZipUtils
+
+import static net.fabricmc.loom.test.LoomTestConstants.STANDARD_TEST_VERSIONS
+import static org.gradle.testkit.runner.TaskOutcome.SUCCESS
+
+class RemapJarContentsTest extends Specification implements GradleProjectTestTrait {
+	@Unroll
+	def "use jar apis on remapJar and remapSourcesJar (gradle #version)"() {
+		setup:
+		def gradle = gradleProject(project: "remapJarContents", version: version)
+
+		when:
+		def result = gradle.run(task: "build")
+
+		then:
+		result.task(":build").outcome == SUCCESS
+		ZipUtils.contains(gradle.getOutputFile('fabric-example-mod-1.0.0.jar').toPath(), 'test_file.txt')
+		ZipUtils.contains(gradle.getOutputFile('fabric-example-mod-1.0.0-sources.jar').toPath(), 'test_src_file.txt')
+		def manifest = readManifest(gradle.getOutputFile('fabric-example-mod-1.0.0.jar'))
+		manifest.mainAttributes.getValue('Hello-World') == 'test'
+
+		where:
+		version << STANDARD_TEST_VERSIONS
+	}
+
+	private static Manifest readManifest(File file) {
+		return new JarFile(file).withCloseable { it.manifest }
+	}
+}

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

@@ -0,0 +1,91 @@
+plugins {
+	id 'fabric-loom'
+	id 'maven-publish'
+}
+
+version = loom.modVersion
+group = project.maven_group
+
+repositories {
+	// Add repositories to retrieve artifacts from in here.
+	// You should only use this when depending on other mods because
+	// Loom adds the essential maven repositories to download Minecraft and libraries from automatically.
+	// See https://docs.gradle.org/current/userguide/declaring_repositories.html
+	// for more information about repositories.
+}
+
+dependencies {
+	// To change the versions see the gradle.properties file
+	minecraft "com.mojang:minecraft:${project.minecraft_version}"
+	mappings "net.fabricmc:yarn:${project.yarn_mappings}:v2"
+	modImplementation "net.fabricmc:fabric-loader:${project.loader_version}"
+
+	// Fabric API. This is technically optional, but you probably want it anyway.
+	modImplementation "net.fabricmc.fabric-api:fabric-api:${project.fabric_version}"
+
+	// PSA: Some older mods, compiled on Loom 0.2.1, might have outdated Maven POMs.
+	// You may need to force-disable transitiveness on them.
+}
+
+test {
+	enabled = false
+}
+
+base {
+	archivesName = project.archives_base_name
+}
+
+tasks.withType(JavaCompile).configureEach {
+	// ensure that the encoding is set to UTF-8, no matter what the system default is
+	// this fixes some edge cases with special characters not displaying correctly
+	// see http://yodaconditions.net/blog/fix-for-java-file-encoding-problems-with-gradle.html
+	// If Javadoc is generated, this must be specified in that task too.
+	it.options.encoding = "UTF-8"
+
+	// The Minecraft launcher currently installs Java 8 for users, so your mod probably wants to target Java 8 too
+	// JDK 9 introduced a new way of specifying this that will make sure no newer classes or methods are used.
+	// We'll use that if it's available, but otherwise we'll use the older option.
+	def targetVersion = 8
+	if (JavaVersion.current().isJava9Compatible()) {
+		it.options.release = targetVersion
+	}
+}
+
+java {
+	// Loom will automatically attach sourcesJar to a RemapSourcesJar task and to the "build" task
+	// if it is present.
+	// If you remove this line, sources will not be generated.
+	withSourcesJar()
+
+	sourceCompatibility = JavaVersion.VERSION_1_8
+	targetCompatibility = JavaVersion.VERSION_1_8
+}
+
+// configure the maven publication
+publishing {
+	publications {
+		mavenJava(MavenPublication) {
+			from components.java
+		}
+	}
+
+	// See https://docs.gradle.org/current/userguide/publishing_maven.html for information on how to set up publishing.
+	repositories {
+		// Add repositories to publish to here.
+		// Notice: This block does NOT have the same function as the block in the top level.
+		// The repositories here will be used for publishing your artifact, not for
+		// retrieving dependencies.
+	}
+}
+
+remapJar {
+	from 'test_file.txt'
+
+	manifest {
+		attributes 'Hello-World': 'test'
+	}
+}
+
+remapSourcesJar {
+	from 'test_src_file.txt'
+}

src/test/resources/projects/remapJarContents/gradle.properties

@@ -0,0 +1,16 @@
+# Done to increase the memory available to gradle.
+org.gradle.jvmargs=-Xmx1G
+
+# Fabric Properties
+	# check these on https://fabricmc.net/use
+	minecraft_version=1.16.5
+	yarn_mappings=1.16.5+build.5
+	loader_version=0.11.2
+
+# Mod Properties
+	maven_group = com.example
+	archives_base_name = fabric-example-mod
+
+# Dependencies
+	# currently not on the main fabric site, check on the maven: https://maven.fabricmc.net/net/fabricmc/fabric-api/fabric-api
+	fabric_version=0.31.0+1.16

src/test/resources/projects/remapJarContents/settings.gradle

@@ -0,0 +1,2 @@
+rootProject.name = "fabric-example-mod"
+

src/test/resources/projects/remapJarContents/src/main/java/net/fabricmc/example/ExampleMod.java

@@ -0,0 +1,21 @@
+package net.fabricmc.example;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import net.fabricmc.api.ModInitializer;
+
+public class ExampleMod implements ModInitializer {
+	public static final Logger LOGGER = LogManager.getLogger("modid");
+
+	/**
+	 * @see net.fabricmc.example
+	 */
+	@Override
+	public void onInitialize() {
+		LOGGER.info("Hello simple Fabric mod!");
+		LOGGER.info("Hello World!");
+
+		net.minecraft.util.Identifier id = null;
+	}
+}

src/test/resources/projects/remapJarContents/src/main/java/net/fabricmc/example/mixin/ExampleMixin.java

@@ -0,0 +1,15 @@
+package net.fabricmc.example.mixin;
+
+import net.minecraft.client.gui.screen.TitleScreen;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+@Mixin(TitleScreen.class)
+public class ExampleMixin {
+	@Inject(at = @At("HEAD"), method = "init()V")
+	private void init(CallbackInfo info) {
+		System.out.println("This line is printed by an example mod mixin!");
+	}
+}

src/test/resources/projects/remapJarContents/src/main/resources/fabric.mod.json

@@ -0,0 +1,36 @@
+{
+  "schemaVersion": 1,
+  "id": "modid",
+  "version": "1.0.0",
+
+  "name": "Example Mod",
+  "description": "This is an example description! Tell everyone what your mod is about!",
+  "authors": [
+    "Me!"
+  ],
+  "contact": {
+    "homepage": "https://fabricmc.net/",
+    "sources": "https://github.com/FabricMC/fabric-example-mod"
+  },
+
+  "license": "CC0-1.0",
+
+  "environment": "*",
+  "entrypoints": {
+    "main": [
+      "net.fabricmc.example.ExampleMod"
+    ]
+  },
+  "mixins": [
+    "modid.mixins.json"
+  ],
+
+  "depends": {
+    "fabricloader": ">=0.7.4",
+    "fabric": "*",
+    "minecraft": "1.16.x"
+  },
+  "suggests": {
+    "another-mod": "*"
+  }
+}

src/test/resources/projects/remapJarContents/src/main/resources/modid.mixins.json

@@ -0,0 +1,14 @@
+{
+  "required": true,
+  "minVersion": "0.8",
+  "package": "net.fabricmc.example.mixin",
+  "compatibilityLevel": "JAVA_8",
+  "mixins": [
+  ],
+  "client": [
+    "ExampleMixin"
+  ],
+  "injectors": {
+    "defaultRequire": 1
+  }
+}

src/test/resources/projects/remapJarContents/test_file.txt

@@ -0,0 +1 @@
+This file should end up inside the output file of remapJar.

src/test/resources/projects/remapJarContents/test_src_file.txt

@@ -0,0 +1 @@
+This file should end up inside the output file of remapSourcesJar.