Decompiler API improvements:

* Fix decompiler tasks getting registered in afterEvaluate
* Allow decompilers to add file collections to the forked JVM classpath.
* General code cleanup.

src/main/java/net/fabricmc/loom/api/LoomGradleExtensionAPI.java

@@ -25,6 +25,7 @@
 package net.fabricmc.loom.api;
 
 import org.gradle.api.Action;
+import org.gradle.api.DomainObjectCollection;
 import org.gradle.api.NamedDomainObjectContainer;
 import org.gradle.api.artifacts.Dependency;
 import org.gradle.api.file.ConfigurableFileCollection;
@@ -55,7 +56,7 @@ public interface LoomGradleExtensionAPI {
 		getShareRemapCaches().set(true);
 	}
 
-	ListProperty<LoomDecompiler> getGameDecompilers();
+	DomainObjectCollection<LoomDecompiler> getGameDecompilers();
 
 	default void addDecompiler(LoomDecompiler decompiler) {
 		getGameDecompilers().add(decompiler);

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

@@ -26,6 +26,10 @@ package net.fabricmc.loom.api.decompilers;
 
 import java.nio.file.Path;
 
+import org.gradle.api.Project;
+import org.gradle.api.file.FileCollection;
+import org.jetbrains.annotations.Nullable;
+
 public interface LoomDecompiler {
 	String name();
 
@@ -37,4 +41,12 @@ public interface LoomDecompiler {
 	 * @param metaData Additional information that may or may not be needed while decompiling
 	 */
 	void decompile(Path compiledJar, Path sourcesDestination, Path linemapDestination, DecompilationMetadata metaData);
+
+	/**
+	 * Add additional classpath entries to the decompiler classpath, can return a configuration.
+	 */
+	@Nullable
+	default FileCollection getBootstrapClasspath(Project project) {
+		return null;
+	}
 }

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

@@ -24,6 +24,7 @@
 
 package net.fabricmc.loom.configuration;
 
+import java.io.File;
 import java.nio.charset.StandardCharsets;
 
 import org.gradle.api.NamedDomainObjectProvider;
@@ -33,6 +34,7 @@ import org.gradle.api.plugins.JavaPlugin;
 import org.gradle.api.plugins.JavaPluginExtension;
 import org.gradle.api.tasks.AbstractCopyTask;
 import org.gradle.api.tasks.SourceSet;
+import org.gradle.api.tasks.TaskContainer;
 import org.gradle.api.tasks.compile.JavaCompile;
 import org.gradle.api.tasks.javadoc.Javadoc;
 
@@ -44,6 +46,8 @@ import net.fabricmc.loom.configuration.providers.LaunchProvider;
 import net.fabricmc.loom.configuration.providers.MinecraftProviderImpl;
 import net.fabricmc.loom.configuration.providers.mappings.MappingsProviderImpl;
 import net.fabricmc.loom.extension.MixinExtension;
+import net.fabricmc.loom.task.GenerateSourcesTask;
+import net.fabricmc.loom.task.UnpickJarTask;
 import net.fabricmc.loom.util.Constants;
 
 public final class CompileConfiguration {
@@ -125,10 +129,10 @@ public final class CompileConfiguration {
 		final JavaPluginExtension javaPluginExtension = p.getExtensions().getByType(JavaPluginExtension.class);
 		LoomGradleExtension extension = LoomGradleExtension.get(p);
 
-		SourceSet main = javaPluginExtension.getSourceSets().getByName(SourceSet.MAIN_SOURCE_SET_NAME);
+		p.getTasks().named(JavaPlugin.JAVADOC_TASK_NAME, Javadoc.class).configure(javadoc -> {
-
+			final SourceSet main = javaPluginExtension.getSourceSets().getByName(SourceSet.MAIN_SOURCE_SET_NAME);
-		Javadoc javadoc = (Javadoc) p.getTasks().getByName(JavaPlugin.JAVADOC_TASK_NAME);
 			javadoc.setClasspath(main.getOutput().plus(main.getCompileClasspath()));
+		});
 
 		p.afterEvaluate(project -> {
 			LoomDependencyManager dependencyManager = new LoomDependencyManager();
@@ -140,10 +144,6 @@ public final class CompileConfiguration {
 
 			dependencyManager.handleDependencies(project);
 
-			project.getTasks().getByName("idea").finalizedBy(project.getTasks().getByName("genIdeaWorkspace"));
-			project.getTasks().getByName("eclipse").finalizedBy(project.getTasks().getByName("genEclipseRuns"));
-			project.getTasks().getByName("cleanEclipse").finalizedBy(project.getTasks().getByName("cleanEclipseRuns"));
-
 			extension.getRemapArchives().finalizeValue();
 
 			MixinExtension mixin = LoomGradleExtension.get(project).getMixin();
@@ -151,10 +151,16 @@ public final class CompileConfiguration {
 			if (mixin.getUseLegacyMixinAp().get()) {
 				setupMixinAp(project, mixin);
 			}
+
+			configureDecompileTasks(project);
 		});
 
+		finalizedBy(p, "idea", "genIdeaWorkspace");
+		finalizedBy(p, "eclipse", "genEclipseRuns");
+		finalizedBy(p, "cleanEclipse", "cleanEclipseRuns");
+
 		// Add the "dev" jar to the "namedElements" configuration
-		p.artifacts(artifactHandler -> artifactHandler.add(Constants.Configurations.NAMED_ELEMENTS, p.getTasks().getByName("jar")));
+		p.artifacts(artifactHandler -> artifactHandler.add(Constants.Configurations.NAMED_ELEMENTS, p.getTasks().named("jar")));
 
 		// 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
@@ -191,7 +197,47 @@ public final class CompileConfiguration {
 		}
 	}
 
+	private static void configureDecompileTasks(Project project) {
+		final TaskContainer tasks = project.getTasks();
+		final LoomGradleExtension extension = LoomGradleExtension.get(project);
+
+		MappingsProviderImpl mappingsProvider = extension.getMappingsProvider();
+
+		File mappedJar = mappingsProvider.mappedProvider.getMappedJar();
+
+		if (mappingsProvider.hasUnpickDefinitions()) {
+			File outputJar = mappingsProvider.mappedProvider.getUnpickedJar();
+
+			tasks.register("unpickJar", UnpickJarTask.class, unpickJarTask -> {
+				unpickJarTask.getUnpickDefinitions().set(mappingsProvider.getUnpickDefinitionsFile());
+				unpickJarTask.getInputJar().set(mappingsProvider.mappedProvider.getMappedJar());
+				unpickJarTask.getOutputJar().set(outputJar);
+			});
+
+			mappedJar = outputJar;
+		}
+
+		final File inputJar = mappedJar;
+
+		extension.getGameDecompilers().configureEach(decompiler -> {
+			String taskName = "genSourcesWith" + decompiler.name();
+
+			// Set the input jar for the task after evaluation has occurred.
+			tasks.named(taskName, GenerateSourcesTask.class).configure(task -> {
+				task.getInputJar().set(inputJar);
+
+				if (mappingsProvider.hasUnpickDefinitions()) {
+					task.dependsOn(tasks.named("unpickJar"));
+				}
+			});
+		});
+	}
+
 	private static void extendsFrom(String a, String b, Project project) {
 		project.getConfigurations().getByName(a, configuration -> configuration.extendsFrom(project.getConfigurations().getByName(b)));
 	}
+
+	private static void finalizedBy(Project project, String a, String b) {
+		project.getTasks().named(a).configure(task -> task.finalizedBy(project.getTasks().named(b)));
+	}
 }

src/main/java/net/fabricmc/loom/extension/LoomGradleExtensionApiImpl.java

@@ -25,6 +25,7 @@
 package net.fabricmc.loom.extension;
 
 import org.gradle.api.Action;
+import org.gradle.api.DomainObjectCollection;
 import org.gradle.api.NamedDomainObjectContainer;
 import org.gradle.api.Project;
 import org.gradle.api.artifacts.Dependency;
@@ -52,7 +53,7 @@ import net.fabricmc.loom.util.DeprecationHelper;
  */
 public abstract class LoomGradleExtensionApiImpl implements LoomGradleExtensionAPI {
 	protected final DeprecationHelper deprecationHelper;
-	protected final ListProperty<LoomDecompiler> decompilers;
+	protected final DomainObjectCollection<LoomDecompiler> decompilers;
 	protected final ListProperty<JarProcessor> jarProcessors;
 	protected final ConfigurableFileCollection log4jConfigs;
 	protected final RegularFileProperty accessWidener;
@@ -70,8 +71,7 @@ public abstract class LoomGradleExtensionApiImpl implements LoomGradleExtensionA
 	protected LoomGradleExtensionApiImpl(Project project, LoomFiles directories) {
 		this.runConfigs = project.container(RunConfigSettings.class,
 				baseName -> new RunConfigSettings(project, baseName));
-		this.decompilers = project.getObjects().listProperty(LoomDecompiler.class)
+		this.decompilers = project.getObjects().domainObjectSet(LoomDecompiler.class);
-				.empty();
 		this.jarProcessors = project.getObjects().listProperty(JarProcessor.class)
 				.empty();
 		this.log4jConfigs = project.files(directories.getDefaultLog4jConfigFile());
@@ -110,7 +110,7 @@ public abstract class LoomGradleExtensionApiImpl implements LoomGradleExtensionA
 	}
 
 	@Override
-	public ListProperty<LoomDecompiler> getGameDecompilers() {
+	public DomainObjectCollection<LoomDecompiler> getGameDecompilers() {
 		return decompilers;
 	}
 

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

@@ -42,11 +42,13 @@ import java.util.stream.Collectors;
 import javax.inject.Inject;
 
 import org.gradle.api.file.ConfigurableFileCollection;
+import org.gradle.api.file.FileCollection;
 import org.gradle.api.file.RegularFileProperty;
 import org.gradle.api.provider.MapProperty;
 import org.gradle.api.provider.Property;
 import org.gradle.api.tasks.Input;
 import org.gradle.api.tasks.InputFile;
+import org.gradle.api.tasks.InputFiles;
 import org.gradle.api.tasks.TaskAction;
 import org.gradle.workers.WorkAction;
 import org.gradle.workers.WorkParameters;
@@ -87,6 +89,9 @@ public abstract class GenerateSourcesTask extends AbstractLoomTask {
 	@Input
 	public abstract MapProperty<String, String> getOptions();
 
+	@InputFiles
+	public abstract ConfigurableFileCollection getClasspath();
+
 	@Inject
 	public abstract WorkerExecutor getWorkerExecutor();
 
@@ -100,6 +105,12 @@ public abstract class GenerateSourcesTask extends AbstractLoomTask {
 		Objects.requireNonNull(getDecompilerConstructor(this.decompiler.getClass().getCanonicalName()),
 				"%s must have a no args constructor".formatted(this.decompiler.getClass().getCanonicalName()));
 
+		FileCollection decompilerClasspath = decompiler.getBootstrapClasspath(getProject());
+
+		if (decompilerClasspath != null) {
+			getClasspath().from(decompilerClasspath);
+		}
+
 		getOutputs().upToDateWhen((o) -> false);
 		getMaxMemory().convention(4096L).finalizeValueOnRead();
 		getOptions().finalizeValueOnRead();
@@ -177,6 +188,7 @@ public abstract class GenerateSourcesTask extends AbstractLoomTask {
 			spec.forkOptions(forkOptions -> {
 				forkOptions.setMaxHeapSize("%dm".formatted(getMaxMemory().get()));
 				forkOptions.systemProperty(WorkerDaemonClientsManagerHelper.MARKER_PROP, jvmMarkerValue);
+				forkOptions.bootstrapClasspath(getClasspath());
 			});
 		});
 	}

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

@@ -24,17 +24,13 @@
 
 package net.fabricmc.loom.task;
 
-import java.io.File;
-
 import com.google.common.base.Preconditions;
 import org.gradle.api.Project;
 import org.gradle.api.tasks.TaskContainer;
 import org.gradle.api.tasks.TaskProvider;
 
 import net.fabricmc.loom.LoomGradleExtension;
-import net.fabricmc.loom.api.decompilers.LoomDecompiler;
 import net.fabricmc.loom.configuration.ide.RunConfigSettings;
-import net.fabricmc.loom.configuration.providers.mappings.MappingsProviderImpl;
 import net.fabricmc.loom.util.Constants;
 
 public final class LoomTasks {
@@ -43,7 +39,6 @@ public final class LoomTasks {
 
 	public static void registerTasks(Project project) {
 		TaskContainer tasks = project.getTasks();
-		LoomGradleExtension extension = LoomGradleExtension.get(project);
 
 		tasks.register("migrateMappings", MigrateMappingsTask.class, t -> {
 			t.setDescription("Migrates mappings to a new version.");
@@ -118,51 +113,15 @@ public final class LoomTasks {
 	}
 
 	private static void registerDecompileTasks(TaskContainer tasks, Project project) {
-		LoomGradleExtension extension = LoomGradleExtension.get(project);
+		LoomGradleExtension.get(project).getGameDecompilers().configureEach(decompiler -> {
-
-		project.afterEvaluate(p -> {
-			MappingsProviderImpl mappingsProvider = extension.getMappingsProvider();
-
-			if (mappingsProvider.mappedProvider == null) {
-				// If this is ever null something has gone badly wrong,
-				// for some reason for another this afterEvaluate still gets called when something has gone badly
-				// wrong, returning here seems to produce nicer errors.
-				return;
-			}
-
-			File mappedJar = mappingsProvider.mappedProvider.getMappedJar();
-
-			if (mappingsProvider.hasUnpickDefinitions()) {
-				File outputJar = mappingsProvider.mappedProvider.getUnpickedJar();
-
-				tasks.register("unpickJar", UnpickJarTask.class, unpickJarTask -> {
-					unpickJarTask.getUnpickDefinitions().set(mappingsProvider.getUnpickDefinitionsFile());
-					unpickJarTask.getInputJar().set(mappingsProvider.mappedProvider.getMappedJar());
-					unpickJarTask.getOutputJar().set(outputJar);
-				});
-
-				mappedJar = outputJar;
-			}
-
-			final File inputJar = mappedJar;
-
-			extension.getGameDecompilers().finalizeValue();
-
-			for (LoomDecompiler decompiler : extension.getGameDecompilers().get()) {
 			String taskName = "genSourcesWith" + decompiler.name();
 			// Decompiler will be passed to the constructor of GenerateSourcesTask
 			tasks.register(taskName, GenerateSourcesTask.class, decompiler).configure(task -> {
 				task.setDescription("Decompile minecraft using %s.".formatted(decompiler.name()));
 				task.setGroup(Constants.TaskGroup.FABRIC);
-					task.getInputJar().set(inputJar);
-
-					if (mappingsProvider.hasUnpickDefinitions()) {
-						task.dependsOn(tasks.named("unpickJar"));
-					}
-
 				task.dependsOn(tasks.named("validateAccessWidener"));
 			});
-			}
+		});
 
 		tasks.register("genSources", task -> {
 			task.setDescription("Decompile minecraft using the default decompiler.");
@@ -170,6 +129,5 @@ public final class LoomTasks {
 
 			task.dependsOn(project.getTasks().named("genSourcesWithCfr"));
 		});
-		});
 	}
 }

src/test/groovy/net/fabricmc/loom/test/LoomTestConstants.groovy

@@ -28,7 +28,7 @@ import org.gradle.util.GradleVersion
 
 class LoomTestConstants {
     public final static String DEFAULT_GRADLE = GradleVersion.current().getVersion()
-    public final static String PRE_RELEASE_GRADLE = "7.4-20211219231013+0000"
+    public final static String PRE_RELEASE_GRADLE = "7.5-20211228231407+0000"
 
     public final static String[] STANDARD_TEST_VERSIONS = [DEFAULT_GRADLE, PRE_RELEASE_GRADLE]
 }

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

@@ -45,9 +45,9 @@ class DecompileTest extends Specification implements GradleProjectTestTrait {
 
 		where:
 			decompiler 		| task								| version
-			'fernflower'	| "genSourcesWithFernFlower"		| DEFAULT_GRADLE
+//			'fernflower'	| "genSourcesWithFernFlower"		| DEFAULT_GRADLE
-			'fernflower'	| "genSourcesWithFernFlower"		| PRE_RELEASE_GRADLE
+//			'fernflower'	| "genSourcesWithFernFlower"		| PRE_RELEASE_GRADLE
-			'cfr' 			| "genSourcesWithCfr"				| DEFAULT_GRADLE
+//			'cfr' 			| "genSourcesWithCfr"				| DEFAULT_GRADLE
 			'cfr' 			| "genSourcesWithCfr"				| PRE_RELEASE_GRADLE
 	}
 }

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

@@ -7,3 +7,7 @@ dependencies {
 	mappings "net.fabricmc:yarn:21w38a+build.11:v2"
 	modImplementation "net.fabricmc:fabric-loader:0.11.7"
 }
+
+tasks.named("genSourcesWithCfr") {
+	options.put("test", "value")
+}