Add loom.forge.useForgeLoggerConfig

Closes #126.

src/main/java/dev/architectury/loom/util/ForgeLoggerConfig.java

@@ -0,0 +1,91 @@
+package dev.architectury.loom.util;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+import java.util.StringJoiner;
+
+import com.google.gson.JsonArray;
+import com.google.gson.JsonElement;
+import org.gradle.api.Project;
+import org.jetbrains.annotations.Nullable;
+
+import net.fabricmc.loom.LoomGradleExtension;
+import net.fabricmc.loom.util.FileSystemUtil;
+
+public final class ForgeLoggerConfig {
+	private static final List<ArtifactCoordinates> LOGGER_CONFIG_ARTIFACTS = List.of(
+			// 1.17 -
+			new ArtifactCoordinates("net.minecraftforge", "fmlloader", null),
+			// 1.14 - 1.16
+			new ArtifactCoordinates("net.minecraftforge", "forge", "launcher")
+	);
+
+	public static void copyToPath(Project project, Path outputFile) {
+		try {
+			Files.deleteIfExists(outputFile);
+		} catch (IOException e) {
+			throw new UncheckedIOException(e);
+		}
+
+		final JsonArray libraries = LoomGradleExtension.get(project)
+				.getForgeUserdevProvider()
+				.getJson()
+				.getAsJsonArray("libraries");
+		boolean found = false;
+
+		for (JsonElement library : libraries) {
+			final String notation = library.getAsString();
+
+			if (LOGGER_CONFIG_ARTIFACTS.stream().anyMatch(artifact -> artifact.matches(notation))) {
+				final File libraryFile = project.getConfigurations()
+						.detachedConfiguration(project.getDependencies().create(notation))
+						.setTransitive(false)
+						.getSingleFile();
+
+				try (FileSystemUtil.Delegate fs = FileSystemUtil.getJarFileSystem(libraryFile, false)) {
+					final Path configPath = fs.getPath("log4j2.xml");
+					Files.copy(configPath, outputFile);
+					found = true;
+					break;
+				} catch (IOException e) {
+					throw new UncheckedIOException(e);
+				}
+			}
+		}
+
+		if (!found) {
+			StringBuilder sb = new StringBuilder("Could not find Forge dependency with logger config. Tried to find:");
+
+			for (ArtifactCoordinates artifact : LOGGER_CONFIG_ARTIFACTS) {
+				sb.append('\n').append(" - ").append(artifact);
+			}
+
+			throw new RuntimeException(sb.toString());
+		}
+	}
+
+	private record ArtifactCoordinates(String group, String name, @Nullable String classifier) {
+		boolean matches(String notation) {
+			final String[] parts = notation.split(":");
+			return group.equals(parts[0]) && name.equals(parts[1]) &&
+					(classifier == null || (parts.length >= 4 && classifier.equals(parts[3])));
+		}
+
+		@Override
+		public String toString() {
+			final StringJoiner joiner = new StringJoiner(":");
+			joiner.add(group);
+			joiner.add(name);
+
+			if (classifier != null) {
+				joiner.add(classifier);
+			}
+
+			return joiner.toString();
+		}
+	}
+}

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

@@ -1,7 +1,7 @@
 /*
  * This file is part of fabric-loom, licensed under the MIT License (MIT).
  *
- * Copyright (c) 2021 FabricMC
+ * Copyright (c) 2021-2023 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
@@ -104,6 +104,14 @@ public interface ForgeExtensionAPI {
 	 */
 	Property<Boolean> getUseCustomMixin();
 
+	/**
+	 * If true, Loom will use Forge's Log4J config file instead of its own.
+	 * This is disabled by default.
+	 *
+	 * @return the property
+	 */
+	Property<Boolean> getUseForgeLoggerConfig();
+
 	/**
 	 * A list of mod IDs for mods applied for data generation.
 	 * The returned list is unmodifiable but not immutable - it will reflect changes done with

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

@@ -1,7 +1,7 @@
 /*
  * This file is part of fabric-loom, licensed under the MIT License (MIT).
  *
- * Copyright (c) 2021 FabricMC
+ * Copyright (c) 2021-2023 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
@@ -48,6 +48,7 @@ public class ForgeExtensionImpl implements ForgeExtensionAPI {
 	private final ConfigurableFileCollection accessTransformers;
 	private final SetProperty<String> mixinConfigs;
 	private final Property<Boolean> useCustomMixin;
+	private final Property<Boolean> useForgeLoggerConfig;
 	private final List<String> dataGenMods = new ArrayList<>(); // not a property because it has custom adding logic
 
 	@Inject
@@ -58,6 +59,7 @@ public class ForgeExtensionImpl implements ForgeExtensionAPI {
 		accessTransformers = project.getObjects().fileCollection();
 		mixinConfigs = project.getObjects().setProperty(String.class).empty();
 		useCustomMixin = project.getObjects().property(Boolean.class).convention(true);
+		useForgeLoggerConfig = project.getObjects().property(Boolean.class).convention(false);
 	}
 
 	@Override
@@ -95,6 +97,11 @@ public class ForgeExtensionImpl implements ForgeExtensionAPI {
 		return useCustomMixin;
 	}
 
+	@Override
+	public Property<Boolean> getUseForgeLoggerConfig() {
+		return useForgeLoggerConfig;
+	}
+
 	@Override
 	public List<String> getDataGenMods() {
 		// unmod list prevents uncontrolled additions (we want to create the run config too)

src/main/java/net/fabricmc/loom/task/launch/GenerateLog4jConfigTask.java

@@ -29,6 +29,7 @@ import java.io.InputStream;
 import java.nio.file.Files;
 import java.nio.file.Path;
 
+import dev.architectury.loom.util.ForgeLoggerConfig;
 import org.gradle.api.tasks.TaskAction;
 
 import net.fabricmc.loom.task.AbstractLoomTask;
@@ -38,6 +39,11 @@ public abstract class GenerateLog4jConfigTask extends AbstractLoomTask {
 	public void run() {
 		Path outputFile = getExtension().getFiles().getDefaultLog4jConfigFile().toPath();
 
+		if (getExtension().isForge() && getExtension().getForge().getUseForgeLoggerConfig().get()) {
+			ForgeLoggerConfig.copyToPath(getProject(), outputFile);
+			return;
+		}
+
 		try (InputStream is = GenerateLog4jConfigTask.class.getClassLoader().getResourceAsStream("log4j2.fabric.xml")) {
 			Files.deleteIfExists(outputFile);
 			Files.copy(is, outputFile);

src/test/groovy/net/fabricmc/loom/test/integration/forge/FmlLogConfigTest.groovy

@@ -0,0 +1,37 @@
+package net.fabricmc.loom.test.integration.forge
+
+import net.fabricmc.loom.test.util.GradleProjectTestTrait
+import spock.lang.Specification
+import spock.lang.Unroll
+
+import static net.fabricmc.loom.test.LoomTestConstants.DEFAULT_GRADLE
+import static org.gradle.testkit.runner.TaskOutcome.SUCCESS
+
+class FmlLogConfigTest extends Specification implements GradleProjectTestTrait {
+    @Unroll
+    def "use fml logger config (minecraft #minecraft, forge #forge)"() {
+        setup:
+        def gradle = gradleProject(project: 'forge/loggerConfig', version: DEFAULT_GRADLE)
+        gradle.gradleProperties << """
+        
+        minecraft_version=$minecraft
+        forge_version=$forge
+        """.stripIndent()
+
+        when:
+        def result = gradle.run(task: 'generateLog4jConfig')
+
+        then:
+        result.task(':generateLog4jConfig').outcome == SUCCESS
+        def logFile = new File(gradle.projectDir, '.gradle/loom-cache/log4j.xml')
+        logFile.text.contains('forge.logging')
+
+        where:
+        minecraft | forge
+        //'1.19.4'  | '45.0.43'
+        //'1.18.1'  | '39.0.63'
+        //'1.17.1'  | '37.0.67'
+        '1.16.5'  | '36.2.4'
+        '1.14.4'  | '28.2.23'
+    }
+}

src/test/resources/projects/forge/loggerConfig/build.gradle

@@ -0,0 +1,20 @@
+plugins {
+	id 'dev.architectury.loom'
+}
+
+archivesBaseName = project.archives_base_name
+version = project.mod_version
+group = project.maven_group
+
+loom {
+	forge {
+		useForgeLoggerConfig = true
+	}
+}
+
+dependencies {
+	// To change the versions see the gradle.properties file
+	minecraft "com.mojang:minecraft:$project.minecraft_version"
+	mappings loom.officialMojangMappings()
+	forge "net.minecraftforge:forge:$project.minecraft_version-$project.forge_version"
+}

src/test/resources/projects/forge/loggerConfig/gradle.properties

@@ -0,0 +1,9 @@
+# Done to increase the memory available to gradle.
+org.gradle.jvmargs=-Xmx1G
+
+# Mod Properties
+mod_version = 1.0.0
+maven_group = com.example
+archives_base_name = fabric-example-mod
+
+loom.platform=forge

src/test/resources/projects/forge/loggerConfig/settings.gradle

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