add mcpforge plugin for 1.12.2 support

.gitignore

@@ -1,5 +1,7 @@
 .gradle
+.gradle-user-home/
 build/
+run/
 !gradle/wrapper/gradle-wrapper.jar
 !**/src/main/**/build/
 !**/src/test/**/build/

LEGACY.md

@@ -1,6 +1,6 @@
 # ModDevGradle Legacy Forge Plugin
 ModDevGradle has a secondary plugin (ID: `net.neoforged.moddev.legacyforge`, released alongside the normal plugin with the same version)
-that adds support for developing mods against MinecraftForge and Vanilla Minecraft versions 1.17 up to 1.20.1.  
+that adds support for developing mods against MinecraftForge and Vanilla Minecraft versions 1.12.2 up to 1.20.1.
 
 The legacy plugin is an "addon" plugin, meaning it operates on top of the normal plugin. This means that the APIs normally used
 are also available when using the legacy plugin.
@@ -41,6 +41,30 @@ legacyForge {
 }
 ```
 
+For Minecraft 1.12.2, use a Forge version such as:
+
+```groovy
+legacyForge {
+    version = "1.12.2-14.23.5.2860"
+}
+```
+
+MDG will use Forge's `userdev3` artifact for 1.12.2. This requires an NFRT build with legacy MCP support
+(`--mcp-mappings` and the legacy MCP mapping result IDs). Until that NFRT release is the MDG default, set
+`neoForge.neoFormRuntime.version` to a compatible published version or substitute a local NFRT legacy build.
+
+NFRT's 1.12.2 legacy MCP pipeline uses `de.oceanlabs.mcp:mcp_stable:39-1.12@zip` by default; if you need a
+different MCP CSV mapping zip, configure it explicitly:
+
+```groovy
+legacyForge {
+    enable {
+        forgeVersion = "1.12.2-14.23.5.2860"
+        mcpMappings = "de.oceanlabs.mcp:mcp_stable:39-1.12@zip"
+    }
+}
+```
+
 ## Reobfuscating artifacts
 Forge used SRG mappings as intermediary mappings in 1.20.1 and below. While your mod is developed against the mappings provided
 by Mojang (known as official mappings), you need to reobfuscate it to SRG mappings for it to work in production.  

build.gradle

@@ -71,9 +71,12 @@ sourceSets {
         runtimeClasspath += java8.output
     }
     legacy
+    mcpforge
     test {
         compileClasspath += legacy.output
         runtimeClasspath += legacy.output
+        compileClasspath += mcpforge.output
+        runtimeClasspath += mcpforge.output
     }
 }
 
@@ -83,6 +86,7 @@ configurations {
     // Place shaded dependencies into `compileOnly` so that they do not leak into our publications' dependencies.
     compileOnly.extendsFrom shaded
     legacyCompileOnly.extendsFrom shaded
+    mcpforgeCompileOnly.extendsFrom shaded
     testCompileOnly.extendsFrom shaded
     testRuntimeOnly.extendsFrom shaded
     shadowRuntimeElements {
@@ -113,6 +117,8 @@ dependencies {
     compileOnly "com.intellij:annotations:9.0.4"
     testCompileOnly "com.intellij:annotations:9.0.4"
     shaded "com.google.code.gson:gson:2.11.0"
+    shaded "org.ow2.asm:asm-commons:9.7.1"
+    shaded "org.tukaani:xz:1.10"
     implementation "gradle.plugin.org.jetbrains.gradle.plugin.idea-ext:gradle-idea-ext:1.2"
     shaded "net.neoforged:EclipseLaunchConfigs:0.1.11"
     shaded "net.neoforged:VscLaunchConfigs:1.0.8"
@@ -134,6 +140,11 @@ dependencies {
     legacyImplementation(sourceSets.main.output)
     legacyImplementation(sourceSets.java8.output)
     legacyImplementation gradleApi()
+
+    mcpforgeImplementation(sourceSets.main.output)
+    mcpforgeImplementation(sourceSets.legacy.output)
+    mcpforgeImplementation(sourceSets.java8.output)
+    mcpforgeImplementation gradleApi()
 }
 
 java {
@@ -147,13 +158,15 @@ jar {
     archiveClassifier = 'slim'
     from sourceSets.java8.output
     from sourceSets.legacy.output
+    from sourceSets.mcpforge.output
 }
 
 shadowJar {
     archiveClassifier = "" // Required for the Plugin Publish Plugin to publish this jar
 
     from sourceSets.java8.output
     from sourceSets.legacy.output
+    from sourceSets.mcpforge.output
 
     configurations = [project.configurations.shaded]
     enableRelocation = true
@@ -164,8 +177,9 @@ assemble.dependsOn shadowJar
 
 tasks.named("compileJava8Java").configure {
     javaCompiler = javaToolchains.compilerFor {
-        languageVersion = JavaLanguageVersion.of(8)
+        languageVersion = JavaLanguageVersion.of(17)
     }
+    options.release = 8
 }
 
 javadoc {
@@ -205,7 +219,7 @@ gradlePlugin {
             id = 'net.neoforged.moddev.legacyforge'
             implementationClass = 'net.neoforged.moddevgradle.boot.LegacyForgeModDevPlugin'
             displayName = "Mod Development Plugin for Legacy Forge"
-            description = "This plugin helps you create Minecraft mods using the Forge platform, up to 1.20.1"
+            description = "This plugin helps you create Minecraft mods using the Forge platform, from 1.12.2 up to 1.20.1"
             tags = ["minecraft", "neoforge", "forge", "java", "mod"]
         }
         repositories {
@@ -219,9 +233,16 @@ gradlePlugin {
             id = 'net.neoforged.moddev.legacyforge.repositories'
             implementationClass = 'net.neoforged.moddevgradle.boot.LegacyRepositoriesPlugin'
             displayName = "Mod Development Repositories Plugin for Legacy Forge"
-            description = "This plugin adds the repositories needed for developing Minecraft mods using the Forge platform, up to 1.20.1. It is applied automatically by the legacyforge plugin, but can be applied manually in settings.gradle to make use of Gradle dependency management."
+            description = "This plugin adds the repositories needed for developing Minecraft mods using the Forge platform, from 1.12.2 up to 1.20.1. It is applied automatically by the legacyforge plugin, but can be applied manually in settings.gradle to make use of Gradle dependency management."
             tags = ["minecraft", "neoforge", "forge", "java", "mod"]
         }
+        mcpforge {
+            id = 'net.neoforged.moddev.mcpforge'
+            implementationClass = 'net.neoforged.moddevgradle.boot.McpForgePlugin'
+            displayName = "Mod Development Plugin for Legacy Forge 1.12.2 (MCP)"
+            description = "This plugin helps you create Minecraft mods using the Forge platform for 1.12.2 (MCP mappings). It is the isolated home for the 1.12.2/MCP-specific toolchain, distinct from legacyforge."
+            tags = ["minecraft", "forge", "java", "mod", "1.12.2", "mcp"]
+        }
     }
 }
 
@@ -337,6 +358,9 @@ abstract class GenerateRepoFilter extends DefaultTask {
                 artifacts.add(new Artifact(location[0], location[1]))
             }
         }
+        // Required by Forge 1.12.2 and still hosted on Mojang's libraries maven, but not
+        // referenced by Mojang's vanilla version manifests.
+        artifacts.add(new Artifact('lzma', 'lzma'))
         final artifactList = artifacts.toList()
         Collections.sort(artifactList)
         final clazz = """

legacytest/forge1122/build.gradle

@@ -0,0 +1,39 @@
+plugins {
+    id 'net.neoforged.moddev.legacyforge'
+}
+
+repositories {
+    // The Forge 1.12.2 smoke can use a locally published NFRT build until a compatible release is default.
+    mavenLocal()
+}
+
+java {
+    toolchain {
+        languageVersion = JavaLanguageVersion.of(8)
+    }
+}
+
+neoFormRuntime {
+    version = '2.0.19-legacy'
+}
+
+legacyForge {
+    enable {
+        forgeVersion = '1.12.2-14.23.5.2860'
+        mcpMappings = 'de.oceanlabs.mcp:mcp_stable:39-1.12@zip'
+        // Recompilation now works end-to-end: NFRT runs ForgeFlower/MCPCleanup/recompile, with the legacy
+        // Java-8 toolchain auto-provisioned by Gradle (Azul Zulu on aarch64) and the legacy Maven repositories
+        // (Maven Central, Mojang libraries, Forge Maven) passed to NFRT via CreateMinecraftArtifacts.
+        disableRecompilation = false
+    }
+    runs {
+        client {
+            client()
+        }
+    }
+    mods {
+        mymod1122 {
+            sourceSet(sourceSets.main)
+        }
+    }
+}

legacytest/forge1122/src/main/java/mymod1122/MyMod1122.java

@@ -0,0 +1,8 @@
+package mymod1122;
+
+import net.minecraftforge.fml.common.Mod;
+
+@Mod(modid = MyMod1122.MOD_ID, name = "Legacy 1.12.2 Smoke Test", version = "1.0.0")
+public class MyMod1122 {
+    public static final String MOD_ID = "mymod1122";
+}

legacytest/forge1122/src/main/resources/mcmod.info

@@ -0,0 +1,16 @@
+[
+  {
+    "modid": "mymod1122",
+    "name": "Legacy 1.12.2 Smoke Test",
+    "description": "Minimal Forge 1.12.2 fixture for ModDevGradle.",
+    "version": "1.0.0",
+    "mcversion": "1.12.2",
+    "url": "",
+    "updateUrl": "",
+    "authorList": [],
+    "credits": "",
+    "logoFile": "",
+    "screenshots": [],
+    "dependencies": []
+  }
+]

legacytest/forge1122/src/main/resources/pack.mcmeta

@@ -0,0 +1,6 @@
+{
+  "pack": {
+    "pack_format": 3,
+    "description": "Legacy 1.12.2 smoke test resources"
+  }
+}

legacytest/settings.gradle

@@ -6,5 +6,6 @@ plugins {
 includeBuild '..'
 
 include 'forge'
+include 'forge1122'
 include 'forgedownstream'
 include 'nonmc'

src/generated/java/net/neoforged/moddevgradle/internal/generated/MojangRepositoryFilter.java

@@ -58,6 +58,7 @@ public static void filter(org.gradle.api.artifacts.repositories.RepositoryConten
         filter.includeModule("io.netty", "netty-transport-native-unix-common");
         filter.includeModule("it.unimi.dsi", "fastutil");
         filter.includeModule("java3d", "vecmath");
+        filter.includeModule("lzma", "lzma");
         filter.includeModule("net.java.dev.jna", "jna");
         filter.includeModule("net.java.dev.jna", "jna-platform");
         filter.includeModule("net.java.dev.jna", "platform");
@@ -92,6 +93,7 @@ public static void filter(org.gradle.api.artifacts.repositories.RepositoryConten
         filter.includeModule("org.lwjgl.lwjgl", "lwjgl");
         filter.includeModule("org.lwjgl.lwjgl", "lwjgl-platform");
         filter.includeModule("org.lwjgl.lwjgl", "lwjgl_util");
+        filter.includeModule("org.lwjgl.lwjgl", "parent");
         filter.includeModule("org.lz4", "lz4-java");
         filter.includeModule("org.ow2.asm", "asm");
         filter.includeModule("org.ow2.asm", "asm-all");

src/java8/java/net/neoforged/moddevgradle/boot/McpForgePlugin.java

@@ -0,0 +1,14 @@
+package net.neoforged.moddevgradle.boot;
+
+import org.gradle.api.Project;
+
+/**
+ * Boot trampoline for the {@code net.neoforged.moddev.mcpforge} plugin (the isolated 1.12.2/MCP toolchain).
+ * Mirrors {@link LegacyForgeModDevPlugin}. Kept in the java8 source set so it can be loaded by the
+ * bootstrap classloader before the main plugin classpath is wired up.
+ */
+public class McpForgePlugin extends TrampolinePlugin<Project> {
+    public McpForgePlugin() {
+        super("net.neoforged.moddevgradle.mcpforge.internal.McpForgeModDevPlugin");
+    }
+}

src/legacy/java/net/neoforged/moddevgradle/legacyforge/internal/LegacyForgeLibraryMetadataRule.java

@@ -0,0 +1,60 @@
+package net.neoforged.moddevgradle.legacyforge.internal;
+
+import java.util.ArrayList;
+import org.gradle.api.artifacts.CacheableRule;
+import org.gradle.api.artifacts.ComponentMetadataContext;
+import org.gradle.api.artifacts.ComponentMetadataRule;
+import org.gradle.api.artifacts.DirectDependenciesMetadata;
+import org.gradle.api.artifacts.DirectDependencyMetadata;
+
+/**
+ * Normalizes old Forge library metadata that predates today's Maven Central coordinates or only
+ * exists as jar-only artifacts on Forge's Maven.
+ */
+@CacheableRule
+public class LegacyForgeLibraryMetadataRule implements ComponentMetadataRule {
+    @Override
+    public void execute(ComponentMetadataContext context) {
+        var id = context.getDetails().getId();
+        if (!id.getVersion().equals("1.12.2-14.23.5.2860")) {
+            return;
+        }
+
+        context.getDetails().allVariants(variant -> variant.withDependencies(dependencies -> {
+            removeMatching(dependencies, dependency -> {
+                var group = dependency.getGroup();
+                var name = dependency.getName();
+                return group.equals("org.scala-lang.plugins")
+                        || group.equals("org.scala-lang") && name.equals("scala-actors-migration_2.11");
+            });
+
+            replaceDependency(dependencies, "org.scala-lang:scala-parser-combinators_2.11:1.0.1",
+                    "org.scala-lang.modules:scala-parser-combinators_2.11:1.0.1");
+            replaceDependency(dependencies, "org.scala-lang:scala-swing_2.11:1.0.1",
+                    "org.scala-lang.modules:scala-swing_2.11:1.0.1");
+            replaceDependency(dependencies, "org.scala-lang:scala-xml_2.11:1.0.2",
+                    "org.scala-lang.modules:scala-xml_2.11:1.0.2");
+        }));
+    }
+
+    private static void replaceDependency(DirectDependenciesMetadata dependencies,
+            String oldNotation,
+            String newNotation) {
+        var oldParts = oldNotation.split(":");
+        removeMatching(dependencies, dependency -> dependency.getGroup().equals(oldParts[0])
+                && dependency.getName().equals(oldParts[1])
+                && dependency.getVersionConstraint().getRequiredVersion().equals(oldParts[2]));
+        dependencies.add(newNotation);
+    }
+
+    private static void removeMatching(DirectDependenciesMetadata dependencies,
+            java.util.function.Predicate<DirectDependencyMetadata> predicate) {
+        var toRemove = new ArrayList<DirectDependencyMetadata>();
+        for (var dependency : dependencies) {
+            if (predicate.test(dependency)) {
+                toRemove.add(dependency);
+            }
+        }
+        dependencies.removeAll(toRemove);
+    }
+}