Use privileged lookup if possible

Fix jopt help messages
Add module-info to our built jar

Author: LexManos

build.gradle

@@ -10,6 +10,7 @@ plugins {
     alias libs.plugins.changelog
     alias libs.plugins.licenser
     alias libs.plugins.shadow
+    alias libs.plugins.multirelease
 }
 
 gradleutils.displayName = 'Slime Launcher'
@@ -45,7 +46,8 @@ tasks.named('jar', Jar) {
     manifest {
         attributes([
             'Main-Class':            'net.minecraftforge.launcher.Main',
-            'Automatic-Module-Name': 'net.minecraftforge.launcher'
+            'Automatic-Module-Name': 'net.minecraftforge.launcher',
+            'Add-Opens':             'java.base/java.lang.invoke=net.minecraftforge.launcher'
         ])
 
         gradleutils.manifestDefaults(it, 'net/minecraftforge/launcher/')
@@ -54,9 +56,38 @@ tasks.named('jar', Jar) {
     archiveClassifier = 'thin'
 }
 
+
+multiRelease.register {
+    add(JavaLanguageVersion.of(9), project(':slime-launcher-j9'))
+}
+def multiReleaseJar = tasks.named('multiReleaseJar', Jar) {
+    includeEmptyDirs = false
+    eachFile({
+        if (name == 'module-info.class')
+            path = 'module-info.class'
+        if (name == 'DummyForModule.class')
+            exclude()
+    })
+}
+
 tasks.named('shadowJar', ShadowJar) {
+    duplicatesStrategy = DuplicatesStrategy.EXCLUDE
+
+    dependsOn multiReleaseJar
+    from({zipTree(multiReleaseJar.get().archiveFile.get().asFile)})
+    exclude('META-INF/maven/**')
+    exclude('META-INF/proguard/**')
+
     enableAutoRelocation = true
     relocationPrefix = 'net.minecraftforge.launcher.shadow'
+    relocate 'com.google.errorprone.annotations', 'net.minecraftforge.launcher.shadow.errorprone'
+    relocate 'com.google.gson', 'net.minecraftforge.launcher.shadow.gson'
+    relocate 'net.minecraftforge.util', 'net.minecraftforge.launcher.shadow.util'
+    // Rewrite JOpt's message files, so that help text is displayed nicely.
+    transform(com.github.jengelman.gradle.plugins.shadow.transformers.PropertiesFileTransformer) {
+        paths = [ 'Messages.properties$' ]
+        keyTransformer = { key -> 'net.minecraftforge.launcher.shadow.' + key }
+    }
 
     archiveClassifier = ''
 }

settings.gradle

@@ -19,11 +19,12 @@ gradle.beforeProject { Project project ->
 
 //@formatter:off
 dependencyResolutionManagement.versionCatalogs.register('libs') {
-    plugin 'licenser',    'net.minecraftforge.licenser'    version '1.2.0'
-    plugin 'gradleutils', 'net.minecraftforge.gradleutils' version '3.3.21'
-    plugin 'gitversion',  'net.minecraftforge.gitversion'  version '3.1.6'
-    plugin 'changelog',   'net.minecraftforge.changelog'   version '3.1.3'
-    plugin 'shadow',      'com.gradleup.shadow'            version '9.2.2'
+    plugin 'licenser',     'net.minecraftforge.licenser'      version '1.2.0'
+    plugin 'gradleutils',  'net.minecraftforge.gradleutils'   version '3.3.21'
+    plugin 'gitversion',   'net.minecraftforge.gitversion'    version '3.1.6'
+    plugin 'changelog',    'net.minecraftforge.changelog'     version '3.1.3'
+    plugin 'shadow',       'com.gradleup.shadow'              version '9.2.2'
+    plugin 'multirelease', 'net.minecraftforge.multi-release' version '0.1.4'
 
     library 'gson', 'com.google.code.gson', 'gson'        version '2.11.0'
     library 'jopt', 'net.sf.jopt-simple',   'jopt-simple' version '6.0-alpha-3'
@@ -37,3 +38,5 @@ dependencyResolutionManagement.versionCatalogs.register('libs') {
     library 'nulls', 'org.jetbrains', 'annotations' version '26.0.2'
 }
 //@formatter:on
+
+include 'slime-launcher-j9'

slime-launcher-j9/build.gradle

@@ -0,0 +1,12 @@
+plugins {
+    id 'java'
+    alias libs.plugins.gradleutils
+    alias libs.plugins.licenser
+}
+
+java.toolchain.languageVersion = JavaLanguageVersion.of(9)
+
+license {
+    header = rootProject.file('LICENSE-header.txt')
+    newLine = false
+}

slime-launcher-j9/src/main/java/module-info.java

@@ -0,0 +1,7 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+module net.minecraftforge.launcher {
+    exports net.minecraftforge.launcher;
+}

slime-launcher-j9/src/main/java/net/minecraftforge/launcher/DummyForModule.java

@@ -0,0 +1,8 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+package net.minecraftforge.launcher;
+
+class DummyForModule {
+}

src/main/java/net/minecraftforge/launcher/Main.java

@@ -20,6 +20,7 @@
 import java.lang.invoke.MethodHandle;
 import java.lang.invoke.MethodHandles;
 import java.lang.invoke.MethodType;
+import java.lang.reflect.Field;
 import java.lang.reflect.Method;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipFile;
@@ -144,7 +145,7 @@ private static Class<?> findMainClass(String mainClass) {
     }
 
     private static MethodHandle findMainMethod(Class<?> main) {
-        MethodHandles.Lookup lookup = MethodHandles.lookup();
+        MethodHandles.Lookup lookup = findLookup();
         try {
             return lookup.findStatic(main, "main", MethodType.methodType(void.class, String[].class));
         } catch (IllegalAccessException e) {
@@ -153,15 +154,28 @@ private static MethodHandle findMainMethod(Class<?> main) {
                 Method mtd = main.getDeclaredMethod("main", String[].class);
                 return lookup.unreflect(mtd);
             } catch (NoSuchMethodException | IllegalAccessException ex) {
-                IllegalStateException error = new IllegalStateException("Could not find main(String[]) in " + main.getName() + '!', e);
-                error.addSuppressed(e);
+                IllegalStateException error = new IllegalStateException("Could not find main(String[]) in " + main.getName() + "!\r\n" +
+                    "Try running with --add-opens java.base/java.lang.invoke=ALL-UNNAMED", e);
+                error.addSuppressed(ex);
                 throw error;
             }
         } catch (NoSuchMethodException e) {
             throw new IllegalStateException("Could not find main(String[]) in " + main.getName() + '!', e);
         }
     }
 
+    private static MethodHandles.Lookup findLookup() {
+        // try and find the privileged lookup, this typically needs a command line argument but it **should** detect it from our Manifest
+        try {
+            Field field = MethodHandles.Lookup.class.getDeclaredField("IMPL_LOOKUP");
+            field.setAccessible(true);
+            return (MethodHandles.Lookup)field.get(null);
+        } catch (Exception ignored) {
+            // This is expected if we don't have --add-opens java.base/java.lang.invoke=net.minecraftforge.launcher
+        }
+        return MethodHandles.lookup();
+    }
+
     private static final class Launcher {
         private final String name;
         private final MethodHandle main;