Create an MRJ to set the classloader name

build.gradle

@@ -4,7 +4,7 @@ import org.slf4j.LoggerFactory
 buildscript {
 	dependencies {
 		classpath 'org.kohsuke:github-api:1.135'
-		classpath 'com.guardsquare:proguard-gradle:' + (JavaVersion.current().isCompatibleWith(JavaVersion.VERSION_11) ? '7.4.0-beta02' : '7.1.0')
+		classpath 'com.guardsquare:proguard-gradle:7.5.0'
 	}
 }
 
@@ -59,6 +59,7 @@ sourceSets {
 	main {
 		java.srcDirs = ['src/main/java', 'src/main/legacyJava']
 	}
+	java17
 }
 
 configurations {
@@ -164,7 +165,7 @@ shadowJar {
 import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
 
 // Renaming in the shadow jar task doesnt seem to work, so do it here
-task getSat4jAbout(type: Copy) {
+tasks.register('getSat4jAbout', Copy) {
 	dependsOn project.configurations.include
 	duplicatesStrategy = DuplicatesStrategy.EXCLUDE
 
@@ -181,19 +182,21 @@ task getSat4jAbout(type: Copy) {
 	into layout.buildDirectory.dir("sat4j")
 }
 
-task fatJar(type: ShadowJar, dependsOn: getSat4jAbout) {
+tasks.register('fatJar', ShadowJar) {
+	dependsOn getSat4jAbout
 	from sourceSets.main.output
 	from project(":minecraft").sourceSets.main.output
 	from getSat4jAbout.destinationDir
 	from("LICENSE") {
-		rename { "${it}_${project.base.archivesName.get()}"}
+		rename { "${it}_${project.base.archivesName.get()}" }
 	}
 
 	manifest {
-		attributes (
+		attributes(
 			'Main-Class': 'net.fabricmc.loader.impl.launch.server.FabricServerLauncher',
 			'Fabric-Loom-Remap': 'false',
-			'Automatic-Module-Name': 'net.fabricmc.loader'
+			'Automatic-Module-Name': 'net.fabricmc.loader',
+			'Multi-Release': 'true'
 		)
 	}
 
@@ -218,28 +221,46 @@ task fatJar(type: ShadowJar, dependsOn: getSat4jAbout) {
 	outputs.upToDateWhen { false }
 }
 
-File proguardFile = file("build/libs/fabric-loader-${version}.jar")
+File proguardTmpFile = file("build/tmp/fabric-loader-${version}.jar")
 
 import proguard.gradle.ProGuardTask
-task proguardJar(type: ProGuardTask, dependsOn: fatJar) {
+
+tasks.register('proguardJar', ProGuardTask) {
+	dependsOn fatJar
 	def classpath = project(":minecraft").configurations.compileClasspath
 
 	inputs.files(fatJar, classpath)
-	outputs.files(proguardFile)
+	outputs.files(proguardTmpFile)
 
 	doFirst {
 		classpath.resolve().forEach {
 			libraryjars it
 		}
 	}
 
-	libraryjars JavaVersion.current().java9Compatible ? "${System.getProperty('java.home')}/jmods" : "${System.getProperty('java.home')}/lib/rt.jar"
+	def java8 = javaToolchains.launcherFor {
+		languageVersion = JavaLanguageVersion.of(8)
+	}.get()
+	libraryjars java8.metadata.installationPath.file("jre/lib/rt.jar")
 
 	injars fatJar.archiveFile
-	outjars proguardFile
+	outjars proguardTmpFile
 	configuration file("proguard.conf")
 }
-build.dependsOn proguardJar
+
+// As proguard does not support MRJ's we must add the MRJ classes to the final jar
+// Use a Zip task to not alter the manifest
+tasks.register('finalJar', Zip) {
+	from zipTree(proguardTmpFile)
+	dependsOn(proguardJar)
+	into('META-INF/versions/17') {
+		from sourceSets.java17.output
+	}
+	destinationDirectory = file("build/libs")
+	archiveExtension = "jar"
+}
+
+build.dependsOn finalJar
 
 tasks.withType(AbstractArchiveTask) {
 	preserveFileTimestamps = false
@@ -252,19 +273,19 @@ sourcesJar {
 }
 
 // useful for creating test mod jar
-task testJar(type: Jar) {
+tasks.register('testJar', Jar) {
 	archiveClassifier = "test"
 	from sourceSets.test.output
 }
 
-task copyJson() {
+tasks.register('copyJson') {
 	def inJson = file('src/main/resources/fabric-installer.json')
 	def inLwJson = file('src/main/resources/fabric-installer.launchwrapper.json')
 
 	def outJson = file("build/libs/${project.base.archivesName.get()}-${version}.json")
 	def outLwJson = file("build/libs/${project.base.archivesName.get()}-${version}.launchwrapper.json")
 
-	inputs.files (inJson, inLwJson)
+	inputs.files(inJson, inLwJson)
 	outputs.files(outJson, outLwJson)
 
 	doLast {
@@ -277,13 +298,7 @@ tasks.build.dependsOn "copyJson"
 
 tasks.withType(JavaCompile).configureEach {
 	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.
-	if (JavaVersion.current().isJava9Compatible()) {
-		it.options.release = 8
-	}
+	it.options.release = it.name.contains("Java17") ? 17 : 8
 }
 
 javadoc {
@@ -310,7 +325,7 @@ javadoc {
 	failOnError false
 }
 
-task javadocJar(type: Jar) {
+tasks.register('javadocJar', Jar) {
 	dependsOn javadoc
 	from javadoc.destinationDir
 	archiveClassifier = 'javadoc'
@@ -337,33 +352,30 @@ tasks.withType(GenerateModuleMetadata) {
 	enabled = false
 }
 
-def signingEnabled = ENV.SIGNING_SERVER
-File proguardFileSigned = null
+File signedJar = file("build/libs/fabric-loader-${version}-signed.jar")
 
-if (signingEnabled) {
-	proguardFileSigned = file("build/libs/fabric-loader-${version}-signed.jar")
+remoteSign {
+	requestUrl = ENV.SIGNING_SERVER
+	pgpAuthKey = ENV.SIGNING_PGP_KEY
+	jarAuthKey = ENV.SIGNING_JAR_KEY
 
-	remoteSign {
-		requestUrl = ENV.SIGNING_SERVER
-		pgpAuthKey = ENV.SIGNING_PGP_KEY
-		jarAuthKey = ENV.SIGNING_JAR_KEY
+	useDummyForTesting = ENV.SIGNING_SERVER == null
 
-		sign(proguardFile, proguardFileSigned, "proguard").configure {
-			dependsOn proguardJar
-		}
+	sign(finalJar.archiveFile.get().getAsFile(), signedJar, "final").configure {
+		dependsOn finalJar
+	}
 
-		afterEvaluate {
-			sign publishing.publications.mavenJava
-		}
+	afterEvaluate {
+		sign publishing.publications.mavenJava
 	}
 }
 
 publishing {
 	publications {
 		mavenJava(MavenPublication) {
 			// add all the jars that should be included when publishing to maven
-			artifact(signingEnabled ? proguardFileSigned : proguardFile) {
-				builtBy(signingEnabled ? signProguard : proguardJar)
+			artifact(signedJar) {
+				builtBy(tasks.signFinal)
 				classifier = null
 			}
 			artifact(sourcesJar)

minecraft/minecraft-test/build.gradle

@@ -84,7 +84,7 @@ dependencies {
 	productionRuntimeMods "net.fabricmc.fabric-api:fabric-api:0.89.3+1.20.2:testmod"
 }
 
-def loaderJarTask = project(":").tasks.proguardJar
+def loaderJarTask = project(":").tasks.finalJar
 
 // This is very far beyond loom's API if you copy this, you're on your own.
 task runProductionAutoTestClient(type: JavaExec, dependsOn: [loaderJarTask, remapJar]) {

settings.gradle

@@ -7,13 +7,17 @@ pluginManagement {
 		gradlePluginPortal()
 	}
 }
+
+plugins {
+	id("org.gradle.toolchains.foojay-resolver-convention") version "0.8.0"
+}
+
 rootProject.name='fabric-loader'
 
+if (!JavaVersion.current().isCompatibleWith(JavaVersion.VERSION_17)) {
+	throw new UnsupportedOperationException("Fabric Loader requires Java 17+ to build.")
+}
+
 include "minecraft"
 include "junit"
-
-if (JavaVersion.current().isCompatibleWith(JavaVersion.VERSION_17)) {
-	include "minecraft:minecraft-test"
-} else {
-	println("Minecraft test sub project requires java 17 or higher!")
-}
+include "minecraft:minecraft-test"

src/java17/java/net/fabricmc/loader/impl/mrj/AbstractSecureClassLoader.java

@@ -0,0 +1,25 @@
+/*
+ * Copyright 2016 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.loader.impl.mrj;
+
+import java.security.SecureClassLoader;
+
+public abstract class AbstractSecureClassLoader extends SecureClassLoader {
+	public AbstractSecureClassLoader(String name, ClassLoader parent) {
+		super(name, parent);
+	}
+}

src/main/java/net/fabricmc/loader/impl/launch/knot/KnotClassLoader.java

@@ -21,16 +21,16 @@
 import java.net.URL;
 import java.net.URLClassLoader;
 import java.security.CodeSource;
-import java.security.SecureClassLoader;
 import java.util.Enumeration;
 import java.util.Objects;
 
 import net.fabricmc.api.EnvType;
 import net.fabricmc.loader.impl.game.GameProvider;
 import net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.ClassLoaderAccess;
+import net.fabricmc.loader.impl.mrj.AbstractSecureClassLoader;
 
 // class name referenced by string constant in net.fabricmc.loader.impl.util.LoaderUtil.verifyNotInTargetCl
-final class KnotClassLoader extends SecureClassLoader implements ClassLoaderAccess {
+final class KnotClassLoader extends AbstractSecureClassLoader implements ClassLoaderAccess {
 	private static final class DynamicURLClassLoader extends URLClassLoader {
 		private DynamicURLClassLoader(URL[] urls) {
 			super(urls, new DummyClassLoader());
@@ -51,7 +51,7 @@ public void addURL(URL url) {
 	private final KnotClassDelegate<KnotClassLoader> delegate;
 
 	KnotClassLoader(boolean isDevelopment, EnvType envType, GameProvider provider) {
-		super(new DynamicURLClassLoader(new URL[0]));
+		super("knot", new DynamicURLClassLoader(new URL[0]));
 		this.originalLoader = getClass().getClassLoader();
 		this.urlLoader = (DynamicURLClassLoader) getParent();
 		this.delegate = new KnotClassDelegate<>(isDevelopment, envType, this, originalLoader, provider);

src/main/java/net/fabricmc/loader/impl/mrj/AbstractSecureClassLoader.java

@@ -0,0 +1,25 @@
+/*
+ * Copyright 2016 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.loader.impl.mrj;
+
+import java.security.SecureClassLoader;
+
+public abstract class AbstractSecureClassLoader extends SecureClassLoader {
+	public AbstractSecureClassLoader(String name, ClassLoader parent) {
+		super(parent);
+	}
+}