Mixin VS MCPConfig

And one day maybe you'll need that to inject code into specific location, but it's to do advanced things: https://github.com/SpongePowered/Mixin/wiki

SpongePowered isn't a Mod, they're the group that maintain the Framework for Mixins. The next mod in the stacktrace is cpw.mods.modlauncher

That source was probably outdated. Forge didn't natively allow you to do that. You could do Java voodoo to allow a library that implemented(? Not sure if it implemented the feature or simply allowed it to be used in a specific way) Mixins, those allow you to modify the game's bytecode. Modern Forge has that library natively. Source: First paragraph of https://github.com/SpongePowered/Mixin/wiki/Mixins-on-Minecraft-Forge

These days Mojang provides obfuscation maps, so you can work with proper class and method names (though no parameter or local variable names). There's also been a lot of effort been put into the tooling. Nowadays there exists Gradle plugins that will download the game jar, decompile it and deobfuscate it using the official mappings. You develop against the deobfuscated code, then the plugin will turn the unobfuscated names back into their obfuscated versions when you compile. There's also been technology developed that lets you easily modify specific parts of a method in the game, so you can e.g. insert calls to your own functions at runtime.[1] This saves from you having to modify the game jar itself.

[1]: https://github.com/SpongePowered/Mixin

quilt (and fabric) take mojang's jar and preprocess it similarly, but the rest of the modifications to the code are done at runtime using a ridiculously powerful instrumenting classloader. the game is not decompiled at all, other than giving you something to look at in the IDE.

If you can't use the API, I suggest you to use Mixins or really asking yourself if your idea should worth the instability/effort of creating a coremod.

see spongepowered's mixin wiki

forge takes the jar as released by mojang, does a couple preprocessing tasks (renaming everything away from meaningless proguard names, merging the client and server .jars, etc), then decompiles it with forgeflower, applies a large number of source-level diffs to the decompiler output to account for deficiencies in the decompiler that cause the output to be mostly correct but not exactly recompilable, applies another set of source-level diffs to produce a jar augmented with the fun stuff that the forge project wants, recompiles this source, then writes the forge modloader against that. (actual mods are written against the modloader and patched minecraft as well, modders cannot write their own source patches, only forge itself has source patches.)

Java: 16.0.2 JVM: 16.0.2+7(Eclipse Foundation) Arch: amd64 WARNING: This project is configured to use the official obfuscation mappings provided by Mojang. These mapping fall under their associated license, you should be fully aware of this license. For the lat est license text, refer below, or the reference copy here: https://github.com/MinecraftForge/MCPConfig/blob/master/Mojang.md, You can hide this warning by running the `hideOfficialWarningUntilChanged` t ask WARNING: (c) 2020 Microsoft Corporation. These mappings are provided "as-is" and you bear the risk of using them. You may copy and use the mappings for development purposes, but you may not redistribute the mappings complete and unmodified. Microsoft makes no warranties, express or implied, with respect to the mappings provided here. Use and modification of this document or the source code (in any fo rm) of Minecraft: Java Edition is governed by the Minecraft End User License Agreement available at https://account.mojang.com/documents/minecraft_eula. java.lang.IllegalStateException: Could not find tools.jar. Please check that C:\Program Files\Java\jre1.8.0_301 contains a valid JDK installation. at org.gradle.api.internal.tasks.compile.JdkTools.(JdkTools.java:77) at org.gradle.api.internal.tasks.compile.JavaHomeBasedJavaCompilerFactory.createJdkTools(JavaHomeBasedJavaCompilerFactory.java:48) at java.util.concurrent.ConcurrentHashMap.computeIfAbsent(Unknown Source) at org.gradle.api.internal.tasks.compile.JavaHomeBasedJavaCompilerFactory.create(JavaHomeBasedJavaCompilerFactory.java:43) at org.gradle.api.internal.tasks.compile.JavaHomeBasedJavaCompilerFactory.create(JavaHomeBasedJavaCompilerFactory.java:29) at org.gradle.api.internal.tasks.compile.JdkJavaCompiler.createCompileTask(JdkJavaCompiler.java:63) at org.gradle.api.internal.tasks.compile.JdkJavaCompiler.execute(JdkJavaCompiler.java:53) at org.gradle.api.internal.tasks.compile.JdkJavaCompiler.execute(JdkJavaCompiler.java:39) at org.gradle.api.internal.tasks.compile.daemon.AbstractDaemonCompiler$CompilerWorkAction.execute(AbstractDaemonCompiler.java:135) at org.gradle.workers.internal.DefaultWorkerServer.execute(DefaultWorkerServer.java:63) at org.gradle.workers.internal.AbstractClassLoaderWorker$1.create(AbstractClassLoaderWorker.java:49) at org.gradle.workers.internal.AbstractClassLoaderWorker$1.create(AbstractClassLoaderWorker.java:43) at org.gradle.internal.classloader.ClassLoaderUtils.executeInClassloader(ClassLoaderUtils.java:97) at org.gradle.workers.internal.AbstractClassLoaderWorker.executeInClassLoader(AbstractClassLoaderWorker.java:43) at org.gradle.workers.internal.FlatClassLoaderWorker.run(FlatClassLoaderWorker.java:32) at org.gradle.workers.internal.FlatClassLoaderWorker.run(FlatClassLoaderWorker.java:22) at org.gradle.workers.internal.WorkerDaemonServer.run(WorkerDaemonServer.java:85) at org.gradle.workers.internal.WorkerDaemonServer.run(WorkerDaemonServer.java:55) at org.gradle.process.internal.worker.request.WorkerAction$1.call(WorkerAction.java:138) at org.gradle.process.internal.worker.child.WorkerLogEventListener.withWorkerLoggingProtocol(WorkerLogEventListener.java:41) at org.gradle.process.internal.worker.request.WorkerAction.run(WorkerAction.java:135) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:36) at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24) at org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:182) at org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:164) at org.gradle.internal.remote.internal.hub.MessageHub$Handler.run(MessageHub.java:414) at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:64) at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:48) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:56) at java.lang.Thread.run(Unknown Source) java.lang.IllegalStateException: Could not find tools.jar. Please check that C:\Program Files\Java\jre1.8.0_301 contains a valid JDK installation. at org.gradle.api.internal.tasks.compile.JdkTools.(JdkTools.java:77) at org.gradle.api.internal.tasks.compile.JavaHomeBasedJavaCompilerFactory.createJdkTools(JavaHomeBasedJavaCompilerFactory.java:48) at java.util.concurrent.ConcurrentHashMap.computeIfAbsent(Unknown Source) at org.gradle.api.internal.tasks.compile.JavaHomeBasedJavaCompilerFactory.create(JavaHomeBasedJavaCompilerFactory.java:43) at org.gradle.api.internal.tasks.compile.JavaHomeBasedJavaCompilerFactory.create(JavaHomeBasedJavaCompilerFactory.java:29) at org.gradle.api.internal.tasks.compile.JdkJavaCompiler.createCompileTask(JdkJavaCompiler.java:63) at org.gradle.api.internal.tasks.compile.JdkJavaCompiler.execute(JdkJavaCompiler.java:53) at org.gradle.api.internal.tasks.compile.JdkJavaCompiler.execute(JdkJavaCompiler.java:39) at org.gradle.api.internal.tasks.compile.daemon.AbstractDaemonCompiler$CompilerWorkAction.execute(AbstractDaemonCompiler.java:135) at org.gradle.workers.internal.DefaultWorkerServer.execute(DefaultWorkerServer.java:63) at org.gradle.workers.internal.AbstractClassLoaderWorker$1.create(AbstractClassLoaderWorker.java:49) at org.gradle.workers.internal.AbstractClassLoaderWorker$1.create(AbstractClassLoaderWorker.java:43) at org.gradle.internal.classloader.ClassLoaderUtils.executeInClassloader(ClassLoaderUtils.java:97) at org.gradle.workers.internal.AbstractClassLoaderWorker.executeInClassLoader(AbstractClassLoaderWorker.java:43) at org.gradle.workers.internal.FlatClassLoaderWorker.run(FlatClassLoaderWorker.java:32) at org.gradle.workers.internal.FlatClassLoaderWorker.run(FlatClassLoaderWorker.java:22) at org.gradle.workers.internal.WorkerDaemonServer.run(WorkerDaemonServer.java:85) at org.gradle.workers.internal.WorkerDaemonServer.run(WorkerDaemonServer.java:55) at org.gradle.process.internal.worker.request.WorkerAction$1.call(WorkerAction.java:138) at org.gradle.process.internal.worker.child.WorkerLogEventListener.withWorkerLoggingProtocol(WorkerLogEventListener.java:41) at org.gradle.process.internal.worker.request.WorkerAction.run(WorkerAction.java:135) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:36) at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24) at org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:182) at org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:164) at org.gradle.internal.remote.internal.hub.MessageHub$Handler.run(MessageHub.java:414) at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:64) at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:48) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:56) at java.lang.Thread.run(Unknown Source) FAILURE: Build failed with an exception. * What went wrong: Could not resolve all files for configuration ':runtimeClasspathCopy'. > Could not find net.minecraftforge:forge:1.16.5-36.2.2_mapped_official_1.16.5. Searched in the following locations: - file:/C:/Users/memjk/.gradle/caches/forge_gradle/bundeled_repo/net/minecraftforge/forge/1.16.5-36.2.2_mapped_official_1.16.5/forge-1.16.5-36.2.2_mapped_official_1.16.5.pom - file:/C:/Users/memjk/.gradle/caches/forge_gradle/bundeled_repo/net/minecraftforge/forge/1.16.5-36.2.2_mapped_official_1.16.5/forge-1.16.5-36.2.2_mapped_official_1.16.5.jar Required by: project :

See our official updated thoughts on it: https://github.com/MinecraftForge/MCPConfig/blob/master/Mojang.md Forge uses the mojmaps in our repository, and it is the default for MDKs. Be mindful of the terms of the license, but we don't believe there is any danger to using it.