Mixin VS vineflower

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That source was probably outdated.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

this is kind of a silly point, but the quilt community is just nicer to be around than any of the other ones in my experience, which has real effects: e.g., you attract people really really good at decompiler tech and create quiltflower which is a decompiler so good Java professionals use it. inclusivity matters! the cutting edge happens on quilt

The only way is to reverse-engineer it. Use something like quiltflower or javap if you want to be extra sure, and have a look through the Java code

Firstly, we have to decompile the JAR, turning the bytecode back into Java. This is a very difficult job: a lot of work has been put into the tools to make this happen.

Alternatively, there's this new project that I haven't tried yet: https://github.com/QuiltMC/quiltflower

The decompiler they used to view that code is not very good, that output is garbled.

If you're going to take apart JVM bytecode, you're better off using Recafe or Quiltflower.

https://github.com/Col-E/Recaf

https://github.com/QuiltMC/quiltflower

They are community contributed (through using decompilers to see what the classes do) and decompiler toolchains have ways of instrumenting classes with javadoc. They are also incomplete, you really can't write a mod using only a javadocs page

runs nice with jbang https://github.com/QuiltMC/quiltflower/releases/download/1.8.1/quiltflower-1.8.1.jar