Integrating Rust IPA word detection with Minecraft

With the IPA based magic keyword detection (which is written in Rust) working I spent all of this devlog integrating it into Minecraft. I created a new repo for the mod, using the Jared’s template. I decided to go with supporting both Fabric and Neoforge, and picked the 1.21.1 Minecraft version, though in the future I’m planning to move to 26.2 or later. I set up an additional gradle subproject and a rust package, that both together act as a Java to Rust bridge, using the j4rs crate.
Using it I managed to initialize Sepple (the detection system), and get it running. The tricky part was going the other direction, to pass detected words from Rust to Java. For some reason Rust wasn’t detecting the JVM and was trying to spawn a new one!
After a bit of experimentation I concluded, that I can only call Java from Rust only during the period when Java calls Rust, and only on the same thread. In the end I managed to get it working, by spawning a new thread on the Java side, and calling a blocking Rust function, that kept calling a Java callback passed to it. Originally I tried to use a static function as a callback, but for some reason (probably some kind of classloading isolation) the system was failing with some crazy null errors.

I also had to adjust Sepple a bit, to not require a bunch of random json files at specific paths, and to provide an mpsc chanell directly outside its pipeline, for less boilerplate.

With that I have a proof of concept working! Minecraft is receiving the detected words and printing them to chat.

Note that those are all custom words, created by me specifically for this mod. This is why I had to create an entire new system for detecting them, and why they are written in the International Phonetic Language, which is also why they look a little weird in the minecraft’s font.

The Java<->Rust setup is also not very good yet. For example the packaging of compiled Rust is very basic, and you can’t control the word detection from Java - no way to stop it or restart. There is also no good error handling, which means if a file is missing it will just crash everything.
But it works, and I can continue working on the mod, and making it better!