Bucket Desync Fix (MC-12363) — Forge 1.12.2 MDK project

Client-side backport of Mojang's fix for https://mojira.dev/MC-12363 (lava/water bucket desync when using a bucket while turning the camera quickly).

How it works

ItemBucket#onItemRightClick raytraces on the SERVER with the last position/rotation the client reported, so fast camera movement makes client and server pick different blocks. The fix (Mojang, 21w11a / 1.17): right before the "use item" packet, the client sends its CURRENT position+rotation. MixinPlayerControllerMP does exactly that for 1.12.2.

Build

Needs JDK 8 (the MDK uses Gradle 4.9 + ForgeGradle 3).

gradlew --refresh-dependencies
gradlew build

The jar is in build/libs/. The task reobfJar runs automatically after jar.

Install / test

Standalone SpongePowered Mixin 0.7.11 is bundled inside the jar and started through the manifest (TweakClass: org.spongepowered.asm.launch.MixinTweaker, MixinConfigs: mixins.bucketsyncfix.json). Just drop the jar in the mods folder of a Forge 1.12.2 instance - no MixinBooter needed. If a modpack already contains MixinBooter (or another mod that bundles its own Mixin) there can be conflicts between the two Mixin copies; in that case use the MixinBooter variant instead.

Reproduce: give yourself a lava bucket, spin the camera and place/pick up lava repeatedly.