Mixin tricks

Common and not so common mixins

Player respawn

Local

@Mixin(value = Minecraft.class, remap = false)
public class MinecraftMixin {

    @Shadow public PlayerLocal thePlayer;

    @Inject(method = "respawn", at = @At(value = "INVOKE", target = "Lnet/minecraft/client/entity/player/PlayerLocal;setGamemode(Lnet/minecraft/core/player/gamemode/Gamemode;)V"), remap = false)
    public void keepInfo(boolean multiplayer, int targetDimension, CallbackInfo ci, @Local Player previousPlayer) {
        // Copy your data here
    }
}

Multiplayer

@Mixin(value = PlayerList.class, remap = false)
public class PlayerListMixin {
    @Inject(method = "recreatePlayerEntity", at = @At(value = "INVOKE", target = "Lnet/minecraft/core/player/inventory/container/ContainerInventory;transferAllContents(Lnet/minecraft/core/player/inventory/container/ContainerInventory;)V"), remap = false)
    public void keepInfoMP(final PlayerServer previousPlayer, final int i, final CallbackInfoReturnable<PlayerServer> cir, @Local(name = "newPlayer") final PlayerServer newPlayer) {
        // Copy your data here
    }
}

Remove a Mob

@Mixin(value = Biome.class, remap = false)
public abstract class BiomeMixin {

    @Shadow(remap = false)
    protected List<SpawnListEntry> spawnableMonsterList;

    @Inject(method = "<init>", at = @At("TAIL"), remap = false)
    private void onConstructed(String key, CallbackInfo ci) {
        this.spawnableMonsterList.add(new SpawnListEntry(MyCustomMob.class, 4));
        this.spawnableMonsterList.remove(3); // Bye Bye Mob Zombie Armored :) 😈
    }
}

Replace an Item

@Mixin(value = Items.class, remap = false)
public class ItemsMixin {
    @Inject(method = "setupItems", at = @At("TAIL"))
    private static void replaceItems(CallbackInfo ci) {
        Item.itemsList[Items.PAPER.id] = null;
        Item.itemsMap.remove(Items.PAPER.namespaceID);
        String name = Items.PAPER.getKey().substring(Items.PAPER.getKey().indexOf(".") + 1);
        Items.PAPER = new CustomItemPaper(name, Items.PAPER.namespaceID.toString(), Items.PAPER.id);
    }
}

Replace a Recipe

@Mixin(
    value = {RecipeRegistry.class},
    remap = false
)
public class RecipeDenier {
    @Unique private final static List<String> toDeny = new ArrayList<>();

    static {
        toDeny.add("minecraft:workbench/paper");
    }

    @Inject(method = "addCustomRecipe", at = @At("HEAD"), cancellable = true)
    private void RecipeDenierInject(String recipeKey, RecipeEntryBase<?, ?, ?> recipe, CallbackInfo ci) {
        if (toDeny.contains(recipeKey)) {
            LOGGER.info("Recipe {} is denied in Mixin", recipeKey);
            ci.cancel();
        }
    }
}