NoClassDefFoundError when cancelling mixins

[Vekhove]

Using CallbackInfo#cancel inside a mixin causes NoClassDefFoundError.

This code:

@Mixin(Player.class)
public final class PlayerMixin {

    @Inject(
            method = "notifyPickupItem",
            at = @At("HEAD"),
            cancellable = true
    )
    public void mixintests_injectNotifyPickupItem(Ref<EntityStore> ref, ItemStack itemStack, Vector3d position, ComponentAccessor<EntityStore> componentAccessor, CallbackInfo ci) {
        System.out.println("Picked up!");
        ci.cancel();
    }

}

causes this error:

java.lang.NoClassDefFoundError: org/spongepowered/asm/mixin/injection/callback/CallbackInfo
	at com.hypixel.hytale.server.core.entity.entities.Player.notifyPickupItem(Player.java)
	at com.hypixel.hytale.server.core.modules.entity.player.PlayerItemEntityPickupSystem.tick(PlayerItemEntityPickupSystem.java:190)
	at com.hypixel.hytale.component.system.tick.EntityTickingSystem.doTick(EntityTickingSystem.java:92)
	at com.hypixel.hytale.component.system.tick.EntityTickingSystem.tick(EntityTickingSystem.java:36)
	at com.hypixel.hytale.component.Store.tick(Store.java:1971)
	at com.hypixel.hytale.component.system.tick.ArchetypeTickingSystem.tick(ArchetypeTickingSystem.java:36)
	at com.hypixel.hytale.component.Store.tickInternal(Store.java:1927)
	at com.hypixel.hytale.component.Store.tick(Store.java:1897)
	at com.hypixel.hytale.server.core.universe.world.World.tick(World.java:398)
	at com.hypixel.hytale.server.core.util.thread.TickingThread.run(TickingThread.java:89)
	at java.base/java.lang.Thread.run(Thread.java:1474)
Caused by: java.lang.ClassNotFoundException: org.spongepowered.asm.mixin.injection.callback.CallbackInfo
	at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:377)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:557)
	at com.hypixel.hytale.plugin.early.TransformingClassLoader.loadClass(TransformingClassLoader.java:89)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:490)
	... 11 more

Removing ci.cancel() works as expected, prints the message when the item is picked up.

[DavidutzDev]

I'm actually having the same issue. Hooking any class and trying to call CallbackInfo result in a java.lang.NoClassDefFoundError: org/spongepowered/asm/mixin/injection/callback/CallbackInfo

[AJ4real]

@Mixin(HytaleServer.class)
public class HytaleServerMixin {
    @Inject(method = "<init>", at = @At("HEAD"))
    private static void init(CallbackInfo info) {
        try {
            Optional<ClassTransformer> possible = EarlyPluginLoader.getTransformers().stream().filter(
                    (t) -> t.getClass().getCanonicalName().equalsIgnoreCase("com.build_9.hyxin.HyxinTransformer")).findAny();
            if(possible.isPresent()) {
                URL url = possible.get().getClass().getProtectionDomain().getCodeSource().getLocation();
                TransformingClassLoader loader = (TransformingClassLoader) Thread.currentThread().getContextClassLoader();
                Method method = URLClassLoader.class.getDeclaredMethod("addURL", URL.class);
                method.setAccessible(true);
                method.invoke(loader, url);
            } else throw new RuntimeException("failed to load mixins");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

This is a quick fix I found for this issue, I'm sure there is a better way to do this though.

The classloader used to load early plugins gets replaced after loading earlyplugins, so during actual runtime the server doesn't have it loaded anymore

[Exotik850]

This is a quick fix I found for this issue, I'm sure there is a better way to do this though.

This is a really nice solution but it requires the JVM args --add-opens java.base/java.net=ALL-UNNAMED to be present in order to function. I looked into writing a mixin for the TransformingClassLoader class itself to make the addURL function accessible, but I wasn't able to access any of my methods I added in the mixin within another mixin, as casting to an interface always threw a ClassCastError