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[1.16.5] Capabilities attached to ItemStacks continuously trigger writeNBT


Phi
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Hello, I've been trying to attach a capability to an ItemStack, but while the capability itself attaches fine, any data I write to it is reset to 0 at one point or another. Really the only possible cause that I've been able to find for this is with a Logger in the writeNBT function of the capability class, which shows that it will just continuously call this function while the capability persists.

I've attached the same capability to an Entity instead, which works fine, and I've attached a different previously working capability to an ItemStack which produces the same problem as described above. 

The attach event code (same code with different types of items also produces the problem) :

@SubscribeEvent
public static void onItemAttachCapabilitiesEvent(AttachCapabilitiesEvent<ItemStack> event) {
  if (event.getObject().getItem() instanceof PotionItem) {
    PotionChargesProvider provider = new PotionChargesProvider();
    event.addCapability(new ResourceLocation(VanillaSpice.MOD_ID, "potioncharges"), provider);
    event.addListener(provider::invalidate);
  }
}

The capability class:

public class CapabilityPotionCharges {

    private static final Logger LOGGER = LogManager.getLogger();

    @CapabilityInject(IPotionCharges.class)
    public static Capability<IPotionCharges> POTION_CHARGES_CAPABILITY = null;

    public static void register() {
        CapabilityManager.INSTANCE.register(IPotionCharges.class, new Storage(), DefaultPotionCharges::new);
    }

    private static class Storage implements Capability.IStorage<IPotionCharges> {

        @Nullable
        @Override
        public INBT writeNBT(Capability<IPotionCharges> capability, IPotionCharges instance, Direction side) {
            LOGGER.info("potion writeNBT");
            CompoundNBT tag = new CompoundNBT();
            tag.putInt("charges", instance.getCharges());
            return tag;
        }

        @Override
        public void readNBT(Capability<IPotionCharges> capability, IPotionCharges instance, Direction side, INBT nbt) {
            LOGGER.info("potion readNBT");
            int charges = ((CompoundNBT) nbt).getInt("charges");
            instance.setCharges(charges);
        }

    }

}

The provider class:

public class PotionChargesProvider implements ICapabilitySerializable<CompoundNBT> {

    private final DefaultPotionCharges potionCharges = new DefaultPotionCharges();
    private final LazyOptional<IPotionCharges> potionChargesOptional = LazyOptional.of(() -> potionCharges);

    public void invalidate() { potionChargesOptional.invalidate(); }

    @Nonnull
    @Override
    public <T> LazyOptional<T> getCapability(@Nonnull Capability<T> cap, @Nullable Direction side) {
        return potionChargesOptional.cast();
    }

    @Override
    public CompoundNBT serializeNBT() {
        if (CapabilityPotionCharges.POTION_CHARGES_CAPABILITY == null) {
            return new CompoundNBT();
        } else {
            return (CompoundNBT) CapabilityPotionCharges.POTION_CHARGES_CAPABILITY.writeNBT(potionCharges, null);
        }
    }

    @Override
    public void deserializeNBT(CompoundNBT nbt) {
        if (CapabilityPotionCharges.POTION_CHARGES_CAPABILITY != null) {
            CapabilityPotionCharges.POTION_CHARGES_CAPABILITY.readNBT(potionCharges, null, nbt);
        }
    }

}

The default capability class is just a getter and a setter for a private int.

I'm really hoping there's just something stupid I'm forgetting about ItemStacks, been trying to figure this one out for way too long now.

latest.log

Edited by Phi
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Whenever a player removes a potion from a brewing stand it sets the charges on that potion to 3 (currently also has an xp check on it). Then in LivingEntityUseItemEvent.Start/Finish (I tested both to be sure) it checks the charges, at which point they show as 0.

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Because I didn't know there were other ways to do it up to just now 😛 

As for the xp, the code should run fine without the check, but else it's just setAlchemyTier(1 or higher) on the playerStats capability on the player

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Alright, I have identified the problem. First of all I simplified the code to just add an nbt tag to the potion instead of a whole capability. The system now looks like this:

    @SubscribeEvent
    public static void onPlayerBrewPotionEvent(PlayerBrewedPotionEvent event) {
        PlayerEntity player = event.getPlayer();
        ItemStack stack = event.getStack();
        if (!player.level.isClientSide()) {            
            CompoundNBT tag = stack.getTag();
            if (tag == null) { tag = new CompoundNBT(); }
            tag.putInt("vs_charges", 3);
            LOGGER.info(tag.getInt("vs_charges"));
            stack.setTag(tag);
        }
    }

    @SubscribeEvent
    public static void onItemUseFinishEvent(LivingEntityUseItemEvent.Finish event) {
        ItemStack stack = event.getItem();
        LivingEntity entity = event.getEntityLiving();

        if (entity instanceof PlayerEntity && !entity.level.isClientSide()) {
            PlayerEntity player = (PlayerEntity) entity;

            if (stack.getItem() instanceof PotionItem) {
                CompoundNBT tag = stack.getTag();
                int charges = 0;
                if (tag != null) { charges = tag.getInt("vs_charges"); }
                LOGGER.info(charges);
                if (charges > 0) {
                    tag.putInt("vs_charges", charges - 1);
                    stack.setTag(tag);
                    event.setResultStack(stack);
                }
            }
        }
    }

Initially, this had the same problem as before, where on drinking a potion the charges would read 0 again. However it seems that this is only the case when shift-clicking the potion from the brewing stand. If picked up with just a left click, the charges are saved properly and everything works as it should. The shift-clicking problem doesn't extend to any other containers, i.e. if I pick up a potion from a brewing stand and then shift-click it into a chest and back out, it still works properly.

I guess this means I'm looking for a way to detect a shift-click in a brewing stand to save the data elsewhere, and then restore it later?

Edited by Phi
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