So I have the following code to add a tooltip to an item:

@SubscribeEvent
public void onItemTooltip(ItemTooltipEvent event) {
    ItemStack stack = event.getItemStack();
    NBTTagCompound tag = stack.getTagCompound();
    if (tag == null) {
        return;
    }

    if (!tag.getString("infused_element").equals("")) {
        Element element = Element.valueOf(tag.getString("infused_element"));
        int level = tag.getInteger("infusion_level");

        event.getToolTip().add(String.format(TOOLTIP_FORMAT, element.toString(), RomanNumber.toRoman(level)));
    }
}

 

When in game I look at an item with this NBT tag the game crashes with the following error:

[12:03:21] [server thread/ERROR]: Encountered an unexpected exception
net.minecraft.util.ReportedException: Ticking player
at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:789) ~[MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:687) ~[MinecraftServer.class:?]
at net.minecraft.server.integrated.IntegratedServer.tick(IntegratedServer.java:156) ~[integratedServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:536) [MinecraftServer.class:?]
at java.lang.Thread.run(Thread.java:745) [?:1.8.0_111]
Caused by: java.lang.StackOverflowError
at net.minecraft.nbt.NBTTagCompound.copy(NBTTagCompound.java:523) ~[NBTTagCompound.class:?]
at net.minecraft.nbt.NBTTagCompound.copy(NBTTagCompound.java:17) ~[NBTTagCompound.class:?]
at net.minecraft.nbt.NBTTagCompound.copy(NBTTagCompound.java:525) ~[NBTTagCompound.class:?]
at net.minecraft.nbt.NBTTagCompound.copy(NBTTagCompound.java:17) ~[NBTTagCompound.class:?]
at net.minecraft.nbt.NBTTagCompound.copy(NBTTagCompound.java:525) ~[NBTTagCompound.class:?]
at net.minecraft.nbt.NBTTagCompound.copy(NBTTagCompound.java:17) ~[NBTTagCompound.class:?]
at net.minecraft.nbt.NBTTagCompound.copy(NBTTagCompound.java:525) ~[NBTTagCompound.class:?]
at net.minecraft.nbt.NBTTagCompound.copy(NBTTagCompound.java:17) ~[NBTTagCompound.class:?]
at net.minecraft.nbt.NBTTagCompound.copy(NBTTagCompound.java:525) ~[NBTTagCompound.class:?]
at net.minecraft.nbt.NBTTagCompound.copy(NBTTagCompound.java:17) ~[NBTTagCompound.class:?]
at net.minecraft.nbt.NBTTagCompound.copy(NBTTagCompound.java:525) ~[NBTTagCompound.class:?]
at net.minecraft.nbt.NBTTagCompound.copy(NBTTagCompound.java:17) ~[NBTTagCompound.class:?]
at net.minecraft.nbt.NBTTagCompound.copy(NBTTagCompound.java:525) ~[NBTTagCompound.class:?]
at net.minecraft.nbt.NBTTagCompound.copy(NBTTagCompound.java:17) ~[NBTTagCompound.class:?]
at net.minecraft.nbt.NBTTagCompound.copy(NBTTagCompound.java:525) ~[NBTTagCompound.class:?]
at net.minecraft.nbt.NBTTagCompound.copy(NBTTagCompound.java:17) ~[NBTTagCompound.class:?]
at net.minecraft.nbt.NBTTagCompound.copy(NBTTagCompound.java:525) ~[NBTTagCompound.class:?]

 

Any idea what I'm doing wrong?

Add some break points, then slowly debug it (step into) and find where it roughly appears to be recursively calling

 

net.minecraft.nbt.NBTTagCompound.copy

at lines

523

17

525

Hi

 

It looks to me like you've somehow managed to create an NBTTagCompound "A" which contains an element that has been set to itself (i.e. "A").

So when vanilla tries to copy your "A", it keeps trying to copy all the elements including the one that points to "A", i.e. a recursive loop.

 

I'm not sure how you managed to do that.  Personally I would follow hugo's advice and use your debugger to set a breakpoint at onItemTooltip and then check what is happening when you modify the tag.

 

-TGG