Custom Item Signature Updates on Inventory Movement Preventing Stacking

[VinceSMC]

Expected behavior

When moving a custom item inside the inventory, the custom signature of the item should remain unchanged, ensuring the item can stack with other identical items without issue.

Observed/Actual behavior

When moving a custom item within the inventory, the custom signature is updated. While the item's visible properties (e.g., display name, lore) remain identical, the updated custom field prevents it from stacking with other items.

Steps/models to reproduce

1. Create a custom item that has a custom signature.
2. Place the item in your inventory.
3. Move the item to a different inventory slot.
4. Inspect the item's data.
5. Compare the custom signature before and after moving the item.

Plugin and Datapack List

Paper version

This server is running Paper version 1.21.3-81

Other

No response

[electronicboy]

custom signature?

[VinceSMC]

custom signature?

Metadata

[electronicboy]

You're going to need to provide more information, such as means of reproduction and how you're adding that data, I'm not going to run an interrogation

[dawon]

If any property of two items except the amount is different then the items cannot stack. Not much you can do with that, because by stacking the two stacks become one and the conflicting data would be lost...

The only way I can think of is to manually handle inventory operations and stack the items manually, while preserving how big part of the stack is marked which way... But I wouldn't go that rabbit hole....

[VinceSMC]

The data is being automatically generated for the item when using custom attributes like a textured head.

This is the data of an example item, the only difference is a slight change in the custom data. To be specific:

Data 1:
H4sIAAAAAAAA/83Uz27TMBwHcA8VkZWXsMK1QqGlRavEAY2tc9SkrOu/BCHk...
Data 2:
H4sIAAAAAAAA/83Uz27TMBgAcA8VkZWXsMK1QqGlRavEAY2uc9SkrOu/BCHk...

These are nearly identical but differ at specific characters, such as "MBw" in Data 1 vs. "MBg" in Data 2.
This change only happens when moving the items around in your inventory making them unable to stack again.

[electronicboy]

stack1

Gzip
Compound ""
        Compound "display"
                ...
                End
        Compound "SkullOwner"
                String "Name" ""
                IntArray "Id" 4
                        0
                        1231420745
                        -1
                        -1073674128
                Compound "Properties"
                        List "textures" Compound 1
                                        String "Value" "eyJ0ZXh0dXJlcyI6eyJTS0lOIjp7InVybCI6Imh0dHA6Ly90ZXh0dXJlcy5taW5lY3JhZnQubmV0L3RleHR1cmUvZmU0NzNjNzdiZWJmMjExNjI3OGQxY2I4YjkyMWZjM2YzY2RjZGMzZTUxMTg5N2EzMjJlOWI3MGEyOGJiYmZlYiJ9fX0="
                                        End
                        End
                End
        End
End

stack2

Gzip
Compound ""
        Compound "display"
                ...
                End
        Compound "SkullOwner"
                Compound "Properties"
                        List "textures" Compound 1
                                        String "Value" "eyJ0ZXh0dXJlcyI6eyJTS0lOIjp7InVybCI6Imh0dHA6Ly90ZXh0dXJlcy5taW5lY3JhZnQubmV0L3RleHR1cmUvZmU0NzNjNzdiZWJmMjExNjI3OGQxY2I4YjkyMWZjM2YzY2RjZGMzZTUxMTg5N2EzMjJlOWI3MGEyOGJiYmZlYiJ9fX0="
                                        End
                        End
                IntArray "Id" 4
                        0
                        1231420745
                        -1
                        -1073674128
                End
        End
End

So, ItemMeta looks to be stripping data from the skull, in part due to the skull not being properly populated with data

[VinceSMC]

Apologies for the delay in responding. After some digging, I’ve found the root cause of the issue. It seems that the bug occurs when joining the server using the Fabric Loader mod.

To help illustrate the problem, I’ve made a screen recording: https://imgur.com/a/9vT6Y9G

[VinceSMC]

Appears to be a problem with ViaVersion.