The bug
Previously (as in 1.12), in the advancement icon tag, you could specify a "data": x and in your resource pack have that damaged item correspond to another texture in-game. With the flattening and the removal of the "data" in 1.13, this functionality has been compromised.
The changing of textures due to damage taken by a tool is an officially supported feature, and hence the removal of this feature may be an oversight by the developers, hence a bug.
Comments 7
Is there an explanation on how this was fixed? What tag do we use now? Does it support unbreakable items?
The fix allows for a new section called "nbt" in the "item" block of the json. This way you can provide any nbt you want for the items to be rendered as you like, and they should be rendered as they would be in your inventory!
the problem is that the durability of an item is now stored inside of the nbt tag, they would need to allow setting custom nbt data for advancement display icons