The bug
Upon dropping an undamaged item it has no Damage:0
tag, so you can't check via commands if the item is not damaged.
How to reproduce
Get a diamond pickaxe from creative mode
Drop it
Run this command:
/data get entity @e[type=item,limit=1]
→ Inside the Item NBTTag there's no
{Damage:0
} tag
Exiting and re-entering the world writes the {Damage:0
} tag to the item (both if on ground on your inventory).
Linked issues
is duplicated by 3
relates to 2
Comments 5
this bug can make a zombie constantly switch between a damaged diamond armor and a diamond armor without damage tag
Confirmed for 1.13.2-pre1.