Data command doesn't remove leash from a mob

Can confirm in 20w51a.

I apologize for the edit spam, the formatting keeps getting messed up by all the brackets.

Can confirm in 1.18.1 and 1.18.2-pre3. This seems to be a larger issue with the /data command, I cannot remove data tags or replace them at all, and sometimes it copies tags or changes unrelated tags in unexpected ways. I suggest renaming the ticket to "/data command does not behave properly when modifying or removing tags".

I summoned a villager using the command /summon villager ~ ~ ~ {Inventory:[{id:"minecraft:potato",Count:7b}],NoAI:1}, and tried modifying its entity data using several commands. After each one, I checked its data using the command /data get entity @e[type=villager,limit=1,sort=nearest] Inventory. Here are my results:

Replacing the Inventory array with an empty array: /data modify entity @e[type=villager,limit=1,sort=nearest] Inventory set value [] (Villager has the following entity data: [{id:"minecraft:potato",Count:7b}], No change)

Removing the first item in the Inventory array: /data remove entity @e[type=villager,limit=1,sort=nearest] Inventory[0] (Villager has the following entity data: [{id:"minecraft:potato",Count:7b}], No change)

Removing the Inventory tag: /data remove entity @e[type=villager,limit=1,sort=nearest] Inventory (Villager has the following entity data: [{id:"minecraft:potato",Count:7b}], No change)

Replacing the id of the item with wheat seeds: /data modify entity @e[type=villager,limit=1,sort=nearest] Inventory[0].id set value "minecraft:wheat_seeds" (Villager has the following entity data: [{id:"minecraft:potato",Count:7b},{id:"minecraft:wheat_seeds",Count:7b}]), Somehow duplicated the first array item with a changed id instead)

Changing the Count of the first item to 1b: /data modify entity @e[type=villager,limit=1,sort=nearest] Inventory[0].Count set value 1b (Villager has the following entity data: [{id:"minecraft:potato",Count:8b},{id:"minecraft:wheat_seeds",Count:14b}]), Somehow the Count of both array items changed by random amounts)

Please revert your changes to make this report only about leads again. The issue with villager inventories has already been addressed in MC-112826

Until this gets fixed, you can leash the wanted mob to itself and it will act as a non-leashed mob in every way except dropping the lead on death.

Command:

/execute as <entity> run data modify entity @s Leash.UUID set from entity @s UUID

Can confirm for 1.19.2.

Relates to MC-128225, MC-153392, MC-122008, MC-207605, MC-135044, MC-138100, MC-248264.

Can confirm for 1.19.4.

Until this is fixed, another possible solution is to set the Leash UUID to a faraway entity (in a forceloaded chunk, for example) which will automatically break the Lead.