[MC-226344] Changing the "Owner" tag of a projectile doesn't affect the outcome of the projectile unless the world is reloaded

The bug

The Owner tag of projectiles (arrows, snowballs, eggs, tridents, ender pearls, etc.) determines which mob/player the target mob becomes angry at when it is hit by a projectile. The Owner tag is also used by ender pearls to determine which mob/player to teleport when an ender pearl lands. Datapacks sometimes change the Owner tag of projectiles. In 1.16.5, this works properly. However, now, changing the Owner tag of projectiles does not have any effect until the world is reloaded.

To reproduce

Ender Pearl Teleportation

Spawn a mooshroom.
Throw an ender pearl straight up.

Before the ender pearl lands, run the below command:

/data modify entity @e[type=minecraft:ender_pearl,limit=1,sort=nearest] Owner set from entity @e[type=minecraft:mooshroom,limit=1,sort=nearest] UUID

Wait for the ender pearl to land. Notice that you are teleported instead of the mooshroom. ❌
Repeat steps 1-4, but this time, exit and reload the world in between steps 3 and 4. This time, when the ender pearl lands, the mooshroom is teleported instead of you. ✔
Optional: Repeat steps 1-4 in 1.16.5. The mooshroom is teleported even though you didn't reload the world. ✔

Neutral Mob Aggravation

Spawn a polar bear.
Spawn a mooshroom.

Put the below command into a repeating command block:

/execute at @e[type=minecraft:polar_bear] run data modify entity @e[type=minecraft:snowball,distance=..20,limit=1,sort=nearest] Owner set from entity @e[type=minecraft:mooshroom,limit=1,sort=nearest] UUID

Switch to survival mode.
Throw a snowball at the polar bear.
The polar bear attacks and kills you instead of the mooshroom. ❌
Throw a snowball at the polar bear again, but this time, exit and reload the world before the snowball hits the polar bear. The polar bear attacks and kills the mooshroom. ✔
Optional: Repeat steps 1-6 in 1.16.5. The polar bear attacks the mooshroom even though you didn't reload the world. ✔

Related issues

is duplicated by

MC-233189 The Owner tag of ender pearl works unexpected

MC-234181 NBT tag "Owner" does not update until singleplayer world is reloaded

MC-258392 Projectiles that have their Owner tag modified mid-flight cannot hurt the original Owner

relates to

MC-271732 Adding or removing the loyalty enchantment from thrown tridents doesnt affect the outcome unless the trident is reloaded

Comments

migrated 2021-08-01T03:05:17Z

Can confirm in 1.17.1.

migrated 2021-08-09T00:47:02Z

At section "Neutral Mob Aggravation", you are let the polar bear attack the mooshroom based on snowball.

All mobs that is able to be angry has NBT tag "AngryAt". You can try modify the tag directly, and add the result to your report.

pine1needle 2021-08-15T04:07:33Z

Directly modifying the AngryAt tag of the polar bear works as expected.

migrated 2021-08-29T18:29:55Z

Confirmed for 1.17.1.

In my case, it affects fireballs. Reflecting Ghast fireballs back at the Ghast (using commands), after modifying the Owner NBT, doesn't trigger Return To Sender, as I'd expect it to.