Fix entities with persist=false copied in an invalid state

[brickmonster]

Remove a redundant passenger check, as entity.save() returns false in that case.

This also causes leash knots to not be copied. I don't think this is a problem because:

• They would not be saved to disk, it's misleading for users that they appear.
• Pasted leashed mobs still think they're leashed to the original position and get unleashed* - no change in behaviour.
  * Unless they're pasted close enough to the original position, in which case this has better behaviour because they create their own leash_knot entity.

Fixes #2719

[me4502]

Thanks for this, does this issue also affect the other platforms? (NeoForge, Fabric, Sponge)

[brickmonster]

I don't think they have the same persist flag, it was added by bukkit not mojang.
It looks like fabric is also disregarding ignoring when entities ask not to be saved, but maybe modded has different expectations? I only use bukkit so I don't know. Didn't check forge.

[me4502]

my understanding of this is that it's fixing a wider bug, where the persist tag was basically one of the symptoms on Bukkit. given worldedit is a cross platform mod, generally if something is fixed/changed in one platform it's best to keep it consistently applied across all

[wizjany]

I'm a bit perplexed by the minecraft behavior here. the save method returns a bool, but still fills the tag in? doesn't this mean that if, for example, there's extra data on a leash entity, it will get lost after a save/load? does the leashed animal recreate a new one each time?

[brickmonster]

Using fabric as a reference here just because I have it open:

Minecraft calls saveSelfNbt and returns false if it's a passenger or if it's not allowed to save that entity type.

WorldEdit instead calls a deeper function, writeNbt, fetching the entity type itself and checking if it's a passenger, but does not check if it's allowed to save the entity type.

And yes the leashed animal creates the leash on spawn.

[brickmonster]

Applied patch to other targets. Sponge does not expose the correct function, so emulate it.