Path Finding for Baby Zombie Pigmen appears to have changed

Just because a change is not listed in the change log does not mean it's a bug. Can you please explain how their path finding changed in more detail?

Sorry. For the vagueness of description. I find the search in the MC JIRA a little bit confusing and was not sure if I had new unreported issue.

The issue is reproduced by loading the world file of Zombie Pigmen Farm design available at https://www.mediafire.com/file/by2w8r7dp8qtua6/Nether+gold_xp+farm+ilmango.zip

In 1.12 the Baby ZPFs will properly track to the player and end up in the destruction trap. In 1.13 their tracking has changed and they stackup on the the path that is not direct but one block off.

Workaround for the build is to add some half slabs at the 8 points where they are tracking which then allows them to track over to the trap.

I would confirm this issue. From my testing, it appears as though baby pigmen (and zombies/drowned) now think that they can fit in 1/2 block tall spaces if it is a bottom slab and will attempt to pathfind to the player through 1/2 block tall spaces. I suppose that would make this issue a bug?

Issue still exists in 1.13 pre 8. Closing Half slab windows will change the pathing of Baby ZPs back to the destruction spot.

Issue still present in 1.13

I have observed the same behaviour of baby zombie pigmen and jockeys seemingly attempting to pathfind through half-block spaces, making them pile up.

 EDIT: I have also had Baby Zombie Pigmen glitch into the gold/xp farm several times now. Not sure if related, but it didn't happen in 1.12 with much longer afk times.

Attempted to illustrate this in a non-farming, simple nether environment:

When using the pictured simple layout, baby pigmen walk up the stair blocks and pile up in front of the gap. Adult pigmen will pathfind into the pit with the trapdoors. Even when spawning in a bunch of pigmen and mostly keeping the little guys to attempt this without the pit being there at all, they will still pile up, while the single adult in range correctly pathfinds and kills me.

Relates to MC-134118

Does MC-135803 describes this issue?

Yes that appears to be describing this exact issue. Mobs just seem to be unaware of half slabs. Regular zombies attempt to walk through 1.5 block gaps, babies attemt to walk through 0.5 block gaps.