Does it have a solid top?

[end-user]

If I have a BlockPos, how can I tell if it's a full-height block (ie, not farmland, not bottom slab, but top slab would return true)?  Essentially if the block at that location could support spawning (ignoring transparency and air above it, I've tested for those - I just need to verify the shape height).

[warjort]

Depending upon what you are doing there is more you need to do with this.

 

You should really be using SpawnPlacements.checkSpawnRules().

That way you will include the rules defined by vanilla and mods for their blocks and entities.

As part of it, it uses BlockStateBase.isValidSpawn(), which by default uses BlockStateBase.isFaceSturdy(). That is essentially what you asked for but not the complete answer.

 

You can also look at NaturalSpawner and BaseSpawner if you are interested in the full logic for mob spawning.

e.g. firing the forge events canEntitySpawn() and doSpecialSpawn() to allow other "3rd party" mods to apply their policies to spawns for entities they didn't write (such as vanilla mobs).

[end-user]

Yeah, I hesitated to add that last sentence.  I really just want to test whether the block has a solid top.