Zombie Reinforcements can spawn on glass

Seems to be consistent issue into 1.14.4 as far as I can tell.

What I expected to happen was...:
No zombie reinforcements to spawn

What actually happened was...:
Zombie reinforcements spawned on transparent spawn proof blocks.

Steps to Reproduce:
1. Create a flat world with one of the blocks listed below
2. Set time to night
3. Set difficulty to Hard
4. Spawn a zombie
5. Punch the zombie until zombie reinforcement is spawned. (will likely take a few dozen punches)

I encountered this issue in 1.14.4 in my survival world. I notice this happening at my wither skeleton farm. I also experienced the same bug on the roof of the nether. I was building on top of the nether and attacked a pigman and it spawned a zombie on the bedrock. I did some additional testing in a flat world with a layer of blocks at y=0 in the overworld with one trapped zombie on hard difficulty using version 1.14.4. I punched the zombie in survival mode approximately 100 times or until a zombie reinforcement spawned for each block I test. I did not test every non-spawnable block in the game, but I did test many of the traditionally non-spawnable blocks. I have also uploaded images of zombies that spawned on some of the blocks I tested. Here is a list of blocks that I observed zombie reinforcements spawn even though they should not:

• Glass

• Stained glass varients

• Ice

• Bedrock

• Magma blocks

• Buttons varients

• Levers

• Pressure plates varients

• Redstone wire

• Rail varients

• Leaf varients

• Barrier Blocks

I can't repro this on 1.15 Pre-release 3. Can you @unknown ?

I was able to recreate it in all of the 1.15 snapshots I tested and every 1.15 Pre-release. I must have overlooked the difficulty setting. Difficulty must be set to "Hard" for zombie reinforcements to spawn.

Can confirm, added precise reproduction steps to the ticket. Since not every zombie has high chances of spawning reinforcements, multiple tries might be required.

Same here. turning up the difficulty made all the difference.

When playing on 1.13.2 and prior, zombie reinforcements spawn on some of the blocks I listed before. Prior to 1.14.X zombie reinforcements could spawn on blocks that redstone could be placed on. In 1.14 that list was expanded to include glass and ice, so it is rather interesting that in 1.14 zombies can spawn on leaves(a block redstone cannot be placed on). It appears that in 1.14 zombie reinforcements now check for 16x16 pixel top surfaces.

Listed below are the blocks additional blocks zombie reinforcements can spawn on in 1.14 that they could not spawn on previously.

• Glass and stained glass varients

• Ice

• Leaf varients

Can confirm, still happens in 1.15 final release, on Hard difficulty.

Relates to

1. MC-171585