[MC-3927] Iron golems spawning in slabs, glass, farmland and grass path

Risk of confusion

This report describes only iron golems spawning inside non-opaque non-full cubes.

See MC-130270 for them spawning even inside opaque full cubes, which started during the 1.13 snapshots.

This issue reappeared in 1.14, see MC-148955 for more details.

The bug

Iron golems can spawn in blocks which are considered as not normal cube (normal cubes are: state.getMaterial().isOpaque() && state.isFullCube() && !state.canProvidePower()).

This makes them spawn in slabs, glass, farmland, grass path, ...

How to reproduce

Create village with villagers
Fill all air blocks at the village center with for example glass
Wait for an iron golem to spawn

Code analysis

Based on 1.12.2 decompiled using MCP 9.40

The method net.minecraft.village.Village.isAreaClearAround(BlockPos, BlockPos) only considers a spawn location as invalid if the blocks at this position are net.minecraft.block.state.IBlockProperties.isNormalCube(), it should probably instead use logic similar to the one used in net.minecraft.world.WorldEntitySpawner.findChunksForSpawning(WorldServer, boolean, boolean, boolean).

Linked issues

is cloned by 1

MC-148955 Iron golems can spawn inside of non-full blocks Resolved

is duplicated by 16

MC-40992 Iron golems can spawn through slabs and glass Resolved

MC-42117 Iron golems spawn in blocks Resolved

MC-55312 Golems spawn in Glass Resolved

MC-67816 the Iron Golem appear through the glass Resolved

MC-69919 Iron golems spawning inside of glass Resolved

11 more links

relates to 2

MC-130270 Iron golem spawning inside blocks Resolved

MC-135128 Iron golems don't spawn inside of slabs Resolved

Attachments

Comments 23

Afzal Rahman 2013-10-28T16:49:18Z

Should I open a new issue, or can this be reopened? I have had Golems spawn anywhere there's at least 3 blocks of space. And that includes stairs. And golems don't spawn on stairs, they spawn on the ground below, and thus get completely stuck.

EDIT: Minecraft 1.7.2.

KeenWolfPaw 2013-12-09T21:55:22Z

I'd like to add a bit more info because the main post is hard to follow.

The main issue here is:
If all of the default spawn conditions are met, Iron Golems are able to spawn inside of slabs and glass.

They do require a solid ground block for them to spawn on top of, they still spawn even if half slabs or glass is in the way.

Ezekiel 2013-12-09T21:56:29Z

Is this still a concern in the latest Minecraft version 1.7.4? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.

KeenWolfPaw 2013-12-09T23:41:54Z

Confirmed still an issue in 1.7.4.

You can check out the image proof here:
http://i.imgur.com/osB6WUb.png

Edit: Sorry for the late reply, I was waiting to see if any spawned for about 2 hours, which he eventually did. Anyway, if this might help he spawned through 2 slabs, I have a layer of stone, a slab and then another slab floating above that, it seems he spawned through both of them.
Edit 2: For further evidence, you can check out the screenshot of the floor cutaway attached to the bug post for verification.
Edit 3: Grammar.

Ezekiel 2014-02-24T14:15:42Z

Is this still a concern in the latest Minecraft version 14w08a? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.

13 more comments

Bob Saggot 2014-11-10T16:52:15Z

This bug is still present in Minecraft 1.8.

Bill Milligan 2015-02-15T18:27:54Z

I found this behavior in cases where I was trying to prevent a golem spawn in a certain area, and attempted to solve this by topping that area with half-slabs and glass blocks but ran straight into this defect.

I've found a workaround for this that seems to work in 1.8.x. Put a solid block underneath the half-slab, at a level at which golems would not be too short in any covered area underneath. Of course now my problem is that the golems are spawning on top of the half-slab (see MC-77620).

kumasasa 2015-12-06T22:07:17Z

Is this still an issue in the current Minecraft Snapshot 15w49b or later? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.

dvdmchl 2016-02-27T17:56:58Z

It is still a problem in the latest snapshot 1.9-pre4.

Trent 2016-03-18T22:17:31Z

I'm getting a similar issue, but I don't even need half slabs! I have attached an image showing what happens. I have done some experimentation, and found the following:
The Iron Golems will NOT spawn if the dirt is only 1 high (I cleared out 3 high under the dirt, then under the 3 air it is just stone etc). The Iron Golems don't appear to even spawn in the opening (ie: they are not spawning anywhere)

If I put another layer of dirt under the top layer of dirt (as per the image with "3 Iron Golems in ground"), then they spawn again, however half in the dirt so they can't actually move. When this happens I can just walk up to them and hit them with my sword, and they do nothing, unless I get very very close, then they can attack.

This is Minecraft 1.9 final.

Trent 2016-03-20T08:31:47Z

I have been testing this further, and I have found that if I move that entire section of the world down 1 block (using a clone/move command), the issue goes away. In case it's of value I have uploaded the worlds both before and after (I have set the worldspawn, but in case it does not work, go to about 130 70 -1460).

The original world having the issue: http://sillyfrog.com/tmp/Iron_Golem_in_Ground.zip

And the world where I have moved it down one block, and it appears to be fixed: http://sillyfrog.com/tmp/Iron_Golem_NOT_in_Ground.zip

AceMcCrank 2016-03-30T02:53:30Z

1.9, this also occurs on farmland, and on paths created by the shovel.
I have a screenshot of it happening on the path if needed.

Seamus Callaghan 2016-03-30T18:08:06Z

It looks like golems are spawning on rails too, but possibly aren't spawning in running water. I built an iron farm, and they're only spawning in one specific 1x2 spot which isn't on the spawn platforms. Not sure if this is a separate issue or a related one.

Debatra 2016-04-12T16:09:05Z

You can pull it out of farmland with a lead if you can fly or get some ladders close enough. Haven't tested with other blocks. Still needs fixing though.

matthew 2016-04-26T05:33:08Z

I just want to say it's been fun watching this thread gain and lose interest over the past 4 years since I submitted it, I doubt it's ever going to get fixed though.

Tanisha Angelia 2016-05-31T11:44:42Z

Now that they are having villages generate with grass paths rather than gravel roads this issue need fixing more than ever...

Quinn Roundy 2018-07-08T17:29:24Z

Can confirm this happens in 1.13-pre6 . I attempted to place glass panes alternating blocks to fix problem but they are either spawning on the panes or diagonally between them. World was created in 1.13 pre6 never loaded in any other versions.

[Mod] Neko 2018-07-29T00:09:01Z

According to MC-135128, this has been fixed in 18w30b. Can anyone confirm?

Aidan Oh 2018-08-01T07:23:26Z

This should be marked as Fixed, I can confirm that iron golems no longer spawn in slabs. Also the bug report MC-135128 that stated that golems could no longer spawn in slabs has been marked as Works as Intended, thus proving Mojang has intentionally fixed this bug!

[Mod] Neko 2018-08-01T07:24:42Z

Are glass, farmland, and grass paths fixed as well?

Aidan Oh 2018-08-01T07:31:13Z

I don't know about those blocks, but it can be easily tested by using a large multi village iron farm and placing the glass/farmlang on top of a solid, opaque spawning platform (allowing for the golems to spawn there) to see if the golems spawn within the glass/farmland blocks.

Patrick Callahan 2019-11-24T20:39:46Z

In 1.14.4 Golems are spawning in farmland and it's really annoying - it would be nice to have a command to stop any certain mob from spawning at all.

FaRo1 2019-11-24T21:47:09Z

Then please create a new report with exact reproduction steps for that version.