[MC-50647] Slime mob spawners spawn slimes only in slime chunks

How to reproduce

Create a superflat world with the seed: 7606204815140416435
First, execute these commands: /gamerule doMobSpawning false and /kill @e[type=!minecraft:player] (untill all entities are dead)
Teleport to 102 5 223 using /tp @s 102 5 223
Execute the command 'Spawner 1', afterwards execute command 'Spawner 2'

Observe the two spawners, only 'Spawner 1' will spawn slimes

Spawner 1: /setblock 98 6 229 spawner{SpawnData:{id:slime},SpawnCount:2,MaxNearbyEntities:100,Delay:300,MaxSpawnDelay:500,RequiredPlayerRange:16} replace

Spawner 2: /setblock 64 6 229 spawner{SpawnData:{id:slime},SpawnCount:2,MaxNearbyEntities:100,Delay:300,MaxSpawnDelay:500,RequiredPlayerRange:16} replace

Video proof: http://usetapes.com/v/TQQ1qEYHiC

Comments 22

Wojciech Drzymała 2014-03-09T00:05:06Z

/setblock ~ ~1 ~ minecraft:mob_spawner 0 destroy {EntityId:Slime,SpawnRange:5b}

Actually works fine, when added SpawnRange.

kumasasa 2014-03-09T08:18:11Z

@Wojciech Drzymała : According to http://minecraft.gamepedia.com/Chunk_format SpawnRange is a short, not a byte ?!

Piotr Petrus (ridddle) 2014-03-09T08:59:27Z

Is it possible that slime chunks affect this? I made a void map to make sure nothing else interefered with mob spawner mechanics and could not get any spawns:

http://usetapes.com/v/fghpJAKf2e

Piotr Petrus (ridddle) 2014-03-09T09:04:09Z

Yes! It definitely depends on slime chunks! Used my world’s seed and http://chunkbase.com/apps/slime-finder, created a spawner in a slime chunk and boom, slimes started spawning like mad.

kumasasa 2014-03-09T09:06:52Z

Aha. Probably a bug, a mob spawner should override the other spawning dependancies.

12 more comments

Piotr Petrus (ridddle) 2014-03-09T09:06:54Z

Proof: http://usetapes.com/v/TQQ1qEYHiC

Can we update the issue or should I make the new one?

kumasasa 2014-03-09T09:08:14Z

Adjusted already the title, please update the description.
Put the links to your videos also in the description.

Itouch2 2014-05-07T13:28:32Z

Confirmed for 14w18b.

user-f2760 2014-05-07T15:30:05Z

the spawner looks at all spawn conditions of a normal mobs spawn, slime spawners look at can this slime spawn in this chunk (slime chunk or swamp biome)

Avantir_Yihn 2015-12-13T01:04:06Z

Confirmed for 15w47c.

kumasasa 2015-12-13T01:38:27Z

@unknown: 15w47c is outdated, please do not report/confirm issues with outdated snapsnots.

bob 2016-11-19T23:34:28Z

Can confirm for 1.11

user-2a4c8 2017-03-23T00:37:09Z

Confirmed for 1.11.2. Making custom craftable spawners, and was testing all the spawners, and the slime one would only spawn slimes in slime chunks, at levels only a slime can normally spawn at (0-30 or whatever.. I tested at y=25)

Oval 2018-09-12T19:43:57Z

Confirmed for 1.13.1.

Please copy/paste this in the description or link my comment.

How to reproduce

Create a superflat world with the seed: 7606204815140416435
First, execute these commands: /gamerule doMobSpawning false and /kill @e[type=!minecraft:player] (untill all entities are dead)
Teleport to 102 5 223 using /tp @s 102 5 223
Execute the command 'spawner 1', afterwards execute command 'spawner 2'

Observe the two spawners, only 'spawner 1' will spawn slimes.

Spawner 1: /setblock 98 6 229 spawner{SpawnData:{id:slime},SpawnCount:2,MaxNearbyEntities:100,Delay:300,MaxSpawnDelay:500,RequiredPlayerRange:16} replace

Spawner 2: /setblock 64 6 229 spawner{SpawnData:{id:slime},SpawnCount:2,MaxNearbyEntities:100,Delay:300,MaxSpawnDelay:500,RequiredPlayerRange:16} replace

user-2a4c8 2019-10-02T16:13:16Z

19w40a

YourCoal 2019-11-25T01:31:31Z

Still an issue in all 1.14 versions, 1.15 snapshots, and 1.15pre1.