[MC-16290] [crash] mob spawner crashing game

It seems like mob spawners are crashing the game, cause the new attributes on the mobs.

I created a standard mob spawner in mc edit. All works fine, but if i enter the world in minecraft, it crashes instantly.
If i move the spawner away in an unloaded chunk minecraft works fine, until it´s trying to load the spawner. So it has to be the spawner i guess.

Crash report:

---- Minecraft Crash Report ----
// Hi. I'm Minecraft, and I'm a crashaholic.

Time: 24.05.13 00:41
Description: Loading entity NBT

java.lang.UnsupportedOperationException: Cannot modify readonly attribute
	at oi.a(SourceFile:54)
	at sx.a(SourceFile:87)
	at sx.a(SourceFile:70)
	at np.a(SourceFile:348)
	at nq.a(SourceFile:251)
	at sn.a(SourceFile:84)
	at mx.f(SourceFile:1061)
	at aas.a(SourceFile:116)
	at aas.h(SourceFile:234)
	at bhe.a(SourceFile:22)
	at bhe.a(SourceFile:17)
	at bhe.a(SourceFile:12)
	at bhj.a(SourceFile:106)
	at bhj.a(SourceFile:98)
	at bdt.a(SourceFile:317)
	at bdm.a(SourceFile:836)
	at bdm.b(SourceFile:682)
	at asx.R(SourceFile:674)
	at asx.d(SourceFile:607)
	at net.minecraft.client.main.Main.main(SourceFile:78)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Stacktrace:
	at oi.a(SourceFile:54)
	at sx.a(SourceFile:87)
	at sx.a(SourceFile:70)
	at np.a(SourceFile:348)
	at nq.a(SourceFile:251)
	at sn.a(SourceFile:84)

-- Entity being loaded --
Details:
	Entity Type: Creeper (sn)
	Entity ID: 4535
	Entity Name: Creeper
	Entity's Exact location: 0,00, 0,00, 0,00
	Entity's Block location: World: (0,0,0), Chunk: (at 0,0,0 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Entity's Momentum: 0,00, -0,08, 0,00
Stacktrace:
	at mx.f(SourceFile:1061)
	at aas.a(SourceFile:116)
	at aas.h(SourceFile:234)
	at bhe.a(SourceFile:22)
	at bhe.a(SourceFile:17)
	at bhe.a(SourceFile:12)

-- Tile Entity Details --
Details:
	Name: MobSpawner // arm
	Block type: ID #52 (tile.mobSpawner // aol)
	Block data value: 0 / 0x0 / 0b0000
	Block location: World: (-310,56,-362), Chunk: (at 10,3,6 in -20,-23; contains blocks -320,0,-368 to -305,255,-353), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
	Actual block type: ID #52 (tile.mobSpawner // aol)
	Actual block data value: 0 / 0x0 / 0b0000
Stacktrace:
	at bhj.a(SourceFile:106)
	at bhj.a(SourceFile:98)
	at bdt.a(SourceFile:317)
	at bdm.a(SourceFile:836)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bbq['RF_Darter'/4390, l='MpServer', x=-309,90, y=57,62, z=-359,97]]
	Chunk stats: MultiplayerChunkCache: 30
	Level seed: 0
	Level generator: ID 01 - flat, ver 0. Features enabled: false
	Level generator options: 
	Level spawn location: World: (-279,4,-348), Chunk: (at 9,0,4 in -18,-22; contains blocks -288,0,-352 to -273,255,-337), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
	Level time: 11941 game time, 11941 day time
	Level dimension: 0
	Level storage version: 0x00000 - Unknown?
	Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
	Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: false
	Forced entities: 3 total; [bbq['RF_Darter'/4390, l='MpServer', x=-309,90, y=57,62, z=-359,97], sn['Creeper'/4389, l='MpServer', x=-286,75, y=56,00, z=-361,50], rf['Ocelot'/4388, l='MpServer', x=-328,22, y=56,00, z=-333,84]]
	Retry entities: 0 total; []
Stacktrace:
	at bbn.a(SourceFile:282)
	at asx.b(SourceFile:1793)
	at asx.d(SourceFile:616)
	at net.minecraft.client.main.Main.main(SourceFile:78)

-- System Details --
Details:
	Minecraft Version: 13w21a
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.7.0_07, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 195029752 bytes (185 MB) / 384565248 bytes (366 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 21638 (1211728 bytes; 1 MB) allocated, 94 (5264 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	LWJGL: 2.9.0
	OpenGL: GeForce GT 540M/PCIe/SSE2 GL version 4.2.0, NVIDIA Corporation
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Texture Pack: Default
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 156 (8736 bytes; 0 MB) allocated, 59 (3304 bytes; 0 MB) used

Linked issues

is duplicated by 10

MC-16331 World crashes upon loading, possible Spawener issue. Resolved

MC-16405 When moving, the game crashes Resolved

MC-16510 Crash upon loading world with custom spawners Resolved

MC-16546 I was flying around in my CTM map and I suddenly crashed. Has happened 3 times now. Resolved

MC-16644 sometimes. randomly the game crashes Resolved

5 more links

relates to 2

MC-17622 Baby Zombies Spawner crash the game Resolved

MC-16191 When the world loads skeletons it crashes Resolved

Attachments

MCEditSpawner.schematic

Comments 29

mike 2013-05-23T23:23:00Z

What exactly happened?

Matthias 2013-05-24T16:06:13Z

I updated the post

Teddy 2013-05-25T11:43:49Z

Yeah same happened to me. I was working on my CTM Map (spawners of course) and it kept crashing. I didn't know it was from the spawners though.

Maxwell 2013-05-25T22:27:48Z

Same here. I was playing with spawners in MCedit and my game kept crashing on world load. I think it has to do with the new Attributes system. I don't know anything about coding but this line looks like a potential crash culprit: java.lang.UnsupportedOperationException: Cannot modify readonly attribute

Matthias 2013-05-27T12:00:54Z

Not fixed in 13w21b

19 more comments

Matthias 2013-05-30T17:00:54Z

Not fixed in 13w22a

DiEvAl 2013-05-30T17:24:51Z

Can you attach a schematic of that spawner?

Matthias 2013-05-30T17:30:25Z

Sure, just did it

Afflicted One 2013-05-30T18:03:40Z

Confirmed for still bugged in 13w22a.

The game will crash if a mob spawner is trying to spawn a mob with certain modified attributes, like potion effects, villager zombies, baby mobs, electrified creepers, etc.

Matthias 2013-05-30T18:36:52Z

I am pretty sure its relaed to the new attribute system. If i create a spawner by a normal Zombie, the spawner will have the SpawnData give by the zombie. So like the zombie had, the spawner will have an TAG_List Attributes. if minecraft now wanna load this spawner, it will crash. But if i remove the Attributes List from the spawner it works fine.

Anon Ymus 2013-05-30T19:00:19Z

Confirmed.

DiEvAl 2013-05-30T21:03:38Z

@Matthias the schematic you attached is a zombie spawner, but that error log mentions creepers. Are you sure it's the same spawner?

Anon Ymus 2013-05-30T21:30:07Z

It doesn't matter. Any mob crashes the game, as far as I can tell.

Matthias 2013-05-30T21:38:24Z

The crash log is only listing a creeper, because i spawned a creeper earlier with a mob egg in the world. The spawner itself is a zombie spawner. If it´s needed i can update the crash log with just a spawner in the world

Charles Janssen 2013-05-31T12:30:16Z

this bug needs fixing

Maxwell 2013-05-31T21:35:06Z

What does it take for the Mojang team to notice these reports? This bug has effectively locked me out of one of my favorite worlds.

Tails 2013-05-31T21:40:02Z

Reminder: Snapshots are WIP, may contain bugs, crashes and might corrupt your worlds. You play these at your own risk.

DiEvAl 2013-05-31T21:45:49Z

@Maxwell
I guess this: https://twitter.com/Dinnerbone/status/340148991469699072 😛

Matthias 2013-06-01T00:27:46Z

Yeah, i was sending him this message, because i saw nobody of the mojang team noticed this bug.

WolfieMario 2013-06-03T23:19:33Z

From what I can tell, this is an unfortunate consequence of attempting to make (at least some) Attributes read-only.

Spawner behavior has an interesting implementation: first, an entity is spawned in the world with vanilla spawning properties and location. After this, SpawnData is read as an entity, and the properties of that entity get applied to the spawned entity. This has many useful consequences, for Mojang and mapmakers alike. It allows spawners to retain their natural behavior with regards to spawning conditions, and it makes many important concepts, such as redstone-controlled spawners, possible for mapmakers.

For example, a mapmaker can hide a spawner in the walls outside of a room, and have it surrounded by light - when the lights are turned off, monsters are spawned. If the SpawnData contains a Pos tag, said monsters are "teleported" instantly to that location - the location, for example, could be within the room. In this manner, monsters which normally require darkness to spawn can instead be spawned within a fully-lit room, and the player cannot do something silly, such as placing torches, to stop a wave - instead, the redstone will determine when the wave ends. There are countless other applications for this concept, but I won't bother going into detail here.

Anyways, the cause of this crash is the fact that a spawner with an Attributes tag in its SpawnData is actually attempting to modify existing Attributes on the spawned mob. As some (or all) Attributes are now read-only, this has been rendered an "unsupported operation" in 13w21a+.

I'm not sure why we need read-only Attributes (perhaps it's for the Plugin API?), but an exception should either be made for SpawnData, or Attributes should be read from SpawnData before the mob is created. Either way, I hope Mojang does not elect to make SpawnData be read and applied before a mob is spawned (if this concept would even be possible), at least for the Pos tag, because this would break a great number of contraptions and even entire adventure maps. Although there are other ways to have redstone-controlled spawners, there are many other things which would fail to be possible if the mob's Pos tag actually caused its spawning restrictions to be observed at the specified position instead of the spawner's random spawning range.

Nathan Adams 2013-06-04T07:56:37Z

Actually it's because the client shouldn't have any modifiers that the server didn't tell it about, and the display-mob for mobspawners try to register modifiers.

DiEvAl 2013-06-04T10:14:16Z

"Fix Version/s: Future Version - 1.6"
Does this mean that there will be no more snapshots until 1.6?

WolfieMario 2013-06-04T14:29:21Z

Ah, that makes sense. I'll admit I still haven't fully figured out how the modifier/attribute registry system works out; obfuscated code can be a pain and I usually only bother figuring out enough to document the useful-to-mapmakers info on the wiki. Sorry for jumping to conclusions - I'm glad to see the apply-SpawnData-after-spawn behavior doesn't have to be changed to fix this.

@DiEvAl: No, whenever there's a fix before a snapshot, it says "Future Version - ", followed by the next major version number. When the next snapshot/prerelease is released, that text will be replaced by the actual version name. I mean, it's possible 13w22a was our last snapshot, but that text doesn't actually imply it.

Maxwell 2013-06-06T16:37:41Z

So does that mean the issue will be fixed in the future? Or is it a non-issue that can be fixed by changing things in-game or with 3rd party editors? If the latter, please let me know how to do that.

WolfieMario 2013-06-06T17:09:04Z

It means it's already fixed, but the version with the fix hasn't been publicly released yet. In the next snapshot or pre-release, the bug is fixed.

asdf 2013-06-07T19:36:23Z

This is not actually fixed. Map "The Lands of Reminiscence" still crashes when loading a spawner.
Map can be found here: http://www.planetminecraft.com/project/the-lands-of-reminiscence-a-survivaladventure-map-for-single-and-multi-players/

Maxwell 2013-06-10T14:34:28Z

@Christian Does the map have baby zombie spawners? I found recently that they will crash the game. I haven't made an issue for it yet because for whatever reason this site is all messed up on my end. I'll try to add it whenever.

Thomas Overbeeke 2013-07-10T16:36:58Z

got it too, super weird

Warren Liddell 2013-11-03T13:26:36Z

This is not quite fixed, i have made a custom spawner and now that apr tof the map is un-usable and crashes the game client in 1.7.2 everytime it loads that chunk, outside othat chunk all works perfectly fine. Crash report for this can be read at http://pastebin.com/54gZxkiQ