Monsters Spawning Inside Blocks / Spawner ignoring light levels

This seems to come from the fix for MC-55260: it appears that fix was to split the "can mob spawn here?" check into two functions, one for checks that should only be done once (e.g. random failure chances) and one for checks that can be done multiple times (e.g. whether the mob fits and satisfies light levels).

The code for spawners is calling only the first, where it should probably either call both or just the second (depending on what the actual semantics of the first are).

I experienced this bug too. When trying to make a system for capturing zombie villagers by forcing zombies to spawn in 1x2x1 holes, this is very annoying.

Can confirm even with a skeleton spawner. They spawn in the walls of the area and on a pillar above the spawner.

Can confirm.
I try to prevent the spawn by remove all block in a 11*11*13 (13 for the z value) center on the mob spawner (in my case skelleton one). They continue to spawn : they apear in the air and shut down on the floor. The light level is up to 7. To prevent any problem with this bug and don't destroy the spawner (hardcore party, I don't want free skelletons in my mine ^^), I put a lava pull at the botton of my cube, to kill them at the spawn. I don't know why, but the spawn stop after it.
Why the spawn stop. two possibility for me :

• mobs from mobs spawner can appear on any block (even air) is the luminosity is under 7 (of course, when he appears in a wall, the luminisity is under 7). I am not satisfy of this theory because in my cube, I am pretty sure than all the air bloc are up to 7 for light level (but I dont check carrefully. Hardcore, one more time).

• The mob from spawner care only about the light from lava (what I seen here : torch, redstone lamp, sun don't seem to work. If someone can try with the othe light block it's can be usefull (remember to remove all wall before) (To test : glowstone, the new light block from the last snapshot, Jacks'o lantern).
  I prefer my second theory, because one more time, I am pretty sure that all air block are OK for the light level and I dont change anything between before putting lava and after. (but it's only a theory, and it is still a bug).

edit : I hope my english is not so bad. Is not my mother language and I don't have a vocabulary checker for this computer.

Confirmed for 14w25b

Confirmed mobs spawning inside blocks in w26a.

Confirmed for 14w26b on regular and on custom mob spawners

Also confirmed for 14w26b. New world created in 14w21b. No mods. When I clear abandoned mines and dungeons, I always leave spawners in place (with the typical surrounding torches on the spawner and walls. Anything after 14w21b, monsters spawn in the walls or in nearby hallway if right next door. Just tested again with 14w26b. Might be my imagination, but they only spawn in walls now - never in adjacent open areas as the previous 2 snapshots.

tested again on the 14w26b

light levels.. ignores them completely in all directions..

spawn range... spawns mobs in a range of +4 blocks in x,y directions, and 1 up and down in z

if you make the room wide and lower than that.. won't spawn anything, it NEEDS a block in the mentioned range, even if there is a floor of lava 2 blocks lower

i tested EVERY block in the pic i upload (2014-06-25_21.50.00.png), the space inside the iron block structure will trigger the spawn.

Drunsy, they spawn in all the block of iron we can see ? It's a 2 height lava pull ?

I put the iron blocks as a ruler, no mobs spawn inside the area (see the noblocks attach), while adding any block inside will (see the blocks attach)

from what i can tell.. currently the spawner works like this (see the range attach):
+ spawns inside any valid block (light level around is ignored) in a 9x9x3 area with the spawner in the center and middle row
instead of been:
+ spawns only on empty (air) blocks at certain light level in a 7x7x3 area with the spawner in the center and bottom

EDIT: after reading Kahless comment light level does affect the spawner, so clearing the whole area won't work if it remains dark enough.

Note: it still respects valid blocks to spawn inside them but may appear it doesn't since it will still spawn in the block above them if it's valid or air, since doesn't detect the height or "free room" for the mob.

Confirmed for 14w26c

After playing with it a bit in my spider spawner, I think it's not ignoring light levels, it's just ignoring solid blocks as non-spawnable spaces, and solid blocks have a light level of 0 inside. So if you light up the whole place, they'll only spawn inside solid blocks.

So if you have a spawner that's annoying you, clear out all solid blocks in a 9x9x3 area around the spawner and light it up. Mob Grinders should behave normally (including turning them off by lighting them), provided you don't have any solid blocks/walls in the 9x9x3 area around the spawner.

Confirmed for 14w27a...

confirming this bug... they make alot of noise lol.

Yeah, there is one pro to this bug - it makes finding spawners a lot easier. Just listen for a bunch of suffocating mobs.

Confirmed: 14w27b on Mac OSX java 7 update 60.

Yup, same issue here. I like to hide my mob spawners under one block, so they don't show in the adventure map. That usually works, but as of 26b, I had mobs spawning into the blocks, many of them suffocating. About half do that. Kinda annoying.

Confirmed. OS X 10.9.4, 14w27b, skeleton spawner, Java 7 update 55.

Confirmed, 14w25b, spider spawner

Confirmed, 14w27b, blaze spawner and zombie spawner. Has anyone tried analyzing the code, to see if they can discover the issue within the code?

So far, this is duplicated by 52 people, and spawners are #52 😛
Edit: 52 people not showed

I have the same bug in 14w27b since 14w25a, for older and for new worlds

I found that if you dig out an area one down and 4 to each side of the spawner, mobs don't spawn in light.
In other words its the light level at there feet that seems to count, and if they spawn with feet under a block, well its dark under the block.
Anyway it seems that no checking for blocks is happening, they can spawn in the blocks of walls and floors of a dungeon.
I tested this on a new world on 14w27b.

Yes, confirmed for 14w27b

Confirmed for 14w28a, no fix yet...

I WONDER WHY.

Mods, why hasn't this bug been assigned yet after 2-3 weeks. It's a pretty major issue, and I'm kinda confused that it still hasn't got a mojangster assigned. Not to say you aren't doing good work, but there's a lot of people waiting on a fix 😉

Other then that, confirmed for 14w28a.

w00, thanks dinnerbone!

Version: Minecraft 14w28b
Environment: Java 7 Update 55 (64bit)
Windows 7 Ultimate (64bit)
Game Mode: Creative

I can confirm the existence of this bug report.
I placed numerous torches around a Blaze Spawner.
The Spawner continued to "flare" no matter how many torches I used.