Sky light levels underground too high (since 18w05a)

I just migrated a world from 18w16a to 18w20b, and have that same behavior. I have an underground spawner that I have used for some time as a zombie farm, and the light level just went too high to spawn. All that was happening was Zombies were fighting a few Skeletons that spawned while I was away, the light level went to 8, and the spawner stopped working.. World is 800mb, wasn't sure if you wanted that uploaded. Seed is -1778555556, position is 97 15 428.

Having the same thing after having loaded an 18w16a in 18w20b, happening in multiple places including a zombie spawner. My world on MediaFire @ http://www.mediafire.com/file/6mofhyqs52q3990/Underwater%20Adventure.zip . Location is (-690 17 8220) if it doesn't spawn you there already.

World file: https://drive.google.com/file/d/1-36lVztVp6yjFtyOjuxXWrqC8L0S6K-F/view?usp=sharing

18w16a world upgraded to 18w20a then 18w20b (still seeing this under 18w20c), There is a skeleton spawner at (-19 55 129), with the killing floor underneath. Even though there is no light in the spawner chamber it is well lit.

Confirme bug in my  world too. Sky light goes trough the solid blocks. It seem to work like areas (sometimes there is the bug, sometimes no). When I reload the world, it's always the same blocks having this bug. No option change correct it.

Appear suddenly (world created in 18w16, converted in 18w20c). After a few time playing in 18w20c it shows up.

Images: https://drive.google.com/file/d/1vcXfNdo5pweN9vskYMpH6gkA35jx0wkT/view?usp=sharing

World: https://drive.google.com/file/d/1ELXnCsqUeIVheiRtp84BkUDhZ_PyEid6/view?usp=sharing

can confirm is sky lighting. Have a skeleton farm that only works at night. Noticed no other mobs spawning and light levels seems unreasonably bright even when at lvl 11 deep in caves.

Yup, solid blocks must act as transparent allowing light to pass directly through

Looks like this bug is i can found. I just find an problem: Looks like the block light make sky light stronger.

Still an issue in 18w21b

Also got this problem with some weird results. Light levels are stuck at 15, but it only seems to be a single chunk. Tried restarting the game, but no luck. During the night there are shadows, but it's still at light level 15. This happened when I had slept in a bed, alt tabbed out, then came back to the game only to find the light glitched.

Confirmed on 18w22a

Is the original issue of @unknown of 18w05/18w07 the same issue as the recent issues when upgrading a 18w16 world to 18w20+ ?

@Kumasasa: I don't think so. As mentioned in earlier comments, the original bug was not easily reproducible. This one though, I can easily reproduce. May be MC-129674 should be the "main"-issue?

Confirmed for 1.13 pre-release 1.

Also water still has the old light levels when converting so this can be fixed by recalculating the light levels for each chunk when converting the world.

Confirmed for 1.13 pre-release 2.

Confirmed for 1.13 pre-release 2.

Is there a way if your world is effected by this issue that you can fix your world?

I dont have a backup. The problem is that all blocks are letting light trough as if they are glass. If i replace a block it fixes the issue but its literally all blocks in my survival world.

Supposedly Mojang was going to recalculate all light levels in existing worlds when 1.13 came out to fix the change to how light passes through water. There's a reason that Mojang strongly recommends not playing full-time on the snapshots.

Is this a problem when upgrading a world from 1.12.2 to 1.13-pre3?

Grum i made a new world in 1.12.2 and when i open it in the pre3 it keeps loading for a really really long time. It takes for long for me to try

(there is also a map bug that i think is related to this that has been fixed in the pre3)

@unknown, loading too long may be a different issue. Please take a look at the launcher_log.txt or attach it here

It's MC-125258, please attach your logfile there and remove it here

Not sure if this is part of the issue but the water lighting still has the old one when converting the world to 1.13

Because faFrom my own observation it seems like this issue was a transitory issue between two snapshots, meaning it is highly unlikely that it would be fixed by devs. Because of this I made a script to (mostly) fix my own world. Would it be appropriate to post a script I made to fix this here?

I couldn't find rules regarding this on the Jira anywhere so I figured I'd ask first.

@unknown, glad you're asking, but the answer is no. This Jira isn't support or help, only tracking the bugs in Minecraft.

You can, however, share it on the r/mojira subreddit.

Does this happen when opening a 1.12.2 world in 1.13-pre3? If this works from 1.12.2 -> 1.13-pre3 we are going to have to consider this bug fixed.

Light Levels are still not working underground. As you can see in the screenshot, the light level at this spawner is 14. Bright as day....

@unknown, did you upgrade the world from 1.12.2 or from any 1.13 snapshot/prerelease or create new in 1.13-pre4?

I'm having the exact same problem as Kari Williams. It was fine in pre 1 started having the issue when I upgraded to pre 4. Checked same world in both single player and on my server. Same light levels underground in both.

@unknown: Same question: World created in -pre4 or earlier snapshot or upgraded from 1.12.2?