[MC-88097] Snow blocks receive (useless) random updates and can get destroyed when there is a light glitch

The bug

I always was under the impression that snow blocks (other than snow layers) are not intended to melt. However, recently I managed to get some to melt when trying to move a giant flying machine.

I would expect snow blocks to not randomly disappear, but instead snow blocks pop out as items under certain conditions.

How to reproduce

Create a new super flat world and don't move while executing these commands
Make sure you are on render distance 16
/gamemode spectator
/tp ~1024 ~ ~
/fill ~ ~-1 ~ ~3 ~-1 ~15 minecraft:glowstone
/fill ~ ~ ~ ~ ~ ~15 minecraft:piston[facing=east]
/fill ~1 ~ ~ ~1 ~ ~15 minecraft:snow_block
/tp ~-256 ~ ~
/fill ~255 ~ ~ ~255 ~ ~15 minecraft:redstone_block
/tp ~256 ~ ~
/gamemode creative
You may move now and see snow blocks disappear. (/gamerule randomTickSpeed 100, to speed it up)

Video demonstrating the issue: https://youtu.be/ZkI3uU7hoBA?t=1m38s

What's going on?

So apparently snow blocks have the same part of code to them that makes snow layers melt. It never comes to play though because it checks for the light level inside the block (which is always 0, unless you cause a light glitch).

It is likely that at some point snow blocks where actually intended to melt but didn't due to the light level.
But please don't make them melt now. I'm someone (and not the only one) who builds a lot with snow. So all the old builds would melt if snow would ever melt.
So my request is to remove this part of code and take snow blocks of the list of tickable blocks (as that currently doesn't do anything anyway).

Linked issues

relates to 1

MC-100342 Several Non-Ticking blocks are marked as ticking forcing the growth-algorithm to check chunks needlessly Resolved

Comments 13

Panda4994 2015-09-16T15:31:55Z

So it is intended to have code in there that can only be executed when abusing light glitches and would (if working) break many builds? 🙂

I just want to make sure the post was read and understood. This is not about melting snow layers, I know that is intended.
It's about the melting of snow blocks that don't melt (which is good, but the not melting should be a feature and not just due to a bug).

Thanks for reading this. I hope I was able to explain the issue properly.

qmagnet 2015-09-17T11:42:13Z

I'd like to know this as well

Meri Diana 2015-09-17T11:46:54Z

I'd also like to have this either reopened and then properly solved, as suggested by Panda4994, or an explanation as of why this is a "Works as intended".

[Mod] redstonehelper 2015-09-23T14:43:43Z

Reopened to be looked at again at a later date.

qmagnet 2015-09-23T14:53:12Z

Perhaps the word "melt" misled the previous resolution

3 more comments

Noah Larkin 2016-02-19T02:43:40Z

Confirmed for 1.9-pre2.

Noah Larkin 2016-02-27T12:41:42Z

Confirmed for 1.9-pre4.

Zitchas 2016-10-08T22:11:21Z

I was just about to start a major survival build using snow blocks as the white element (didn't want to use wool due to high exposure to the sky and quartz is far too rare), and I'm reluctant to start until there is some confirmation as to which direction this is going.

It makes sense that snow blocks should melt (ice blocks do, after all), but I'd much rather they didn't, since there are far to few non-flamable pure white blocks.

atomizer 2017-06-20T15:11:32Z

confirmed for 1.12

boq 2018-09-26T07:23:11Z

Relax, I'm not going to make snow melt: it was in that broken state longer then we had source repository, so no point in fixing it 9 years into project. I just noticed that oddity during semi-related refactor and want to remove completely pointless class and source of random ticks.