The bug
When a line of redstone dust updates and does not / points at a block, the block is not updated under certain circumstances. (redstone redirection)
Affected situations
Block connecting to redstone dust is placed. This includes all blocks that connect to redstone dust (like repeaters, levers...) without creating a redstone signal, see
Redstone dust which was blocked before connects, see
Redstone dust connecting downwards from glowstone (see
), slabs, hoppers, redstone blocks (see also MC-123850)
Related issues
is duplicated by
relates to
Attachments
Comments

Still in 13w01b.
Could not reproduce in 13w09b.
Reproduced in 13w09b: A little "random BUD-Flop" as seen in the screenshot. Observe how the torch is off eventhough no wire is connected. (the randomness comes from the fact that the torch receives updates randomly)
Hmmm. This looks too stable and consistent to be a BUD... at first glance.
I toggle the switch - torch goes off - piston retracts - redstone orientation changes - torch magically stays depowered. Then I toggle the switch again - torch magically regains power - piston extends - redstone reorientates to correct state. I get this 100% of the time, but when left alone for some time in this magic state, torch updates itself and piston performs a cycle. Such a funny device...
The pistonless setup on the first screenshot works as expected to me though.
With "detector rails" also works, alias, you can move the rails with pistons without breaking, that is also a bug?
Still here in snapshot 14w02c ...

*Confirmed for 14w21b
No, Tails' device still exploits this bug like it ever did.
14w33a - not fixed
Yes. Tails' device behaves just as in description.

Reopened, Thanks.
Still happens in 1.8.3

Confirmed for
15w39c
Gave the ticket to Marcono1234.
Still happens in Minecraft 1.12, i think
It seems that technical users find this behavior to be extremely useful, while pretty much nobody finds it to be harmful. BUDs weren't initially intended, but it's one of those "emergent behaviors" that even Mojang developers have acknowledged it as being generally productive and desirable, even if some less experienced uses may initially find it to be unintuitive. Intuitive behavior is always a good objective, but we can see how trying to make redstone more intuitive has basically made it broken and useless in Bedrock edition, while at the same time introducing even uglier bugs and even more nondeterminism.
If you want to see an example of productive use of this feature, check out this video: https://www.youtube.com/watch?v=vMYygzMYUs4&feature=youtu.be
I suggest marking this but as "works as intended" or "won't fix," because of all the frustration "fixing" it would cause.
Any further discussion, we can move to /r/mojira or the EigenCraft discord.
Thanks.
Just because a bug is useful to technical users does not justify calling it a feature or leaving it as is.
Can confirm for 1.13-pre3

Confirmed for 20w18a.

Confirmed for 20w19a.

Confirmed for 20w20b.

Can confirm in 1.17.1.

Affects 1.21