Observer block doesn't detect all block state changes

Affected:

1. Fence Gates activated by redstone.

2. Change the daylight sensor.

3. Placing painting.
   Edit: Thanks @unknown, I thought the painting was different from PC. (Like Item Frames)

4. Burned redstone torch.

5. Place mob eggs inside mob spawner.

6. Reducing snowlayers height when shoot some arrows.

Paintings and mob spawners are most likely intended to not work since paintings aren't blocks and applying eggs to spawners only changes the block entity and doesn't update the actual block.

Confirmed for Samsung Galaxy Tab 4. 0.15.0 build 1

Confirmed for 0.15.0 official release on Windows 10 Edition.

Also, some additional notes:
1. Redstone torches changing state don't affect the Observer at all. It's not just burned-out torches, it's any redstone torch changing state. Could it be possible that redstone torches do not use blockstates like the Java edition, and instead only use block entities? It may be works-as-intended for redstone torches. It could also be that redstone torches don't cause block updates at all when changing states, which could be the cause of several other redstone-related bugs as well...
2. Fence gates do not make any sound when powered by redstone... possibly related to the problem?

And also affected the activator rails when activated by redstone, lightening nether portal, and growing cocoa pods.

Confirmed for 0.15.1 alpha build 1.
Edit: I found a list in Minecraft Wiki, maybe some of them need to receive a block update.

Also placing redstone next to an observer does not activate it but changes in the redstone's state and breaking the redstone does activate it. Not sure if this is WAI. Seems to me like like placing redstone should count as a block update if breaking it does

Yeah, I think placing redstone dust should be detected. It do wonder, though, if most of these problems are with the observer, or i they're actually caused by the other blocks. Maybe redstone dust doesn't cause a block update when its placed, and perhaps the same thing for redstone ore glowing, cocoa beans growing, and other things like that. This could be technically a bug with lots of blocks, but not actually the observer itself... if anyone has the ability to read the MCPE code, it would be interesting to know how the observer block detects updates and how block updates are caused. That could help in diagnosing the cause of this bug.

Taken from MCPE-15593:

No output when:
Changing what mobs spawn in spawner
Top door half
Activate fencegate via redstone
Activate rail with redstone
Toggling redstone torch in any way
changing daylight detector to inverted and opposite
Both weighted pressure plates sometimes dont make it toggle when atvivate, but always on deactivate

@Mega_Spud: As stated in earlier comments, I don't think changing the type of mob spawner should work with observers because it is an NBT change which doesn't cause a block update.

To remind you: My issue has images attached that explain HOW to reproduce them. Makes me upset if useful stuff is not attached .

Fixed for weighted pressure plates and doors in 0.15.90.2. (Tested on Pocket Edition.) I think the remaining cases may all be due to the blocks themselves not causing updates, and if so (if there isn't already), there should be a bug report for all the instances of blocks not causing block updates when they should. Except for placing a spawn egg in a spawner, because that only changes NBT data and doesn't cause an update on the Java edition either.

I will try and check using the melting-ice-into-floating-water trick to check if the remaining cases even cause block updates at all.

I can confirm that fence gates activated by redstone, switching the orientation of rails, and inverting redstone torches all do NOT cause block updates. Therefore, this bug is incorrect as it is a bug with the blocks themselves, NOT the Observer.

This bug has been reported to our internal bug tracker for further testing and a fix. It is scheduled to be fixed in one of the future updates (no specific date can be provided).

Affects 0.16.0 Beta Build 4 (AKA 0.15.90.7).

Could a moderator please update the description to reflect the fact that this bug is now fixed for doors and weighted pressure plates, and also the fact that placing spawn eggs in a monster spawner should NOT cause a block update and therefore the bug doesn't apply to that block? EDIT: Thanks, but you forgot to remove the top halves of doors from the list.

Fixed (err the description, not the whole bug!), as per @unknown.

Affects 0.15.10. (Tested on Windows 10.)

What about making them act like in PC? (except for the diagonal quasiconnectivity)

@unknown: The observer can be made to output strong power and be coded just like the Java edition observer, but it is important to note that they will still act differently, since block/redstone updates happen differently in the 2 editions. For example, in the Java edition, if you point a repeater into a block and power the repeater, the repeater will update the block, and an observer can detect the block being updated. Actually, the repeater will update the spot in front of it regardless of whether or not there is even a block. And in fact, it actually causes updates on the blocks adjacent to the block in front of it. So the repeater causes at least 6 block updates, not counting itself updating.

In MCPE, repeaters cause no updates (except on themselves) unless there is a redstone component in front of them. If you point a repeater into a block and put redstone dust on the other end, the repeater will cause the redstone dust to turn on, causing a block update, but the block in-between will not be updated, as the repeater causes the redstone dust to update directly, and the redstone dust, in turn, doesn't update anything except itself, as there are no other components near it that it can power.

So because of this, observers in the Java edition will respond to a lot more things than MCPE observers, because the Java edition redstone components cause more redstone updates (most of which are unnecessary and cause lag) than the MCPE redstone components, which remember the location of nearby components and update them directly, rather than flooding the adjacent blocks with unneeded updates.

So even if observers were changed to output strong power like in the Java edition, you wouldn't be able to chain them with air blocks in between each observer, because the air blocks would never get updated by the observers output. I'm also not sure if MCPE observers themselves get updated when they're activated. If they do, then you could chain them by placing them in front of each other, but if they don't, then that would still not work.

It is also currently undetermined as to how many of the Java edition observer behaviors are intended, so its a bit too early to say what would need to be changed on which edition.

But all of that is somewhat unrelated to this bug, which is really misnamed. The observer block IS reading all block updates.

The real issue is that the things listed in this bug report don't cause block updates, even though they should. So this is not an observer bug... this is a bug with multiple blocks not causing block updates when they should.

@unknown Could you please change the name of this bug to something like "Some blocks don't cause block updates when they should" or something like that? I've tested these instances with the floating-water-block-update-trick/test and I can confirm that the observer is working fine... it is the other blocks that aren't causing any updates.

You might want to add Minecraft Java version as an affected Minecraft edition because of the addition of observer blocks in 16w39a. A very similar glitch occurs there. When opening and closing a door or fence gate, the observer does not detect this block update. I'm sure there are other block updates not detected, but that is just one.

@unknown Java edition bugs should be reported on the Java edition bugtracker. The MCPE bugtracker only tracks MCPE bugs.

https://bugs.mojang.com/browse/MC

Added snow layer created by snow golem to the list in the description.

(Snow layers placed by a player are detected)

Revised title to be more accurate. (The observer DOES detect all block updates... some blocks simply aren't causing block updates when they should.)

The lava/water source flowing can't be detected either.
I was trying to build this: https://www.youtube.com/watch?v=myDz5EwyWHw
(Yes, it also uses quasi-connectivity, but that can be easily changed).

Observers still not detecting Redstone Ore activation on 1.2.5. Why no fix yet? this was reported a year ago!