Julian Wright
Comments
If you build the structure referenced in my report MC-12198, that is three pistons in a row, with three blocks on top of them, and power the middle block with a button, lever or pressure plate, then you will notice that under 1.4.7 only the middle piston appears to be powered (as it is the only one to extend). However if you leave the middle block powered and place a block next to either of the other pistons then they extend too.
Therefor, under 1.4.7, the middle block is powering all three pistons, but only updating the middle one.
If you then try it under 1.5, you will find that powering the middle block causes all three pistons to extend. Hence my observation that it appears that updates are being propagated now.
Ultimately though, my main problem is that I don't think the two pistons to the sides should be getting power from the middle block, let alone needing to be updated.
Looks like my recent report MC-12198 is also marked as a duplicate of this bug. As @Eddie commented earlier though I only experienced the problem myself once updating to 1.5. It looks like half of the bug has been resolved in 1.5, namely that pistons who are being powered by a block are now being updated by that block, even if the block is above and to the side. Whereas before pistons were being powered but not updated by such a block.
But I still have a problem with the other half of the bug - pistons diagonally adjacent to a powered block shouldn't be powered by it.
Ok that makes more sense. To test it I removed the middle piston, and now the other two pistons only extend or retract after an adjacent block update. Regardless, something has changed between 1.4.7 and 1.5 with respect to these updates, such that now the middle piston is updating the two side pistons whereas before it did not. Maybe it's the new 2-ticks-to-extend piston timing.
I think I'll just add my vote to this issue and hope it gets corrected soon. 🙂