I found this when testing snapshot 13w05a in my redstone world.
I had built a few devices using a dropper/hopper based randomizer in the 13w04a snapshot, and they all worked as expected. After installing 13w05a I found none of them worked.
When an item is placed into a hopper by a dropper, the hopper does not change the state of any comparator attached to it.
Process:
1. Place a dropper anywhere.
2. Place a hopper facing the output side of the dropper.
3. Place a comparator for redstone output of the hopper.
4. Put any item of any amount in the dropper.
5. Power the dropper. A button works well for this example.
Expected result:
The dropper puts one item in the hopper.
The comparator would activate and stay on for as long as the item remains in the hopper.
The hopper puts the item back in the dropper.
Observed result:
The comparator did not activate.
The comparator becomes a BUD, activating by any block update around it, provided the hopper still holds items.
Linked issues
is duplicated by 5
MC-9182
Comparator redstone strength update
Resolved
MC-9652
Comparators don't update signal when a hopper is filled from a dropper
Resolved
MC-9815
Dropper to Hopper - comparator glitch
Resolved
MC-10009
Hoppers do not update comparators as to their fullness when given a block by a dropper.
Resolved
MC-10881
Comparator coming off of chests, droppers, hoppers ... behave strangely.
Resolved
Comments 7
Thanks for the quick confirmation. I was really disappointed by this one. Looking forward to a fix soon.
Duplicate of MC-8776.
Not a duplicate. Tested in 13w06a, and it still exists as reported, even though MC 8776 and duplicates have been fixed.
The strange this is that this bug only occurs when a dropper puts an item into a hopper. A comparator does update its output if another hopper would transfer an item into the hopper (throwing an item into the hopper would trigger it as well). And replacing the hopper by any other block (or entity) with an inventory (chest, furnace, dropper, dispenser, hopper, minecart with chest/hopper) does update the comparator when a dropper would drop an item into it.
This also bugs out for Dropper-to-Dropper updates with the comparator. I was making a counter, and the comparator should have lit up when one dropper is filled up by another. This doesn't happen unless I update a block next to the comparator connected to the receiving dropper. I know my wiring is correct because all I have to do is update a block or replace the comparator and all works as intended. This was the case in both 13w05a and 13w06a in SSP. Thanks.
Just tested this out in 13w09a and the bug still exists in it's reported form, even though the general comparators not getting updated by Hoppers bug (MC-9687) has been fixed.
Confirmed.