When a hopper pushes an item into another hopper that already holds some items, it does not reset that hopper’s transfer cooldown.
When a dropper or crafter pushes an item into a hopper that already holds some items, it does reset that hopper’s transfer cooldown if the hopper is locked (powered) at the time. This is inconsistent, and limits the use of redstone to time the interaction of droppers and crafters with hoppers.
Steps to reproduce (in 1.20.41)
Load
. It contains 6 test stations labelled A-F. Each consists of hoppers and droppers and redstone timing mechanisms that control their operation. The hopper at the left of each station is the output. A comparator in front of the output hopper shows if/when an item reaches the output. The hopper in the middle position and the hopper or dropper at the right each contain a stack of items. The structure block all the way at the right can be used to reset all of the stations.
Press the button at each station A-E, and flip the lever to turn on station F.
Expected results
An item reaches the output hopper at each station.
Observed results
Station | Item reaches output? |
|---|---|
A | yes - non-empty hopper can push if unlocked 4 ticks after receiving item from hopper |
B-D | no - non-empty hopper cannot push if unlocked 2, 4, or 6 ticks after receiving item from dropper |
E | yes - non-empty hopper can push if unlocked 8 ticks after receiving item from dropper |
F | no - non-empty hopper cannot push if unlocked on 8 tick clock only within < 8 ticks after it receives items from dropper |
Attachments
Comments 4
migrated
shows how this bug can impact builds that would use hoppers to move items through multi-step crafting with the example of rockets. Rockets require 1 paper and 1 gunpowder, but paper is crafted 3-at-a-time. Therefore, if you want to craft paper and then rockets in sequence you need to cache the paper outputs of the first crafter so that they don't fill all of the slots in the second crafter. However, if you use a hopper to cache the paper and happen to craft additional paper within 8 ticks of when you are ready to put paper into the rocket crafter, then the operation will fail.