Paper: Vertical hopper transferring two items at once

[EvilOlaf]

Incompatibility (Bug)

What behaviour is expected:

Vanilla hopper functionality

What behaviour is observed:

Hopper always transferring two items at once when stacked vertically

Steps/models to reproduce:

Stack three or more hoppers vertically
Put a random item stack into the top hopper (tested with wool and cobblestone)
Check hopper to notice two items are transferred at once.

Tested with default spigot.yml and paper.yml

Plugin list:

No plugins whatsoever, completely stock

Paper build number:

git-Paper-1269 (MC: 1.12.2)

[zachbr]

This is vanilla behavior.
Tested against the vanilla minecraft server version 1.12 using variously stacked numbers of hoppers.

[EvilOlaf]

Well, then sorry for bothering. Never thought that it would be vanilla behavior that vertically stacked hoppers transfer two items at once. Weird stuff.

[zachbr]

It is weird, I thought it was a bug when I initially glanced through.
Mojang may very well consider this a bug, I certainly would, but we can't fix it without breaking hopper behavior.
Thanks for the report though 👍

[SpiderRobotMan]

From testing this is due to the top hopper pushing items into the one below, while at the same time the bottom hopper pulls items out of the hopper above it. You can disable one of them using redstone to notice this. The official bug for this issue has been marked Works As Intended. https://bugs.mojang.com/browse/MC-8361

[EvilOlaf]

Alright, thank you for the follow up. Still odd ¯_(ツ)_/¯