📍 Description (REQUIRED)

Block placer dupes any place-able blocks by placing them & extracting the item out of it at the same time.

📑 Steps to reproduce the Issue (REQUIRED)

https://www.youtube.com/watch?v=dV0yUkVHJwM

1. Set up a block placer w/ a hopper minecart under it (or any other mechanism that allows for 1-tick extraction)
2. Use hoppers (or other mechanism) to pipe items into block placer
3. Set up a clock to rapidly activate the block placer
4. Block placer places the block, and it is extracted by the hopper minecart as well.

If you use a rapid clock, this method is not consistent as the dupe depends on extracting the item 1-gt after it is placed, but it's also possible to set up a gt-delay circuit for 100% reliable duping. I can provide more detailed screenshots of this setup if needed, but you should be able to reproduce the dupe by just adding an observer clock at the back of the block placer.

💡 Expected behavior (REQUIRED)

No item duping. The item should not be able to be extracted out of the Block Placer if the Block Placer places the block.

📜 Server Log

N/A

📂 /error-reports/ Folder

N/A

🧭 Environment (REQUIRED)

• Server Software: PaperMC 1.16.5 latest
• Minecraft Version: 1.16.5
• Slimefun Version: DEV-811 (should work on latest as well, though)

The dupe bug occurs because of the 2-tick delays here:

• Slimefun4/src/main/java/io/github/thebusybiscuit/slimefun4/implementation/items/blocks/BlockPlacer.java

  Line 219 in 45a4828

  SlimefunPlugin.runSync(() -> dispenser.getInventory().removeItem(item), 2L);

• Slimefun4/src/main/java/io/github/thebusybiscuit/slimefun4/implementation/items/blocks/BlockPlacer.java

  Line 182 in 45a4828

  SlimefunPlugin.runSync(() -> dispenser.getInventory().removeItem(item), 2L);

I do not recommend introducing a specific check for hopper minecarts, as there will still potentially be other ways to pull the item out of the block placer inventory 1-gt after it gets placed and result in a dupe. e.g. activating an explosion, using cargo nodes, or pipes from any other mod (all untested)