Overview

Sable Assembly Fix fixes an item duplication bug that occurs during Sable assembly/disassembly for block entities that do not implement the Clearable interface.

The Problem

Sable's SubLevelAssemblyHelper.moveBlocks() calls Clearable.tryClear() on every block entity during the assembly process. The issue is:

For block entities that implement Clearable (e.g. chests, hoppers) — works fine, contents are properly cleared
For block entities that do NOT implement Clearable (e.g. TableCloth, Mechanical Arm, Ejector, etc.) — tryClear() is a no-op, nothing happens
The block is destroyed and its items drop into the world, but the NBT data containing the item inventory is still there
When the block is recreated in the sub-level, the NBT items are read back
Result: the same items exist both on the ground and inside the block — item duplication

Triggering this bug is trivially cheap:

simply toggle the ship between physics mode and block mode (or vice versa) — each transition triggers assembly/disassembly, which duplicates the contents of any non-Clearable block entity on the ship. No expensive resources or complex setup required.

How It Works

A single @Redirect mixin intercepts the Clearable.tryClear() call inside SubLevelAssemblyHelper.moveBlocks() :

If the block entity implements Clearable → passes through normally, no intervention
If the block entity does not implement Clearable → calls level.removeBlockEntity(pos) to remove the block entity entirely, preventing it from dropping any contents

Affected Block Entities (Create + Addons)

Block Entity	Items per dupe
TableCloth	up to 4
Mechanical Arm	entire held stack (e.g. 64 items at once)

Plus any modded BE with inventory that doesn't implement Clearable.

Note: The Mechanical Arm is especially severe — it duplicates the entire held stack in one operation. If the arm is holding a full stack of 64 items, you get 64 duplicated items per assembly/disassembly cycle. Any modded block entity with an inventory that doesn't implement Clearable is also affected.

Configuration

A whitelist system is included. The config file config/sableassemblyfix/whitelist.json is automatically created on first launch.

Add block entity IDs to the whitelist to skip the fix (e.g. if a mod handles Clearable on its own). Requires a game restart to reload.

Dependencies

NeoForge >=21.1.228
Sable >=2.0
Create: Aeronautics >=1.0.2

License

MIT