[1.12.2] Exploding Nested LittleTiles Structure May Lead to Crash

[littlecube8152]

What

Exploding nested LittleTiles structures can crash the game. One instance of the crash report is as follows.

crash-2025-02-12_22.58.31-server.txt

Additionally, the log will be flooded by messages like these:

partial-latest.log

Reproduction

1. Use Little Importer to import this block:

{tiles:[{boxes:[[I;1,0,1,2,16,15],[I;2,1,1,15,16,2],[I;14,1,2,15,16,15],[I;2,0,1,15,1,15],[I;1,16,1,2,31,15],[I;2,30,2,15,31,15],[I;2,16,1,15,31,2],[I;14,16,2,15,30,15]],tile:{block:"minecraft:planks"}}],min:[I;1,0,1],size:[I;14,31,15],children:[{tiles:[{boxes:[[I;3,1,6,4,13,13],[I;4,1,6,13,11,13],[I;4,11,6,12,13,12],[I;4,12,12,13,13,13],[I;12,11,6,13,12,13],[I;12,12,6,13,13,12]],tile:{block:"minecraft:sandstone:2"}},{bBox:[I;4,11,12,12,12,13],tile:{invisible:1b,block:"littletiles:ltstorageblocktile"}}],count:7,dynamic:1b,structure:{stackSizeLimit:64,invisibleStorage:1b,lastSlot:8,filled:65528,numberOfSlots:1,dynamic:1b,id:"storage",accessed:0,inventory:{size:1,slot0:{id:"minecraft:tnt",Count:1b,Damage:0s}},inventorySize:8}},{tiles:[{boxes:[[I;3,13,6,13,16,13],[I;3,16,6,4,25,13],[I;4,16,6,13,23,13],[I;4,23,6,12,25,12],[I;4,24,12,13,25,13],[I;12,23,6,13,24,13],[I;12,24,6,13,25,12]],tile:{block:"minecraft:sandstone:2"}},{bBox:[I;4,23,12,12,24,13],tile:{invisible:1b,block:"littletiles:ltstorageblocktile"}}],count:8,dynamic:1b,structure:{stackSizeLimit:64,invisibleStorage:1b,lastSlot:8,filled:65528,numberOfSlots:1,dynamic:1b,id:"storage",accessed:0,inventory:{size:1,slot0:{id:"minecraft:tnt",Count:1b,Damage:0s}},inventorySize:8}},{tiles:[{boxes:[[I;1,0,15,15,16,16],[I;1,16,15,15,31,16]],tile:{block:"minecraft:bone_block"}}],count:2,dynamic:1b,structure:{clockwise:1b,activateParent:0b,opened:1b,axis:1,rot-type:0,duration:10,axisCenter:[I;14,0,15,15,1,16,16],interpolation:0,sounds:1b,dynamic:1b,id:"door",state:{mode:"TOGGLE",delay:0,state:0},events:[],disableRightClick:0b}}],count:8,structure:{blocks:[I;],id:"fixed"}}

2. Place down multiple of them and explode them with TNT.
3. Repeat step 2 until the crash happens.

Some notes:

• The crash seems to be chance-based. Putting down several such structures and blow them up at once is more likely to trigger it. However, it can still happen when blowing up one at a time.
• The structure is not the only one that can induce this crash. Blowing LittleTiles locker blocks causes a crash (Important!) SymmetricDevs/Supersymmetry#1289 includes another example.
• The structure above is made from three components: trim made from wood block, door made from bone block, and storage made from smooth sandstone.

Technical Investigation

I have only roughly traced the code but it seems that when a structure is exploded, LittleStructure.onLittleTileDestroy() will be called, and perhaps multiple components are removed from the game. However, the following handler

LittleTiles/src/main/java/com/creativemd/littletiles/common/block/BlockTile.java

Lines 1025 to 1042 in 286a797

	public void onBlockExploded(World world, BlockPos pos, Explosion explosion) {
	TileEntityLittleTiles te = loadTe(world, pos);
	if (te != null) {
	te.updateTiles((x) -> {
	ParentTileList parent = x.noneStructureTiles();
	for (LittleTile tile : parent)
	tile.onTileExplodes(parent, explosion);
	parent.clear();
	for (StructureTileList list : x.structures())
	try {
	list.getStructure().onLittleTileDestroy();
	} catch (CorruptedConnectionException | NotYetConnectedException e) {
	e.printStackTrace();
	}
	});
	}
	}

list.getStructure().onLittleTileDestroy(); does not check if the current StructureTileList is removed or not (since a StructureTileList can only have parent of null when its removed).