Correctly remove prefabs when overwritten

Author: BitcoderCZ

FancadeLoaderLib.Tests/PrefabListTests.cs

@@ -363,6 +363,35 @@ public async Task AddSegmentToPrefab_WithObstruction_OverwriteTrue_DoesNotThrow(
 		}
 	}
 
+	[Test]
+	public async Task AddSegmentToPrefab_OverwritesPrefabsCorrectly()
+	{
+		var prefabList = new PrefabList()
+		{
+			IdOffset = 1,
+		};
+
+		var prefab1 = CreateDummyPrefab(1, 1);
+		var prefab2 = CreateDummyPrefab(2, 2);
+
+		var blocks = prefab1.Blocks;
+		blocks.SetPrefab(new int3(0, 0, 0), prefab1);
+		blocks.SetPrefab(new int3(1, 0, 0), prefab2);
+
+		prefabList.AddPrefab(prefab1);
+		prefabList.AddPrefab(prefab2);
+
+		var newSegment = new PrefabSegment(1, new byte3(1, 0, 0));
+		prefabList.AddSegmentToPrefab(1, newSegment, true);
+
+		using (Assert.Multiple())
+		{
+			await Assert.That(blocks.GetBlock(new int3(0, 0, 0))).IsEqualTo((ushort)1);
+			await Assert.That(blocks.GetBlock(new int3(1, 0, 0))).IsEqualTo((ushort)2);
+			await Assert.That(blocks.GetBlock(new int3(2, 0, 0))).IsEqualTo((ushort)0);
+		}
+	}
+
 	[Test]
 	public async Task TryAddSegmentToPrefab_WithObstruction_ReturnsFalse()
 	{

FancadeLoaderLib/PrefabList.cs

@@ -586,7 +586,19 @@ private void AddIdToPrefab(ushort prefabId, int3 offset, ushort id)
 
 						if (array[i] == prefabId)
 						{
-							prefab.Blocks.SetBlock(pos + offset, id);
+							int iNew = prefab.Blocks.Index(pos + offset);
+							ushort idOld = array[iNew];
+							if (TryGetPrefab(idOld, out var oldPrefab))
+							{
+								int3 prefabPos = (pos + offset) - GetSegment(idOld).PosInPrefab;
+
+								foreach (var segPos in oldPrefab.Keys)
+								{
+									prefab.Blocks.SetBlockUnchecked(prefabPos + segPos, 0);
+								}
+							}
+
+							array[iNew] = id;
 						}
 					}
 				}