Only remove worldgen block entity on changed block (#10794)

patches/server/1053-Fix-creation-of-invalid-block-entity-during-world-ge.patch

@@ -5,14 +5,33 @@ Subject: [PATCH] Fix creation of invalid block entity during world generation
 
 
 diff --git a/src/main/java/net/minecraft/server/level/WorldGenRegion.java b/src/main/java/net/minecraft/server/level/WorldGenRegion.java
-index 5ece375eaf6bcc61864997a389bb5e24625e4505..9c3f8f79c2b3389a118dce9a1558edda52446833 100644
+index 5ece375eaf6bcc61864997a389bb5e24625e4505..17e3c28f738504082733859f5ebfccc3dc046b6d 100644
 --- a/src/main/java/net/minecraft/server/level/WorldGenRegion.java
 +++ b/src/main/java/net/minecraft/server/level/WorldGenRegion.java
-@@ -352,6 +352,7 @@ public class WorldGenRegion implements WorldGenLevel {
+@@ -336,7 +336,7 @@ public class WorldGenRegion implements WorldGenLevel {
+             return false;
+         } else {
+             ChunkAccess ichunkaccess = this.getChunk(pos);
+-            BlockState iblockdata1 = ichunkaccess.setBlockState(pos, state, false);
++            BlockState iblockdata1 = ichunkaccess.setBlockState(pos, state, false); final BlockState previousBlockState = iblockdata1; // Paper - Clear block entity before setting up a DUMMY block entity
+ 
+             if (iblockdata1 != null) {
+                 this.level.onBlockStateChange(pos, iblockdata1, state);
+@@ -352,6 +352,17 @@ public class WorldGenRegion implements WorldGenLevel {
                          ichunkaccess.removeBlockEntity(pos);
                      }
                  } else {
-+                    ichunkaccess.removeBlockEntity(pos); // Paper - Clear the block entity before setting up a DUMMY block entity
++                    // Paper start - Clear block entity before setting up a DUMMY block entity
++                    // The concept of removing a block entity when the block itself changes is generally lifted
++                    // from LevelChunk#setBlockState.
++                    // It is however to note that this may only run if the block actually changes.
++                    // Otherwise a chest block entity generated by a structure template that is later "updated" to
++                    // be waterlogged would remove its existing block entity (see PaperMC/Paper#10750)
++                    // This logic is *also* found in LevelChunk#setBlockState.
++                    if (previousBlockState != null && !java.util.Objects.equals(previousBlockState.getBlock(), state.getBlock())) {
++                        ichunkaccess.removeBlockEntity(pos);
++                    }
++                    // Paper end - Clear block entity before setting up a DUMMY block entity
                      CompoundTag nbttagcompound = new CompoundTag();
  
                      nbttagcompound.putInt("x", pos.getX());