PaperMC/paper-server/nms-patches/net/minecraft/world/level/block/BlockBamboo.patch

--- a/net/minecraft/world/level/block/BlockBamboo.java
+++ b/net/minecraft/world/level/block/BlockBamboo.java
@@ -185,7 +185,7 @@
             BlockPosition blockposition1 = blockposition.above(i);
             IBlockData iblockdata1 = worldserver.getBlockState(blockposition1);
 
-            if (k >= 16 || (Integer) iblockdata1.getValue(BlockBamboo.STAGE) == 1 || !worldserver.isEmptyBlock(blockposition1.above())) {
+            if (k >= 16 || !iblockdata1.is(Blocks.BAMBOO) || (Integer) iblockdata1.getValue(BlockBamboo.STAGE) == 1 || !worldserver.isEmptyBlock(blockposition1.above())) { // CraftBukkit - If the BlockSpreadEvent was cancelled, we have no bamboo here
                 return;
             }
 
@@ -206,14 +206,18 @@
         BlockPosition blockposition1 = blockposition.below(2);
         IBlockData iblockdata2 = world.getBlockState(blockposition1);
         BlockPropertyBambooSize blockpropertybamboosize = BlockPropertyBambooSize.NONE;
+        boolean shouldUpdateOthers = false; // CraftBukkit
 
         if (i >= 1) {
             if (iblockdata1.is(Blocks.BAMBOO) && iblockdata1.getValue(BlockBamboo.LEAVES) != BlockPropertyBambooSize.NONE) {
                 if (iblockdata1.is(Blocks.BAMBOO) && iblockdata1.getValue(BlockBamboo.LEAVES) != BlockPropertyBambooSize.NONE) {
                     blockpropertybamboosize = BlockPropertyBambooSize.LARGE;
                     if (iblockdata2.is(Blocks.BAMBOO)) {
-                        world.setBlock(blockposition.below(), (IBlockData) iblockdata1.setValue(BlockBamboo.LEAVES, BlockPropertyBambooSize.SMALL), 3);
-                        world.setBlock(blockposition1, (IBlockData) iblockdata2.setValue(BlockBamboo.LEAVES, BlockPropertyBambooSize.NONE), 3);
+                        // CraftBukkit start - moved down
+                        // world.setBlock(blockposition.below(), (IBlockData) iblockdata1.setValue(BlockBamboo.LEAVES, BlockPropertyBambooSize.SMALL), 3);
+                        // world.setBlock(blockposition1, (IBlockData) iblockdata2.setValue(BlockBamboo.LEAVES, BlockPropertyBambooSize.NONE), 3);
+                        shouldUpdateOthers = true;
+                        // CraftBukkit end
                     }
                 }
             } else {
@@ -224,7 +228,14 @@
         int j = (Integer) iblockdata.getValue(BlockBamboo.AGE) != 1 && !iblockdata2.is(Blocks.BAMBOO) ? 0 : 1;
         int k = (i < 11 || random.nextFloat() >= 0.25F) && i != 15 ? 0 : 1;
 
-        world.setBlock(blockposition.above(), (IBlockData) ((IBlockData) ((IBlockData) this.defaultBlockState().setValue(BlockBamboo.AGE, j)).setValue(BlockBamboo.LEAVES, blockpropertybamboosize)).setValue(BlockBamboo.STAGE, k), 3);
+        // CraftBukkit start
+        if (org.bukkit.craftbukkit.event.CraftEventFactory.handleBlockSpreadEvent(world, blockposition, blockposition.above(), (IBlockData) ((IBlockData) ((IBlockData) this.defaultBlockState().setValue(BlockBamboo.AGE, j)).setValue(BlockBamboo.LEAVES, blockpropertybamboosize)).setValue(BlockBamboo.STAGE, k), 3)) {
+            if (shouldUpdateOthers) {
+                world.setBlock(blockposition.below(), (IBlockData) iblockdata1.setValue(BlockBamboo.LEAVES, BlockPropertyBambooSize.SMALL), 3);
+                world.setBlock(blockposition1, (IBlockData) iblockdata2.setValue(BlockBamboo.LEAVES, BlockPropertyBambooSize.NONE), 3);
+            }
+        }
+        // CraftBukkit end
     }
 
     protected int getHeightAboveUpToMax(IBlockAccess iblockaccess, BlockPosition blockposition) {