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

--- a/net/minecraft/world/level/block/BlockConcretePowder.java
+++ b/net/minecraft/world/level/block/BlockConcretePowder.java
@@ -11,6 +11,12 @@
 import net.minecraft.world.level.block.state.BlockBase;
 import net.minecraft.world.level.block.state.IBlockData;
 
+// CraftBukkit start
+import org.bukkit.craftbukkit.block.CraftBlockState;
+import org.bukkit.craftbukkit.block.CraftBlockStates;
+import org.bukkit.event.block.BlockFormEvent;
+// CraftBukkit end
+
 public class BlockConcretePowder extends BlockFalling {
 
     private final IBlockData concrete;
@@ -23,7 +29,7 @@
     @Override
     public void onLand(World world, BlockPosition blockposition, IBlockData iblockdata, IBlockData iblockdata1, EntityFallingBlock entityfallingblock) {
         if (shouldSolidify(world, blockposition, iblockdata1)) {
-            world.setBlock(blockposition, this.concrete, 3);
+            org.bukkit.craftbukkit.event.CraftEventFactory.handleBlockFormEvent(world, blockposition, this.concrete, 3); // CraftBukkit
         }
 
     }
@@ -34,7 +40,24 @@
         BlockPosition blockposition = blockactioncontext.getClickedPos();
         IBlockData iblockdata = world.getBlockState(blockposition);
 
-        return shouldSolidify(world, blockposition, iblockdata) ? this.concrete : super.getStateForPlacement(blockactioncontext);
+        // CraftBukkit start
+        if (!shouldSolidify(world, blockposition, iblockdata)) {
+            return super.getStateForPlacement(blockactioncontext);
+        }
+
+        // TODO: An event factory call for methods like this
+        CraftBlockState blockState = CraftBlockStates.getBlockState(world, blockposition);
+        blockState.setData(this.concrete);
+
+        BlockFormEvent event = new BlockFormEvent(blockState.getBlock(), blockState);
+        world.getServer().server.getPluginManager().callEvent(event);
+
+        if (!event.isCancelled()) {
+            return blockState.getHandle();
+        }
+
+        return super.getStateForPlacement(blockactioncontext);
+        // CraftBukkit end
     }
 
     private static boolean shouldSolidify(IBlockAccess iblockaccess, BlockPosition blockposition, IBlockData iblockdata) {
@@ -70,7 +93,25 @@
 
     @Override
     public IBlockData updateShape(IBlockData iblockdata, EnumDirection enumdirection, IBlockData iblockdata1, GeneratorAccess generatoraccess, BlockPosition blockposition, BlockPosition blockposition1) {
-        return touchesLiquid(generatoraccess, blockposition) ? this.concrete : super.updateShape(iblockdata, enumdirection, iblockdata1, generatoraccess, blockposition, blockposition1);
+        // CraftBukkit start
+        if (touchesLiquid(generatoraccess, blockposition)) {
+            // Suppress during worldgen
+            if (!(generatoraccess instanceof World)) {
+                return this.concrete;
+            }
+            CraftBlockState blockState = CraftBlockStates.getBlockState(generatoraccess, blockposition);
+            blockState.setData(this.concrete);
+
+            BlockFormEvent event = new BlockFormEvent(blockState.getBlock(), blockState);
+            ((World) generatoraccess).getCraftServer().getPluginManager().callEvent(event);
+
+            if (!event.isCancelled()) {
+                return blockState.getHandle();
+            }
+        }
+
+        return super.updateShape(iblockdata, enumdirection, iblockdata1, generatoraccess, blockposition, blockposition1);
+        // CraftBukkit end
     }
 
     @Override