Paper/nms-patches/BlockCauldron.patch

--- a/net/minecraft/server/BlockCauldron.java
+++ b/net/minecraft/server/BlockCauldron.java
@@ -3,6 +3,7 @@
 import java.util.List;
 import java.util.Random;
 import javax.annotation.Nullable;
+import org.bukkit.event.block.CauldronLevelChangeEvent; // CraftBukkit
 
 public class BlockCauldron extends Block {
 
@@ -43,8 +44,13 @@
         float f = (float) blockposition.getY() + (6.0F + (float) (3 * i)) / 16.0F;
 
         if (!world.isClientSide && entity.isBurning() && i > 0 && entity.getBoundingBox().b <= (double) f) {
+            // CraftBukkit start
+            if (!this.changeLevel(world, blockposition, iblockdata, i - 1, entity, CauldronLevelChangeEvent.ChangeReason.EXTINGUISH)) {
+                return;
+            }
             entity.extinguish();
-            this.a(world, blockposition, iblockdata, i - 1);
+            // this.a(world, blockposition, iblockdata, i - 1);
+            // CraftBukkit end
         }
 
     }
@@ -58,17 +64,26 @@
 
             if (item == Items.WATER_BUCKET) {
                 if (i < 3 && !world.isClientSide) {
+                    // CraftBukkit start
+                    if (!this.changeLevel(world, blockposition, iblockdata, 3, entityhuman, CauldronLevelChangeEvent.ChangeReason.BUCKET_EMPTY)) {
+                        return true;
+                    }
                     if (!entityhuman.abilities.canInstantlyBuild) {
                         entityhuman.a(enumhand, new ItemStack(Items.BUCKET));
                     }
 
                     entityhuman.b(StatisticList.K);
-                    this.a(world, blockposition, iblockdata, 3);
+                    // this.a(world, blockposition, iblockdata, 3);
+                    // CraftBukkit end
                 }
 
                 return true;
             } else if (item == Items.BUCKET) {
                 if (i == 3 && !world.isClientSide) {
+                    // CraftBukkit start
+                    if (!this.changeLevel(world, blockposition, iblockdata, 0, entityhuman, CauldronLevelChangeEvent.ChangeReason.BUCKET_FILL)) {
+                        return true;
+                    }
                     if (!entityhuman.abilities.canInstantlyBuild) {
                         --itemstack.count;
                         if (itemstack.count == 0) {
@@ -79,7 +94,8 @@
                     }
 
                     entityhuman.b(StatisticList.L);
-                    this.a(world, blockposition, iblockdata, 0);
+                    // this.a(world, blockposition, iblockdata, 0);
+                    // CraftBukkit end
                 }
 
                 return true;
@@ -88,6 +104,10 @@
 
                 if (item == Items.GLASS_BOTTLE) {
                     if (i > 0 && !world.isClientSide) {
+                        // CraftBukkit start
+                        if (!this.changeLevel(world, blockposition, iblockdata, i - 1, entityhuman, CauldronLevelChangeEvent.ChangeReason.BOTTLE_FILL)) {
+                            return true;
+                        }
                         if (!entityhuman.abilities.canInstantlyBuild) {
                             itemstack1 = PotionUtil.a(new ItemStack(Items.POTION), Potions.b);
                             entityhuman.b(StatisticList.L);
@@ -100,7 +120,8 @@
                             }
                         }
 
-                        this.a(world, blockposition, iblockdata, i - 1);
+                        // this.a(world, blockposition, iblockdata, i - 1);
+                        // CraftBukkit end
                     }
 
                     return true;
@@ -109,8 +130,13 @@
                         ItemArmor itemarmor = (ItemArmor) item;
 
                         if (itemarmor.d() == ItemArmor.EnumArmorMaterial.LEATHER && itemarmor.e_(itemstack) && !world.isClientSide) {
+                            // CraftBukkit start
+                            if (!this.changeLevel(world, blockposition, iblockdata, i - 1, entityhuman, CauldronLevelChangeEvent.ChangeReason.ARMOR_WASH)) {
+                                return true;
+                            }
                             itemarmor.c(itemstack);
-                            this.a(world, blockposition, iblockdata, i - 1);
+                            // this.a(world, blockposition, iblockdata, i - 1);
+                            // CraftBukkit end
                             entityhuman.b(StatisticList.M);
                             return true;
                         }
@@ -135,7 +161,7 @@
                             }
 
                             if (!entityhuman.abilities.canInstantlyBuild) {
-                                this.a(world, blockposition, iblockdata, i - 1);
+                                this.changeLevel(world, blockposition, iblockdata, i - 1, entityhuman, CauldronLevelChangeEvent.ChangeReason.BANNER_WASH); // CraftBukkit
                             }
                         }
 
@@ -148,9 +174,25 @@
         }
     }
 
+    // CraftBukkit start
     public void a(World world, BlockPosition blockposition, IBlockData iblockdata, int i) {
-        world.setTypeAndData(blockposition, iblockdata.set(BlockCauldron.LEVEL, Integer.valueOf(MathHelper.clamp(i, 0, 3))), 2);
+        this.changeLevel(world, blockposition, iblockdata, i, null, CauldronLevelChangeEvent.ChangeReason.UNKNOWN);
+    }
+
+    private boolean changeLevel(World world, BlockPosition blockposition, IBlockData iblockdata, int i, Entity entity, CauldronLevelChangeEvent.ChangeReason reason) {
+        int newLevel = Integer.valueOf(MathHelper.clamp(i, 0, 3));
+        CauldronLevelChangeEvent event = new CauldronLevelChangeEvent(
+                world.getWorld().getBlockAt(blockposition.getX(), blockposition.getY(), blockposition.getZ()),
+                (entity == null) ? null : entity.getBukkitEntity(), reason, iblockdata.get(BlockCauldron.LEVEL), newLevel
+        );
+        world.getServer().getPluginManager().callEvent(event);
+        if (event.isCancelled()) {
+            return false;
+        }
+        world.setTypeAndData(blockposition, iblockdata.set(BlockCauldron.LEVEL, newLevel), 2);
         world.updateAdjacentComparators(blockposition, this);
+        return true;
+        // CraftBukkit end
     }
 
     public void h(World world, BlockPosition blockposition) {
@@ -161,7 +203,7 @@
                 IBlockData iblockdata = world.getType(blockposition);
 
                 if (((Integer) iblockdata.get(BlockCauldron.LEVEL)).intValue() < 3) {
-                    world.setTypeAndData(blockposition, iblockdata.a((IBlockState) BlockCauldron.LEVEL), 2);
+                    a(world, blockposition, iblockdata.a((IBlockState) BlockCauldron.LEVEL), 2); // CraftBukkit
                 }
 
             }