PaperMC/paper-server/nms-patches/net/minecraft/world/entity/animal/Bucketable.patch

--- a/net/minecraft/world/entity/animal/Bucketable.java
+++ b/net/minecraft/world/entity/animal/Bucketable.java
@@ -15,6 +15,14 @@
 import net.minecraft.world.item.Items;
 import net.minecraft.world.level.World;
 
+// CraftBukkit start
+import net.minecraft.network.protocol.game.PacketPlayOutEntityMetadata;
+import net.minecraft.network.protocol.game.PacketPlayOutSpawnEntityLiving;
+import org.bukkit.craftbukkit.event.CraftEventFactory;
+import org.bukkit.craftbukkit.inventory.CraftItemStack;
+import org.bukkit.event.player.PlayerBucketEntityEvent;
+// CraftBukkit end
+
 public interface Bucketable {
 
     boolean isFromBucket();
@@ -92,10 +100,22 @@
         ItemStack itemstack = entityhuman.b(enumhand);
 
         if (itemstack.getItem() == Items.WATER_BUCKET && t0.isAlive()) {
-            t0.playSound(((Bucketable) t0).t(), 1.0F, 1.0F);
+            // CraftBukkit start
+            // t0.playSound(((Bucketable) t0).t(), 1.0F, 1.0F); // CraftBukkit - moved down
             ItemStack itemstack1 = ((Bucketable) t0).getBucketItem();
 
             ((Bucketable) t0).setBucketName(itemstack1);
+
+            PlayerBucketEntityEvent playerBucketFishEvent = CraftEventFactory.callPlayerFishBucketEvent(t0, entityhuman, itemstack, itemstack1);
+            itemstack1 = CraftItemStack.asNMSCopy(playerBucketFishEvent.getEntityBucket());
+            if (playerBucketFishEvent.isCancelled()) {
+                ((EntityPlayer) entityhuman).containerMenu.updateInventory(); // We need to update inventory to resync client's bucket
+                ((EntityPlayer) entityhuman).connection.sendPacket(new PacketPlayOutSpawnEntityLiving(t0)); // We need to play out these packets as the client assumes the fish is gone
+                ((EntityPlayer) entityhuman).connection.sendPacket(new PacketPlayOutEntityMetadata(t0.getId(), t0.getDataWatcher(), true)); // Need to send data such as the display name to client
+                return Optional.of(EnumInteractionResult.FAIL);
+            }
+            t0.playSound(((Bucketable) t0).t(), 1.0F, 1.0F);
+            // CraftBukkit end
             ItemStack itemstack2 = ItemLiquidUtil.a(itemstack, entityhuman, itemstack1, false);
 
             entityhuman.a(enumhand, itemstack2);