From 0caf75f8392e4ad4c4c7189d1b1f4922b18133b6 Mon Sep 17 00:00:00 2001
From: Owen <23108066+Owen1212055@users.noreply.github.com>
Date: Wed, 25 Jun 2025 14:16:03 -0400
Subject: [PATCH] Fix #12721 (#12725)

* Fix #12721

Track when knots are created and only fire the event then

* Use mutable boolean + check if actually spawned
---
 .../LeashFenceKnotEntity.java.patch           | 22 +++++++++++++++++++
 .../minecraft/world/item/LeadItem.java.patch  | 20 ++++++++++-------
 2 files changed, 34 insertions(+), 8 deletions(-)

diff --git a/paper-server/patches/sources/net/minecraft/world/entity/decoration/LeashFenceKnotEntity.java.patch b/paper-server/patches/sources/net/minecraft/world/entity/decoration/LeashFenceKnotEntity.java.patch
index 51f18a9293..65331b4049 100644
--- a/paper-server/patches/sources/net/minecraft/world/entity/decoration/LeashFenceKnotEntity.java.patch
+++ b/paper-server/patches/sources/net/minecraft/world/entity/decoration/LeashFenceKnotEntity.java.patch
@@ -27,3 +27,25 @@
          }
      }
  
+@@ -120,7 +_,12 @@
+         return this.level().getBlockState(this.pos).is(BlockTags.FENCES);
+     }
+ 
++    // Paper start - Track if a knot was created
+     public static LeashFenceKnotEntity getOrCreateKnot(Level level, BlockPos pos) {
++        return getOrCreateKnot(level, pos, null);
++    }
++    public static LeashFenceKnotEntity getOrCreateKnot(Level level, BlockPos pos, @Nullable org.apache.commons.lang3.mutable.MutableBoolean created) {
++        // Paper end - Track if a knot was created
+         int x = pos.getX();
+         int y = pos.getY();
+         int z = pos.getZ();
+@@ -134,7 +_,7 @@
+         }
+ 
+         LeashFenceKnotEntity leashFenceKnotEntity1 = new LeashFenceKnotEntity(level, pos);
+-        level.addFreshEntity(leashFenceKnotEntity1);
++        if (level.addFreshEntity(leashFenceKnotEntity1) && created != null) { created.setTrue(); } // Paper - Track if a knot was created
+         return leashFenceKnotEntity1;
+     }
+ 
diff --git a/paper-server/patches/sources/net/minecraft/world/item/LeadItem.java.patch b/paper-server/patches/sources/net/minecraft/world/item/LeadItem.java.patch
index c9fcda66a5..632e534029 100644
--- a/paper-server/patches/sources/net/minecraft/world/item/LeadItem.java.patch
+++ b/paper-server/patches/sources/net/minecraft/world/item/LeadItem.java.patch
@@ -1,6 +1,6 @@
 --- a/net/minecraft/world/item/LeadItem.java
 +++ b/net/minecraft/world/item/LeadItem.java
-@@ -26,24 +_,43 @@
+@@ -26,24 +_,46 @@
          if (blockState.is(BlockTags.FENCES)) {
              Player player = context.getPlayer();
              if (!level.isClientSide && player != null) {
@@ -22,15 +22,19 @@
 +        for (java.util.Iterator<Leashable> iterator = list.iterator(); iterator.hasNext();) { // Paper - use iterator to remove
 +            Leashable leashable = iterator.next(); // Paper - use iterator to remove
              if (leashFenceKnotEntity == null) {
-                 leashFenceKnotEntity = LeashFenceKnotEntity.getOrCreateKnot(level, pos);
+-                leashFenceKnotEntity = LeashFenceKnotEntity.getOrCreateKnot(level, pos);
 +                // CraftBukkit start - fire HangingPlaceEvent
-+                org.bukkit.inventory.EquipmentSlot hand = org.bukkit.craftbukkit.CraftEquipmentSlot.getHand(interactionHand);
-+                org.bukkit.event.hanging.HangingPlaceEvent event = new org.bukkit.event.hanging.HangingPlaceEvent((org.bukkit.entity.Hanging) leashFenceKnotEntity.getBukkitEntity(), player != null ? (org.bukkit.entity.Player) player.getBukkitEntity() : null, org.bukkit.craftbukkit.block.CraftBlock.at(level, pos), org.bukkit.block.BlockFace.SELF, hand);
-+                level.getCraftServer().getPluginManager().callEvent(event);
++                org.apache.commons.lang3.mutable.MutableBoolean created = new org.apache.commons.lang3.mutable.MutableBoolean(false);
++                leashFenceKnotEntity = LeashFenceKnotEntity.getOrCreateKnot(level, pos, created);
++                if (created.booleanValue()) {
++                    org.bukkit.inventory.EquipmentSlot hand = org.bukkit.craftbukkit.CraftEquipmentSlot.getHand(interactionHand);
++                    org.bukkit.event.hanging.HangingPlaceEvent event = new org.bukkit.event.hanging.HangingPlaceEvent((org.bukkit.entity.Hanging) leashFenceKnotEntity.getBukkitEntity(), player != null ? (org.bukkit.entity.Player) player.getBukkitEntity() : null, org.bukkit.craftbukkit.block.CraftBlock.at(level, pos), org.bukkit.block.BlockFace.SELF, hand);
++                    level.getCraftServer().getPluginManager().callEvent(event);
 +
-+                if (event.isCancelled()) {
-+                    leashFenceKnotEntity.discard(null); // CraftBukkit - add Bukkit remove cause
-+                    return InteractionResult.PASS;
++                    if (event.isCancelled()) {
++                        leashFenceKnotEntity.discard(null); // CraftBukkit - add Bukkit remove cause
++                        return InteractionResult.PASS;
++                    }
 +                }
 +                // CraftBukkit end
                  leashFenceKnotEntity.playPlacementSound();