From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Jake Potrebic <jake.m.potrebic@gmail.com>
Date: Sat, 29 Oct 2022 17:02:42 -0700
Subject: [PATCH] Fix possible StackOverflowError for some dispenses

For saddles, carpets, horse armor, and chests for horse-likes
a BlockDispenseEvent handler that always mutated the item without
changing the type would result in a SO error because when it went
to find the replacement dispense behavior (since the item "changed")
it didn't properly handle if the replacement was the same instance
of dispense behavior.

Additionally equippable mob heads, wither skulls, and carved pumpkins
are subject to the same possible error.

diff --git a/src/main/java/net/minecraft/core/dispenser/DispenseItemBehavior.java b/src/main/java/net/minecraft/core/dispenser/DispenseItemBehavior.java
index 18304349c9ab24657c4152aff800dba969174665..63b8c806b6ee0ea3cc5e6a7f613b5e57c94bfcf1 100644
--- a/src/main/java/net/minecraft/core/dispenser/DispenseItemBehavior.java
+++ b/src/main/java/net/minecraft/core/dispenser/DispenseItemBehavior.java
@@ -232,7 +232,7 @@ public interface DispenseItemBehavior {
                         // Chain to handler for new item
                         ItemStack eventStack = CraftItemStack.asNMSCopy(event.getItem());
                         DispenseItemBehavior idispensebehavior = (DispenseItemBehavior) DispenserBlock.DISPENSER_REGISTRY.get(eventStack.getItem());
-                        if (idispensebehavior != DispenseItemBehavior.NOOP && idispensebehavior != EquipmentDispenseItemBehavior.INSTANCE) {
+                        if (idispensebehavior != DispenseItemBehavior.NOOP && idispensebehavior != EquipmentDispenseItemBehavior.INSTANCE && idispensebehavior != this) { // Paper - fix possible StackOverflowError
                             idispensebehavior.dispense(pointer, eventStack);
                             return stack;
                         }
@@ -283,7 +283,7 @@ public interface DispenseItemBehavior {
                     // Chain to handler for new item
                     ItemStack eventStack = CraftItemStack.asNMSCopy(event.getItem());
                     DispenseItemBehavior idispensebehavior = (DispenseItemBehavior) DispenserBlock.DISPENSER_REGISTRY.get(eventStack.getItem());
-                    if (idispensebehavior != DispenseItemBehavior.NOOP && idispensebehavior != EquipmentDispenseItemBehavior.INSTANCE) {
+                    if (idispensebehavior != DispenseItemBehavior.NOOP && idispensebehavior != EquipmentDispenseItemBehavior.INSTANCE && idispensebehavior != this) { // Paper - fix possible StackOverflowError
                         idispensebehavior.dispense(pointer, eventStack);
                         return stack;
                     }
@@ -645,7 +645,7 @@ public interface DispenseItemBehavior {
                     stack.shrink(1);
                     this.setSuccess(true);
                 } else {
-                    this.setSuccess(EquipmentDispenseItemBehavior.dispenseEquipment(pointer, stack));
+                    this.setSuccess(EquipmentDispenseItemBehavior.dispenseEquipment(pointer, stack, this)); // Paper - fix possible StackOverflowError
                 }
 
                 return stack;
@@ -691,7 +691,7 @@ public interface DispenseItemBehavior {
                     stack.shrink(1);
                     this.setSuccess(true);
                 } else {
-                    this.setSuccess(EquipmentDispenseItemBehavior.dispenseEquipment(pointer, stack));
+                    this.setSuccess(EquipmentDispenseItemBehavior.dispenseEquipment(pointer, stack, this)); // Paper - fix possible StackOverflowError
                 }
 
                 return stack;
@@ -819,7 +819,7 @@ public interface DispenseItemBehavior {
                         // Chain to handler for new item
                         ItemStack eventStack = CraftItemStack.asNMSCopy(event.getItem());
                         DispenseItemBehavior idispensebehavior = (DispenseItemBehavior) DispenserBlock.DISPENSER_REGISTRY.get(eventStack.getItem());
-                        if (idispensebehavior != DispenseItemBehavior.NOOP && idispensebehavior != EquipmentDispenseItemBehavior.INSTANCE) {
+                        if (idispensebehavior != DispenseItemBehavior.NOOP && idispensebehavior != EquipmentDispenseItemBehavior.INSTANCE && idispensebehavior != this) { // Paper - fix possible StackOverflowError
                             idispensebehavior.dispense(pointer, eventStack);
                             return stack;
                         }
diff --git a/src/main/java/net/minecraft/core/dispenser/EquipmentDispenseItemBehavior.java b/src/main/java/net/minecraft/core/dispenser/EquipmentDispenseItemBehavior.java
index a03cc350973fda213251cad273a2db86f438904b..036dd3b15dfee4cd079710eba1255d2bdb4d7220 100644
--- a/src/main/java/net/minecraft/core/dispenser/EquipmentDispenseItemBehavior.java
+++ b/src/main/java/net/minecraft/core/dispenser/EquipmentDispenseItemBehavior.java
@@ -23,10 +23,15 @@ public class EquipmentDispenseItemBehavior extends DefaultDispenseItemBehavior {
 
     @Override
     protected ItemStack execute(BlockSource pointer, ItemStack stack) {
-        return EquipmentDispenseItemBehavior.dispenseEquipment(pointer, stack) ? stack : super.execute(pointer, stack);
+        return EquipmentDispenseItemBehavior.dispenseEquipment(pointer, stack, null) ? stack : super.execute(pointer, stack); // Paper - fix possible StackOverflowError
     }
 
-    public static boolean dispenseEquipment(BlockSource pointer, ItemStack stack) {
+    @Deprecated @io.papermc.paper.annotation.DoNotUse // Paper
+    public static boolean dispenseEquipment(BlockSource pointer, ItemStack armor) {
+        // Paper start
+        return dispenseEquipment(pointer, armor, null);
+    }
+    public static boolean dispenseEquipment(BlockSource pointer, ItemStack stack, @javax.annotation.Nullable DispenseItemBehavior currentBehavior) {
         BlockPos blockposition = pointer.pos().relative((Direction) pointer.state().getValue(DispenserBlock.FACING));
         List<LivingEntity> list = pointer.level().getEntitiesOfClass(LivingEntity.class, new AABB(blockposition), (entityliving) -> {
             return entityliving.canEquipWithDispenser(stack);
@@ -59,7 +64,7 @@ public class EquipmentDispenseItemBehavior extends DefaultDispenseItemBehavior {
                 // Chain to handler for new item
                 ItemStack eventStack = CraftItemStack.asNMSCopy(event.getItem());
                 DispenseItemBehavior idispensebehavior = (DispenseItemBehavior) DispenserBlock.DISPENSER_REGISTRY.get(eventStack.getItem());
-                if (idispensebehavior != DispenseItemBehavior.NOOP && idispensebehavior != EquipmentDispenseItemBehavior.INSTANCE) {
+                if (idispensebehavior != DispenseItemBehavior.NOOP && (currentBehavior == null || idispensebehavior != EquipmentDispenseItemBehavior.INSTANCE)) { // Paper - fix possible StackOverflowError
                     idispensebehavior.dispense(pointer, eventStack);
                     return true;
                 }