PaperMC/patches/server/0946-Fix-possible-StackOverflowError-for-some-dispenses.patch

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 7826e2a52da47914aca39fef958b8f398a2ff937..0c0b8a49b3342cd015381c6a93fab23c32cd32e6 100644
--- a/src/main/java/net/minecraft/core/dispenser/DispenseItemBehavior.java
+++ b/src/main/java/net/minecraft/core/dispenser/DispenseItemBehavior.java
@@ -239,7 +239,7 @@ 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 != ArmorItem.DISPENSE_ITEM_BEHAVIOR) {
+                        if (idispensebehavior != DispenseItemBehavior.NOOP && idispensebehavior != this) { // Paper - fix possible StackOverflowError
                             idispensebehavior.dispense(pointer, eventStack);
                             return stack;
                         }
@@ -295,7 +295,7 @@ 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 != ArmorItem.DISPENSE_ITEM_BEHAVIOR) {
+                    if (idispensebehavior != DispenseItemBehavior.NOOP && idispensebehavior != this) { // Paper - fix possible StackOverflowError
                         idispensebehavior.dispense(pointer, eventStack);
                         return stack;
                     }
@@ -369,7 +369,7 @@ 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 != ArmorItem.DISPENSE_ITEM_BEHAVIOR) {
+                    if (idispensebehavior != DispenseItemBehavior.NOOP && idispensebehavior != this) { // Paper - fix possible StackOverflowError
                         idispensebehavior.dispense(pointer, eventStack);
                         return stack;
                     }
@@ -690,7 +690,7 @@ public interface DispenseItemBehavior {
         OptionalDispenseItemBehavior dispensebehaviormaybe1 = new OptionalDispenseItemBehavior() {
             @Override
             protected ItemStack execute(BlockSource pointer, ItemStack stack) {
-                this.setSuccess(ArmorItem.dispenseArmor(pointer, stack));
+                this.setSuccess(ArmorItem.dispenseArmor(pointer, stack, this)); // Paper - fix possible StackOverflowError
                 return stack;
             }
         };
@@ -744,7 +744,7 @@ public interface DispenseItemBehavior {
                     stack.shrink(1);
                     this.setSuccess(true);
                 } else {
-                    this.setSuccess(ArmorItem.dispenseArmor(pointer, stack));
+                    this.setSuccess(ArmorItem.dispenseArmor(pointer, stack, this)); // Paper - fix possible StackOverflowError
                 }
 
                 return stack;
@@ -790,7 +790,7 @@ public interface DispenseItemBehavior {
                     stack.shrink(1);
                     this.setSuccess(true);
                 } else {
-                    this.setSuccess(ArmorItem.dispenseArmor(pointer, stack));
+                    this.setSuccess(ArmorItem.dispenseArmor(pointer, stack, this)); // Paper - fix possible StackOverflowError
                 }
 
                 return stack;
@@ -918,7 +918,7 @@ 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 != ArmorItem.DISPENSE_ITEM_BEHAVIOR) {
+                        if (idispensebehavior != DispenseItemBehavior.NOOP && idispensebehavior != this) { // Paper - fix possible StackOverflowError
                             idispensebehavior.dispense(pointer, eventStack);
                             return stack;
                         }
diff --git a/src/main/java/net/minecraft/world/item/ArmorItem.java b/src/main/java/net/minecraft/world/item/ArmorItem.java
index fb518f87cc4ccd810fb32cade2fdd7e09ab0abfc..647a4601deace52f8d855f512a73671f82b4762a 100644
--- a/src/main/java/net/minecraft/world/item/ArmorItem.java
+++ b/src/main/java/net/minecraft/world/item/ArmorItem.java
@@ -39,14 +39,20 @@ public class ArmorItem extends Item implements Equipable {
     public static final DispenseItemBehavior DISPENSE_ITEM_BEHAVIOR = new DefaultDispenseItemBehavior() {
         @Override
         protected ItemStack execute(BlockSource pointer, ItemStack stack) {
-            return ArmorItem.dispenseArmor(pointer, stack) ? stack : super.execute(pointer, stack);
+            return ArmorItem.dispenseArmor(pointer, stack, this) ? stack : super.execute(pointer, stack); // Paper - fix possible StackOverflowError
         }
     };
     protected final ArmorItem.Type type;
     protected final Holder<ArmorMaterial> material;
     private final Supplier<ItemAttributeModifiers> defaultModifiers;
 
+    @Deprecated @io.papermc.paper.annotation.DoNotUse // Paper
     public static boolean dispenseArmor(BlockSource pointer, ItemStack armor) {
+        // Paper start
+        return dispenseArmor(pointer, armor, null);
+    }
+    public static boolean dispenseArmor(BlockSource pointer, ItemStack armor, @javax.annotation.Nullable DispenseItemBehavior currentBehavior) {
+        // Paper end
         BlockPos blockposition = pointer.pos().relative((Direction) pointer.state().getValue(DispenserBlock.FACING));
         List<LivingEntity> list = pointer.level().getEntitiesOfClass(LivingEntity.class, new AABB(blockposition), EntitySelector.NO_SPECTATORS.and(new EntitySelector.MobCanWearArmorEntitySelector(armor)));
 
@@ -77,7 +83,7 @@ public class ArmorItem extends Item implements Equipable {
                 // 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 != ArmorItem.DISPENSE_ITEM_BEHAVIOR) {
+                if (idispensebehavior != DispenseItemBehavior.NOOP && (currentBehavior == null || idispensebehavior != currentBehavior)) { // Paper - fix possible StackOverflowError
                     idispensebehavior.dispense(pointer, eventStack);
                     return true;
                 }