PaperMC/paper-server/nms-patches/net/minecraft/world/item/ItemArmor.patch

--- a/net/minecraft/world/item/ItemArmor.java
+++ b/net/minecraft/world/item/ItemArmor.java
@@ -31,6 +31,12 @@
 import net.minecraft.world.level.block.BlockDispenser;
 import net.minecraft.world.phys.AxisAlignedBB;
 
+// CraftBukkit start
+import org.bukkit.craftbukkit.block.CraftBlock;
+import org.bukkit.craftbukkit.inventory.CraftItemStack;
+import org.bukkit.event.block.BlockDispenseArmorEvent;
+// CraftBukkit end
+
 public class ItemArmor extends Item implements Equipable {
 
     private static final EnumMap<ItemArmor.a, UUID> ARMOR_MODIFIER_UUID_PER_TYPE = (EnumMap) SystemUtils.make(new EnumMap(ItemArmor.a.class), (enummap) -> {
@@ -60,8 +66,34 @@
             EntityLiving entityliving = (EntityLiving) list.get(0);
             EnumItemSlot enumitemslot = EntityInsentient.getEquipmentSlotForItem(itemstack);
             ItemStack itemstack1 = itemstack.split(1);
+            // CraftBukkit start
+            World world = sourceblock.level();
+            org.bukkit.block.Block block = CraftBlock.at(world, sourceblock.pos());
+            CraftItemStack craftItem = CraftItemStack.asCraftMirror(itemstack1);
 
-            entityliving.setItemSlot(enumitemslot, itemstack1);
+            BlockDispenseArmorEvent event = new BlockDispenseArmorEvent(block, craftItem.clone(), (org.bukkit.craftbukkit.entity.CraftLivingEntity) entityliving.getBukkitEntity());
+            if (!BlockDispenser.eventFired) {
+                world.getCraftServer().getPluginManager().callEvent(event);
+            }
+
+            if (event.isCancelled()) {
+                itemstack.grow(1);
+                return false;
+            }
+
+            if (!event.getItem().equals(craftItem)) {
+                itemstack.grow(1);
+                // Chain to handler for new item
+                ItemStack eventStack = CraftItemStack.asNMSCopy(event.getItem());
+                IDispenseBehavior idispensebehavior = (IDispenseBehavior) BlockDispenser.DISPENSER_REGISTRY.get(eventStack.getItem());
+                if (idispensebehavior != IDispenseBehavior.NOOP && idispensebehavior != ItemArmor.DISPENSE_ITEM_BEHAVIOR) {
+                    idispensebehavior.dispense(sourceblock, eventStack);
+                    return true;
+                }
+            }
+
+            entityliving.setItemSlot(enumitemslot, CraftItemStack.asNMSCopy(event.getItem()));
+            // CraftBukkit end
             if (entityliving instanceof EntityInsentient) {
                 ((EntityInsentient) entityliving).setDropChance(enumitemslot, 2.0F);
                 ((EntityInsentient) entityliving).setPersistenceRequired();