Paper/nms-patches/DispenseBehaviorShulkerBox.patch

--- a/net/minecraft/server/DispenseBehaviorShulkerBox.java
+++ b/net/minecraft/server/DispenseBehaviorShulkerBox.java
@@ -1,5 +1,10 @@
 package net.minecraft.server;
 
+// CraftBukkit start
+import org.bukkit.craftbukkit.inventory.CraftItemStack;
+import org.bukkit.event.block.BlockDispenseEvent;
+// CraftBukkit end
+
 public class DispenseBehaviorShulkerBox extends DispenseBehaviorMaybe {
 
     public DispenseBehaviorShulkerBox() {}
@@ -14,6 +19,30 @@
             BlockPosition blockposition = isourceblock.getBlockPosition().shift(enumdirection);
             EnumDirection enumdirection1 = isourceblock.getWorld().isEmpty(blockposition.down()) ? enumdirection : EnumDirection.UP;
 
+            // CraftBukkit start
+            org.bukkit.block.Block bukkitBlock = isourceblock.getWorld().getWorld().getBlockAt(isourceblock.getBlockPosition().getX(), isourceblock.getBlockPosition().getY(), isourceblock.getBlockPosition().getZ());
+            CraftItemStack craftItem = CraftItemStack.asCraftMirror(itemstack);
+
+            BlockDispenseEvent event = new BlockDispenseEvent(bukkitBlock, craftItem.clone(), new org.bukkit.util.Vector(blockposition.getX(), blockposition.getY(), blockposition.getZ()));
+            if (!BlockDispenser.eventFired) {
+                isourceblock.getWorld().getServer().getPluginManager().callEvent(event);
+            }
+
+            if (event.isCancelled()) {
+                return itemstack;
+            }
+
+            if (!event.getItem().equals(craftItem)) {
+                // Chain to handler for new item
+                ItemStack eventStack = CraftItemStack.asNMSCopy(event.getItem());
+                IDispenseBehavior idispensebehavior = (IDispenseBehavior) BlockDispenser.REGISTRY.get(eventStack.getItem());
+                if (idispensebehavior != IDispenseBehavior.NONE && idispensebehavior != this) {
+                    idispensebehavior.dispense(isourceblock, eventStack);
+                    return itemstack;
+                }
+            }
+            // CraftBukkit end
+
             this.dispensed = ((ItemBlock) item).a((BlockActionContext) (new BlockActionContextDirectional(isourceblock.getWorld(), blockposition, enumdirection, itemstack, enumdirection1))) == EnumInteractionResult.SUCCESS;
             if (this.dispensed) {
                 itemstack.subtract(1);