Paper/nms-patches/DispenseBehaviorItem.patch

--- a/net/minecraft/server/DispenseBehaviorItem.java
+++ b/net/minecraft/server/DispenseBehaviorItem.java
@@ -1,5 +1,11 @@
 package net.minecraft.server;
 
+// CraftBukkit start
+import org.bukkit.craftbukkit.inventory.CraftItemStack;
+import org.bukkit.craftbukkit.util.CraftVector;
+import org.bukkit.event.block.BlockDispenseEvent;
+// CraftBukkit end
+
 public class DispenseBehaviorItem implements IDispenseBehavior {
 
     public DispenseBehaviorItem() {}
@@ -18,11 +24,19 @@
         IPosition iposition = BlockDispenser.a(isourceblock);
         ItemStack itemstack1 = itemstack.cloneAndSubtract(1);
 
-        a(isourceblock.getWorld(), itemstack1, 6, enumdirection, iposition);
+        // CraftBukkit start
+        if (!a(isourceblock.getWorld(), itemstack1, 6, enumdirection, isourceblock)) {
+            itemstack.add(1);
+        }
+        // CraftBukkit end
         return itemstack;
     }
 
-    public static void a(World world, ItemStack itemstack, int i, EnumDirection enumdirection, IPosition iposition) {
+    // CraftBukkit start - void -> boolean return, IPosition -> ISourceBlock last argument
+    public static boolean a(World world, ItemStack itemstack, int i, EnumDirection enumdirection, ISourceBlock isourceblock) {
+        if (itemstack.isEmpty()) return true;
+        IPosition iposition = BlockDispenser.a(isourceblock);
+        // CraftBukkit end
         double d0 = iposition.getX();
         double d1 = iposition.getY();
         double d2 = iposition.getZ();
@@ -37,7 +51,39 @@
         double d3 = world.random.nextDouble() * 0.1D + 0.2D;
 
         entityitem.setMot(world.random.nextGaussian() * 0.007499999832361937D * (double) i + (double) enumdirection.getAdjacentX() * d3, world.random.nextGaussian() * 0.007499999832361937D * (double) i + 0.20000000298023224D, world.random.nextGaussian() * 0.007499999832361937D * (double) i + (double) enumdirection.getAdjacentZ() * d3);
+
+        // CraftBukkit start
+        org.bukkit.block.Block block = world.getWorld().getBlockAt(isourceblock.getBlockPosition().getX(), isourceblock.getBlockPosition().getY(), isourceblock.getBlockPosition().getZ());
+        CraftItemStack craftItem = CraftItemStack.asCraftMirror(itemstack);
+
+        BlockDispenseEvent event = new BlockDispenseEvent(block, craftItem.clone(), CraftVector.toBukkit(entityitem.getMot()));
+        if (!BlockDispenser.eventFired) {
+            world.getServer().getPluginManager().callEvent(event);
+        }
+
+        if (event.isCancelled()) {
+            return false;
+        }
+
+        entityitem.setItemStack(CraftItemStack.asNMSCopy(event.getItem()));
+        entityitem.setMot(CraftVector.toNMS(event.getVelocity()));
+
+        if (!event.getItem().getType().equals(craftItem.getType())) {
+            // 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.getClass() != DispenseBehaviorItem.class) {
+                idispensebehavior.dispense(isourceblock, eventStack);
+            } else {
+                world.addEntity(entityitem);
+            }
+            return false;
+        }
+
         world.addEntity(entityitem);
+
+        return true;
+        // CraftBukkit end
     }
 
     protected void a(ISourceBlock isourceblock) {