PaperMC/nms-patches/EntityItem.patch

--- a/net/minecraft/server/EntityItem.java
+++ b/net/minecraft/server/EntityItem.java
@@ -5,6 +5,10 @@
 import java.util.Objects;
 import java.util.UUID;
 import javax.annotation.Nullable;
+// CraftBukkit start
+import org.bukkit.event.entity.EntityPickupItemEvent;
+import org.bukkit.event.player.PlayerPickupItemEvent;
+// CraftBukkit end
 
 public class EntityItem extends Entity {
 
@@ -15,6 +19,7 @@
     private UUID thrower;
     private UUID owner;
     public final float b;
+    private int lastTick = MinecraftServer.currentTick - 1; // CraftBukkit
 
     public EntityItem(EntityTypes<? extends EntityItem> entitytypes, World world) {
         super(entitytypes, world);
@@ -50,9 +55,12 @@
             this.die();
         } else {
             super.tick();
-            if (this.pickupDelay > 0 && this.pickupDelay != 32767) {
-                --this.pickupDelay;
-            }
+            // CraftBukkit start - Use wall time for pickup and despawn timers
+            int elapsedTicks = MinecraftServer.currentTick - this.lastTick;
+            if (this.pickupDelay != 32767) this.pickupDelay -= elapsedTicks;
+            if (this.age != -32768) this.age += elapsedTicks;
+            this.lastTick = MinecraftServer.currentTick;
+            // CraftBukkit end
 
             this.lastX = this.locX();
             this.lastY = this.locY();
@@ -108,9 +116,11 @@
                 }
             }
 
+            /* CraftBukkit start - moved up
             if (this.age != -32768) {
                 ++this.age;
             }
+            // CraftBukkit end */
 
             this.impulse |= this.aJ();
             if (!this.world.isClientSide) {
@@ -122,6 +132,12 @@
             }
 
             if (!this.world.isClientSide && this.age >= 6000) {
+                // CraftBukkit start - fire ItemDespawnEvent
+                if (org.bukkit.craftbukkit.event.CraftEventFactory.callItemDespawnEvent(this).isCancelled()) {
+                    this.age = 0;
+                    return;
+                }
+                // CraftBukkit end
                 this.die();
             }
 
@@ -197,10 +213,11 @@
     private static void a(EntityItem entityitem, ItemStack itemstack, ItemStack itemstack1) {
         ItemStack itemstack2 = a(itemstack, itemstack1, 64);
 
-        entityitem.setItemStack(itemstack2);
+        if (!itemstack2.isEmpty()) entityitem.setItemStack(itemstack2); // CraftBukkit - don't set empty stacks
     }
 
     private static void a(EntityItem entityitem, ItemStack itemstack, EntityItem entityitem1, ItemStack itemstack1) {
+        if (org.bukkit.craftbukkit.event.CraftEventFactory.callItemMergeEvent(entityitem1, entityitem).isCancelled()) return; // CraftBukkit
         a(entityitem, itemstack, itemstack1);
         entityitem.pickupDelay = Math.max(entityitem.pickupDelay, entityitem1.pickupDelay);
         entityitem.age = Math.min(entityitem.age, entityitem1.age);
@@ -224,6 +241,11 @@
         } else if (!this.getItemStack().getItem().a(damagesource)) {
             return false;
         } else {
+            // CraftBukkit start
+            if (org.bukkit.craftbukkit.event.CraftEventFactory.handleNonLivingEntityDamageEvent(this, damagesource, f)) {
+                return false;
+            }
+            // CraftBukkit end
             this.velocityChanged();
             this.f = (int) ((float) this.f - f);
             if (this.f <= 0) {
@@ -285,6 +307,46 @@
             Item item = itemstack.getItem();
             int i = itemstack.getCount();
 
+            // CraftBukkit start - fire PlayerPickupItemEvent
+            int canHold = entityhuman.inventory.canHold(itemstack);
+            int remaining = i - canHold;
+
+            if (this.pickupDelay <= 0 && canHold > 0) {
+                itemstack.setCount(canHold);
+                // Call legacy event
+                PlayerPickupItemEvent playerEvent = new PlayerPickupItemEvent((org.bukkit.entity.Player) entityhuman.getBukkitEntity(), (org.bukkit.entity.Item) this.getBukkitEntity(), remaining);
+                playerEvent.setCancelled(!entityhuman.canPickUpLoot);
+                this.world.getServer().getPluginManager().callEvent(playerEvent);
+                if (playerEvent.isCancelled()) {
+                    itemstack.setCount(i); // SPIGOT-5294 - restore count
+                    return;
+                }
+
+                // Call newer event afterwards
+                EntityPickupItemEvent entityEvent = new EntityPickupItemEvent((org.bukkit.entity.Player) entityhuman.getBukkitEntity(), (org.bukkit.entity.Item) this.getBukkitEntity(), remaining);
+                entityEvent.setCancelled(!entityhuman.canPickUpLoot);
+                this.world.getServer().getPluginManager().callEvent(entityEvent);
+                if (entityEvent.isCancelled()) {
+                    itemstack.setCount(i); // SPIGOT-5294 - restore count
+                    return;
+                }
+
+                // Update the ItemStack if it was changed in the event
+                ItemStack current = this.getItemStack();
+                if (!itemstack.equals(current)) {
+                    itemstack = current;
+                } else {
+                    itemstack.setCount(canHold + remaining); // = i
+                }
+
+                // Possibly < 0; fix here so we do not have to modify code below
+                this.pickupDelay = 0;
+            } else if (this.pickupDelay == 0) {
+                // ensure that the code below isn't triggered if canHold says we can't pick the items up
+                this.pickupDelay = -1;
+            }
+            // CraftBukkit end
+
             if (this.pickupDelay == 0 && (this.owner == null || this.owner.equals(entityhuman.getUniqueID())) && entityhuman.inventory.pickup(itemstack)) {
                 entityhuman.receive(this, i);
                 if (itemstack.isEmpty()) {
@@ -328,7 +390,9 @@
     }
 
     public void setItemStack(ItemStack itemstack) {
+        com.google.common.base.Preconditions.checkArgument(!itemstack.isEmpty(), "Cannot drop air"); // CraftBukkit
         this.getDataWatcher().set(EntityItem.ITEM, itemstack);
+        this.getDataWatcher().markDirty(EntityItem.ITEM); // CraftBukkit - SPIGOT-4591, must mark dirty
     }
 
     @Override