Paper/patches/server/0344-Fix-item-duplication-and-teleport-issues.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sat, 25 Apr 2020 06:46:35 -0400
Subject: [PATCH] Fix item duplication and teleport issues

This notably fixes the newest "Donkey Dupe", but also fixes a lot
of dupe bugs in general around nether portals and entity world transfer

We also fix item duplication generically by anytime we clone an item
to drop it on the ground, destroy the source item.

This avoid an itemstack ever existing twice in the world state pre
clean up stage.

So even if something NEW comes up, it would be impossible to drop the
same item twice because the source was destroyed.

diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index 5b8e264098f1b713de15f714bae59d3efda365cf..4faba83eb73e0d313e9131794962b727f7628a50 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -2630,11 +2630,12 @@ public abstract class Entity implements SyncedDataHolder, Nameable, EntityAccess
         } else {
             // CraftBukkit start - Capture drops for death event
             if (this instanceof net.minecraft.world.entity.LivingEntity && !((net.minecraft.world.entity.LivingEntity) this).forceDrops) {
-                ((net.minecraft.world.entity.LivingEntity) this).drops.add(org.bukkit.craftbukkit.inventory.CraftItemStack.asBukkitCopy(stack));
+                ((net.minecraft.world.entity.LivingEntity) this).drops.add(org.bukkit.craftbukkit.inventory.CraftItemStack.asCraftMirror(stack)); // Paper - mirror so we can destroy it later
                 return null;
             }
             // CraftBukkit end
             ItemEntity entityitem = new ItemEntity(world, this.getX(), this.getY() + (double) yOffset, this.getZ(), stack);
+            stack.setCount(0); // Paper - destroy this item - if this ever leaks due to game bugs, ensure it doesn't dupe
 
             entityitem.setDefaultPickUpDelay();
             // CraftBukkit start
@@ -3462,6 +3463,12 @@ public abstract class Entity implements SyncedDataHolder, Nameable, EntityAccess
     public Entity teleport(TeleportTransition teleportTarget) {
         Level world = this.level();
 
+        // Paper start - Fix item duplication and teleport issues
+        if (!this.isAlive() || !this.valid) {
+            LOGGER.warn("Illegal Entity Teleport " + this + " to " + teleportTarget.newLevel() + ":" + teleportTarget.pos(), new Throwable());
+            return null;
+        }
+        // Paper end - Fix item duplication and teleport issues
         if (world instanceof ServerLevel worldserver) {
             if (!this.isRemoved()) {
                 // CraftBukkit start
@@ -3550,6 +3557,11 @@ public abstract class Entity implements SyncedDataHolder, Nameable, EntityAccess
             gameprofilerfiller.pop();
             return null;
         } else {
+            // Paper start - Fix item duplication and teleport issues
+            if (this instanceof Leashable leashable) {
+                leashable.dropLeash(true, true); // Paper drop lead
+            }
+            // Paper end - Fix item duplication and teleport issues
             entity.restoreFrom(this);
             this.removeAfterChangingDimensions();
             // CraftBukkit start - Forward the CraftEntity to the new entity
@@ -3662,6 +3674,7 @@ public abstract class Entity implements SyncedDataHolder, Nameable, EntityAccess
     }
 
     public boolean canTeleport(Level from, Level to) {
+        if (!this.isAlive() || !this.valid) return false; // Paper - Fix item duplication and teleport issues
         if (from.dimension() == Level.END && to.dimension() == Level.OVERWORLD) {
             Iterator iterator = this.getPassengers().iterator();
 
diff --git a/src/main/java/net/minecraft/world/entity/LivingEntity.java b/src/main/java/net/minecraft/world/entity/LivingEntity.java
index 68e5f6f7013d6a014b9014d945cf3f7dc7a37cb2..65909e0a8f8b68f9a4dacefda9069c8263a96ada 100644
--- a/src/main/java/net/minecraft/world/entity/LivingEntity.java
+++ b/src/main/java/net/minecraft/world/entity/LivingEntity.java
@@ -1767,9 +1767,9 @@ public abstract class LivingEntity extends Entity implements Attackable {
                 // Paper start
                 org.bukkit.event.entity.EntityDeathEvent deathEvent = this.dropAllDeathLoot(worldserver, damageSource);
                 if (deathEvent == null || !deathEvent.isCancelled()) {
-                    if (this.deathScore >= 0 && entityliving != null) {
-                        entityliving.awardKillScore(this, this.deathScore, damageSource);
-                    }
+                    // if (this.deathScore >= 0 && entityliving != null) { // Paper - Fix item duplication and teleport issues; moved to be run earlier in #dropAllDeathLoot before destroying the drop items in CraftEventFactory#callEntityDeathEvent
+                    //     entityliving.awardKillScore(this, this.deathScore, damageSource);
+                    // }
                     // Paper start - clear equipment if event is not cancelled
                     if (this instanceof Mob) {
                         for (EquipmentSlot slot : this.clearedEquipmentSlots) {
@@ -1863,8 +1863,13 @@ public abstract class LivingEntity extends Entity implements Attackable {
             this.dropCustomDeathLoot(world, damageSource, flag);
             this.clearEquipmentSlots = prev; // Paper
         }
-        // CraftBukkit start - Call death event
-        org.bukkit.event.entity.EntityDeathEvent deathEvent = CraftEventFactory.callEntityDeathEvent(this, damageSource, this.drops); // Paper
+        // CraftBukkit start - Call death event // Paper start - call advancement triggers with correct entity equipment
+        org.bukkit.event.entity.EntityDeathEvent deathEvent = CraftEventFactory.callEntityDeathEvent(this, damageSource, this.drops, () -> {
+            final LivingEntity entityliving = this.getKillCredit();
+            if (this.deathScore >= 0 && entityliving != null) {
+                entityliving.awardKillScore(this, this.deathScore, damageSource);
+            }
+        }); // Paper end
         this.postDeathDropItems(deathEvent); // Paper
         this.drops = new ArrayList<>();
         // CraftBukkit end
diff --git a/src/main/java/net/minecraft/world/entity/decoration/ArmorStand.java b/src/main/java/net/minecraft/world/entity/decoration/ArmorStand.java
index e20565cf256aacd012a1722c5ebbf9016bc82e42..59fbfe8de2dc5ec020dd61a5e446b0b6f67d76e4 100644
--- a/src/main/java/net/minecraft/world/entity/decoration/ArmorStand.java
+++ b/src/main/java/net/minecraft/world/entity/decoration/ArmorStand.java
@@ -633,7 +633,7 @@ public class ArmorStand extends LivingEntity {
         for (i = 0; i < this.handItems.size(); ++i) {
             itemstack = (ItemStack) this.handItems.get(i);
             if (!itemstack.isEmpty()) {
-                this.drops.add(org.bukkit.craftbukkit.inventory.CraftItemStack.asBukkitCopy(itemstack)); // CraftBukkit - add to drops
+                this.drops.add(org.bukkit.craftbukkit.inventory.CraftItemStack.asCraftMirror(itemstack)); // CraftBukkit - add to drops // Paper - mirror so we can destroy it later - though this call site was safe
                 this.handItems.set(i, ItemStack.EMPTY);
             }
         }
@@ -641,7 +641,7 @@ public class ArmorStand extends LivingEntity {
         for (i = 0; i < this.armorItems.size(); ++i) {
             itemstack = (ItemStack) this.armorItems.get(i);
             if (!itemstack.isEmpty()) {
-                this.drops.add(org.bukkit.craftbukkit.inventory.CraftItemStack.asBukkitCopy(itemstack)); // CraftBukkit - add to drops
+                this.drops.add(org.bukkit.craftbukkit.inventory.CraftItemStack.asCraftMirror(itemstack)); // CraftBukkit - add to drops // Paper - mirror so we can destroy it later - though this call site was safe
                 this.armorItems.set(i, ItemStack.EMPTY);
             }
         }
diff --git a/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java b/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java
index 41f23ce732b6e90828b1bbda7f4b3470cd462c4a..0b9c96105bea9a0d1af17b7ecf4479d3596faa80 100644
--- a/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java
+++ b/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java
@@ -903,6 +903,11 @@ public class CraftEventFactory {
     }
 
     public static EntityDeathEvent callEntityDeathEvent(net.minecraft.world.entity.LivingEntity victim, DamageSource damageSource, List<org.bukkit.inventory.ItemStack> drops) {
+        // Paper start
+        return CraftEventFactory.callEntityDeathEvent(victim, damageSource, drops, com.google.common.util.concurrent.Runnables.doNothing());
+    }
+    public static EntityDeathEvent callEntityDeathEvent(net.minecraft.world.entity.LivingEntity victim, DamageSource damageSource, List<org.bukkit.inventory.ItemStack> drops, Runnable lootCheck) {
+        // Paper end
         CraftLivingEntity entity = (CraftLivingEntity) victim.getBukkitEntity();
         CraftDamageSource bukkitDamageSource = new CraftDamageSource(damageSource);
         CraftWorld world = (CraftWorld) entity.getWorld();
@@ -917,11 +922,13 @@ public class CraftEventFactory {
         playDeathSound(victim, event);
         // Paper end
         victim.expToDrop = event.getDroppedExp();
+        lootCheck.run(); // Paper - advancement triggers before destroying items
 
         for (org.bukkit.inventory.ItemStack stack : event.getDrops()) {
             if (stack == null || stack.getType() == Material.AIR || stack.getAmount() == 0) continue;
 
-            world.dropItem(entity.getLocation(), stack);
+            world.dropItem(entity.getLocation(), stack); // Paper - note: dropItem already clones due to this being bukkit -> NMS
+            if (stack instanceof CraftItemStack) stack.setAmount(0); // Paper - destroy this item - if this ever leaks due to game bugs, ensure it doesn't dupe, but don't nuke bukkit stacks of manually added items
         }
 
         return event;