Paper/patches/server/0383-Fix-numerous-item-duplication-issues-and-teleport-is.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 numerous item duplication issues 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 eed16b541a9c39ed4697e783612e6f7b7ff23b70..1d2dd9b8ae43f22d875cb530130118df247b87dc 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -2457,11 +2457,12 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
         } 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(this.level(), this.getX(), this.getY() + (double) yOffset, this.getZ(), stack);
+            ItemEntity entityitem = new ItemEntity(this.level(), this.getX(), this.getY() + (double) yOffset, this.getZ(), stack.copy()); // Paper - copy so we can destroy original
+            stack.setCount(0); // Paper - destroy this item - if this ever leaks due to game bugs, ensure it doesn't dupe
 
             entityitem.setDefaultPickUpDelay();
             // CraftBukkit start
@@ -3263,6 +3264,12 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
     @Nullable
     public Entity teleportTo(ServerLevel worldserver, Vec3 location) {
         // CraftBukkit end
+        // Paper start - fix bad state entities causing dupes
+        if (!this.isAlive() || !this.valid) {
+            LOGGER.warn("Illegal Entity Teleport " + this + " to " + worldserver + ":" + location, new Throwable());
+            return null;
+        }
+        // Paper end
         if (this.level() instanceof ServerLevel && !this.isRemoved()) {
             this.level().getProfiler().push("changeDimension");
             // CraftBukkit start
@@ -3289,6 +3296,11 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
                 // CraftBukkit end
 
                 this.level().getProfiler().popPush("reloading");
+                // Paper start - Change lead drop timing to prevent dupe
+                if (this instanceof Mob) {
+                    ((Mob) this).dropLeash(true, true); // Paper drop lead
+                }
+                // Paper end
                 Entity entity = this.getType().create(worldserver);
 
                 if (entity != null) {
@@ -3302,10 +3314,6 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
                     // CraftBukkit start - Forward the CraftEntity to the new entity
                     this.getBukkitEntity().setHandle(entity);
                     entity.bukkitEntity = this.getBukkitEntity();
-
-                    if (this instanceof Mob) {
-                        ((Mob) this).dropLeash(true, false); // Unleash to prevent duping of leads.
-                    }
                     // CraftBukkit end
                 }
 
@@ -3426,7 +3434,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
     }
 
     public boolean canChangeDimensions() {
-        return !this.isPassenger() && !this.isVehicle();
+        return !this.isPassenger() && !this.isVehicle() && isAlive() && valid; // Paper
     }
 
     public float getBlockExplosionResistance(Explosion explosion, BlockGetter world, BlockPos pos, BlockState blockState, FluidState fluidState, float max) {
diff --git a/src/main/java/net/minecraft/world/entity/LivingEntity.java b/src/main/java/net/minecraft/world/entity/LivingEntity.java
index 4edf7a989f12cae065977d1f529e856a7d3a932b..f01a5ba97d391292192100b6cd7fa018cdeb7e05 100644
--- a/src/main/java/net/minecraft/world/entity/LivingEntity.java
+++ b/src/main/java/net/minecraft/world/entity/LivingEntity.java
@@ -1711,9 +1711,9 @@ public abstract class LivingEntity extends Entity implements Attackable {
                 // Paper start
                 org.bukkit.event.entity.EntityDeathEvent deathEvent = this.dropAllDeathLoot(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 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) {
@@ -1814,8 +1814,13 @@ public abstract class LivingEntity extends Entity implements Attackable {
             this.dropCustomDeathLoot(source, i, flag);
             this.clearEquipmentSlots = prev; // Paper
         }
-        // CraftBukkit start - Call death event
-        org.bukkit.event.entity.EntityDeathEvent deathEvent = CraftEventFactory.callEntityDeathEvent(this, 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, this.drops, () -> {
+            final LivingEntity entityliving = this.getKillCredit();
+            if (this.deathScore >= 0 && entityliving != null) {
+                entityliving.awardKillScore(this, this.deathScore, source);
+            }
+        }); // 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 86c08e36779af6f85932c1c346c54594f543db0d..7e996a527a632a2b382f5eea6df6be839a7a0ef4 100644
--- a/src/main/java/net/minecraft/world/entity/decoration/ArmorStand.java
+++ b/src/main/java/net/minecraft/world/entity/decoration/ArmorStand.java
@@ -637,7 +637,7 @@ public class ArmorStand extends LivingEntity {
         for (i = 0; i < this.handItems.size(); ++i) {
             itemstack = (ItemStack) this.handItems.get(i);
             if (!itemstack.isEmpty()) {
-                drops.add(org.bukkit.craftbukkit.inventory.CraftItemStack.asBukkitCopy(itemstack)); // CraftBukkit - add to drops
+                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);
             }
         }
@@ -645,7 +645,7 @@ public class ArmorStand extends LivingEntity {
         for (i = 0; i < this.armorItems.size(); ++i) {
             itemstack = (ItemStack) this.armorItems.get(i);
             if (!itemstack.isEmpty()) {
-                drops.add(org.bukkit.craftbukkit.inventory.CraftItemStack.asBukkitCopy(itemstack)); // CraftBukkit - add to drops
+                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 accf3399f813ad062a3dba6eba99c16afe66045a..1a2f03895f348e4c2620caef74f12cb1f41dec1b 100644
--- a/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java
+++ b/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java
@@ -868,6 +868,11 @@ public class CraftEventFactory {
     }
 
     public static EntityDeathEvent callEntityDeathEvent(net.minecraft.world.entity.LivingEntity victim, List<org.bukkit.inventory.ItemStack> drops) {
+        // Paper start
+        return CraftEventFactory.callEntityDeathEvent(victim, drops, com.google.common.util.concurrent.Runnables.doNothing());
+    }
+    public static EntityDeathEvent callEntityDeathEvent(net.minecraft.world.entity.LivingEntity victim, List<org.bukkit.inventory.ItemStack> drops, Runnable lootCheck) {
+        // Paper end
         CraftLivingEntity entity = (CraftLivingEntity) victim.getBukkitEntity();
         EntityDeathEvent event = new EntityDeathEvent(entity, drops, victim.getExpReward());
         populateFields(victim, event); // Paper - make cancellable
@@ -881,11 +886,13 @@ 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;