Paper/patches/server/0918-Restore-vanilla-entity-drops-behavior.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Jake Potrebic <jake.m.potrebic@gmail.com>
Date: Tue, 22 Mar 2022 09:34:41 -0700
Subject: [PATCH] Restore vanilla entity drops behavior

Instead of just tracking the itemstacks, this tracks with it, the
action to take with that itemstack to apply the correct logic
on dropping the item instead of generalizing it for all dropped
items like CB does.

diff --git a/src/main/java/net/minecraft/server/level/ServerPlayer.java b/src/main/java/net/minecraft/server/level/ServerPlayer.java
index f568fa18ddcb1a1cd060c469edd6db45431bb53c..191dfbd0f15c3a21278f3c4f9ce29f1698e0836c 100644
--- a/src/main/java/net/minecraft/server/level/ServerPlayer.java
+++ b/src/main/java/net/minecraft/server/level/ServerPlayer.java
@@ -978,20 +978,20 @@ public class ServerPlayer extends net.minecraft.world.entity.player.Player {
         if (this.isRemoved()) {
             return;
         }
-        java.util.List<org.bukkit.inventory.ItemStack> loot = new java.util.ArrayList<>(this.getInventory().getContainerSize());
+        List<DefaultDrop> loot = new java.util.ArrayList<>(this.getInventory().getContainerSize()); // Paper - Restore vanilla drops behavior
         boolean keepInventory = this.level().getGameRules().getBoolean(GameRules.RULE_KEEPINVENTORY) || this.isSpectator();
 
         if (!keepInventory) {
             for (ItemStack item : this.getInventory().getContents()) {
                 if (!item.isEmpty() && !EnchantmentHelper.has(item, EnchantmentEffectComponents.PREVENT_EQUIPMENT_DROP)) {
-                    loot.add(CraftItemStack.asCraftMirror(item));
+                    loot.add(new DefaultDrop(item, stack -> this.drop(stack, true, false, false))); // Paper - Restore vanilla drops behavior; drop function taken from Inventory#dropAll (don't fire drop event)
                 }
             }
         }
         if (this.shouldDropLoot() && this.level().getGameRules().getBoolean(GameRules.RULE_DOMOBLOOT)) { // Paper - fix player loottables running when mob loot gamerule is false
         // SPIGOT-5071: manually add player loot tables (SPIGOT-5195 - ignores keepInventory rule)
         this.dropFromLootTable(damageSource, this.lastHurtByPlayerTime > 0);
-        this.dropCustomDeathLoot(this.serverLevel(), damageSource, flag);
+        // Paper - Restore vanilla drops behaviour; custom death loot is a noop on server player, remove.
 
         loot.addAll(this.drops);
         this.drops.clear(); // SPIGOT-5188: make sure to clear
diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index 24aacf9997c9ea0bd68ef3803f4a3ee4a920ab44..363fe1aff439983199f5137547cef9516fbab2a8 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -2563,6 +2563,25 @@ public abstract class Entity implements SyncedDataHolder, Nameable, EntityAccess
 
     @Nullable
     public ItemEntity spawnAtLocation(ItemStack stack, float yOffset) {
+        // Paper start - Restore vanilla drops behavior
+        return this.spawnAtLocation(stack, yOffset, null);
+    }
+    public record DefaultDrop(Item item, org.bukkit.inventory.ItemStack stack, @Nullable java.util.function.Consumer<ItemStack> dropConsumer) {
+        public DefaultDrop(final ItemStack stack, final java.util.function.Consumer<ItemStack> dropConsumer) {
+            this(stack.getItem(), org.bukkit.craftbukkit.inventory.CraftItemStack.asCraftMirror(stack), dropConsumer);
+        }
+
+        public void runConsumer(final org.bukkit.World fallbackWorld, final Location fallbackLoc) {
+            if (this.dropConsumer == null || org.bukkit.craftbukkit.inventory.CraftItemType.bukkitToMinecraft(this.stack.getType()) != this.item) {
+                fallbackWorld.dropItem(fallbackLoc, this.stack);
+            } else {
+                this.dropConsumer.accept(org.bukkit.craftbukkit.inventory.CraftItemStack.asNMSCopy(this.stack));
+            }
+        }
+    }
+    @Nullable
+    public ItemEntity spawnAtLocation(ItemStack stack, float yOffset, @Nullable java.util.function.Consumer<? super ItemEntity> delayedAddConsumer) {
+        // Paper end - Restore vanilla drops behavior
         if (stack.isEmpty()) {
             return null;
         } else if (this.level().isClientSide) {
@@ -2570,14 +2589,21 @@ 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.asCraftMirror(stack)); // Paper - mirror so we can destroy it later
+                // Paper start - Restore vanilla drops behavior
+                ((net.minecraft.world.entity.LivingEntity) this).drops.add(new net.minecraft.world.entity.Entity.DefaultDrop(stack, itemStack -> {
+                    ItemEntity itemEntity = new ItemEntity(this.level, this.getX(), this.getY() + (double) yOffset, this.getZ(), itemStack); // stack is copied before consumer
+                    itemEntity.setDefaultPickUpDelay();
+                    this.level.addFreshEntity(itemEntity);
+                    if (delayedAddConsumer != null) delayedAddConsumer.accept(itemEntity);
+                }));
+                // Paper end - Restore vanilla drops behavior
                 return null;
             }
             // CraftBukkit end
             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();
+            entityitem.setDefaultPickUpDelay(); // Paper - diff on change (in dropConsumer)
             // Paper start - Call EntityDropItemEvent
             return this.spawnAtLocation(entityitem);
         }
diff --git a/src/main/java/net/minecraft/world/entity/LivingEntity.java b/src/main/java/net/minecraft/world/entity/LivingEntity.java
index 2cbb4ff57117382791eefa4881fc0b328c77d58a..3def6b7919484c330bc1c4aea1a8e2c6ad21f999 100644
--- a/src/main/java/net/minecraft/world/entity/LivingEntity.java
+++ b/src/main/java/net/minecraft/world/entity/LivingEntity.java
@@ -278,7 +278,7 @@ public abstract class LivingEntity extends Entity implements Attackable {
     protected float appliedScale;
     // CraftBukkit start
     public int expToDrop;
-    public ArrayList<org.bukkit.inventory.ItemStack> drops = new ArrayList<org.bukkit.inventory.ItemStack>();
+    public ArrayList<DefaultDrop> drops = new ArrayList<>(); // Paper - Restore vanilla drops behavior
     public final org.bukkit.craftbukkit.attribute.CraftAttributeMap craftAttributes;
     public boolean collides = true;
     public Set<UUID> collidableExemptions = new HashSet<>();
diff --git a/src/main/java/net/minecraft/world/entity/boss/wither/WitherBoss.java b/src/main/java/net/minecraft/world/entity/boss/wither/WitherBoss.java
index 1b49090a466bc74d9e5f2815314955b6dfbb83dc..62271e74399a827a488159da234465ef18e15e6e 100644
--- a/src/main/java/net/minecraft/world/entity/boss/wither/WitherBoss.java
+++ b/src/main/java/net/minecraft/world/entity/boss/wither/WitherBoss.java
@@ -538,10 +538,9 @@ public class WitherBoss extends Monster implements PowerableMob, RangedAttackMob
     @Override
     protected void dropCustomDeathLoot(ServerLevel world, DamageSource source, boolean causedByPlayer) {
         super.dropCustomDeathLoot(world, source, causedByPlayer);
-        ItemEntity entityitem = this.spawnAtLocation((ItemLike) Items.NETHER_STAR);
-
+        ItemEntity entityitem = this.spawnAtLocation(new net.minecraft.world.item.ItemStack(Items.NETHER_STAR), 0, ItemEntity::setExtendedLifetime); // Paper - Restore vanilla drops behavior; spawnAtLocation returns null so modify the item entity with a consumer
         if (entityitem != null) {
-            entityitem.setExtendedLifetime();
+            entityitem.setExtendedLifetime(); // Paper - diff on change
         }
 
     }
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 5bcb9a53ebebeef4bd6ec2458df4b63002ebd804..2f398750bfee5758ad8b1367b6fc14364e4de776 100644
--- a/src/main/java/net/minecraft/world/entity/decoration/ArmorStand.java
+++ b/src/main/java/net/minecraft/world/entity/decoration/ArmorStand.java
@@ -621,7 +621,7 @@ public class ArmorStand extends LivingEntity {
         ItemStack itemstack = new ItemStack(Items.ARMOR_STAND);
 
         itemstack.set(DataComponents.CUSTOM_NAME, this.getCustomName());
-        this.drops.add(org.bukkit.craftbukkit.inventory.CraftItemStack.asBukkitCopy(itemstack)); // CraftBukkit - add to drops
+        this.drops.add(new DefaultDrop(itemstack, stack -> Block.popResource(this.level(), this.blockPosition(), stack))); // CraftBukkit - add to drops // Paper - Restore vanilla drops behavior
         return this.brokenByAnything(world, damageSource); // Paper
     }
 
@@ -635,7 +635,7 @@ 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.asCraftMirror(itemstack)); // CraftBukkit - add to drops // Paper - mirror so we can destroy it later - though this call site was safe
+                this.drops.add(new DefaultDrop(itemstack, stack -> Block.popResource(this.level(), this.blockPosition().above(), stack))); // CraftBukkit - add to drops // Paper - Restore vanilla drops behavior; mirror so we can destroy it later - though this call site was safe & spawn drops correctly
                 this.handItems.set(i, ItemStack.EMPTY);
             }
         }
@@ -643,7 +643,7 @@ 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.asCraftMirror(itemstack)); // CraftBukkit - add to drops // Paper - mirror so we can destroy it later - though this call site was safe
+                this.drops.add(new DefaultDrop(itemstack, stack -> Block.popResource(this.level(), this.blockPosition().above(), stack))); // CraftBukkit - add to drops // Paper - Restore vanilla drops behavior; mirror so we can destroy it later - though this call site was safe & spawn drops correctly
                 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 e079e8f4078078d737a9d554dbcd2568b1a1f9eb..1d958323eccd4cf5e369e99e32d2f1dec0959591 100644
--- a/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java
+++ b/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java
@@ -966,18 +966,24 @@ public class CraftEventFactory {
     }
 
     public static EntityDeathEvent callEntityDeathEvent(net.minecraft.world.entity.LivingEntity victim, DamageSource damageSource) {
-        return CraftEventFactory.callEntityDeathEvent(victim, damageSource, new ArrayList<org.bukkit.inventory.ItemStack>(0));
+        return CraftEventFactory.callEntityDeathEvent(victim, damageSource, new ArrayList<>(0)); // Paper - Restore vanilla drops behavior
     }
 
-    public static EntityDeathEvent callEntityDeathEvent(net.minecraft.world.entity.LivingEntity victim, DamageSource damageSource, List<org.bukkit.inventory.ItemStack> drops) {
+    public static EntityDeathEvent callEntityDeathEvent(net.minecraft.world.entity.LivingEntity victim, DamageSource damageSource, List<Entity.DefaultDrop> drops) { // Paper - Restore vanilla drops behavior
         // 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) {
+
+    private static final java.util.function.Function<org.bukkit.inventory.ItemStack, Entity.DefaultDrop> FROM_FUNCTION = stack -> {
+        if (stack == null) return null;
+        return new Entity.DefaultDrop(CraftItemType.bukkitToMinecraft(stack.getType()), stack, null);
+    };
+
+    public static EntityDeathEvent callEntityDeathEvent(net.minecraft.world.entity.LivingEntity victim, DamageSource damageSource, List<Entity.DefaultDrop> drops, Runnable lootCheck) { // Paper
         // Paper end
         CraftLivingEntity entity = (CraftLivingEntity) victim.getBukkitEntity();
         CraftDamageSource bukkitDamageSource = new CraftDamageSource(damageSource);
-        EntityDeathEvent event = new EntityDeathEvent(entity, bukkitDamageSource, drops, victim.getExpReward(damageSource.getEntity()));
+        EntityDeathEvent event = new EntityDeathEvent(entity, bukkitDamageSource, new io.papermc.paper.util.TransformingRandomAccessList<>(drops, Entity.DefaultDrop::stack, FROM_FUNCTION), victim.getExpReward(damageSource.getEntity())); // Paper - Restore vanilla drops behavior
         populateFields(victim, event); // Paper - make cancellable
         CraftWorld world = (CraftWorld) entity.getWorld();
         Bukkit.getServer().getPluginManager().callEvent(event);
@@ -991,20 +997,24 @@ public class CraftEventFactory {
         victim.expToDrop = event.getDroppedExp();
         lootCheck.run(); // Paper - advancement triggers before destroying items
 
-        for (org.bukkit.inventory.ItemStack stack : event.getDrops()) {
+        // Paper start - Restore vanilla drops behavior
+        for (Entity.DefaultDrop drop : drops) {
+            if (drop == null) continue;
+            final org.bukkit.inventory.ItemStack stack = drop.stack();
+            // Paper end - Restore vanilla drops behavior
             if (stack == null || stack.getType() == Material.AIR || stack.getAmount() == 0) continue;
 
-            world.dropItem(entity.getLocation(), stack); // Paper - note: dropItem already clones due to this being bukkit -> NMS
+            drop.runConsumer(world, entity.getLocation()); // Paper - Restore vanilla drops behavior
             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;
     }
 
-    public static PlayerDeathEvent callPlayerDeathEvent(ServerPlayer victim, DamageSource damageSource, List<org.bukkit.inventory.ItemStack> drops, net.kyori.adventure.text.Component deathMessage, boolean keepInventory) { // Paper - Adventure
+    public static PlayerDeathEvent callPlayerDeathEvent(ServerPlayer victim, DamageSource damageSource, List<Entity.DefaultDrop> drops, net.kyori.adventure.text.Component deathMessage, boolean keepInventory) { // Paper - Adventure & Restore vanilla drops behavior
         CraftPlayer entity = victim.getBukkitEntity();
         CraftDamageSource bukkitDamageSource = new CraftDamageSource(damageSource);
-        PlayerDeathEvent event = new PlayerDeathEvent(entity, bukkitDamageSource, drops, victim.getExpReward(damageSource.getEntity()), 0, deathMessage);
+        PlayerDeathEvent event = new PlayerDeathEvent(entity, bukkitDamageSource, new io.papermc.paper.util.TransformingRandomAccessList<>(drops, Entity.DefaultDrop::stack, FROM_FUNCTION), victim.getExpReward(damageSource.getEntity()), 0, deathMessage); // Paper - Restore vanilla drops behavior
         event.setKeepInventory(keepInventory);
         event.setKeepLevel(victim.keepLevel); // SPIGOT-2222: pre-set keepLevel
         populateFields(victim, event); // Paper - make cancellable
@@ -1022,10 +1032,14 @@ public class CraftEventFactory {
         victim.expToDrop = event.getDroppedExp();
         victim.newExp = event.getNewExp();
 
-        for (org.bukkit.inventory.ItemStack stack : event.getDrops()) {
+        // Paper start - Restore vanilla drops behavior
+        for (Entity.DefaultDrop drop : drops) {
+            if (drop == null) continue;
+            final org.bukkit.inventory.ItemStack stack = drop.stack();
+            // Paper end - Restore vanilla drops behavior
             if (stack == null || stack.getType() == Material.AIR) continue;
 
-            victim.drop(CraftItemStack.asNMSCopy(stack), true, false, false); // SPIGOT-7800, SPIGOT-7801: Vanilla Behaviour for dropped items
+            drop.runConsumer(entity.getWorld(), entity.getLocation()); // Paper - Restore vanilla drops behavior
         }
 
         return event;