Paper/patches/server/0751-Prevent-entity-loading-causing-async-lookups.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Owen1212055 <23108066+Owen1212055@users.noreply.github.com>
Date: Sun, 6 Mar 2022 11:09:09 -0500
Subject: [PATCH] Prevent entity loading causing async lookups


diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index a9bc659a89009f430105c8524688130a01baaecf..c02181318220d544aca15c030b54650404205519 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -727,6 +727,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
 
     public void baseTick() {
         this.level().getProfiler().push("entityBaseTick");
+        if (firstTick && this instanceof net.minecraft.world.entity.NeutralMob neutralMob) neutralMob.tickInitialPersistentAnger(level); // Paper - Prevent entity loading causing async lookups
         this.feetBlockState = null;
         if (this.isPassenger() && this.getVehicle().isRemoved()) {
             this.stopRiding();
diff --git a/src/main/java/net/minecraft/world/entity/NeutralMob.java b/src/main/java/net/minecraft/world/entity/NeutralMob.java
index fa64c7baa7587f2cfe80b78ed83be011239618cf..47d5a0928f3c86d71f851738bfe7beedc98cfbb3 100644
--- a/src/main/java/net/minecraft/world/entity/NeutralMob.java
+++ b/src/main/java/net/minecraft/world/entity/NeutralMob.java
@@ -42,18 +42,11 @@ public interface NeutralMob {
                 UUID uuid = nbt.getUUID("AngryAt");
 
                 this.setPersistentAngerTarget(uuid);
-                Entity entity = ((ServerLevel) world).getEntity(uuid);
-
-                if (entity != null) {
-                    if (entity instanceof Mob) {
-                        this.setLastHurtByMob((Mob) entity);
-                    }
-
-                    if (entity.getType() == EntityType.PLAYER) {
-                        this.setLastHurtByPlayer((Player) entity);
-                    }
-
-                }
+                // Paper - Prevent entity loading causing async lookups; Moved diff to separate method
+                // If this entity already survived its first tick, e.g. is loaded and ticked in sync, actively
+                // tick the initial persistent anger.
+                // If not, let the first tick on the baseTick call the method later down the line.
+                if (this instanceof Entity entity && !entity.firstTick) this.tickInitialPersistentAnger(world);
             }
         }
     }
@@ -127,4 +120,27 @@ public interface NeutralMob {
 
     @Nullable
     LivingEntity getTarget();
+
+    // Paper start - Prevent entity loading causing async lookups
+    // Update last hurt when ticking
+    default void tickInitialPersistentAnger(Level level) {
+        UUID target = getPersistentAngerTarget();
+        if (target == null) {
+            return;
+        }
+
+        Entity entity = ((ServerLevel) level).getEntity(target);
+
+        if (entity != null) {
+            if (entity instanceof Mob) {
+                this.setLastHurtByMob((Mob) entity);
+            }
+
+            if (entity.getType() == EntityType.PLAYER) {
+                this.setLastHurtByPlayer((Player) entity);
+            }
+
+        }
+    }
+    // Paper end - Prevent entity loading causing async lookups
 }