From 78aed292564c995e7aec1bcfd4fe1c89acb58e31 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Fri, 28 Sep 2018 21:49:53 -0400
Subject: [PATCH] Fix issues with entity loss due to unloaded chunks

Vanilla has risk of losing entities by causing them to be
removed from all chunks if they try to move into an unloaded chunk.

This pretty much means high chance this entity will be lost in this scenario.

There is another case that adding an entity to the world can fail if
the chunk isn't loaded.

Lots of the server is designed around addEntity never expecting to fail for these reasons,
nor is it really logical.

This change ensures the chunks are always loaded when entities are
added to the world, or a valid entity moves between chunks.

diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
index 739448d8b..e88e265bf 100644
--- a/src/main/java/net/minecraft/server/World.java
+++ b/src/main/java/net/minecraft/server/World.java
@@ -1081,7 +1081,7 @@ public abstract class World implements IEntityAccess, GeneratorAccess, IIBlockAc
 
         int i = MathHelper.floor(entity.locX / 16.0D);
         int j = MathHelper.floor(entity.locZ / 16.0D);
-        boolean flag = entity.attachedToPlayer;
+        boolean flag = true; // Paper - always load chunks for entity adds
 
         // Paper start - Set origin location when the entity is being added to the world
         if (entity.origin == null) {
@@ -1585,7 +1585,7 @@ public abstract class World implements IEntityAccess, GeneratorAccess, IIBlockAc
                 this.getChunkAt(entity.chunkX, entity.chunkZ).a(entity, entity.chunkY);
             }
 
-            if (!entity.bN() && !this.isChunkLoaded(i, k, true)) {
+            if (!entity.valid && !entity.bN() && !this.isChunkLoaded(i, k, true)) { // Paper - always load chunks to register valid entities location
                 entity.inChunk = false;
             } else {
                 this.getChunkAt(i, k).a(entity);
-- 
2.21.0