From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: AJMFactsheets <AJMFactsheets@gmail.com>
Date: Wed, 22 Jan 2020 19:52:28 -0600
Subject: [PATCH] Fix items vanishing through end portal

If the Paper configuration option "keep-spawn-loaded" is set to false,
items entering the overworld from the end will spawn at Y = 0.

This is due to logic in the getHighestBlockYAt method in World.java
only searching the heightmap if the chunk is loaded.

Quickly loading the exact world spawn chunk before searching the
heightmap resolves the issue without having to load all spawn chunks.

diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index 32dad0b72ee0d0a1ac30decb0fb52f4399f9f39f..b1495da5fdead24caf9e936a385d97fd2db2a0cc 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -2735,6 +2735,9 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, ne
             BlockPosition blockposition1;
 
             if (flag1) {
+                // Paper start - Ensure spawn chunk is always loaded before calculating Y coordinate
+                this.world.getChunkAtWorldCoords(this.world.getSpawn());
+                // Paper end
                 blockposition1 = WorldServer.a;
             } else {
                 blockposition1 = worldserver.getHighestBlockYAt(HeightMap.Type.MOTION_BLOCKING_NO_LEAVES, worldserver.getSpawn());