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 bc136276cad4e87d8658072b2f62f608670f39ca..d676eaad8179cdeae410038e58ddafe0fe541ccc 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -2730,6 +2730,9 @@ 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());