From f77100dc057c84378f22ee9a6f81baef5b45aff9 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/server/Entity.java b/src/main/java/net/minecraft/server/Entity.java
index a550a81bea..0e7641a3c5 100644
--- a/src/main/java/net/minecraft/server/Entity.java
+++ b/src/main/java/net/minecraft/server/Entity.java
@@ -2610,6 +2610,11 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, Ke
 
         if (blockposition == null) { // CraftBukkit
             if (dimensionmanager1.getType() == DimensionManager.THE_END && dimensionmanager == DimensionManager.OVERWORLD) { // CraftBukkit
+                // Paper start - Ensure spawn chunk is always loaded before calculating Y coordinate
+                if (!worldserver1.isLoaded(worldserver1.getSpawn())) {
+                    worldserver1.getChunkAtWorldCoords(worldserver1.getSpawn());
+                }
+                // Paper end
                 // CraftBukkit start
                 EntityPortalEvent event = CraftEventFactory.callEntityPortalEvent(this, worldserver1, worldserver1.getHighestBlockYAt(HeightMap.Type.MOTION_BLOCKING_NO_LEAVES, worldserver1.getSpawn()), 0);
                 if (event == null) {
-- 
2.25.1