Paper/Spigot-Server-Patches/0428-Fix-items-vanishing-through-end-portal.patch

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/server/Entity.java b/src/main/java/net/minecraft/server/Entity.java
index 067420f19559f66860a2859a33e7d11786273315..599bcabd14a7f234d2cf7f2755d76413e7d0ceac 100644
--- a/src/main/java/net/minecraft/server/Entity.java
+++ b/src/main/java/net/minecraft/server/Entity.java
@@ -2611,6 +2611,11 @@ 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) {