PaperMC/Spigot-Server-Patches/0392-Don-t-load-Chunks-from-Hoppers-and-other-things.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Thu, 3 Nov 2016 20:28:12 -0400
Subject: [PATCH] Don't load Chunks from Hoppers and other things

Hoppers call this to I guess "get the primary side" of a double sided chest.

If the double sided chest crosses chunk lines, it causes the chunk to load.
This will end up causing sync chunk loads, which will unload with Chunk GC,
only to be reloaded again the next tick.

This of course is undesirable, so just return the loaded side as "primary"
and treat it as a single chest if the other sides are unloaded

diff --git a/src/main/java/net/minecraft/world/level/block/DoubleBlockFinder.java b/src/main/java/net/minecraft/world/level/block/DoubleBlockFinder.java
index d51f89fed6129c4b37ef63971f8f61dc14e8032d..efa98e87eead036246348f3915b401f0f52f2242 100644
--- a/src/main/java/net/minecraft/world/level/block/DoubleBlockFinder.java
+++ b/src/main/java/net/minecraft/world/level/block/DoubleBlockFinder.java
@@ -29,7 +29,12 @@ public class DoubleBlockFinder {
                 return new DoubleBlockFinder.Result.Single<>(s0);
             } else {
                 BlockPosition blockposition1 = blockposition.shift((EnumDirection) function1.apply(iblockdata));
-                IBlockData iblockdata1 = generatoraccess.getType(blockposition1);
+                // Paper start
+                IBlockData iblockdata1 = generatoraccess.getTypeIfLoaded(blockposition1);
+                if (iblockdata1 == null) {
+                    return new DoubleBlockFinder.Result.Single<>(s0);
+                }
+                // Paper end
 
                 if (iblockdata1.a(iblockdata.getBlock())) {
                     DoubleBlockFinder.BlockType doubleblockfinder_blocktype1 = (DoubleBlockFinder.BlockType) function.apply(iblockdata1);