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/server/DoubleBlockFinder.java b/src/main/java/net/minecraft/server/DoubleBlockFinder.java
index 3cb6e60895637405f163c1fac731926ee2cf0d2c..7a16a3e0e209b254db0ec15212d51fab71c17f60 100644
--- a/src/main/java/net/minecraft/server/DoubleBlockFinder.java
+++ b/src/main/java/net/minecraft/server/DoubleBlockFinder.java
@@ -21,8 +21,12 @@ 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 - don't load chunks if the other side of the chest is in unloaded chunk
+                IBlockData iblockdata1 = generatoraccess.getTypeIfLoaded(blockposition1);
+                if (iblockdata1 == null) {
+                    return new DoubleBlockFinder.Result.Single<>(s0);
+                }
+                // Paper end
                 if (iblockdata1.getBlock() == iblockdata.getBlock()) {
                     DoubleBlockFinder.BlockType doubleblockfinder_blocktype1 = (DoubleBlockFinder.BlockType) function.apply(iblockdata1);
 
