From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Wed, 12 Sep 2018 21:12:57 -0400
Subject: [PATCH] Prevent mob spawning from loading/generating chunks

also prevents if out of world border bounds

diff --git a/src/main/java/net/minecraft/world/level/NaturalSpawner.java b/src/main/java/net/minecraft/world/level/NaturalSpawner.java
index 6ac513d3044fab1cb1ca0b0c7e85ff871d49d572..2503d4691e47083a9d99a38c4ed3f50a2374821a 100644
--- a/src/main/java/net/minecraft/world/level/NaturalSpawner.java
+++ b/src/main/java/net/minecraft/world/level/NaturalSpawner.java
@@ -170,9 +170,9 @@ public final class NaturalSpawner {
         StructureManager structuremanager = world.structureManager();
         ChunkGenerator chunkgenerator = world.getChunkSource().getGenerator();
         int i = pos.getY();
-        BlockState iblockdata = chunk.getBlockState(pos);
+        BlockState iblockdata = world.getBlockStateIfLoadedAndInBounds(pos); // Paper - don't load chunks for mob spawn
 
-        if (!iblockdata.isRedstoneConductor(chunk, pos)) {
+        if (iblockdata != null && !iblockdata.isRedstoneConductor(chunk, pos)) { // Paper - don't load chunks for mob spawn
             BlockPos.MutableBlockPos blockposition_mutableblockposition = new BlockPos.MutableBlockPos();
             int j = 0;
             int k = 0;
@@ -201,7 +201,7 @@ public final class NaturalSpawner {
                             if (entityhuman != null) {
                                 double d2 = entityhuman.distanceToSqr(d0, (double) i, d1);
 
-                                if (NaturalSpawner.isRightDistanceToPlayerAndSpawnPoint(world, chunk, blockposition_mutableblockposition, d2)) {
+                                if (world.isLoadedAndInBounds(blockposition_mutableblockposition) && NaturalSpawner.isRightDistanceToPlayerAndSpawnPoint(world, chunk, blockposition_mutableblockposition, d2)) { // Paper - don't load chunks for mob spawn
                                     if (biomesettingsmobs_c == null) {
                                         Optional<MobSpawnSettings.SpawnerData> optional = NaturalSpawner.getRandomSpawnMobAt(world, structuremanager, chunkgenerator, group, world.random, blockposition_mutableblockposition);