PaperMC/Spigot-Server-Patches/0112-Chunk-registration-fixes.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Wed, 21 Sep 2016 22:54:28 -0400
Subject: [PATCH] Chunk registration fixes

World checks and the Chunk Add logic are inconsistent on how Y > 256, < 0, is treated

Keep them consistent

diff --git a/src/main/java/net/minecraft/server/level/WorldServer.java b/src/main/java/net/minecraft/server/level/WorldServer.java
index e008ef98d6902f5e1000da99870b12ae9d61bddb..6137a88e1dc8d19a4e35ad97500dabeddba008a8 100644
--- a/src/main/java/net/minecraft/server/level/WorldServer.java
+++ b/src/main/java/net/minecraft/server/level/WorldServer.java
@@ -847,7 +847,7 @@ public class WorldServer extends World implements GeneratorAccessSeed {
         if (entity.cl()) {
             this.getMethodProfiler().enter("chunkCheck");
             int i = MathHelper.floor(entity.locX() / 16.0D);
-            int j = MathHelper.floor(entity.locY() / 16.0D);
+            int j =  Math.min(15, Math.max(0, MathHelper.floor(entity.locY() / 16.0D))); // Paper - stay consistent with chunk add/remove behavior
             int k = MathHelper.floor(entity.locZ() / 16.0D);
 
             if (!entity.inChunk || entity.chunkX != i || entity.chunkY != j || entity.chunkZ != k) {