From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Newwind <support@newwindserver.com>
Date: Sat, 27 Jul 2024 11:09:37 +0200
Subject: [PATCH] Paper PR: Prevent zombie reinforcements loading chunks

Original license: GPLv3
Original project: https://github.com/PaperMC/Paper
Paper pull request: https://github.com/PaperMC/Paper/pull/11175

When a zombie calls reinforcements it tries to spawn them in a random location within a 40 block radius of the zombie,
before spawning, it checks isSpawnPositionOk() for the position which loads the block to check if a mob can spawn on said block.
This patch ensures the chunk at the random location is loaded before trying to spawn the reinforcement zombie in it.

diff --git a/src/main/java/net/minecraft/world/entity/monster/Zombie.java b/src/main/java/net/minecraft/world/entity/monster/Zombie.java
index aa1fd8f2fba06292e93aba279cf18640b6909add..49c37853a0c26cef749a8a5ef4130554c0319ad9 100644
--- a/src/main/java/net/minecraft/world/entity/monster/Zombie.java
+++ b/src/main/java/net/minecraft/world/entity/monster/Zombie.java
@@ -384,6 +384,12 @@ public class Zombie extends Monster {
                     BlockPos blockposition = new BlockPos(i1, j1, k1);
                     EntityType<?> entitytypes = entityzombie.getType();
 
+                    // Paper start - Prevent reinforcement checks from loading chunks
+                    if (this.level().getChunkIfLoadedImmediately(blockposition.getX() >> 4, blockposition.getZ() >> 4) == null) {
+                        continue;
+                    }
+                    // Paper end - Prevent reinforcement checks from loading chunks
+
                     if (SpawnPlacements.isSpawnPositionOk(entitytypes, this.level(), blockposition) && SpawnPlacements.checkSpawnRules(entitytypes, worldserver, MobSpawnType.REINFORCEMENT, blockposition, this.level().random)) {
                         entityzombie.setPos((double) i1, (double) j1, (double) k1);
                         if (!this.level().hasNearbyAlivePlayerThatAffectsSpawning((double) i1, (double) j1, (double) k1, 7.0D) && this.level().isUnobstructed(entityzombie) && this.level().noCollision((Entity) entityzombie) && !this.level().containsAnyLiquid(entityzombie.getBoundingBox())) { // Paper - Affects Spawning API