From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sun, 24 Mar 2019 01:01:32 -0400
Subject: [PATCH] Only count Natural Spawned mobs towards natural spawn mob
 limit

This resolves the super common complaint about mobs not spawning.

This was ultimately a flaw in the vanilla count algorithim that allows
spawners and other misc mobs to count against the mob limit, which are
not bounded, and can prevent the entire world from spawning new.

I believe Bukkits changes around persistence may of actually made it
worse than vanilla.

This should fully solve all of the issues around it so that only natural
influences natural spawns.

diff --git a/src/main/java/net/minecraft/world/level/NaturalSpawner.java b/src/main/java/net/minecraft/world/level/NaturalSpawner.java
index 9ed7abddf30d298a5abb04974efd1b470d015b09..fe38079d69f3e9987ad5ab077ae09d05017a681a 100644
--- a/src/main/java/net/minecraft/world/level/NaturalSpawner.java
+++ b/src/main/java/net/minecraft/world/level/NaturalSpawner.java
@@ -88,6 +88,13 @@ public final class NaturalSpawner {
             MobCategory enumcreaturetype = entity.getType().getCategory();
 
             if (enumcreaturetype != MobCategory.MISC) {
+                // Paper start - Only count natural spawns
+                if (!entity.level().paperConfig().entities.spawning.countAllMobsForSpawning &&
+                    !(entity.spawnReason == org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.NATURAL ||
+                        entity.spawnReason == org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.CHUNK_GEN)) {
+                    continue;
+                }
+                // Paper end
                 BlockPos blockposition = entity.blockPosition();
 
                 chunkSource.query(ChunkPos.asLong(blockposition), (chunk) -> {