From 07bc019d7485fc75328f148ca9498a5216a3f657 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/com/destroystokyo/paper/PaperWorldConfig.java b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
index a70a64070e..bfd690eccd 100644
--- a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
+++ b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
@@ -598,4 +598,14 @@ public class PaperWorldConfig {
             log("Using vanilla redstone algorithm.");
         }
     }
+
+    public boolean countAllMobsForSpawning = false;
+    private void countAllMobsForSpawning() {
+        countAllMobsForSpawning = getBoolean("count-all-mobs-for-spawning", false);
+        if (countAllMobsForSpawning) {
+            log("Counting all mobs for spawning. Mob farms may reduce natural spawns elsewhere in world.");
+        } else {
+            log("Using improved mob spawn limits (Only Natural Spawns impact spawn limits for more natural spawns)");
+        }
+    }
 }
diff --git a/src/main/java/com/destroystokyo/paper/PaperWorldEntityList.java b/src/main/java/com/destroystokyo/paper/PaperWorldEntityList.java
index a10a5bc138..a5a63f8004 100644
--- a/src/main/java/com/destroystokyo/paper/PaperWorldEntityList.java
+++ b/src/main/java/com/destroystokyo/paper/PaperWorldEntityList.java
@@ -7,6 +7,7 @@ import net.minecraft.server.IAnimal;
 import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.World;
 import net.minecraft.server.WorldServer;
+import org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason;
 
 import java.util.ArrayList;
 import java.util.Collection;
@@ -90,7 +91,12 @@ public class PaperWorldEntityList extends ArrayList<Entity> {
     }
 
     public void updateEntityCount(Entity entity, int amt) {
-        if (!(entity instanceof IAnimal)) return;
+        // Only count natural spawns so that mob
+        if (!(entity instanceof IAnimal) || (
+            !world.paperConfig.countAllMobsForSpawning &&
+            entity.spawnReason != SpawnReason.NATURAL &&
+            entity.spawnReason != SpawnReason.CHUNK_GEN
+        )) return;
 
         if (entity instanceof EntityInsentient) {
             EntityInsentient entityinsentient = (EntityInsentient) entity;
-- 
2.21.0