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/com/destroystokyo/paper/PaperWorldConfig.java b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
index c45493e88bf7e8811be2759ff9ac19e3fe9d938a..384cb363eed794551bee6b0ec11ba1be92a3d7ac 100644
--- a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
+++ b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
@@ -464,6 +464,16 @@ public class PaperWorldConfig {
         maxAutoSaveChunksPerTick = getInt("max-auto-save-chunks-per-tick", 24);
     }
 
+    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)");
+        }
+    }
+
     public boolean antiXray;
     public EngineMode engineMode;
     public int maxChunkSectionIndex;
diff --git a/src/main/java/net/minecraft/world/level/NaturalSpawner.java b/src/main/java/net/minecraft/world/level/NaturalSpawner.java
index e23875ae07c23fed1161ea070e63bbc3a30168a0..0fb69f9194078e5e05e36ed909eb48424b6465b4 100644
--- a/src/main/java/net/minecraft/world/level/NaturalSpawner.java
+++ b/src/main/java/net/minecraft/world/level/NaturalSpawner.java
@@ -79,6 +79,13 @@ public final class NaturalSpawner {
             MobCategory enumcreaturetype = entity.getType().getCategory();
 
             if (enumcreaturetype != MobCategory.MISC) {
+                // Paper start - Only count natural spawns
+                if (!entity.level.paperConfig.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();
                 long j = ChunkPos.asLong(blockposition.getX() >> 4, blockposition.getZ() >> 4);