From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sun, 24 Mar 2019 00:24:52 -0400
Subject: [PATCH] Entity#getEntitySpawnReason

Allows you to return the SpawnReason for why an Entity Spawned

Pre existing entities will return NATURAL if it was a non
persistenting Living Entity, SPAWNER for spawners,
or DEFAULT since data was not stored.

diff --git a/src/main/java/net/minecraft/server/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
index 5abcae55b2dc37eea514d194803bc9a851f18c25..2950ad995f322570cd647d3217f340327cc3e7c8 100644
--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
+++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
@@ -1185,6 +1185,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
             return true;
         }
         // Paper end
+        if (entity.spawnReason == null) entity.spawnReason = spawnReason; // Paper
         if (entity.isRemoved()) {
             // Paper start
             if (DEBUG_ENTITIES) {
diff --git a/src/main/java/net/minecraft/server/players/PlayerList.java b/src/main/java/net/minecraft/server/players/PlayerList.java
index 25da9e3252154415303db662286e89e3aa7cfcd8..eea7a625fb00af13944b21e1af4bf1804c5ce6d9 100644
--- a/src/main/java/net/minecraft/server/players/PlayerList.java
+++ b/src/main/java/net/minecraft/server/players/PlayerList.java
@@ -342,7 +342,7 @@ public abstract class PlayerList {
             // CraftBukkit start
             ServerLevel finalWorldServer = worldserver1;
             Entity entity = EntityType.loadEntityRecursive(nbttagcompound1.getCompound("Entity"), finalWorldServer, (entity1) -> {
-                return !finalWorldServer.addWithUUID(entity1) ? null : entity1;
+                return !finalWorldServer.addWithUUID(entity1, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.MOUNT) ? null : entity1; // Paper
                 // CraftBukkit end
             });
 
diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index f015b1990a509071b6154a9eb7405fa2cbacb111..aa5fdc74a3b06b8d8b82b86fb4f1469ddd4c629e 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -67,6 +67,8 @@ import net.minecraft.world.InteractionHand;
 import net.minecraft.world.InteractionResult;
 import net.minecraft.world.Nameable;
 import net.minecraft.world.damagesource.DamageSource;
+import net.minecraft.world.entity.animal.AbstractFish;
+import net.minecraft.world.entity.animal.Animal;
 import net.minecraft.world.entity.item.ItemEntity;
 import net.minecraft.world.entity.player.Player;
 import net.minecraft.world.entity.vehicle.Boat;
@@ -165,6 +167,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, i
             }
         }
     };
+    public org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason spawnReason;
     // Paper end
 
     public com.destroystokyo.paper.loottable.PaperLootableInventoryData lootableData; // Paper
@@ -1859,6 +1862,9 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, i
                 }
                 nbt.put("Paper.Origin", this.newDoubleList(origin.getX(), origin.getY(), origin.getZ()));
             }
+            if (spawnReason != null) {
+                nbt.putString("Paper.SpawnReason", spawnReason.name());
+            }
             // Save entity's from mob spawner status
             if (spawnedViaMobSpawner) {
                 nbt.putBoolean("Paper.FromMobSpawner", true);
@@ -2004,6 +2010,26 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, i
             }
 
             spawnedViaMobSpawner = nbt.getBoolean("Paper.FromMobSpawner"); // Restore entity's from mob spawner status
+            if (nbt.contains("Paper.SpawnReason")) {
+                String spawnReasonName = nbt.getString("Paper.SpawnReason");
+                try {
+                    spawnReason = org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.valueOf(spawnReasonName);
+                } catch (Exception ignored) {
+                    LogManager.getLogger().error("Unknown SpawnReason " + spawnReasonName + " for " + this);
+                }
+            }
+            if (spawnReason == null) {
+                if (spawnedViaMobSpawner) {
+                    spawnReason = org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.SPAWNER;
+                } else if (this instanceof Mob && (this instanceof Animal || this instanceof AbstractFish) && !((Mob) this).removeWhenFarAway(0.0)) {
+                    if (!nbt.getBoolean("PersistenceRequired")) {
+                        spawnReason = org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.NATURAL;
+                    }
+                }
+            }
+            if (spawnReason == null) {
+                spawnReason = org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.DEFAULT;
+            }
             // Paper end
 
         } catch (Throwable throwable) {
diff --git a/src/main/java/net/minecraft/world/level/BaseSpawner.java b/src/main/java/net/minecraft/world/level/BaseSpawner.java
index f08c5ae9d41ec9efb627665f5de4dd6165fd0092..30930a24c197c45f2ed86eaf7a150252005e7a37 100644
--- a/src/main/java/net/minecraft/world/level/BaseSpawner.java
+++ b/src/main/java/net/minecraft/world/level/BaseSpawner.java
@@ -179,6 +179,7 @@ public abstract class BaseSpawner {
                             // Spigot End
                         }
                         entity.spawnedViaMobSpawner = true; // Paper
+                        entity.spawnReason = org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.SPAWNER; // Paper
                         flag = true; // Paper
                         // Spigot Start
                         if (org.bukkit.craftbukkit.event.CraftEventFactory.callSpawnerSpawnEvent(entity, pos).isCancelled()) {
diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
index a1812c570215b14e89ce61ebbd78871fa57c9323..d7dabaa5087f87b97a2e66b871fb618918eb568b 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
@@ -1231,5 +1231,10 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
     public boolean fromMobSpawner() {
         return getHandle().spawnedViaMobSpawner;
     }
+
+    @Override
+    public org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason getEntitySpawnReason() {
+        return getHandle().spawnReason;
+    }
     // Paper end
 }