From a186f2f777fab6c95fb2351c8c5cfa3937cf01fd 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/ChunkRegionLoader.java b/src/main/java/net/minecraft/server/ChunkRegionLoader.java
index 51df075b4..53ae5d509 100644
--- a/src/main/java/net/minecraft/server/ChunkRegionLoader.java
+++ b/src/main/java/net/minecraft/server/ChunkRegionLoader.java
@@ -1131,7 +1131,7 @@ public class ChunkRegionLoader implements IChunkLoader, IAsyncChunkSaver {
             while (iterator.hasNext()) {
                 Entity entity1 = (Entity) iterator.next();
 
-                a(entity1, generatoraccess);
+                a(entity1, generatoraccess, reason); // Paper
             }
         }
 
diff --git a/src/main/java/net/minecraft/server/Entity.java b/src/main/java/net/minecraft/server/Entity.java
index 3c2e79b14..0c58a4766 100644
--- a/src/main/java/net/minecraft/server/Entity.java
+++ b/src/main/java/net/minecraft/server/Entity.java
@@ -63,6 +63,7 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, Ke
         }
     };
     List<Entity> entitySlice = null;
+    public org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason spawnReason;
     // Paper end
     static boolean isLevelAtLeast(NBTTagCompound tag, int level) {
         return tag.hasKey("Bukkit.updateLevel") && tag.getInt("Bukkit.updateLevel") >= level;
@@ -1671,6 +1672,9 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, Ke
             if (origin != null) {
                 nbttagcompound.set("Paper.Origin", this.createList(origin.getX(), origin.getY(), origin.getZ()));
             }
+            if (spawnReason != null) {
+                nbttagcompound.setString("Paper.SpawnReason", spawnReason.name());
+            }
             // Save entity's from mob spawner status
             if (spawnedViaMobSpawner) {
                 nbttagcompound.setBoolean("Paper.FromMobSpawner", true);
@@ -1824,6 +1828,26 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, Ke
             }
 
             spawnedViaMobSpawner = nbttagcompound.getBoolean("Paper.FromMobSpawner"); // Restore entity's from mob spawner status
+            if (nbttagcompound.hasKey("Paper.SpawnReason")) {
+                String spawnReasonName = nbttagcompound.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 EntityInsentient && this instanceof IAnimal && !((EntityInsentient) this).isTypeNotPersistent()) {
+                    if (!nbttagcompound.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/server/MobSpawnerAbstract.java b/src/main/java/net/minecraft/server/MobSpawnerAbstract.java
index b2d2de7f8..af38e5396 100644
--- a/src/main/java/net/minecraft/server/MobSpawnerAbstract.java
+++ b/src/main/java/net/minecraft/server/MobSpawnerAbstract.java
@@ -117,7 +117,7 @@ public abstract class MobSpawnerAbstract {
                         }
                     }
                     // Paper end
-                    Entity entity = ChunkRegionLoader.a(nbttagcompound, world, d3, d4, d5, false);
+                    Entity entity = ChunkRegionLoader.spawnEntity(nbttagcompound, world, d3, d4, d5, false, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.SPAWNER); // Paper
 
                     if (entity == null) {
                         this.i();
diff --git a/src/main/java/net/minecraft/server/PlayerList.java b/src/main/java/net/minecraft/server/PlayerList.java
index b1630137e..df416e3b5 100644
--- a/src/main/java/net/minecraft/server/PlayerList.java
+++ b/src/main/java/net/minecraft/server/PlayerList.java
@@ -196,7 +196,7 @@ public abstract class PlayerList {
 
         if (nbttagcompound != null && nbttagcompound.hasKeyOfType("RootVehicle", 10)) {
             NBTTagCompound nbttagcompound1 = nbttagcompound.getCompound("RootVehicle");
-            Entity entity = ChunkRegionLoader.a(nbttagcompound1.getCompound("Entity"), worldserver, true);
+            Entity entity = ChunkRegionLoader.spawnEntity(nbttagcompound1.getCompound("Entity"), worldserver, true, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.MOUNT); // Paper
 
             if (entity != null) {
                 UUID uuid = nbttagcompound1.a("Attach");
diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
index 0624848cc..9faed9303 100644
--- a/src/main/java/net/minecraft/server/World.java
+++ b/src/main/java/net/minecraft/server/World.java
@@ -1084,6 +1084,7 @@ public abstract class World implements IEntityAccess, GeneratorAccess, IIBlockAc
 
     public boolean addEntity(Entity entity, SpawnReason spawnReason) { // Changed signature, added SpawnReason
         // Paper start
+        if (entity.spawnReason == null) entity.spawnReason = spawnReason;
         if (regionLimited != null) {
             return regionLimited.addEntity(entity, spawnReason);
         }
diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
index d4a8fb16b..51f70c5ee 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
@@ -845,5 +845,9 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
     public boolean fromMobSpawner() {
         return getHandle().spawnedViaMobSpawner;
     }
+
+    public org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason getEntitySpawnReason() {
+        return getHandle().spawnReason;
+    }
     // Paper end
 }
-- 
2.21.0