craftbukkit/nms-patches/net/minecraft/util/SpawnUtil.patch

--- a/net/minecraft/util/SpawnUtil.java
+++ b/net/minecraft/util/SpawnUtil.java
@@ -21,6 +21,12 @@
     public SpawnUtil() {}
 
     public static <T extends EntityInsentient> Optional<T> trySpawnMob(EntityTypes<T> entitytypes, EntitySpawnReason entityspawnreason, WorldServer worldserver, BlockPosition blockposition, int i, int j, int k, SpawnUtil.a spawnutil_a, boolean flag) {
+        // CraftBukkit start
+        return trySpawnMob(entitytypes, entityspawnreason, worldserver, blockposition, i, j, k, spawnutil_a, flag, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.DEFAULT);
+    }
+
+    public static <T extends EntityInsentient> Optional<T> trySpawnMob(EntityTypes<T> entitytypes, EntitySpawnReason entityspawnreason, WorldServer worldserver, BlockPosition blockposition, int i, int j, int k, SpawnUtil.a spawnutil_a, boolean flag, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason reason) {
+        // CraftBukkit end
         BlockPosition.MutableBlockPosition blockposition_mutableblockposition = blockposition.mutable();
 
         for (int l = 0; l < i; ++l) {
@@ -29,16 +35,17 @@
 
             blockposition_mutableblockposition.setWithOffset(blockposition, i1, k, j1);
             if (worldserver.getWorldBorder().isWithinBounds((BlockPosition) blockposition_mutableblockposition) && moveToPossibleSpawnPosition(worldserver, k, blockposition_mutableblockposition, spawnutil_a) && (!flag || worldserver.noCollision(entitytypes.getSpawnAABB((double) blockposition_mutableblockposition.getX() + 0.5D, (double) blockposition_mutableblockposition.getY(), (double) blockposition_mutableblockposition.getZ() + 0.5D)))) {
-                T t0 = (EntityInsentient) entitytypes.create(worldserver, (Consumer) null, blockposition_mutableblockposition, entityspawnreason, false, false);
+                T t0 = entitytypes.create(worldserver, (Consumer<T>) null, blockposition_mutableblockposition, entityspawnreason, false, false); // CraftBukkit - decompile error
 
                 if (t0 != null) {
                     if (t0.checkSpawnRules(worldserver, entityspawnreason) && t0.checkSpawnObstruction(worldserver)) {
-                        worldserver.addFreshEntityWithPassengers(t0);
+                        worldserver.addFreshEntityWithPassengers(t0, reason); // CraftBukkit
+                        if (t0.isRemoved()) return Optional.empty(); // CraftBukkit
                         t0.playAmbientSound();
                         return Optional.of(t0);
                     }
 
-                    t0.discard();
+                    t0.discard(null); // CraftBukkit - add Bukkit remove cause
                 }
             }
         }