[12.x] Fix Closure serialization error in automatic relation loading (#55345)

* Fix Serialization of 'Closure' is not allowed error in automatic relation loading

* Fix tests

Author: litvinchuk

src/Illuminate/Database/Eloquent/Model.php

@@ -2501,6 +2501,7 @@ public function __sleep()
 
         $this->classCastCache = [];
         $this->attributeCastCache = [];
+        $this->relationAutoloadCallback = null;
 
         return array_keys(get_object_vars($this));
     }
@@ -2515,5 +2516,9 @@ public function __wakeup()
         $this->bootIfNotBooted();
 
         $this->initializeTraits();
+
+        if (static::isAutomaticallyEagerLoadingRelationships()) {
+            $this->withRelationshipAutoloading();
+        }
     }
 }

tests/Integration/Database/EloquentModelRelationAutoloadTest.php

@@ -86,6 +86,31 @@ public function testRelationAutoloadForSingleModel()
         $this->assertTrue($post->comments[0]->relationLoaded('likes'));
     }
 
+    public function testRelationAutoloadWithSerialization()
+    {
+        Model::automaticallyEagerLoadRelationships();
+
+        $post = Post::create();
+        $comment1 = $post->comments()->create(['parent_id' => null]);
+        $comment2 = $post->comments()->create(['parent_id' => $comment1->id]);
+        $comment2->likes()->create();
+
+        DB::enableQueryLog();
+
+        $likes = [];
+
+        $post = serialize($post);
+        $post = unserialize($post);
+
+        foreach ($post->comments as $comment) {
+            $likes = array_merge($likes, $comment->likes->all());
+        }
+
+        $this->assertCount(2, DB::getQueryLog());
+
+        Model::automaticallyEagerLoadRelationships(false);
+    }
+
     public function testRelationAutoloadVariousNestedMorphRelations()
     {
         tap(Post::create(), function ($post) {