[8.x] Add support for attaching existing model instances in factories

src/Illuminate/Database/Eloquent/Factories/BelongsToManyRelationship.php

@@ -10,7 +10,7 @@ class BelongsToManyRelationship
     /**
      * The related factory instance.
      *
-     * @var \Illuminate\Database\Eloquent\Factories\Factory
+     * @var \Illuminate\Database\Eloquent\Factories\Factory|\Illuminate\Support\Collection|\Illuminate\Database\Eloquent\Model
      */
     protected $factory;
 
@@ -31,12 +31,12 @@ class BelongsToManyRelationship
     /**
      * Create a new attached relationship definition.
      *
-     * @param  \Illuminate\Database\Eloquent\Factories\Factory  $factory
+     * @param  \Illuminate\Database\Eloquent\Factories\Factory|\Illuminate\Support\Collection|\Illuminate\Database\Eloquent\Model  $factory
      * @param  callable|array  $pivot
      * @param  string  $relationship
      * @return void
      */
-    public function __construct(Factory $factory, $pivot, $relationship)
+    public function __construct($factory, $pivot, $relationship)
     {
         $this->factory = $factory;
         $this->pivot = $pivot;
@@ -51,7 +51,7 @@ public function __construct(Factory $factory, $pivot, $relationship)
      */
     public function createFor(Model $model)
     {
-        Collection::wrap($this->factory->create([], $model))->each(function ($attachable) use ($model) {
+        Collection::wrap($this->factory instanceof Factory ? $this->factory->create([], $model) : $this->factory)->each(function ($attachable) use ($model) {
             $model->{$this->relationship}()->attach(
                 $attachable,
                 is_callable($this->pivot) ? call_user_func($this->pivot, $model) : $this->pivot

src/Illuminate/Database/Eloquent/Factories/BelongsToRelationship.php

@@ -10,7 +10,7 @@ class BelongsToRelationship
     /**
      * The related factory instance.
      *
-     * @var \Illuminate\Database\Eloquent\Factories\Factory
+     * @var \Illuminate\Database\Eloquent\Factories\Factory|\Illuminate\Database\Eloquent\Model
      */
     protected $factory;
 
@@ -31,11 +31,11 @@ class BelongsToRelationship
     /**
      * Create a new "belongs to" relationship definition.
      *
-     * @param  \Illuminate\Database\Eloquent\Factories\Factory  $factory
+     * @param  \Illuminate\Database\Eloquent\Factories\Factory|\Illuminate\Database\Eloquent\Model  $factory
      * @param  string  $relationship
      * @return void
      */
-    public function __construct(Factory $factory, $relationship)
+    public function __construct($factory, $relationship)
     {
         $this->factory = $factory;
         $this->relationship = $relationship;
@@ -52,7 +52,7 @@ public function attributesFor(Model $model)
         $relationship = $model->{$this->relationship}();
 
         return $relationship instanceof MorphTo ? [
-            $relationship->getMorphType() => $this->factory->newModel()->getMorphClass(),
+            $relationship->getMorphType() => $this->factory instanceof Factory ? $this->factory->newModel()->getMorphClass() : $this->factory->getMorphClass(),
             $relationship->getForeignKeyName() => $this->resolver($relationship->getOwnerKeyName()),
         ] : [
             $relationship->getForeignKeyName() => $this->resolver($relationship->getOwnerKeyName()),
@@ -69,7 +69,7 @@ protected function resolver($key)
     {
         return function () use ($key) {
             if (! $this->resolved) {
-                $instance = $this->factory->create();
+                $instance = $this->factory instanceof Factory ? $this->factory->create() : $this->factory;
 
                 return $this->resolved = $key ? $instance->{$key} : $instance->getKey();
             }

src/Illuminate/Database/Eloquent/Factories/Factory.php

@@ -481,12 +481,12 @@ protected function guessRelationship(string $related)
     /**
      * Define an attached relationship for the model.
      *
-     * @param  \Illuminate\Database\Eloquent\Factories\Factory  $factory
+     * @param  \Illuminate\Database\Eloquent\Factories\Factory|\Illuminate\Support\Collection|\Illuminate\Database\Eloquent\Model  $factory
      * @param  callable|array  $pivot
      * @param  string|null  $relationship
      * @return static
      */
-    public function hasAttached(self $factory, $pivot = [], $relationship = null)
+    public function hasAttached($factory, $pivot = [], $relationship = null)
     {
         return $this->newInstance([
             'has' => $this->has->concat([new BelongsToManyRelationship(
@@ -500,11 +500,11 @@ public function hasAttached(self $factory, $pivot = [], $relationship = null)
     /**
      * Define a parent relationship for the model.
      *
-     * @param  \Illuminate\Database\Eloquent\Factories\Factory  $factory
+     * @param  \Illuminate\Database\Eloquent\Factories\Factory|\Illuminate\Database\Eloquent\Model  $factory
      * @param  string|null  $relationship
      * @return static
      */
-    public function for(self $factory, $relationship = null)
+    public function for($factory, $relationship = null)
     {
         return $this->newInstance(['for' => $this->for->concat([new BelongsToRelationship(
             $factory,

tests/Database/DatabaseEloquentFactoryTest.php

@@ -250,6 +250,21 @@ public function test_belongs_to_relationship()
         $this->assertCount(3, FactoryTestPost::all());
     }
 
+    public function test_belongs_to_relationship_with_existing_model_instance()
+    {
+        $user = FactoryTestUserFactory::new(['name' => 'Taylor Otwell'])->create();
+        $posts = FactoryTestPostFactory::times(3)
+                        ->for($user, 'user')
+                        ->create();
+
+        $this->assertCount(3, $posts->filter(function ($post) use ($user) {
+            return $post->user->is($user);
+        }));
+
+        $this->assertCount(1, FactoryTestUser::all());
+        $this->assertCount(3, FactoryTestPost::all());
+    }
+
     public function test_morph_to_relationship()
     {
         $posts = FactoryTestCommentFactory::times(3)
@@ -263,6 +278,20 @@ public function test_morph_to_relationship()
         $this->assertCount(3, FactoryTestComment::all());
     }
 
+    public function test_morph_to_relationship_with_existing_model_instance()
+    {
+        $post = FactoryTestPostFactory::new(['title' => 'Test Title'])->create();
+        $posts = FactoryTestCommentFactory::times(3)
+                        ->for($post, 'commentable')
+                        ->create();
+
+        $this->assertSame('Test Title', FactoryTestPost::first()->title);
+        $this->assertCount(3, FactoryTestPost::first()->comments);
+
+        $this->assertCount(1, FactoryTestPost::all());
+        $this->assertCount(3, FactoryTestComment::all());
+    }
+
     public function test_belongs_to_many_relationship()
     {
         $users = FactoryTestUserFactory::times(3)
@@ -290,6 +319,29 @@ public function test_belongs_to_many_relationship()
         unset($_SERVER['__test.role.creating-user']);
     }
 
+    public function test_belongs_to_many_relationship_with_existing_model_instances()
+    {
+        $roles = FactoryTestRoleFactory::times(3)
+                        ->afterCreating(function ($role) {
+                            $_SERVER['__test.role.creating-role'] = $role;
+                        })
+                        ->create();
+        FactoryTestUserFactory::times(3)
+                        ->hasAttached($roles, ['admin' => 'Y'], 'roles')
+                        ->create();
+
+        $this->assertCount(3, FactoryTestRole::all());
+
+        $user = FactoryTestUser::latest()->first();
+
+        $this->assertCount(3, $user->roles);
+        $this->assertSame('Y', $user->roles->first()->pivot->admin);
+
+        $this->assertInstanceOf(Eloquent::class, $_SERVER['__test.role.creating-role']);
+
+        unset($_SERVER['__test.role.creating-role']);
+    }
+
     public function test_sequences()
     {
         $users = FactoryTestUserFactory::times(2)->sequence(