[9.x] Prevent test issues with relations with the $touches property (#45118)

* #45064 - Added function to remove empty relationships that were causing issues with touched relationships on tests

* #45064 - Fixed code style issue

* formatting

Co-authored-by: Taylor Otwell <[email protected]>

Author: WendellAdriel

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

@@ -328,6 +328,12 @@ protected function store(Collection $results)
 
             $model->save();
 
+            foreach ($model->getRelations() as $name => $items) {
+                if ($items->isEmpty()) {
+                    $model->unsetRelation($name);
+                }
+            }
+
             $this->createChildren($model);
         });
     }

tests/Database/DatabaseEloquentFactoryTest.php

@@ -356,6 +356,14 @@ public function test_belongs_to_many_relationship()
         unset($_SERVER['__test.role.creating-role'], $_SERVER['__test.role.creating-user']);
     }
 
+    public function test_belongs_to_many_relationship_related_models_set_on_instance_when_touching_owner()
+    {
+        $user = FactoryTestUserFactory::new()->create();
+        $role = FactoryTestRoleFactory::new()->hasAttached($user, [], 'users')->create();
+
+        $this->assertCount(1, $role->users);
+    }
+
     public function test_belongs_to_many_relationship_with_existing_model_instances()
     {
         $roles = FactoryTestRoleFactory::times(3)
@@ -913,6 +921,8 @@ class FactoryTestRole extends Eloquent
 {
     protected $table = 'roles';
 
+    protected $touches = ['users'];
+
     public function users()
     {
         return $this->belongsToMany(FactoryTestUser::class, 'role_user', 'role_id', 'user_id')->withPivot('admin');