refresh(): Call to undefined relationship [pivot] on model

[LastDragon-ru]

• Laravel Version: 6.18.0
• PHP Version: 7.2
• Database Driver & Version: Mysql 5.7

Description:

This is a regression introduced in #31125 - all custom pivot models that uses AsPivot trait are broken now due to this line:

framework/src/Illuminate/Database/Eloquent/Model.php

Line 1154 in 898f24e

return $relation instanceof Pivot;

obviously it should also check if the model uses AsPivot trait. Something like:

return $relation instanceof Pivot
    || in_array(AsPivot::class, class_uses_recursive($relation), true);

Steps To Reproduce:

1. Create new laravel 6.x app
2. Create user_users table

   CREATE TABLE IF NOT EXISTS `user_users` (
       `my_user_id` BIGINT(20) UNSIGNED NOT NULL,
       `pivot_my_user_id` BIGINT(20) UNSIGNED NOT NULL
   )

3. Run this test

   <?php
   
   namespace Tests\Unit;
   
   use App\User;
   use Illuminate\Database\Eloquent\Model;
   use Illuminate\Database\Eloquent\Relations\Concerns\AsPivot;
   use Tests\TestCase;
   
   class ExampleTest extends TestCase {
       public function testAsPivotRefresh() {
           $user  = MyUser::query()->findOrFail(factory(User::class)->create()->getKey());
           $child = MyUser::query()->findOrFail(factory(User::class)->create()->getKey());
   
           $user->users()->attach($child->getKey());
   
           $this->assertEquals(1, $user->users->count());
   
           $user->users->first()->refresh();
       }
   }
   
   class MyUser extends User {
       protected $table = 'users';
   
       public function users() {
           return $this
               ->belongsToMany(static::class, (new UserPivot())->getTable(), 'my_user_id', 'pivot_my_user_id')
               ->using(UserPivot::class);
       }
   }
   
   class UserPivot extends Model {
       use AsPivot;
   
       protected $table = 'user_users';
   }

[GrahamCampbell]

in_array(AsPivot::class, class_uses_recursive($relation), true);

This feels kinda hacky. Shouldn't we have an interface for this?

[LastDragon-ru]

This feels kinda hacky. Shouldn't we have an interface for this?

Agreed, but interface will not fix existing code

[ryangjchandler]

in_array(AsPivot::class, class_uses_recursive($relation), true);

This feels kinda hacky. Shouldn't we have an interface for this?

I'd prefer to use the interface in all honesty, and I'm sure if people run into this problem they will find the information in the docs somewhere.

I don't believe traits should be used to enforce outside functionality on the edge of your application. The interface approach has already been taken with other checks & rules for model classes.

Happy to make a PR with the new marker interface.

[driesvints]

Why aren't you extending the Pivot class?

[LastDragon-ru]

Why aren't you extending the Pivot class?

@driesvints for the same reasons as described in initial PR #25851 ("own abstract Model class")

[driesvints]

I see. Then an interface won't work here because people would have to implement it manually to solve the problem. We could maybe go for the solution you proposed above. Feel free to send in a PR.