[10.x] Fix default pivot model values

[iamgergo]

Recently I faced with a situation, when using the withPivotValue method on a BelongsToMany relationship definition does not take effect when saving the pivot record.

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I have the following setup:

class User extends Model
{
    public function categories(): BelongsToMany
    {
        return $this->belongsToMany(Category::class, 'subscriptions')
                    ->withPivotValue('type', 'manager')
                    ->using(Subscription::class);
    }

    public function subscriptions(): BelongsToMany
    {
        return $this->belongsToMany(Category::class, 'subscriptions')
                    ->withPivotValue('type', 'player')
                    ->using(Subscription::class);
    }
}

class Subscription extends Pivot
{
    public $table = 'subscriptions';

    protected $attributes = [
        'type' => 'player',
    ];
}

Before the fix, when attaching a category to a user, the pivot attributes that are defined in the withPivotValue method are overridden by the pivot model's $attributes property.

$category = Category::first();
$user = User::first();

$user->categories()->attach($category); // try to attach as a category NOT as a subscription

$user->categories->isEmpty() // true

$user->subscriptions->isEmpty() // false

$user->subscriptions->first()->pivot->role // palyer

So, when I try to attach a category to a user using the categories relation, since it cannot override the default value using the withPivotValue, the attached category model takes place in the wrong relationship. Also, I think this is a bug.

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The same Pivot Model can be used in different relationships, so overriding its default attributes from a relationship definition would be great.

[taylorotwell]

withPivotValue has nothing to do with updates. Only retrievals. You need to specify the pivot values you want when saving.

[iamgergo]

@taylorotwell @driesvints The withPivotValue and the withPivot methods are doing two different things.

withPivotValue has nothing to do with updates

The withPivotValue defines a wherePivot statement and sets a pivot value when saving the relation. So it is used when saving relations.

The withPivot method just retrieves a pivot column.

If I want to retrieve pivot data, I have to use the withPivot even if I use withPivotValue as well. For example:

    public function categories(): BelongsToMany
    {
        return $this->belongsToMany(Category::class, 'subscriptions')
                    ->withPivotValue('type', 'manager') // sets the type pivot attribute automatically
                    ->withPivot('type') // retrieves the type attribute
                    ->using(Subscription::class);
    }

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Without this fix, the withPivotValue does not work in some scenarios. From my point of view, this is a bug. Please, consider to reopen this PR.

Thank you!