Proposal: pass arguments to relationship functions

[valentinomariotto]

Hi,
I could really use the ability to set an argument to a relationship function from a method such as whereHas, has, doesntHave() etc

I'm not talking about the query callback function. I'm talking about the relationship function itself.

Consider a model like so:

    class UserRelationships extends Model
    {
        // other stuff
        // dynamic scope:
         /**
         *
         * @param  \Illuminate\Database\Eloquent\Builder  $query
         * @param  mixed  $type
         * @return \Illuminate\Database\Eloquent\Builder
         */
        // $relationships = UserRelationships::at( Carbon::parse('2022-10-10') )->get();
        public function scopeAt($query, Carbon $date)
        {
            return $query->where('superseded_at', '>', $date )
                        ->where('created_at', '<=', $date );
        }
    }

And a related model featuring the following relationships:

    class User extends Authenticatable
    {
        public function progenial_relation(Carbon $date=null) // returns this user record in the userRelationships table, which can be used to retrieve this users parent (directly lookup the sponsor_id)
        // when eager loading, this is useful for getting all users whose parent is x, hence the name
        {
            return $this->hasOne(UserRelationships::class, 'user_id', 'id')
                        ->at( @$date ?: Carbon::now() ) // local dynamic scope in userRelationships
                        ->orderByDesc('created_at')
                        ->limit(1);
        }
        public function parental_relation(Carbon $date=null) // returns records from the userRelationships table, of all the users which refer to this user as their sponsor
        // when eager loading, this is useful for getting the user whose child is x, hence the name
        {
            return $this->hasMany(UserRelationships::class, 'sponsor_id', 'id')
                        ->at( @$date ?: Carbon::now() ); // local dynamic scope in userRelationships
        }
    
    }

As you can see my relationships progenial_relation and parental_relation accept an argument (the date).

Now, if you wanted to use those relationships straightforwardly like so, there's no issues:

    $date = Carbon\Carbon::parse('2022-06-01');
    $relations_at_date = User::find(1)->parental_relation( $date )->get();

But what happens if you need to use eager-loading methods such as has(), whereHas(), doesntHave(), whereDoesntHave()?
How do you pass an argument to the relationship? For example, I wanted to add other relationships to my User model.

    public function children(Carbon $date=null)
    {
        $date = @$date ?: Carbon::now();
        return self::whereHas('progenial_relation', function($q) {
            $q->where('sponsor_id', $this->id);
        }, $date); // not working
    }

For completeness I'm going to add what happens if I use a normal closure:

    public function children(Carbon $date=null)
    {
        $date = @$date ?: Carbon::now();
        return self::whereHas('progenial_relation', function($q) use ($date) {
            $q->at($date)->where('sponsor_id', $this->id);
        });
    }

This is the resulting SQL. As you can see the constraints are applied twice. Once by the query callback and once by the relationship. But since I cannot pass the correct argument to the relationship, it gets the default one. The 2 constraints collide and the query does not work.

    select * from `users` 
    where exists (
        select * 
        from `user_relationships` 
        where `users`.`id` = `user_relationships`.`user_id` 
        and `user_relationships`.`superseded_at` > ? 
        and `user_relationships`.`created_at` <= ? 
        and `sponsor_id` = ? 
        and `user_relationships`.`superseded_at` > ? 
        and `user_relationships`.`created_at` <= ?
    )
    and `users`.`deleted_at` is null

I think it would be great if we could pass an argument to the relationship directly, with a syntax such as this:

whereHas('relationship_name', $callback, [$arg1, $arg2]);

Thank you

PS: I also asked on the forums but probably it wasn't the right place https://laravel.io/forum/feature-request-pass-arguments-to-relationship-functions/edit