withDepth method now working correctly when using nested set as a relation on another model

[sasokovacic]

Hi, depth is not calculated properly when fetching a nested set as a relation on another model. Depth is set to -1 for all records.

This is my case:

I have a model called Codelist. It represents a simple table with id and name. This model has a relationship called options that is actually a nested set.

Codelist.php

class Codelist extends Model {

// ...
public function options()
{
    return $this->hasMany(CodelistOption::class, 'codelist_id', 'id')
            ->withDepth()
            ;
    }
}

CodelistOption.php

use Kalnoy\Nestedset\NodeTrait;

class CodelistOption extends Model {

    use NodeTrait;

    // ...
}

And here I try to fetch code lists with options (withDepth method is in the relationship method).

Codelist::with('options')->get()

I also use codelist_id as a nested set scope.

What I did is I created my own scope method scopeIncludingDepth that looks like this:

public function scopeIncludeDepth(QueryBuilder $q, String $columns = '*') {

    $alias = '_d';

    $q->select("codelist_options.{$columns}");

    $query = self::selectRaw('count(1) - 1')
        ->from("codelist_options as {$alias}")
        ->whereRaw("codelist_options._lft between {$alias}._lft and {$alias}._rgt")
        ->whereRaw("codelist_options.codelist_id = {$alias}.codelist_id")
        ->getQuery();

    $q->selectSub($query, 'depth');

    return $q;

}

but this is just a hack. I would prefer to use withDepth method.