voyager: [BUG] Undefined index: relationship_key

Version information

• Laravel: v5.7.24
• Voyager: v1.1
• PHP: 7.2.4
• Database: MySQL 5.7.22

Description

When submitting an edit of a BREAD with a relationship I (sometimes) get the following error: Undefined index: relationship_key_topic_belongstomany_topic_relationship

In DataType.php this key value will be set according to the relationship. Which in my case is topic_belongstomany_topic_relationship.

When inspecting the requestData. The realtionship_key_xxx index is sometimes set and sometimes it’s not. (hence the error)

Steps to reproduce

Not really helpfull, but this is what I’m doing:

1. Select edit BREAD
2. Submit form
3. See whether the update works or not

Expected behavior

The expected behavior is that this index (relationship_key_xxx) is set in the $requestData. Sometimes this is the case and sometimes it’s not.

Screenshots

Additional context

This relationship is a relationship on the table itself. (A topic will show multiple topics and a topic can appear on multiple other topics as well).

I have made 2 models which reference Topic so I can get the related Topics to a certain Topic.

1 model under App\Models\Voyager\Topic (created by Voyager itself)

<?php

namespace App\Models\Voyager;

use Illuminate\Database\Eloquent\Model;
use TCG\Voyager\Traits\Translatable;

class Topic extends Model
{   
    use Translatable;

    protected $table = "topics";

    protected $translatable = [
        "title",
        "intro",
        "content_title",
        "content_sub_title",
        "content",

    ];

    protected $with = ['translations'];

    public function topics()
    {
        return $this->belongsToMany("App\Models\Topic", 'topics_related_topics', 'topic_id', 'related_topic_id');
    }
}

1 model under App\Models\Topic (self created to create a belongsToMany relationship)

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class Topic extends Model
{
    protected $table = "topics";

    public function topics()
    {
        return $this->belongsToMany("App\Models\Voyager\Topic", 'topics_related_topics', 'related_topic_id', 'topic_id');
    }
}