Bug: Not possible to set relations for an empty prop

[neznaika0]

Describe the bug
If Entity have getter:

    /**
     * @return list<Tag>
     */
    public function getTags(): ?array
    {
        return $this->attributes['tags'] ?? [];
    }

in PostModel:

    public function tags(): Relation
    {
        return $this->belongsToMany(TagModel::class);
    }

The lazy loading request is not working. To work, you need to return null.

To Reproduce
Add getter for relation prop and set . Call $entity->tags

Expected behavior
An empty array is expected to be overwritten, not just null/undefined properties.

Screenshots
No.

Environment (please complete the following information):

• PHP: 8.4.13
• Server: cli
• Version dev-latest
• CodeIgniter: 4.6.3

Additional context
To fast fix:

trait HasLazyRelations
{
    public function __get(string $key)
    {
        $result = parent::__get($key);

        if ($result === null || $result === []) {
            $result = $this->handleRelation($key);
        }

        return $result;
    }
//...

[neznaika0]

If this violates logic - the property is always empty []|null even after a query - we need to somehow determine if there was a request. It is important to consider along with with('tags')

[michalsn]

The whole point is to avoid having to create a specific getter for lazy-loaded relations - you should just be able to call $entity->tags without defining a getTags() method in the Entity.

[neznaika0]

It's bad. I know about _getTags(), but I'll try it someday. The method will not work if:

  protected $attributes = [
        'tags' => [],
        'user' => null,
    ];
    protected $original = [
        'tags' => [],
        'user' => null,
    ];

I sent a PR for CI4. If it is accepted, then the empty array will still remain.

[michalsn]

Lazy-loaded relations are meant to be accessed directly via $entity->tags, without defining dedicated attributes in the Entity.

Not sure how _getTags() would help here.

[neznaika0]

I don't like uncontrolled properties. That's why I always try to initialize variables.
I can temporarily redefine the method, but I would like a joint result.

I would like to thank you for the work (not only for that), although this package helped to remove the pain 👍

[michalsn]

Let me think about it.

1. Limiting the entity to make only one request per relation is not an issue - that's easy to handle.
2. The real problem arises when eagerly loading a one-to-many relation. In such cases, the relation may return an empty array. If our entity also supports lazy-loading, accessing that relation will trigger an additional query. That’s why we only check for a null value.

Why force the tags attribute to be an empty array? Doing so would suggest there are no tags, even if they haven't been loaded yet. This can cause issues, for example, if you later decide to update the relation. Using null instead clearly indicates that the relation hasn't been loaded yet.

[neznaika0]

Here's a case where I'm not calling the query. This is possible after the creation of the object.
Probably, yes, it's worth using null for relationships. This should be checked after the experience of using relationships.
Let's leave it as it is for now. If possible, you can add it to the documentation.

[neznaika0]

I didn't see what happens when user = null from the query?

[michalsn]

Right now, it will trigger another query, but one-to-one relations usually have results.