->whereBelongsTo() support for MorphTo relationships

[mstephen77]

I've recently started to explore the ->whereBelongsTo() method of Eloquent. In my specific scenario, I'm trying to use it to query a MorphTo relationship, thinking that it would've worked as both relationships are pretty "similar".

Instead, I kept getting errors. As it turns out, there's a $relationship->getOwnerKeyName() call where with a MorphTo relationship it will most likely return an empty string.

To address this, I'm considering a potential solution by adding a check to determine if the relationship is a MorphTo instance and alternative logic to handle that specific case, something like:

if ($relationship instanceof MorphTo) {
    $this->where(fn ($query) => (
        $relatedCollection->each(fn (Model $model) => (
            $query->orWhere(fn ($innerQuery) => (
                // ->getQualifiedMorphTypeColumn() doesn't exist, probably add it to MorphTo relationship?
                $innerQuery->where($relationship->getQualifiedMorphTypeColumn(), \get_class($model)) 
                    ->where($relationship->getQualifiedForeignKeyName(), $model->getKey())
            ))
        ))
    ));

    /**
     * And the resulting query would be something like
     * ... WHERE (
     *   (qualified_morph_type_column='App\Models\Model' AND qualified_foreign_key_name='id1')
     *   OR (qualified_morph_type_column='App\Models\OtherModel' AND qualified_foreign_key_name='id2')
     *   OR ...
     * )
     */
}

I'm eager to contribute to the Laravel community by refining this functionality. I'd be happy to contribute a pull request to address this issue if it aligns with the project's goals.

[mstephen77]

Opened a PR for this: #53041

[mstephen77]

Closing this as it turns out there's already a similar method for MorphTo relationships (->whereMorphedTo()).