Call to undefined method when using nested relationships on aggregate function

[adesege]

• Laravel Version: 8.57.0
• PHP Version: 8.0
• Database Driver & Version: Postgres 13

Description:

Call to undefined method error is thrown when using nested relationship on aggregate functions like withAvg. I was able to debug this and found out that getRelationWithoutConstraints is directly calling the relation parameter as a function.

In my use case, I'm trying to get the average of book reviews from a shelf model.

Shelf::withAvg('books.reviews', 'rating');

Getting the reviews directly from the book model works fine, however.

Related to #38049 and #38079

Steps To Reproduce:

1. Create 3 models with the following relationships; A -> B -> C.
2. Then get the average of C through model A; A::withAvg('b.c', 'd'); // This will throw an error
3. If you do B::withAvg('c', 'd') instead, it will not throw an error.

[staudenmeir]

withAvg() etc. don't (and basically can't) work with nested relationships. You need to build a direct relationship between Shelf and Review. How are books and reviews defined?

[adesege]

withAvg() etc. don't (and basically can't) work with nested relationships. You need to build a direct relationship between Shelf and Review. How are books and reviews defined?

@staudenmeir Thanks for the clarification. Books hasMany Reviews while Shelf belongs to many Books. I think the clarification that withAvg can't work with nested relationships should be included in the documentation. Spent some days scratching my head on this.

[staudenmeir]

The aggregate functions could also throw an exception when being called with a nested relationship.

You can define a direct relationship by "skipping" the books table:

class Shelf extends Model
{
    public function reviews()
    {
        return $this->belongsToMany(
            Review::class,
            'book_shelf',
            'shelf_id', 'book_id', null, 'book_id'
        );
    }
}

Shelf::withAvg('reviews', 'rating');