[11.x] Support passing default as named parameter in whenLoaded, whenAggregated, whenCounted

[hn-seoai]

Because of the way named parameters affect func_num_args(), only specifying the required parameters and $default would result in the returned value being null

This will allow developers to use named arguments when passing $default to whenLoaded(), whenAggregated() and whenCounted() in Resources, in case the key should still exist in the output while maintaining the current behavior when only passing the required parameters.

Before:

class PostResource extends JsonResource
{
    public function toArray($request)
    {
        return [
            'id' => $this->id,
            'author' => new AuthorResource($this->whenLoaded('author', fn ($author) => $author, null)),
        ];
    }
}

After:

class PostResource extends JsonResource
{
    public function toArray($request)
    {
        return [
            'id' => $this->id,
            'author' => new AuthorResource($this->whenLoaded('author', default: null)),
        ];
    }
}

This will not affect existing Laravel users, as the addition is only being run when $value and/or $default is passed and $value is its default (null).

[taylorotwell]

Can you explain how this works?

[hn-seoai]

Can you explain how this works?

Providing whenLoaded with only the relationship and default parameters will result in func_num_args() returning 3, which makes the default null value of the value parameter persist instead of using the default behavior when only providing the relationship.

value(...) returns the value() method as a closure with the same signature, so the final return statement will return $loadedValue instead of null.

[taylorotwell]

Can you add a test for this?

[driesvints]

@hn-seoai don't forget to mark a PR as ready so Taylor can review it.