Add custom conditional validation rule to the same attribute

I'm trying to add some custom validation logic for file uploads for my admin panel. Right now my file fields can return either Illuminate\Http\UploadedFile or string|null if file is not uploaded or changed or whatever. So, what i'm doing is, i created a custom rule that looks like this:

'image' => [
                'required',
                'admin_file:mimes:jpeg;png,dimensions:min_width=800;min_height=600'
           ]

I then parse all the arguments i pass, and the thing is, i naturally want all of them applied only if my value is an instance of UploadedFile. I use the following code for my custom validation:

class AdminFileValidator
{
    public function validate($attribute, $value, $parameters, Validator $validator)
    {
        $rules = implode(
            "|",
            array_map(function($item) {
                return str_replace(";", ",", $item);
            }, $parameters)
        );

        $validator->sometimes($attribute, $rules, function() use ($value) {
            return $value instanceof UploadedFile;
        });

        return true;
    }
}

The problem is, adding additional rules to an attribute via sometimes doesn't work that way, these added rules are not being processed by a validator.

I'd like to ask, is there any way to validate these rules without revalidating the whole thing manually?

via Eternal1