Laravel 5 custom validation if a file was not uploaded

I am trying to create a custom validation to check if a file was uploaded in a form.

I looked at the custom errors docs but couldn't make it work.

I found this tutorial: Custom Error

In my controller I do this:

if($request->hasFile('file'))
        $has_file = 1;
    else
        $has_file = 0;

 $this->validate($request, ['file' => 'isuploaded']);

In App/ServiceProvider I added this:

Validator::extend('isuploaded', function($attribute, $value, $parameters, $validator) {
        return ?;
    });

What should I return here? How do I send the $has_file to the validator?

via Chebli Mohamed