custom validators won't autoload

Custom Validators

class AlphaNumeric < Grape::Validations::Base
  def validate_param!(attr_name, params)
    unless params[attr_name] =~ /^[[:alnum:]]+$/
      fail Grape::Exceptions::Validation, params: [@scope.full_name(attr_name)], message: "must consist of alpha-numeric characters"
    end
  end
end

params do
  requires :text, alpha_numeric: true
end

This part of code is from Grape's Readme doc.

The problem is, when requires :text, alpha_numeric: true is call, AlphaNumeric won't be autloaded, because of method 'alpha_numeric' called, not Class 'AlphaNumeric'.

Please let me know if I was wrong.

Start with the custom validator example in the README and trace the validation entry point reached by alpha_numeric: true, including how the validator class is resolved. Done means the documented AlphaNumeric validator autoloads and the example works without requiring the class manually.