module Devise::Models

def self.check_fields!(klass)
  failed_attributes = []
  instance = klass.new
  klass.devise_modules.each do |mod|
    constant = const_get(mod.to_s.classify)
    if constant.respond_to?(:required_fields)
      constant.required_fields(klass).each do |field|
        failed_attributes << field unless instance.respond_to?(field)
      end
    else
      ActiveSupport::Deprecation.warn "The module #{mod} doesn't implement self.required_fields(klass). " \
        "Devise uses required_fields to warn developers of any missing fields in their models. " \
        "Please implement #{mod}.required_fields(klass) that returns an array of symbols with the required fields."
    end
  end
  if failed_attributes.any?
    fail Devise::Models::MissingAttribute.new(failed_attributes)
  end
end