class Devise::FailureApp

def scope_url
  opts  = {}
  # Initialize script_name with nil to prevent infinite loops in
  # authenticated mounted engines in rails 4.2 and 5.0
  opts[:script_name] = nil
  route = route(scope)
  opts[:format] = request_format unless skip_format?
  router_name = Devise.mappings[scope].router_name || Devise.available_router_name
  context = send(router_name)
  if relative_url_root?
    opts[:script_name] = relative_url_root
  # We need to add the rootpath to `script_name` manually for applications that use a Rails
  # version lower than 5.1. Otherwise, it is going to generate a wrong path for Engines
  # that use Devise. Remove it when the support of Rails 5.0 is dropped.
  elsif root_path_defined?(context) && !rails_51_and_up?
    rootpath = context.routes.url_helpers.root_path
    opts[:script_name] = rootpath.chomp('/') if rootpath.length > 1
  end
  if context.respond_to?(route)
    context.send(route, opts)
  elsif respond_to?(:root_url)
    root_url(opts)
  else
    "/"
  end
end