# File lib/omniauth/strategies/facebook.rb, line 78
      def callback_url
        if @authorization_code_from_signed_request_in_cookie
          ''
        else
          # Fixes regression in omniauth-oauth2 v1.4.0 by https://github.com/intridea/omniauth-oauth2/commit/85fdbe117c2a4400d001a6368cc359d88f40abc7
          options[:callback_url] || (full_host + script_name + callback_path)
        end
      end