Example of supporting HTTP 404 - Not found status on spray.io http-client unmarshalling pipeline

OptionUnmarshaller.scala

/** Adds support for Http/404 - Not Found to a processing pipeline. 
 *  A 404/Not found is converted to None while other HTTP statuses will get converted as usual 
 *  (HTTP/200 - will result in a marshalled object, errors will throw an exception, failing the future.
 */
def convertOption[T](implicit unmarshaller:FromResponseUnmarshaller[T]): Future[HttpResponse] => Future[Option[T]] = 
      (futRes: Future[HttpResponse]) => futRes.map{res => 
        if (res.status == StatusCodes.NotFound) None
        else Some(unmarshal[T](unmarshaller)(res))  
      }

// Usage example
val optionPipeline =  sendReceive ~> convertOption[MyType]
val result = optionPipeline { Get(url)} // result: Future[Option[MyType]]