Debugging marshalling implicits

[Richard Rodseth]

Can anyone help me with this please?

I have the following in my route:

val result = (requestHandler ? RequestHandler.AskForStatus).mapTo[PimpedResult[(StatusCode, Result[StatusDTO])]]

onSuccess(result) {

  case _ => complete(result)

}

The mapTo is really just to assist my debugging. The result could be a Result[StatusDTO] or a PimpedResult.

Anyway, I get the following error on the complete call:

type mismatch; found : scala.concurrent.Future[PimpedResult[(akka.http.scaladsl.model.StatusCode, Result[StatusDTO])]] (which expands to) scala.concurrent.Future[PimpedResult[(akka.http.scaladsl.model.StatusCode, scala.util.Either[APIError,StatusDTO])]] required: akka.http.scaladsl.marshalling.ToResponseMarshallable

I added the following after the mapTo:

val prm = implicitly[Future[PimpedResult[(StatusCode, Result[StatusDTO])]] => ToResponseMarshallable]

and that line gets this error:

Multiple markers at this line:

not enough arguments for method implicitly: (implicit e: scala.concurrent.Future[PimpedResult[(akka.http.scaladsl.model.StatusCode, Result[StatusDTO])]] ⇒ akka.http.scaladsl.marshalling.ToResponseMarshallable)scala.concurrent.Future[PimpedResult[(akka.http.scaladsl.model.StatusCode, Result[StatusDTO])]] ⇒ akka.http.scaladsl.marshalling.ToResponseMarshallable. Unspecified value parameter e.

No implicit view available from scala.concurrent.Future[PimpedResult[(akka.http.scaladsl.model.StatusCode, Result[StatusDTO])]] ⇒ akka.http.scaladsl.marshalling.ToResponseMarshallable.

Here is the custom marshaller. I know it's in scope because the errorMarshaller works in the case where the response is Result[StatusDTO] rather than PimpedResult

// See https://bitbucket.org/binarycamp/spray-contrib/src

trait APICustomMarshallers {

  implicit def errorMarshaller[T](

implicit translator: ErrorTranslator[T],

statusCodeMapper: ErrorToStatusCodeMapper,

m: ToEntityMarshaller[T]): ToResponseMarshaller[APIError] = {

    val base = PredefinedToResponseMarshallers.fromStatusCodeAndHeadersAndValue

    val result = base.compose {

      error: APIError => (statusCodeMapper.orElse(ErrorToStatusCodeMapper.Default)(error), DefaultHttpHeaders.NoCacheHeaders, translator(error))

    }

    result

  }

  implicit def statusMarshaller[T](implicit m: ToEntityMarshaller[T]): ToResponseMarshaller[PimpedResult[(StatusCode, T)]] = {

    val base = PredefinedToResponseMarshallers.fromStatusCodeAndHeadersAndValue // Needs the entity marshaller

    val result = base.compose {

      pimpedResult: PimpedResult[(StatusCode, T)] =>

        pimpedResult.result match {

          case Right(response) => (response._1, DefaultHttpHeaders.NoCacheHeaders, response._2)

          case _               => throw new RuntimeException("StatusMarshaller got invalid PimpedResult")

        }

    }

    result

  }

}

Thanks for any help.

[Richard Rodseth]

Bump.

Is this the right way to debug the missing conversion?

val prm = implicitly[Future[PimpedResult[(StatusCode, Result[StatusDTO])]] => ToResponseMarshallable]

[Johannes Rudolph]

Hi,

On Tuesday, September 13, 2016 at 4:26:55 PM UTC+2, rrodseth wrote:
> Is this the right way to debug the missing conversion?
> val prm = implicitly[Future[PimpedResult[(StatusCode, Result[StatusDTO])]] => ToResponseMarshallable]

Try

implicitly[ToResponseMarshaller[Future[PimpedResult[(StatusCode, Result[StatusDTO])]]]


then


implicitly[ToResponseMarshaller[PimpedResult[(StatusCode, Result[StatusDTO])]]


then

implicitly[ToEntityMarshaller[Result[StatusDTO]]] // required by APICustomMarshallers.statusMarshaller

or just 

statusMarshaller[Result[StatusDTO]]]


and see which one still succeeds. Then you need to work back from the simple ones to the more complex types, trying to get those to work.

HTH

Johannes

[Richard Rodseth]

Thanks. It appears to be the absence of an Either marshaller ( Result[T] is an alias for Either[APIError,T] )

Is that something that was available in Spray, but not in Akka HTTP ?

I see this got merged:

https://github.com/akka/akka/pull/20274

but it's an Unmarshaller.

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