Consider adding a BodyWritable[Json] type class instance

[tbinna]

With the update to Play 2.6 my Play WS clients broke.

Previously body serialization when calling put, post, etc. worked using play.api.http.Writable and type class instances writableOf_Json in Circe.scala did the job.

Now play-ws requires a type class play.api.libs.ws.BodyWritable which is not included in this project. See https://www.playframework.com/documentation/2.6.x/WSMigration26#Scala

For now I defined this trait in my project which does the job:

trait CirceJsonBodyWritables {

  val defaultPrinter = Printer.noSpaces

  implicit def bodyWritableOf_Json(
      implicit printer: Printer = defaultPrinter): BodyWritable[Json] = {
    BodyWritable(
      json => InMemoryBody(ByteString.fromString(json.pretty(printer))),
      "application/json")
  }

}

Would be nice to add this to the Circe.scala trait but it requires you to add play-ws dependency.

[jilen]

@tbinna Circe trait is basically for Controller, BodyWritable instances seems should be also available somewhere else

[tbinna]

Yes, that's true. It could be a different trait for Play WS. For Play 2.5.x I used the same Circe trait for my WS clients. This worked because play-ws was using the same Writable to serialize bodies. Now with Play 2.6 I still use the Circe trait but I need to define a BodyWritable[io.circe.Json] for WS clients.
If I find some time I will create PR, then we can discuss based on that.

[romanskie]

Hey Guys,

so is there by now a way or workaround to parse WSReponse bodys to case classes? I tried to write a custom CirceJsonBodyReadables trait by myself, but that did not work out. Maybe I am using it wrong, but I cant just use @tbinna writable trait for that right?

trait CirceJsonBodyReadables {

  implicit val circeBodyReadable = BodyReadable[io.circe.Json] { response =>
    import play.shaded.ahc.org.asynchttpclient.{ Response => AHCResponse }
    val ahcResponse = response.asInstanceOf[StandaloneAhcWSResponse].underlying[AHCResponse]
    io.circe.Json.fromString(ahcResponse.getResponseBody)
  }
}

In with my response I am trying to do something like.

wsClient.url(btcURL).get().map { response => response.body[io.circe.Json] }

But that leads to the following error message:

An error has occured: play.api.libs.ws.ahc.AhcWSResponse cannot be cast to play.api.libs.ws.ahc.StandaloneAhcWSResponse

An ugly solution code be to map the body as String and parse it manually?
I would like to help integrating that in play-circe!

[jilen]

@romanskie I think it would be better not casting to StandaloneAhcWSResponse
but relies on WSResponse.

[jilen]

@romanskie Also you may define

implicit def circeBodyReadable[A: io.circe.Decoder] = BodyReadable[io.circe.Decoder.Result[A]]] { response =>
   decode[A](response.body)
}

Which will enable parse response to Decoder.Result[A]

[romanskie]

I wrote this now:

 implicit def circeJsonBodyReadable = BodyReadable[io.circe.Json] { response =>
    io.circe.parser.parse(response.bodyAsBytes.utf8String) match {
      case Left(decodingFailure) => throw decodingFailure
      case Right(json) => json
    }
  }

And now I am able to:

wsClient.url(btcURL).get().map(response => response.body[Json].as[CryptoCompareResponse])

That was the only solution I could apply. It would be very nice if I just could use the following:

wsClient.url(btcURL).get().map(response => response.body[CryptoCompareResponse])

I guess that is what you wanted me to do with your implicit def, but i could not get it to work!