Akka HTTP doesn't render collection when using custom ToEntityMarshaller - akka-http

Question

I have defined a custom ToEntityMarshaller for type Organisation. When requesting localhost:8080/organisations it return an empty JSON array. Only when I remove the implicit def organisationMarshaller: ToEntityMarshaller[Organisation] it return the correct representation of the stream.
Anybody has an idea what is going on here?
import akka.NotUsed
import akka.actor.ActorSystem
import akka.http.scaladsl.Http
import akka.http.scaladsl.common.{EntityStreamingSupport, JsonEntityStreamingSupport}
import akka.http.scaladsl.model.{HttpEntity, StatusCodes, _}
import akka.http.scaladsl.server.Directives._
import akka.stream.ActorMaterializer
import akka.http.scaladsl.marshallers.sprayjson.SprayJsonSupport._
import akka.http.scaladsl.marshalling.{Marshaller, ToEntityMarshaller, ToResponseMarshaller}
import akka.http.scaladsl.model.TransferEncodings.gzip
import akka.http.scaladsl.model.headers.{HttpEncoding, HttpEncodings}
import akka.stream.scaladsl.{Flow, Source}
import akka.util.ByteString
import spray.json.DefaultJsonProtocol
import spray.json.DefaultJsonProtocol._
import scala.concurrent.Future
import scala.io.StdIn
import scala.util.Random
final case class Organisation(name: String, id: String)
trait Protocols extends DefaultJsonProtocol {
import spray.json._
implicit val organisationFormat = jsonFormat2(Organisation)
val `vnd.example.api.v1+json` =
MediaType.applicationWithFixedCharset("vnd.example.api.v1+json", HttpCharsets.`UTF-8`)
// -- WORKS AFTER REMOVING THIS DECLARATION --
implicit def organisationMarshaller: ToEntityMarshaller[Organisation] = Marshaller.oneOf(
Marshaller.withFixedContentType(`vnd.example.api.v1+json`) { organisation =>
HttpEntity(`vnd.example.api.v1+json`, organisation.toJson.compactPrint)
})
}
object Server extends App with Protocols {
implicit val system = ActorSystem("api")
implicit val materializer = ActorMaterializer()
implicit val executionContext = system.dispatcher
implicit val jsonStreamingSupport: JsonEntityStreamingSupport = EntityStreamingSupport.json()
.withParallelMarshalling(parallelism = 10, unordered = false)
// (fake) async database query api
def dummyOrganisation(id: String) = Organisation(s"Organisation $id", id.toString)
def fetchOrganisation(id: String): Future[Option[Organisation]] = Future(Some(dummyOrganisation(id)))
def fetchOrganisations(): Source[Organisation, NotUsed] = Source.fromIterator(() => Iterator.fill(10000) {
val id = Random.nextInt()
dummyOrganisation(id.toString)
})
val route =
encodeResponse {
pathPrefix("organisations") {
get {
val organisations = fetchOrganisations()
complete(organisations)
}
}
}
val bindingFuture = Http().bindAndHandle(route, "localhost", 8080)
println(s"Server online at http://localhost:8080/\nPress RETURN to stop...")
StdIn.readLine()
bindingFuture.flatMap(_.unbind()).onComplete(_ => system.terminate())
}