Unmarshalling nested JSON object with single field fails

[dbronecki]

The following test case:

import org.scalatest.{Matchers, WordSpec}
import pl.iterators.kebs.json.KebsSpray
import spray.json.DefaultJsonProtocol

case class Book(name: String, chapters: List[Chapter])
case class Chapter(name: String)

class KebsTest extends WordSpec with Matchers {

  import ThingProtocol._
  import spray.json._

  "Kebs" should {
    "work with nested single field objects" in {
      val json =
        """
          | {
          |   "name": "Functional Programming in Scala",
          |   "chapters": [{"name":"first"}, {"name":"second"}]
          | }
        """.stripMargin

      json.parseJson.convertTo[Book] shouldBe Book(
        name     = "Functional Programming in Scala",
        chapters = List(Chapter("first"), Chapter("second"))
      )
    }
  }
}

object ThingProtocol extends DefaultJsonProtocol with KebsSpray

Gives error:

spray.json.DeserializationException: Expected String as JsString, but got {"name":"first"}

[marcin-rzeznicki]

So, you can prefer noflat format in current state of things, by marking it explicitly as RootJsonFormat like this:

implicit val chapterRootFormat: RootJsonFormat[Chapter] = jsonFormatN[Chapter]

or, you should have been able to do this, but there'd been bug preventing this usage (fixed in c3bbdeb). I personally prefer this in case you do not have many no-flats . In case where, say, most of what you serialize should be no-flat I think that we should add a trait which simply changes the preference. The problem with annotation like @noflat you added in #10 is that it couples JSON rendering with model definition, akin to slick's @MappedTo . But, I think it is worthy addition nonetheless, especially for people that do not object to this coupling, so we'll merge this PR as well.