Shapeless lens

import shapeless._
import spray.json._

object Main extends App {

  case class Test(optionalBlah: Option[String])
  case class Test2(nested: Test)

  import DefaultJsonProtocol._
  implicit val testFormat = DefaultJsonProtocol.jsonFormat1(Test)
  implicit val test2Format = DefaultJsonProtocol.jsonFormat1(Test2)

  val none = Test2(Test(None))
  val emptySome = Test2(Test(Some("")))
  val some = Test2(Test(Some("blah")))
  println(none.toJson.prettyPrint)
  println(emptySome.toJson.prettyPrint)
  println(some.toJson.prettyPrint)


  val optionStringLens = lens[Test2] >> 'nested >> 'optionalBlah

  //replace some with none
  def normalise(in: Test2) : Test2 = optionStringLens.modify(in)(_.filter(!_.isEmpty))

  println(normalise(none).toJson.prettyPrint)
  println(normalise(emptySome).toJson.prettyPrint)
  println(normalise(some).toJson.prettyPrint)
}

{
"nested": {

}
}
{
"nested": {
"optionalBlah": ""
}
}
{
"nested": {
"optionalBlah": "blah"
}
}
{
"nested": {

}
}
{
"nested": {

}
}
{
"nested": {
"optionalBlah": "blah"
}
}