Object Member Presence Check for spray-json

What is this ?

Default JsonReader of spray-json maps both JSON's null value and no presense of object member to None. Therefore, we cannot determine null or no presence of member if None comes (See Sample Code!).

This library introduces an type to check member presence and None becomes to be used only for JSON's null.

In another words, this library could be thought as a counterpart of NullOptions. NullOptions works in writing json, this library works in reading json too.

Installation

Available from maven central.

If you use SBT you can include in your project with

libraryDependencies += "com.github.bigwheel" %% "spray-json-member-presence" % "<any-version>"

Sample Code

val nullValue = """{ "a": null }""".parseJson
val noMember = """{}""".parseJson

case class CaseClassA(a: Option[Int])
object CaseClassA extends DefaultJsonProtocol {
  implicit val caseClassAFormat = jsonFormat1(CaseClassA.apply)
}

println(nullValue.convertTo[CaseClassA]) // CaseClassA(None)
println(noMember.convertTo[CaseClassA]) // CaseClassA(None)
println("Cannot distinguish 😞")

case class CaseClassB(a: MemberOption[Option[Int]])
object CaseClassB extends MemberPresenceJsonProtocol {
  implicit val caseClassBFormat = jsonFormat1(CaseClassB.apply)
}

println(nullValue.convertTo[CaseClassB]) // CaseClassB(MemberSome(None))
println(noMember.convertTo[CaseClassB]) // CaseClassB(MemberNone)
println("Now we can, yeah ☺️")

Complete code is Main.scala.