Play JSON combinator validates at least a field is specified - json

Question

I have a scenario that when parsing a json to a case class like this
implicit val userRead: Reads[User] = (
(__ \ "name").read[String] ~
(__ \ "email").readNullable[String] ~
(__ \ "phone").readNullable[String] ~
Reads.pure(None)
)(User.apply _)
I don't require both email and phone to be available, but at least one of them have to be available.
In my case class definition, I can prevent the case that both of them are empty with
case class User(name: String, email: Option[String], phone: Option[String], id: Option[Long] = None) {
require(email.nonEmpty || phone.nonEmpty, "must have at least an email or phone number")
}
However, doing this will generate an exception, and a 500 status is responded, when this should be a 400 error due to user input.
I can of course manually perform the verification in my controller, but I wonder if there is a cleaner way to do this.

Answer 1

I can only suggest writing you own "reads" manually
case class A(i: Option[Int], j: Option[Int])
implicit val reads: Reads[A] = new Reads[A] {
override def reads(json: JsValue): JsResult[A] = {
(for {
i <- (json \ "i").validateOpt[Int]
j <- (json \ "j").validateOpt[Int]
} yield A(i, j))
.filter(JsError("both values can't be empty"))(a ⇒ a.j.nonEmpty || a.i.nonEmpty)
}
}
And to test:
scala> Json.parse("""{ "i" : 1} """).validate[A]
res4: play.api.libs.json.JsResult[A] = JsSuccess(A(Some(1),None),)
scala> Json.parse("""{} """).validate[A]
res5: play.api.libs.json.JsResult[A] = JsError(List((,List(ValidationError(List(from and to in range can't be both empty),WrappedArray())))))

Answer 2

You can achieve this with just a small addition to your existing code (.filter(ValidationError("must have at least an email or phone number"))(u => u.email.isDefined || u.phone.isDefined)):
case class User(name: String, email: Option[String], phone: Option[String], id: Option[Long] = None)
implicit val userRead: Reads[User] = (
(__ \ "name").read[String] ~
(__ \ "email").readNullable[String] ~
(__ \ "phone").readNullable[String] ~
Reads.pure(None)
)(User.apply _).filter(ValidationError("must have at least an email or phone number"))(u => u.email.isDefined || u.phone.isDefined)
Now, to show that this works:
scala> Json.parse("""{ "name" : "foobar"} """).validate[User]
res3: play.api.libs.json.JsResult[User] = JsError(List((,List(ValidationError(List(must have at least an email or phone number),WrappedArray())))))
scala> Json.parse("""{ "name" : "foobar", "email":"test"} """).validate[User]
res4: play.api.libs.json.JsResult[User] = JsSuccess(User(foobar,Some(test),None,None),)
scala> Json.parse("""{ "name" : "foobar", "phone":"test"} """).validate[User]
res5: play.api.libs.json.JsResult[User] = JsSuccess(User(foobar,None,Some(test),None),)