Question

I would like to provide a custom error message directly in the Read definition :

implicit val ar = (
 (__ \ "firstName").read[String].customError(ValidationError("bad format", "firstName")) and
 (__ \ "lastName").read[String] and
 (__ \ "address").read[Address]
)(Employee)

is this possible ?

Answer 1

We don’t have a mapError facility yet in Reads[T] or JsResult.
The best way to do that is just to redefine your own Reads[String]

implicit val StringReads = Reads{ json => json match {
  case JsString(s) => JsSuccess(s)
  case _ => JsError(Seq(JsPath() -> Seq(ValidationError("custom.error"))))
} }