Scala 3 case object derivation differs from Scala 2

[hearnadam]

The following code produces differing JSON outputs on Scala 2 and 3:

import zio.json._

sealed trait Parent
object Parent {
  case object Child extends Parent
  def child: Parent = Child
  implicit val codec: JsonCodec[Parent] = DeriveJsonCodec.gen
}

println(Parent.child.toJson)

Scala 2: {"Child":{}}
Scala 3: "Child"

https://scastie.scala-lang.org/WgCoAai8QoeoQ0bbSAeuVg

[plokhotnyuk]

The default value for JsonCodecConfiguration has changed in Scala 3. To prevent unexpected behavior, you should explicitly define your preference before deriving the codec.

You can set enumValuesAsStrings to either true or false depending on your needs:

// Choose one of the following:
implicit val config: JsonCodecConfiguration = JsonCodecConfiguration(enumValuesAsStrings = false)
// or
implicit val config: JsonCodecConfiguration = JsonCodecConfiguration(enumValuesAsStrings = true)