Question: How to teach jsoniter-scala about zio.prelude.Newtype ?

[domdorn]

Hello!

We decided to migrate from

case class RelationTypeId(x: String) extends AnyVal

to

object MyId extends zio.prelude.Newtype[String]

with a

package xxx { 
 type RelationTypeId = RelationTypeId.type
}

Now, I have to create codecs for all these datatypes by hand like

  implicit val relationTypeIdCodec: JsonCodec[RelationTypeId]     = new JsonCodec[RelationTypeId] {
    override def decodeValue(in: JsonReader, default: RelationTypeId): RelationTypeId = RelationTypeId(in.readString(RelationTypeId.unwrap(default)))

    override def encodeValue(x: RelationTypeId, out: JsonWriter): Unit = out.writeVal(RelationTypeId.unwrap(x))

    @SuppressWarnings(Array("AsInstanceOf"))
    override def nullValue: RelationTypeId = null.asInstanceOf[RelationTypeId]

    override def decodeKey(in: JsonReader): RelationTypeId = RelationTypeId(in.readKeyAsString())

    override def encodeKey(x: RelationTypeId, out: JsonWriter): Unit = out.writeVal(RelationTypeId.unwrap(x))
  }

Is there a way I could teach jsoniter-scala how to create the codecs?
I tried creating one like this, but can't get it to compile:

  implicit def newtypeStringCodec[T <: zio.prelude.Newtype[String]]: JsonCodec[T] =
    new JsonCodec[T] {
      override def decodeValue(in: JsonReader, default: T): T = T(in.readString(T.unwrap(default)))

      override def encodeValue(x: T, out: JsonWriter): Unit = out.writeVal(T.unwrap(x))

      @SuppressWarnings(Array("AsInstanceOf"))
      override def nullValue: T = null.asInstanceOf[T]

      override def decodeKey(in: JsonReader): T = T.apply(in.readKeyAsString())

      override def encodeKey(x: T, out: JsonWriter): Unit = out.writeVal(T.unwrap(x))
    }
    ```

[plokhotnyuk]

Hi Dominik,

Could you please share a repository or Scastie link that will reproduce your compilation errors?