Easy api to create custom en-/decoders

[987Nabil]

I do understand, that the main way to create en-/decoders are macros.
But in my experience, you always have some cases, where you'd like to have some custom ones.

I thought of something like the play json api to create reads/writes.

Or in the lights of Scala 3 context functions maybe something like

case class User(name: String, email: EmailAddress)
object User:
  implicit val decoder: JsonDecoder[User] =
    decoder {
      obj {
        field[String]("name"),
        field[EmailAddress]("email")
      }.apply { (name, email) => User(name, email) }
    }

This is more a basic idea and needs discussion, I guess.

Edit
JsonCursor could maybe be used to describe the structure of the data.
And to clarify this: I am talking about having a static description and generate out of it en-/decoders, that do not convert to the json ast first.

[plokhotnyuk]

@987Nabil You can use macrolizer.show to print code of generated codecs.

[Kalin-Rudnicki]

I imagine you mean something like circe's ProductDecoders?

  final case class Person(firstName: String, lastName: String, age: Int)

  io.circe.Decoder.forProduct3[Person, String, String, Option[Int]](
    "firstName",
    "lastName",
    "age",
  ) { (firstName, lastName, age) =>
    Person(firstName, lastName, age.getOrElse(0))
  }