Sum types

Sum types are sealed traits, sealed classes and non-singleton enums.
Since they have one or more subtypes, we need to disambiguate between them somehow.

The default in Tupson is to use the @type property.
Its value is the simple type name of class or enum case.
This makes JSON independent of scala/java package and it is more readable.

Example:

enum Color derives JsonRW:
  case Hex(num: String)
  case Yellow

val color = Color.Hex("FFF")

println(color.toJson)
// { "@type":"Hex", "num":"FFF" }
Scala

Custom type key

You can use some other key by annotating the sum type with @discriminator:

@discriminator("myOtherKey")
enum Color derives JsonRW ...

println(color.toJson)
// { "myOtherKey":"Hex", "num":"FFF" }
Scala