Enum (Discriminated Union) Encoding

Given the following Scala types and values:

// Types:
case class OneStreamSink(topic: String)
sealed trait Sink
object Sink {
  case class OneStream(sinkData: OneStreamSink) extends Sink
  case object ConsoleLog extends Sink
}

// Values:
val os = Sink.OneStream(OneStreamSink(topic = "123"))
val oc = Sink.ConsoleLog

and the equivalent in Morphir/ELM:

-- Types
type alias OneStreamSink = { topic: String }
type Sink =
  OneStream {- sinkData: -} OneStreamSink
  | ConsoleLog

-- Values:
os: Sink
os = OneStream { topic = "123" }

oc: Sink
oc = ConsoleLog

The value os would be represented in the Morphir data-model as the following:

val os = Data.Case(
  values = List(
    EnumLabel.Named("sinkData") -> 
      Data.Record(L("topic") -> Data.String("123")) 
  )
  enumLabel = "OneStream",
  shape = enumConcept /* will be described in just a minute */
)

Note how the OneStream enum fields sinkData is represented as EnumLabel.Named("sinkData"). Not all languages support the naming for enum fields. As you can see in the Morphir/ELM example abovem it is commented out. Therefore instead of EnumLabel.Named("sinkData") in the Moprhir-data model, it would be represented as EnumLabel.Empty.

val os = Data.Case(
  values = List(
    EnumLabel.Empty -> 
      Data.Record(L("topic") -> Data.String("123")) 
  )
  enumLabel = "OneStream",
  shape = enumConcept /* will be described in just a minute */
)

The value oc would be represented as the following:

// val oc: Sink = Sink.ConsoleLog // (Scala)
// oc = ConsoleLog                // (Morphir/ELM)

val oc = Data.Case(
  values = List()
  enumLabel = "ConsoleLog",
  shape = enumConcept /* will be described in just a minute */
)

On a schema-level the Concept for this enum would be the following:

Concept.Enum(
  name = "Sink",
  cases = List(
    Concept.Enum.Case(
      L("OneStream"),
      fields = List(
        EnumLabel.Named("sinkData") -> 
          Concept.Record(L("topic") -> Concept.String)
      )
    ),
    Concept.Enum.Case(
      L("ConsoleLog"),
      fields = List()
    )    
  )
)