BSON serialization with ADT and enumeration

[mikeb]

Hello,

I have problem with BSON serialization with ADT structure and Enumeration library. 
Example structure:

sealed trait Color {
def value: String
}

case class UnknownColor(value : String) extends Color

sealed abstract class KnownColor(val value: String) extends StringEnumEntry with Color

object KnownColor extends StringEnum[KnownColor]{
override def values: IndexedSeq[KnownColor] = findValues

case object Red extends KnownColor("red")
case object Blue extends KnownColor("blue")
}

case class ColorWrapper(
id: UUID,
color: Color
)

I want to save in DB ColorWrapper. To do this I tried to create handlers like this:

implicit val knownColorFormat = new EnumHandler[KnownColor](KnownColor) //my own handler
implicit val unknownColorFormat = Macros.handler[UnknownColor]

type PredefinedColor = UnionType[KnownColor \/ UnknownColor] with Verbose
implicit val predefinedColor = Macros.handlerOpts[Color, PredefinedColor]
implicit val colorWrapperHandler = Macros.handler[ColorWrapper]

It compiles, but while testing writing ColorWrapper(UUID.randomUUID(), KnownColor.Red) I got runtime error:

reactivemongo.api.bson.exceptions.HandlerException, with message: Fails to handle 'color': Value doesn't match: Red.

From verbose I see that there is no KnownColor:

[info] /..../EnumTraitTest.scala:54:52: // Writer (predefinedColor)

[info] {

[info]   val macroCfg$macro$17: _root_.reactivemongo.api.bson.MacroConfiguration = bson.this.MacroConfiguration.default[reactivemongo.api.bson.MacroOptions](MacroOptions.this.ValueOf.optionsDefault);

[info]   macroVal match {

[info]     case (macroVal$macro$18 @ (_: EnumTraitTest.this.UnknownColor)) => EnumTraitTest.this.unknownColorFormat.writeTry(macroVal$macro$18).map(((x$1) => x$1.$plus$plus(_root_.reactivemongo.api.bson.BSONElement(macroCfg$macro$17.discriminator, _root_.reactivemongo.api.bson.BSONString(macroCfg$macro$17.typeNaming(implicitly[_root_.scala.reflect.ClassTag[EnumTraitTest.this.UnknownColor]].runtimeClass))))))

[info]     case _ => _root_.scala.util.Failure(_root_.reactivemongo.api.bson.exceptions.ValueDoesNotMatchException(macroVal.toString))

[info]   }

[info] }

[info]   implicit val predefinedColor = Macros.handlerOpts[Color, PredefinedColor]

Why predefinedColor does not contain KnownColor? Is there any other way to create macro to serialize it?

[Cédric Chantepie]

Which version? Which lib? Why not using enumeratum?

[mikeb]

Sorry, I forgot to add libs I'm using:
"org.reactivemongo" %% "reactivemongo" % "1.0.3",
"com.beachape" %% "enumeratum" % "1.6.1",

StringEnum and StringEnumEntry are from enumeratum. 

To avoid further misunderstanding, I created repository where you can reproduce issue https://github.com/michalbogacz/reactivemongo-playground/blob/master/src/test/scala/EnumTraitTest.scala 

[Cédric Chantepie]

There is an issue with macro options defined as type alias and not directly.

It can be fixed by either trying the 1.0.4-SNAPSHOT or just declaring the options directly:

  implicit val predefinedColor = Macros.handlerOpts[Color, UnionType[KnownColor \/ UnknownColor] with Verbose]

But then, there will a model design issue as your union type is mixing case class (represented as BSON document) and enum type (represented as simple BSON value), whereas all the member of a union type/sealed family need to be represented as document, so a discriminator can be added.

[mikeb]

Thank you for checking this, I was sure I was missing something. 
In the end, I decided to make my own handler, to be sure that serialization won't change with update of library.