Sealed Classes Serialization Support

[julianfalcionelli]

Seems that Kotlinx serialization is failing when trying to persist Sealed Classes in Firebase Realtime Databases.

I have the following hierarchy classes:

@Serializable
sealed class Activity {
  abstract val type: Type
  
  @Serializable
  enum class Type(
    @Transient
    val shortName: StringResource
  ) {
    BJJ(
      MR.strings.activity_bjj,
    ),
    GRAPPLING(
      MR.strings.activity_grappling,
    )
  }
  
  @Serializable
  data class Bjj(
    override val type: Type = Type.BJJ,
    var belt: Belt? = null,
    val stripes: Int = 0
  ) : Activity() {
    @Serializable
    enum class Belt(
      @Transient
      val color: ColorResource.Single
    ) {
      WHITE(MR.colors.belt_white),
      BLUE(MR.colors.belt_blue),
      PURPLE(MR.colors.belt_purple),
      BROWN(MR.colors.belt_brown),
      BLACK(MR.colors.belt_black)
    }
  }
  
  @Serializable
  data class Grappling(
    override val type: Type = Type.GRAPPLING
  ) : Activity()
}

Then I try to persist a list of Activities:

val ref = database
  .child(ROOT_PATH)
  .child(user.id)
  .child("activities")
ref.setValue(ListSerializer(Activity.serializer()), updatedActivities)

And then this error happens:

 java.lang.ClassCastException: kotlinx.serialization.descriptors.PolymorphicKind$SEALED cannot be cast to kotlinx.serialization.descriptors.StructureKind
    at dev.gitlive.firebase._encodersKt.structureEncoder(_encoders.kt:12)
    ...

[nbransby]

Thanks for the report, are you able to send a PR with a failing unit test for this?

[julianfalcionelli]

Yes, I can do it these days 👍

[julianfalcionelli]

I am not being able to run tests in a KMM project, I have to figure out what's going on. Tried with "Invalidate caches and restart", etc and the issue persists :(

[nbransby]

closing as fixed