Is there a way to mark certain enums as being enco...

# serialization

[martmists]

Is there a way to mark certain enums as being encoded as ints rather than strings in JSON?

[hfhbd]

Just write a custom serializer

[damian]

I usually have something like this

// Lib

@PublishedApi
internal class OrdinalEnumSerializer<E : Enum<E>>(
    serialName: String,
    private val entries: EnumEntries<E>,
) : KSerializer<E> {

    override val descriptor = PrimitiveSerialDescriptor(serialName, <http://PrimitiveKind.INT|PrimitiveKind.INT>)

    override fun serialize(encoder: Encoder, value: E) {
        encoder.encodeInt(value.ordinal)
    }

    override fun deserialize(decoder: Decoder): E = entries[decoder.decodeInt()]
}

inline fun <reified E : Enum<E>> ordinalEnumSerializer(): KSerializer<E> {
    return OrdinalEnumSerializer(E::class.qualifiedName!!, enumEntries<E>())
}

// Example usage

@Serializable(with = MyEnum.Serializer::class)
enum class MyEnum {
    ONE,
    TWO,
    ;

    internal object Serializer : KSerializer<MyEnum> by ordinalEnumSerializer()
}

If you want a property other than the ordinal, you can define another interface like interface IntEnum { val intValue: Int }, constrain E to where E : Enum<E>, E : IntEnum, and tweak the serializer logic a bit