Hey guys, what's the best way to deal with this er...

# arrow

[Benoît]

Hey guys, what's the best way to deal with this error? Thanks

[Javier]

If Nel is not serializable you can create a custom serializer for it

[Javier]

https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/serializers.md

[Javier]

in the custom serializer part you can choose among multiple ways to solve it

[simon.vergauwen]

We should support these things from a common module, but it probably belongs in a separate repository (?) 🤔

@Benoît you should be able to delegate to List.serializer

[Javier]

It can be a good idea to have an additional artifact with arrow serializers so we haven't to depend on serialization dependency on arrow as Simon said

[Benoît]

Thanks to both of you for your answers, I was thinking of doing this manually yes, was just wondering first if there was an already existing NelSerializer somewhere that I had missed

[than_]

for serialization of (not just) arrow datatypes I have this handy interface:

interface IsoSerializer<ENTITY, SURROGATE> : KSerializer<ENTITY> {

    val surrogateSerializer: KSerializer<SURROGATE>
    val iso: Iso<ENTITY, SURROGATE>

    override fun deserialize(decoder: Decoder): ENTITY =
        decoder.decodeSerializableValue(surrogateSerializer).let(iso::reverseGet)


    override val descriptor: SerialDescriptor
        get() = surrogateSerializer.descriptor

    override fun serialize(encoder: Encoder, value: ENTITY) {
        encoder.encodeSerializableValue(surrogateSerializer, iso.get(value))
    }

    companion object {
        inline operator fun <ENTITY, reified SURROGATE> invoke(
            iso: Iso<ENTITY, SURROGATE>,
            surrogateSerializer: KSerializer<SURROGATE>,
        ) = object : IsoSerializer<ENTITY, SURROGATE> {
            override val surrogateSerializer = surrogateSerializer
            override val iso = iso
        }
    }
}

here you can easily serialize anything by just providing a serializable surrogate type and an iso between your type and the surrogate

class NelSerializer<T>(elementSerializer: KSerializer<T>) :
    IsoSerializer<NonEmptyList<T>, List<T>> by IsoSerializer(Nel.listIso(),
        ListSerializer(elementSerializer))

fun <T> NonEmptyList.Companion.listIso(): Iso<NonEmptyList<T>, List<T>> = Iso(
    get = ::identity,
    reverseGet = { if (it is Nel<T>) it else Nel.fromListUnsafe(it) }
)

[Benoît]

Amazing! Thanks a lot @than_