working on a multiplatform library which is also s...

# arrow

[S.]

working on a multiplatform library which is also supposed to be used with K/Js, I'm getting [NON_EXPORTABLE_TYPE] Exported declaration uses non-exportable return type: 'arrow.core.Either<A, B>' when I add @JsExport to a class containing an Either. same for NonEmptyList . Is there any possible solution to this?

[Alejandro Serrano.Mena]

maybe we should add @JsExport to every class in arrow-core?

[S.]

@Serializable as well while you're at it 😅

[S.]

regarding the JsExport issue, I have no idea what was going on there. even my domain error interfaces caused uncaught type errors in js, while being annotated with @JsExport . I merged the back and frontend repos and directly import the modules now instead of a maven library and this fixes it

[Alejandro Serrano.Mena]

serialization support for kotlinx.serialization is provided in an additional artifact arrow-core-serialization

[S.]

yeah I saw that but for returning Either I needed to wrap it into a serializable class itself

[Alejandro Serrano.Mena]

it should be enough to add the corresponding module to your kotlinx.serialization configuration

[S.]

it's about the kotlin rpc library, the code is being generated, not sure if I have access to a config for that. but I need to revisit this again

[Alejandro Serrano.Mena]

if you have any more information so I can try to reproduce it, that would be great

[S.]

will look into it! (need to clean up after merging the repos first)

[S.]

alright so it was indeed the module missing, and you still need the UseSerializers annotation.

cbor {
    serializersModule = SerializersModule {
        contextual(Either::class) { (a, b) -> EitherSerializer(a, b) }
        contextual(Ior::class) { (a, b) -> IorSerializer(a, b) }
        contextual(NonEmptyList::class) { (t) -> NonEmptyListSerializer(t) }
        contextual(NonEmptySet::class) { (t) -> NonEmptySetSerializer(t) }
        //  contextual(Option::class) { (t) -> OptionSerializer<*>(t) }
    }
}
...
@file:UseSerializers(
    NonEmptyListSerializer::class,
    EitherSerializer::class,
    OptionSerializer::class,
    UuidSerializer::class
)

I couldn't find the Arrow module from this PR though https://github.com/arrow-kt/arrow/pull/3413

[Alejandro Serrano.Mena]

it's going to be released as part of 2.0

[S.]

ah okay. but what about the OptionSerializer? IJ says it can't infer the type

[Alejandro Serrano.Mena]

it should work similarly to Either and Ior, (I see you wrote OptionSerializer<*> there)

[S.]

Argument type mismatch: actual type is 'kotlinx. serialization. KSerializer<CapturedType(*)>', but 'kotlinx. serialization. KSerializer<T>' was expected. for the t parameter in

contextual(Option::class) { (t) -> OptionSerializer(t) }

[Alejandro Serrano.Mena]

interesting, since that works in the code in the repo https://github.com/arrow-kt/arrow/blob/main/arrow-libs/core/arrow-core-serializati[…]commonMain/kotlin/arrow/core/serialization/SerializersModule.kt

[S.]

yeah. in the provider argument it is <*> but it works for all the others

public override fun <T : Any> contextual(
        kClass: KClass<T>,
        provider: (typeArgumentsSerializers: List<KSerializer<*>>) -> KSerializer<*>
    ): Unit = registerSerializer(kClass, ContextualProvider.WithTypeArguments(provider))