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I've got an API that sends an enum as a string or an empty string in case it does not exist (which I'd like as a null); from googling around it looks like I need a custom serializer *per type.* Is that still correct or is there a better way to do that (e.g. something like @EmptyStringToNull)

Not 100% sure. But with internalised serialisation philosophy - all non standard things require own serialiser to be written

And, I'm probably wrong <https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/json.md#coercing-input-values|github.com/Kotlin/kotlinx.serialization/blob/…/json.md#…>

not sure if that's a great idea for a single case (that I've found yet)

Not sure what network stack you use, but for many of them you can have default json and for one end point have special

I'm using ktor; can you copy the default Json config and just change that part? I'd like to configure a Json bean

I'm a bit stumped who I should even implement the custom serializer

what I'd like to do is to fetch the default serializer for an enum and use that

Quickly checked and looks like whole new ktor instance is needed

```object LanguageIsoSerializer : KSerializer<LanguageIso?> {
    private val delegate = serializer<LanguageIso>().nullable

    override val descriptor: SerialDescriptor
        get() = SerialDescriptor("at.fyayc.emporixapi.i18n.LanguageIso", delegate.descriptor)

    override fun serialize(
        encoder: Encoder,
        value: LanguageIso?
    ) {
        delegate.serialize(encoder, value)
    }

    override fun deserialize(decoder: Decoder): LanguageIso? {
        val string = decoder.decodeString()
        return if (string.isNotEmpty()) {
            delegate.deserialize(decoder)
        } else {
            null
        }
    }
}```

the thing that stumps me a bit is that decoder.decodeString propably consumes the token

you could ofc also try catch, but that would also let invalid values coerce to null I think