What's the recommended approach when creating a ne...

# serialization

[CLOVIS]

What's the recommended approach when creating a new format that has more primitive types than JSON?

I'm adding BSON, which has ObjectId , Uuid , Timestamp etc as primitive types. However, KSerializer doesn't have the equivalent .encodeObjectId , .decodeObjectId etc methods.

I want users to be able to write custom serializers that take advantage of these primitive types. Also, these serializers should still work with other formats (with an appropriate fallback, for example ObjectId can be represented as an hex-encoded string in JSON).

[ephemient]

`SerialKind`/`PrimitiveKind` are sealed so the obvious way of doing it isn't possible

[ephemient]

but you could use an existing kind and an annotation to mark your extended primitive types instead

[ephemient]

it might be annoying if you want kotlin.uuid.Uuid to work by default though, you might have to special case if (serializer.descriptor == Uuid.serializer().descriptor) in your format's `encodeSerializableValue`/`decodeSerializableValue`

[CLOVIS]

you might have to special case

That"s what I'm doing at the moment, but I have no idea if that's a good practice or not.

[CLOVIS]

use an existing kind and an annotation to mark your extended primitive types instead

Is there documentation on how to do that?

[efemoney]

KxS primitives are not about the format but about language so I wouldn’t expect something like this to be supported.

Is there documentation on how to do that?

Mark a custom annotation with @SerialInfo, that means that when your users put that custom annotation on a class / property, then the annotation will be added to the annotations property of the descriptor as metadata that you can use while serializing or deserializing

[Adam S]

> you might have to special case

That"s what I'm doing at the moment, but I have no idea if that's a good practice or not.

I think that's expected. The 'Efficient binary format' example handles ByteArrays specially, by checking if serializer.descriptor == byteArraySerializer.descriptor.

https://github.com/Kotlin/kotlinx.serialization/blob/v1.9.0/docs/formats.md#format-specific-types