What is the benefit of using the `Serializer` annotation?

# serialization

[Paul Woitaschek]

What is the benefit of using the Serializer annotation?

[hfhbd]

You mean Serializer(forClass)? To generate a kotlinx serializer by the compiler for a given Kotlin class. I think, the only use case are classes from 3rd party libs

[Paul Woitaschek]

Ah you mean it creates the synthetic .serializer() function?

[hfhbd]

Yes, it does.

[Paul Woitaschek]

Ah nice. If that was only auto discoverable 🤔

[hfhbd]

Hm, if you use the Serializer annotation, you don't need to implement the object by yourself: https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/serializers.md#deriving-external-serializer-for-another-kotlin-class-experimental
Or you remove the annotation and implement the serializer by yourself.
And yeah, you need to pass the serializer explicitly (or use @file)

[Paul Woitaschek]

It was an example for an external dependency

[hfhbd]

What do you mean?

// external
data class Dog(val name: String)

// your code
@Serializer(forClass = Dog::class)
object DogSerializer

@Serializable
data class Person(@Serializable(with = DogSerializer::class) val dog: Dog)

[Paul Woitaschek]

If that was only auto discoverable 🤔

Yeah I know, but with your example the Serializer annotation is now pointless

[hfhbd]

Yeah, you still need to add the serializer to the uri parameter.

[hfhbd]

Yeah, because you implemented the serializer by yourself.

[Paul Woitaschek]

I know, but from my perspective, kotlinx could already do that logic without me being forced to add file:UseSerializers everywhere

[hfhbd]

Hm, but you could serialize the same type with different strategies, eg handling dates from different apis...

[Paul Woitaschek]

Yep I know. But it could do it if there was only a single available or sth like that

[Paul Woitaschek]

Just dreaming, i know that it doesn't play well with the way how compilation works

[hfhbd]

I agree, I think it is annoying too, buuuut, the serializer could be (in theory) also stored in another module or dependency. 😄

[Paul Woitaschek]

To me, even a compiler flag would greatly simplify things.
Sth like

serialization {
  serializer("some.platform.FancyClass", "my.company.FancyClassSerializer")
}

[hfhbd]

Isn't this possible with the serializerModule? 🤔

[Paul Woitaschek]

Yeah but contextual serialization is an all or nothing thing and you still need to declare it.

[Paul Woitaschek]

I think the best solution for me would be a gradle configuration option, i.e.

serialization {
  contextualSerialization("android.net.Uri", "java.net.URL")
}