kotlinx.serialization

Good API design dictates that you should be flexible as to what you accept and strict about what you serve. Being flexible doesn't really break anything. Elasticsearch and Opensearch both actually have partial support for JSON5 (comments), which is a nice feature if you want to document e.g. a complex query or mapping choice. It won't return any comments in the response. So it won't break other parsers. Implementing JSON 5 support like this is a valid thing to do for any server. More broad support for this in parsers would be nice. I'd probably enable this on my own servers if this was possible. I'd need that to be supported in kotlinx.serialization. See discussion on this here: https://github.com/Kotlin/kotlinx.serialization/issues/797

It makes sense for some use cases but the vast majority of use cases, parsing overhead is simply not a concern. Mobile phones are fast, networks have plenty of bandwidth (and the savings are marginal), parsers are pretty good. But done right, binary protocols are sometimes worth the marginal savings they provide. We switched over one of our APIs to use CBOR instead of json. It's a search API that we hit a lot and I wanted to cut down on the bytesize of the responses a little. The savings are not that impressive. But I'll take 10% when i can get it. Otherwise, this was a pretty simple change. We use kotlinx serialization in a multi-platform library. Basically, all we did is configure it to use CBOR instead of json. https://github.com/Kotlin/kotlinx.serialization/blob/master/... Half hour job. Haven't looked at it since; just works. It supp

You do it like this: https://github.com/Kotlin/kotlinx.serialization/blob/master/...

It's not annotation processing, it's a compiler plugin with IDE support. So pretty deeply integrated. It avoids some of those issues. The kotlinx.serialisation design is pretty nice. It's basically what you describe. The compiler generates generic code that can call into a variety of "codecs" but they don't have to actually be serialisation specific. So there are codecs for JSON, protobufs, CBOR etc but you can also do arbitrary object graph transformations with the framework. A deep clone being a simple hello-world type example. I've never used Shapeless but it sounds pretty similar in some ways. https://github.com/Kotlin/kotlinx.serialization

Kotlin serialization[0] is similar to this, implemented via a compiler plugin that allows optimal serializers/deserializers to be generated at compile time. [0] https://github.com/Kotlin/kotlinx.serialization