Support for Scala 3

[ghostdogpr]

There are currently 2 blockers caused by usage of macros in dependencies:

• the parser is written using fastparse which heavily relies on macros and needs a rewrite. There are some efforts at porting Li Haoyi stack https://contributors.scala-lang.org/t/porting-ammonite-to-dotty/4469/11 but nothing on fastparse yet. An alternative would be using recently released cats-parse that already publishes for dotty
• schemas are derived using magnolia which is also using macros. There are also some ongoing works WIP: Scala 3 support softwaremill/magnolia#249 but nothing usable yet. An alternative would be using dotty native typeclass derivation features to derive the schema without magnolia.

Possible action items:

• migrate the Parser from fastparse to cats-parse (which supports Dotty) and compare the performance (run the benchmarks project and see if there's an impact). If there is no performance impact, we can simply replace it. Otherwise we can make a Scala 3 branch and use it only there.
• make a POC (proof of concept) for deriving caliban Schema using Scala 3 typeclass derivation. Relevant code in Caliban is https://github.com/ghostdogpr/caliban/blob/master/core/src/main/scala/caliban/schema/Schema.scala#L366. This can be done step by step, first focusing on toType() and converting the Scala type to a GraphQL type.

[ghostdogpr]

I added 2 action items. The first one can be done in Scala 2 while the second one requires exploring new territories.

[lvitaly]

@ghostdogpr, I would like to start with the first one. I will migrate the Parser from fastparse to cats-parse.

[ghostdogpr]

@lvitaly awesome! Let me know if you have any question!

[ghostdogpr]

Super helpful article on typeclass derivation with Scala 3: https://blog.philipp-martini.de/blog/magic-mirror-scala3/

[javimartinez]

I was experimenting with type class derivation in Scala 3 last week, and I think there is no support for annotations. We need that for deriving the schema, don't we? Maybe it's necessary to use Macros to achieve the same behavior

[ghostdogpr]

Yeah I guess that part requires a macro. It would be nice if https://github.com/propensive/adversaria supported Scala 3.

By the way by this small change to the link I posted, we can achieve auto derivation without the derives keyword, the way it works currently. Very promising!

[ghostdogpr]

Opened a PR with preliminary work: #847

If someone want to contribute, porting the small gqldoc string literal macro to Scala 3 would be awesome!

[javimartinez]

@ghostdogpr I could try to port the gqldoc macro to Scala 3 this weekend

[ghostdogpr]

Planning to do a first release this week!