Scala 3 support

[aartigao]

Not an issue, just a question: now that Scala 3 is a reality, are there any plans to support it? Specially for UNION types and removing the Shapeless dependency? Thanks!

[yzia2000]

I think shapeless 3 is out: https://github.com/dotty-staging/shapeless/tree/shapeless-3. However, dependency on scala-reflect will be a concern. Is this issue on the roadmap?

[patryk-celinski]

I'm struggling with updating the application using avrohugger from Scala 2 to Scala 3. I did extensive research on the matter.

shapeless-3 won't be much of help - avrohugger will need a complete rewrite to Scala 3. The thing is that Scala 3 removes the need for shapeless and if you look at shapeless 3 this is just a bunch of utils that help to automatically derive type classes - its more of a showcase of how cool Scala 3 is and shapeless is not needed anymore - than a newer version of shapeless.

In Scala 3 the Tuple type is a replacement for HList so generic programming is becoming a language-level feature. Tuples are covering the Product side of the problem, there is a problem with Coproduct/Sum side (related to inheritance, sealed traits family, enums basically) that they don't have their counterparts in Scala 3. It requires expertise in Scala 3 metaprogramming to recreate them - not sure if just inlining + type class derivation, or macros would be needed by avrohugger to update to Scala 3. I think it will be much easier than updating avrohugger to Scala 3 would be writing a new avrohugger-3 using Scala 3 features from start.

[patryk-celinski]

I found out that avrohugger uses treehuger that uses scala 2.12 - which also affects the chances of updating this project to Scala 3. Probably in Scala 3 build treehugger can be replaced only by Scala 3 macros.

[vesko-vujovic]

Are there any updates about plans to rewrite everything in Scala 3? Is this in the roadmap?

[julianpeeters]

Thanks for the helpful assessments, and inquiries. Long term, Scala 3 is a "yes", but I don't foresee having concrete plans or an ETA (PRs welcome, of course).

Current status: crossbuilding for 2.12, 2.13, and 3

• kept treehugger by using CrossVersion.for3Use2_13
• dropped scala-reflect and associated reflective compilation functionality
• punted on unions