Add support to extract all variable or type annotations (issue #1051)

[pgrandjean]

Following issue #1051, adding support to extract all variable or type annotations from case classes.

Closes #1051

[joroKr21]

That looks binary compatible - it could make it into a 2.3 release

[milessabin]

LGTM!

[joroKr21]

@pgrandjean thank you, the implementation looks great 👍

I am only missing tests for all annotations of sealed traits

[pgrandjean]

@pgrandjean thank you, the implementation looks great 👍

I am only missing tests for all annotations of sealed traits

Also added tests for sealed trait, although there are no type annotations for sealed traits.

[pgrandjean]

branch issue_1051 rebased on main.

[joroKr21]

Also added tests for sealed trait, although there are no type annotations for sealed traits.

Hmm it's technically possible:

case class Ann(s: String) extends StaticAnnotation
sealed trait Foo
case object Bar extends Foo @Ann("as")

But the current implementation doesn't find them and I wonder if it makes any sense.
But I also don't know what's the use case of type annotations in general.

[joroKr21]

I'm trying to pull that thread but I encountered an annoying issue - dealias behaves differently in the compiler (preserving type annotations) and in macros (discarding type annotations) 😕

[pgrandjean]

Hmm it's technically possible:

You're right. I don't know why I was convinced of the opposite. Sorry for that.

AllTypeAnnotations fixed for sealed traits. In this case, the type annotations are attached to the parent class (Base2), so one needs to go one layer deeper in the AST in function extract.

[joroKr21]

@pgrandjean that looks good to me already. Sorry to keep expanding the scope but I'm wondering if we should make something like this work, which seems to me like a more compelling use case for type annotations:

  final case class validated(id: String) extends StaticAnnotation
  type PosInt = Int @validated("positive") 
  type Email = String @validated("email")
  final case class User(email: Email, age: PosInt)

I tried it but it seems that .dealias sometimes preserves annotations and sometimes loses them. Anyway I'm happy to merge this as is, just suggesting what we could do next.

[pgrandjean]

@joroKr21 I think it is possible to achieve this without dealias. Just pushed a change to the extract function to take into account TypeRefs. Test added, seems to work.

[joroKr21]

One last thing 🙏

[joroKr21]

Thank you @pgrandjean for your work and patience and congratulations on your first merge to shapeless! 🥳

[pgrandjean]

Thank you @joroKr21 !

[joroKr21]

@pgrandjean wow I completely forgot about #925, sorry!

GitHub lied to me and told me you're a first time contributor - it even asked me to approve your CI run 🙈
But having a bad memory is my own fault 😄 so I guess congratulations on your second PR 👍

I will try to backport them to the 2.3 branch soon, I think there will be no issues 🤞