"knownDirectSubclasses observed before subclass" when deriving for sealed trait

[scalalandio]

"knownDirectSubclasses observed before subclass" when deriving for sealed trait

[MateuszKubuszok]

Hello!

Sorry for the late answer but I am on my vacations and I don't hang around GH, emails and other work-related stuff too often.

I'd say that the problem's you have described are real, but also they are something I had I think with virtually every other macro annotation:

• knownDirectSubclasses is very reliant on compilation order and I usually resolved it by shuffling the other of classes and companions until it works (and I mean here also other annotations like @JsonCodec from Circe)
• I had issues in the past when something started/stopped working locally after reordering and it was completely different on CI or after clean because incremental compiler's cache was a mess.

As for the suggestion of adding ability to annotate companion object directly I could take a look at this, but it could be difficult. There is basically a reason why not so many macro annotations for adding implicits works this way:

• when you add annotation on class, in macro I receive a list of ASTs:
  • if class has no companion, it is classAST :: Nil,
  • if class has companion it is either classAST :: companionAST :: Nil or companionAST :: classAST :: Nil
• then I do pattern matching on it, and use class to extract class information (e.g. FQCN) and I use companion to inject implicits (or create it if it wasn't there)
• but if I annotate object I receive only object's AST. And it's type is different that classes type. So I would probably have to:
  • turn object's type to name , e.g MyCompanion.type
  • remove .type suffix
  • typecheck this string (which would increase the cost of compilation)
  • if type is found then use it to generate macro

It is definitely doable, but would require some hairy logic and a lot of testing. For the next few weeks I will stay off any work-related stuff but if you are interested in making a pull request and working on it I could log-in once in a while to help.