Feature Request: reexported-modules should be able to export other-modules

[ekmett]

Modules that aren't in exposed-modules aren't allowed to be used as reexported-modules.

If we could re-export other-modules, this would give users a lot more freedom when designing project structure without using internal libraries as shims.

[phadej]

I'm a confused (re-exporting "hidden" other-modules?), could you write few examples, how'd you like this too look like?

[23Skidoo]

/cc @ezyang

[ekmett]

If this worked, then with

library
  other-modules: Foo Bar
  reexported-modules: 
     Foo as Crazy.Deep.Path.Foo,
     Bar as Crazy.Deep.Path.Bar

in the project you can work with Foo.hs and Bar.hs in your top level directory.

To do it today you'd need to use

library private
  exposed-modules: Foo Bar

library
  build-depends: private
  reexported-modules:
     Foo as Crazy.Deep.Path.Foo,
     Bar as Crazy.Deep.Path.Bar 

but private is just an administrative detail, and gets in the way when you already have lots of other little private libraries.

[ezyang]

I don't think there is any reason we couldn't do this, but I think ghc-pkg will have to be updated to play ball, which means that you're going to need to hit a GHC release to have this fixed.