id,summary,reporter,owner,description,type,status,priority,milestone,component,version,severity,resolution,keywords,cc,difficulty,ghcversion,platform
788,Optionally exposed modules / APIs should be banned,duncan,,"It is a deliberate decision that packages cannot depend on package + flag combinations, only on packages. The point is that flags are not supposed to change the API of a package.

This needs to be enforced.

Consider a real example (from Chart package: http://hackage.haskell.org/packages/archive/Chart/0.14/Chart.cabal)
{{{
  if flag(gtk)
    build-depends: gtk >= 0.9.11
    exposed-modules: Graphics.Rendering.Chart.Gtk
}}}
The criterion package depends on Chart and imports `Graphics.Rendering.Chart.Gtk` meaning that it breaks if you build Chart with the gtk flag turned off.

The solution is that Chart should be prevented from conditionally exposing modules. We should add a QA check that looks for exposed modules that are conditional on a flag. It is annoying but somewhat less bad for modules to change between platforms.

Should it be a hard failure or just a warning?",defect,new,normal,,Cabal library,1.8.0.6,normal,,,cabal@…,unknown,,