RFC: changes to -i flag for finding source files

[Krzysztof Skrzętnicki]

I would personally love to see this feature ported to GHC.

Best regards,
Krzysztof

On Fri, May 30, 2014 at 11:00 AM, John Meacham <john at repetae.net> wrote:

> JHC has the feature that
>
> Graphics.UI.GTK.Button can live in any of:
>
> Graphics/UI/GTK/Button.hs
> Graphics/UI/GTK.Button.hs
> Graphics/UI.GTK.Button.hs
> Graphics.UI.GTK.Button.hs
>
> It lets you have deep module hiarchies without deep directory
> hierarchies and is not terribly surprising as behaviors go.
>
>      John
>
> On Fri, Apr 25, 2014 at 6:17 AM, Simon Marlow <marlowsd at gmail.com> wrote:
> > I want to propose a simple change to the -i flag for finding source
> files.
> > The problem we often have is that when you're writing code for a library
> > that lives deep in the module hierarchy, you end up needing a deep
> directory
> > structure, e.g.
> >
> >  src/
> >    Graphics/
> >      UI/
> >       Gtk/
> >         Button.hs
> >         Label.hs
> >         ...
> >
> > where the top few layers are all empty.  There have been proposals of
> > elaborate solutions for this in the past (module grafting etc.), but I
> want
> > to propose something really simple that would avoid this problem with
> > minimal additional complexity:
> >
> >   ghc -iGraphics.UI.Gtk=src
> >
> > the meaning of this flag is that when searching for modules, ghc will
> look
> > for the module Graphics.UI.Gtk.Button in src/Button.hs, rather than
> > src/Graphics/UI/Gtk/Button.hs.  The source file itself is unchanged: it
> > still begins with "module Graphics.UI.Gtk.Button ...".
> >
> > The implementation is only a few lines in the Finder (and probably rather
> > more in the manual and testsuite), but I wanted to get a sense of whether
> > people thought this would be a good idea, or if there's a better
> alternative
> > before I push it.
> >
> > Pros:
> >
> >   - simple implementation (but Cabal needs mods, see below)
> >   - solves the deep directory problem
> >
> > Cons:
> >
> >   - It makes the rules about finding files a bit more complicated.
> >     People need to find source files too, not just compilers.
> >   - packages that want to be compatible with older compilers can't
> >     use it yet.
> >   - you can't use '=' in a source directory name (but we could pick
> >     a different syntax if necessary)
> >   - It won't work for Cabal packages until Cabal is modified to
> >     support it (PreProcess and SrcDist and perhaps Haddock are the only
> >     places affected, I think)
> >   - Hackage will need to reject packages that use this feature without
> >     also specifying ghc >= 7.10 and some cabal-version too.
> >   - Are there other tools/libraries that will need changes? Leksah?
> >
> > Cheers,
> > Simon
> > _______________________________________________
> > Glasgow-haskell-users mailing list
> > Glasgow-haskell-users at haskell.org
> > http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
>
>
>
> --
> John Meacham - http://notanumber.net/
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