RFC: changes to -i flag for finding source files
marlowsd at gmail.com
Fri Apr 25 13:17:25 UTC 2014
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.
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:
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.
- simple implementation (but Cabal needs mods, see below)
- solves the deep directory problem
- 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?
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