[Haskell-cafe] Find unused exports

Michael D. Adams mdmkolbe at gmail.com
Sun Nov 16 20:10:36 EST 2008

Within a set of modules, the minimal imports also give you the minimal
exports since each minimal export is required because it is imported
somewhere.  Just compile all your modules with -ddump-minimal-imports,
then cat all your "*.import" files together and sort the result.  The
minimal exports for module Foo will be listed as several lines of the
form "import Foo(x,y,z)", etc.  From there on it's just a bit of text
munging to get it into your export list code (about two lines of

Michael D. Adams

2008/11/16 Jason Dagit <dagit at codersbase.com>:
> On Sun, Nov 16, 2008 at 5:35 AM, Thomas Schilling <nominolo at googlemail.com>
> wrote:
>> The relevant flag is: -ddump-minimal-imports
>> See
>> http://www.haskell.org/ghc/docs/latest/html/users_guide/flag-reference.html#id2630684
> The documentation says this:
>> -ddump-minimal-imports
>>    Dump to the file "M.imports" (where M is the module being compiled) a
>> "minimal" set of import declarations. You can safely replace all the import
>> declarations in "M.hs" with those found in "M.imports". Why would you want
>> to do that? Because the "minimal" imports (a) import everything explicitly,
>> by name, and (b) import nothing that is not required. It can be quite
>> painful to maintain this property by hand, so this flag is intended to
>> reduce the labour.
> I already know the minimal set of import for the modules.  That's why I
> mentioned using -Wall; ghc will complain if you import something and don't
> use it.
> The problem is that you can export names that never get used in other
> modules.  I would like a tool that can look over a project and tell me which
> exported names are never imported.  These names correspond to things that
> can be removed from the project.
> Thanks,
> Jason
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