[Haskell-cafe] Listing package dependencies from GHC

[Thomas Schilling]

> If I'm doing development between ghci and vim, all the different
> dependencies I need get linked in when required without me asking.
> Similarly if I call "ghc --make" from the command line. But I have to
> write them in manually to my *.cabal file otherwise the compilation
> process will fail.
>
> Until now I've just loaded the program in to ghci and noted down all
> the dependencies it links in. Am I missing a trick? There must be an
> easier way, especially for multiple source files.


I once used this perl script to determine the files I was actually  
used (to have proper LOC stats).  It uses ghc -M which usually  
outputs the dependencies as makefile targets, and then grep over this  
to get all the .hs files.  If you have different file types you might  
want to modify this:

#!/usr/bin/env perl

# Prints the .hs files that are actually used to STDOUT

$tmpfile = '/tmp/deps';
$mainfile = 'Foo.hs';
$ghc_deps = `ghc -M $mainfile -optdep-f -optdep$tmpfile`; die "ghc -M  
failed\n" if $? != 0;

open(INF, "< $tmpfile") || die "Could not open $tempfile\n";

@files = ();

while (<INF>) {
   m/(\w+\.hs)/;
   push(@files, $1);
}

close (INF);

undef %saw;
@nodups = grep(!$saw{$_}++, @files);  # remove duplictes

print join(' ', at nodups), "\n";