use Perl

A long, long time ago, in the deep past, at YAPC::Europe 2001 in Amsterdam, Schwern presented an idea. Well, a couple of ideas. He bundled all these ideas up into one and called them CPANTS. You should probably read his synopsis. At the end of the conference he gathered volunteers and Jos came from out of nowhere and started CPANPLUS. Since then CPANPLUS has gotten much cleverer (it can now automatically send test results to CPAN testers). However, CPANTS as a whole hadn't magically emerged from the mailing lists and discussions.

At the German Perl Workshop this year I got started thinking about it with Jos, Nicholas and Thomas. Metadata is very useful. Metrics are useful. Kwalitee (note that it's not quality) is useful. So I thought for a little bit. I wrote a quick scripts to unpack all the modules on CPAN, and a couple of scripts to go through these modules. And decided the best place for metadata about CPAN would be, errr, on CPAN. And it got a little more complicated. Then Richard helped. And I ended up with Module::CPANTS.

For example, this is what Module::CPANTS knows about Acme::Colour:

  'Acme-Colour-0.20.tar.gz' => {
    'author' => 'LBROCARD',
    'description' => 'additive and subtractive human-readable colours',
    'files' => [
      'Makefile.PL',
      'README',
      'MANIFEST'
    ],
    'lines' => {
      'nonpod' => 170,
      'pod' => 95,
      'total' => 265
    },
    'requires' => [
      'Graphics-ColorNames-0.32.tar.gz',
      'Scalar-List-Utils-1.11.tar.gz',
      'Test-Simple-0.47.tar.gz'
    ],
    'requires_module' => {
      'Graphics::ColorNames' => 0,
      'List::Util' => 0,
      'Test::Simple' => 0
    },
    'requires_recursive' => [
      'File-Spec-0.82.tar.gz',
      'Graphics-ColorNames-0.32.tar.gz',
      'Scalar-List-Utils-1.11.tar.gz',
      'Test-Harness-2.26.tar.gz',
      'Test-Simple-0.47.tar.gz'
    ],
    'testers' => {
      'fail' => 1,
      'pass' => 5
    }
  };

Note that it gets the description, even though the module isn't in the modules list (only a quarter of the distributions on CPAN are), lines of code metrics, prerequisites (and recursive prerequisites), CPAN testers data, and a list of notable files. A whole bunch of metadata.

Before you start complaining: it's just the beginning. Module::CPANTS will never do all that the CPANTS synopsis mentions. No, it doesn't have many metrics (I don't want to evaluate all the Perl code on CPAN, for one). And the interface is, well, a really big hash. Adding new metrics is easy (you may need a little disk space to test it ;-). Patches are welcome. The kwalitee() method is uncoded as yet, because I think most people want to weight metrics in different ways. I plan on releasing a version of Module::CPANTS every week, so it's only ever a couple of days out of sync with CPAN, although you can shout "database" and "web service" at me if you want.

Is this interesting? I think so. There are a whole lot of extra metrics that could be added. And if we set up a secure sandbox of some sort so that it's safe to evaluate all that Perl code, a couple more metrics. What easy-to-calculate metrics influence what you think of a Perl module? Want to help out? Check out Module::CPANTS::Generator.

And no, it's not just a plan to create the largest module on CPAN...