Preparing an application for distribution

To distribute an application written in Perl we have to make sure we can easily distribute its dependencies. There might be dependencies outside of CPAN but my focus now is the list of modules one requires from CPAN.

There are several issues we need to address:

  1. Do all the prerequisites work on all the platforms we would like to support?
  2. For easy distribution, we might want them to be actually available on those platforms in the packaging system of the platform.
    Relying on the native packaging systems makes external non-CPAN dependencies also easier to handle.
  3. We have to make sure we adhere to the licence requirements of all the modules
  4. In order to ensure high quality we might want to pick a certain version of each module. We might even want to get a report of the various Kwalitee metrics from CPANTS.

Given an application it would be nice to be able to automatically generate a report with all this information.

  1. First of all we need to find out all our prerequisites. We might know our immediate prerequisites, the modules we use but they might also depend on other modules and this way we might end up with a list a lot longer than what we have direct knowledge about.
    There are several modules on CPAN that might be useful for this task. I saw [dist://Module-Dependency], Devel::Dependencies, CPAN::Unwind which uses Module::Depends::Intrusive. PAR has a script called to do this.
  2. To see if our application works on a certain platform we will have to run our own unit tests there but before doing that we might wand to see if all our prereqs already work there.
    Especially if we don't have direct access to all the platforms.
    As a minimum we have to see if there is at least one passing test report on the CPAN Testers site for each module on the given platform.
    That site has an SQLite database that can be downloaded and queried for the relevant information.
  3. It might be easier to package our application with the standard packaging system of each platform (e.g. rpm, deb, etc...).
    If we plan to do so we should make sure all our prerequisites are available in a packaged version on the specific platforms.
    This information can be partially collected using Module::Packaged.
    That module still needs more work to include further linux distributions and have it more fine grained in relation to the versions of the various distributions.
    The HTML report I created recently can provide some insight without installing the module.
  4. Most of the modules on CPAN are under the "perl license" that is GPL or Artistic but there are exceptions. For example DBD::SQLite also includes software that is in the Public domain, Compress::Zlib contains the source code of Zlib and Spreadsheet::ParsExcel::Simple is GPL only. There might be all kind of other licenses too.
    These issues need to be addressed by the legal department of each organization.
    First we need to collect the licencing information of each module. Some of them already provide their own license information in the META.yml file but most of them (as of late 2006 about 90% of them) still don't have this information available. Module::License::Report can be of help here as it analysis the files in the distribution in addition to checking the Meta.yml file.
    This still does not address the license of the additional code in the modules. I think currently there is no way to automatically collect this information.

So definitely there is some work to do in order to have such a tool. The tasks I see

  1. Add more distros to Module::Packaged and provide it for various versions of each distro.
  2. Download the database from CPANTS and assuming we have a list of modules list all the prereqs modules and all the licensing information.
  3. Integrate with one of the tools that given a script can tell which modules is it using.

Published on 2007-05-04 by Gabor Szabo