David Cantrell


CPAN::FindDependencies - find dependencies for modules on the CPAN


    use CPAN::FindDependencies;
    my @dependencies = CPAN::FindDependencies::finddeps("CPAN");
    foreach my $dep (@dependencies) {
        print ' ' x $dep->depth();
        print $dep->name().' ('.$dep->distribution().")\n";


The module uses the CPAN packages index to map modules to distributions and vice versa, and then fetches distributions' META.yml or Makefile.PL files from http://search.cpan.org/ to determine pre-requisites. This means that a working interwebnet connection is required.


There is just one function, which is not exported by default although you can make that happen in the usual fashion.


Takes a single compulsory parameter, the name of a module (ie Some::Module); and the following optional named parameters:


Warnings about modules where we can't find their META.yml or Makefile.PL, and so can't divine their pre-requisites, will be suppressed;


Failure to get a module's dependencies will be a fatal error instead of merely emitting a warning;


Use this version of perl to figure out what's in core. If not specified, it defaults to 5.005. Three part version numbers (eg 5.8.8) are supported but discouraged.


The location of CPAN.pm's 02packages.details.txt.gz file as a local filename, with either a relative or an absolute path. If not specified, it is fetched from a CPAN mirror instead. The file is fetched just once.


A directory to use for caching. It defaults to no caching. Even if caching is turned on, this is only for META.yml or Makefile.PL files. 02packages is not cached - if you want to read that from a local disk, see the 02packages option.


Cuts off the dependency tree at the specified depth. Your specified module is at depth 0, your dependencies at depth 1, their dependencies at depth 2, and so on.


If set to true, then for any module that doesn't have a META.yml, try to use its Makefile.PL as well. Note that this involves downloading code from the Internet and running it. This obviously opens you up to all kinds of bad juju, hence why it is disabled by default.

Adds recommended modules to the list of dependencies, if set to a true value.

It returns a list of CPAN::FindDependencies::Dependency objects, whose useful methods are:


The module's name;


The distribution containing this module;


The minimum required version of his module (if specified in the requirer's pre-requisites list);


How deep in the dependency tree this module is;


If any warning was generated (even if suppressed) for the module, it will be recorded here.

Any modules listed as dependencies but which are in the perl core distribution for the version of perl you specified are suppressed.

These objects are returned in a semi-defined order. You can be sure that a module will be immediately followed by one of its dependencies, then that dependency's dependencies, and so on, followed by the 'root' module's next dependency, and so on. You can reconstruct the tree by paying attention to the depth of each object.

The ordering of any particular module's immediate 'children' can be assumed to be random - it's actually hash key order.


If you set usemakefilepl to a true value, this module may download code from the internet and execute it. You should think carefully before enabling that feature.


You must have web access to http://search.cpan.org/ and (unless you tell it where else to look for the index) http://www.cpan.org/, or have all the data cached locally.. If any META.yml or Makefile.PL files are missing, the distribution's dependencies will not be found and a warning will be spat out.

Startup can be slow, especially if it needs to fetch the index from the interweb.


I welcome feedback about my code, including constructive criticism and bug reports. The best bug reports include files that I can add to the test suite, which fail with the current code in my git repo and will pass once I've fixed the bug

Feature requests are far more likely to get implemented if you submit a patch yourself.








Copyright 2007 - 2015 David Cantrell <david@cantrell.org.uk>

This software is free-as-in-speech software, and may be used, distributed, and modified under the terms of either the GNU General Public Licence version 2 or the Artistic Licence. It's up to you which one you use. The full text of the licences can be found in the files GPL2.txt and ARTISTIC.txt, respectively.


Stephan Loyd (for fixing problems with some META.yml files)

Alexandr Ciornii (for a patch to stop it segfaulting on Windows)

Brian Phillips (for the code to report on required versions of modules)

Ian Tegebo (for the code to extract deps from Makefile.PL)

Georg Oechsler (for the code to also list 'recommended' modules)

Jonathan Stowe (for making it work through HTTP proxies)


This module is also free-as-in-mason software.