Installing CPAN modules from git

(picture from elevate)

For various reasons, you might want to install CPAN modules from a git repository.

It can be because somehow a git repository is in advance against CPAN:

• A fix was merged in official git repository but never released to CPAN
• A branch or a fork contains some valuable changes (this very-little-but-absolutely-needed fix)

Or it can be because the modules are actually not in CPAN: not public and not in a alternative/private CPAN (see Addendum) or simply they are only "experiments"

But this post is not meant to discuss about the "why" but instead mainly share technically the "how" you could do that 😀

I tested various syntax and installers and will share now some working examples.

☝️ Before we continue, be sure to upgrade your installers (App::cpm and App::cpanminus) to their latest

Installing from command line with cpm

Installing with cpm is straighforward:

$ cpm install https://github.com/plack/Plack.git --verbose
33257 DONE fetch     (0.971sec) https://github.com/plack/Plack.git
33257 DONE configure (0.033sec) https://github.com/plack/Plack.git
33257 DONE resolve   (0.031sec) Clone -> Clone-0.46 (from MetaDB)
...
33257 DONE install   (0.364sec) URI-5.28
33257 DONE install   (0.046sec) https://github.com/plack/Plack.git
31 distributions installed.

It can also work the same with ssh [e-mail]:plack/Plack.git:

$ cpm install [e-mail]:plack/Plack.git --verbose
64383 DONE fetch     (2.498sec) [e-mail]:plack/Plack.git
64383 DONE configure (0.039sec) [e-mail]:plack/Plack.git
...
64383 DONE install   (0.045sec) [e-mail]:plack/Plack.git
31 distributions installed.

Installing from command line with cpanminus

Installing with cpanm is not harder:

$ cpanm https://github.com/plack/Plack.git
Cloning https://github.com/plack/Plack.git ... OK
--> Working on https://github.com/plack/Plack.git
...
Building and testing Plack-1.0051 ... OK
Successfully installed Plack-1.0051
45 distributions installed

Installing from cpanfile

The correct syntax is the following (thank you @haarg):

requires 'Plack', git => 'https://github.com/plack/Plack.git', ref => 'master';

(ref => 'master' is optional)

And it would just work later with cpm:

$ cpm install --verbose
Loading requirements from cpanfile...
33257 DONE fetch     (0.971sec) https://github.com/plack/Plack.git
33257 DONE configure (0.033sec) https://github.com/plack/Plack.git
33257 DONE resolve   (0.031sec) Clone -> Clone-0.46 (from MetaDB)
...
33257 DONE install   (0.364sec) URI-5.28
33257 DONE install   (0.046sec) https://github.com/plack/Plack.git
31 distributions installed.

⚠️ Despite being a cpanfile, please note the use of cpm

Installing from cpmfile

Let's write our first cpmfile and save it as cpm.yml:

prereqs:
  runtime:
    requires:
      Plack:
        git: https://github.com/plack/Plack.git
        ref: master

And then it would just work with cpm:

$ cpm install --verbose
Loading requirements from cpm.yml...
66419 DONE resolve   (0.000sec) Plack -> https://github.com/plack/Plack.git@master (from Custom)
66419 DONE fetch     (1.695sec) https://github.com/plack/Plack.git
66419 DONE configure (0.034sec) https://github.com/plack/Plack.git
...
66419 DONE install   (0.023sec) https://github.com/plack/Plack.git
31 distributions installed.

Beware of "incomplete" repositories

Releases on CPAN are standardized and generally contain what is needed for installers, but distributions living in git repositories are more for development and very often not in a "ready to install" state.

(thank you @karenetheridge)

There's some limitations that you can encounter:

• cpm would refuse to install if no META file is found (but cpanm would be OK with that)
• cpm would refuse to install if no Makefile.PL nor Build.PL is found, except if x_static_install: 1 is declared in META (cpanm would still refuse)

Should I mention the repositories with only a dist.ini? (used by authors to generate everything else)

And you would get similar trouble with distributions using Module::Install but having not versioned it.

Conclusion

You should probably not rely too much on "install from git" method but still, it can provide an handy way to install modules to test fixes or experiments.

And now with this post you should have good examples of “how” you can achieve that.

Addendum

For alternative/private CPAN, several tools can come to your rescue:

• minicpan
• opan
• OrePAN2
• pinto