Auto install of a perl package if 'use' statement fails

[Zubinix]

Hi all

Has anyone ever written some code that would install a perl package dependency if the corrosponding 'use' statement failed?

For example, if I've written code that relies on a perl module that is not part of the standard distribution and this code is to be distributed to many machines, how can I check that the required module is missing and auto install it - and do it without user intervention?

Thanks Perl Monks!

[randyk]

Try CPAN::AutoINC.

[Zubinix]

Thanks. This seems to be more along the lines of what I'm after.

[tilly]

Yes. I've seen it done. I believe that Abigail did it, but I can't find the code.

Anyways the idea is simple. If you read the documentation for require, you'll find that you can put subroutines in @INC. Then you can pull tricks like this untested code:

use LWP::Simple qw(get);

BEGIN {
  push @INC, sub {
    shift;
    my $file = shift; # eg "Foo/Bar.pm"
    my $content = get("http://myrepository.com/modules/$file");
    if ($content) {
      open(my $fh, "<", \$content);
      return $fh;
    }
    else {
      return;
    }
  }
}

(This one grabs the module off of a webserver, and loads it directly. No local installation needed! With older versions of Perl you'll need IO::Scalar instead of the open trick that I used to put the contents of a scalar into a filehandle.)

[Zubinix]

Thanks for this. I will follow up on it :-)

[Old_Gray_Bear]

I also am afraid of 'automatic installation' tools. Like jbruger I prefer to exercise (a modicum) of control over what gets installed on my machines. It's not that I don't trust my User community, I can't. I am the 'responsible party' when the SEC auditors come through, and I don't want to have to explain what package Xyz::IOwn::TheWorld is doing on a (supposedly) secure server that happens to be handling credit-card data. I am willing to install what the user wants/needs (within reason), when asked, but I do need to have a piece of paper for the files.

And the other side of that coin is the tyographical error problem: The number of times I type "use warnigns;" is legion. With 'auto-install of package on use failure', then every time I typoed, Perl would have to take time out to search CPAN, determine that the module didn't exist, and report back; I'd get a lot grayer waiting. I'd be sorely tempted to build my own pragmas (with the appropriate mis-spelled name) to get around it. That would get to be both a maintenance headache and a distribution nightmare. I much prefer the current polite error message followed by a quick exit, stage left.

[syphilis]

Acme::Everything ?

Cheers,
Rob

[jbrugger]

To be honest, i would not want that kind of behavior. I, and only i am to decide if a new package is installed on my machine.
Using a good documentation along with your program, and anyone familiar using cpan should be able to deal with it.
Why?
If only by the fact that i rather use the deb / rpm packages (if they exist) in the standard linux distribution i use, than a self compiled one.
All system upgrades take care of new packages as well then for me.
Don't mess with auto installation.
For perl-only packages, well, just put them in your program library.

[Zubinix]

This program is to operate in a build farm which has approx 200 Windows and Linux machines - so it multi-platform as well. I'd rather have a 'pull' mechanism over a 'push' mechanism so the correct perl modules get installed only on the required machines on demand.

[Anonymous Monk]

you could use an eval to test the existance of a particular module.

use CPAN;

eval "use My::Module" 
 or do { 
  CPAN::install("My::Module");
  # or your code to install your custom module
};

[idsfa]

See, for example, Remote Module "use" and the responses for a couple of solutions.