Perl Hacks

Hack #17. Collect Configuration Information

Save and re-use configuration information.

Some code you write needs configuration information when you build and install it. For example, consider a program that can use any of several optional and conflicting plug-ins. The user must decide what to use when she builds the module, especially if some of the dependencies themselves have dependencies.

When you run your tests and the code in general, having this information available in one spot is very valuable—you can avoid expensive and tricky checks if you hide everything behind a single, consistent interface.

How do you collect and store this information? Ask the user, and then write it into a simple configuration module!

The Hack

Both Module::Build and ExtUtils::MakeMaker provide user prompting features to ask questions and get answers. The benefit of this is that they silently accept the defaults during automated installations. Users at the keyboard can still answer a prompt, while users who just want the software to install won't launch the installer, turn away, and return an hour later to find that another prompt has halted the process in the meantime.

Module::Build is easier to extend, so here's a simple subclass that allows you to specify questions, default values, and configuration keys before writing out a standard module containing this information:

package Module::Build::Configurator;

use strict;
use warnings;

use base 'Module::Build';

use SUPER; use File::Path; use Data::Dumper; ...