NAME

Dist::CheckConflicts - declare version conflicts for your dist

VERSION

version 0.11

SYNOPSIS

    use Dist::CheckConflicts
        -dist => 'Class-MOP',
        -conflicts => {
            'Moose'                => '1.14',
            'namespace::autoclean' => '0.08',
        },
        -also => [
            'Package::Stash::Conflicts',
        ];

    __PACKAGE__->check_conflicts;

DESCRIPTION

One shortcoming of the CPAN clients that currently exist is that they have no way of specifying conflicting downstream dependencies of modules. This module attempts to work around this issue by allowing you to specify conflicting versions of modules separately, and deal with them after the module is done installing.

For instance, say you have a module Foo, and some other module Bar uses Foo. If Foo were to change its API in a non-backwards-compatible way, this would cause Bar to break until it is updated to use the new API. Foo can't just depend on the fixed version of Bar, because this will cause a circular dependency (because Bar is already depending on Foo), and this doesn't express intent properly anyway - Foo doesn't use Bar at all. The ideal solution would be for there to be a way to specify conflicting versions of modules in a way that would let CPAN clients update conflicting modules automatically after an existing module is upgraded, but until that happens, this module will allow users to do this manually.

This module accepts a hash of options passed to its use statement, with these keys being valid:

-conflicts: A hashref of conflict specifications, where keys are module names, and values are the last broken version - any version greater than the specified version should work.
-also: Additional modules to get conflicts from (potentially recursively). This should generally be a list of modules which use Dist::CheckConflicts, which correspond to the dists that your dist depends on. (In an ideal world, this would be intuited directly from your dependency list, but the dependency list isn't available outside of build time).
-dist: The name of the distribution, to make the error message from check_conflicts more user-friendly.

The methods listed below are exported by this module into the module that uses it, so you should call these methods on your module, not Dist::CheckConflicts.

As an example, this command line can be used to update your modules, after installing the Foo dist (assuming that Foo::Conflicts is the module in the Foo dist which uses Dist::CheckConflicts):

    perl -MFoo::Conflicts -e'print "$_\n"
        for map { $_->{package} } Foo::Conflicts->calculate_conflicts' | cpanm

As an added bonus, loading your conflicts module will provide warnings at runtime if conflicting modules are detected (regardless of whether they are loaded before or afterwards).