NAME

Role::Inspector - introspection for roles

SYNOPSIS

use strict;
use warnings;
use feature qw(say);

{
   package Local::Role;
   use Role::Tiny;   # or Moose::Role, Mouse::Role, etc...
   
   requires qw( foo );
   
   sub bar { ... }
}

use Role::Inspector qw( get_role_info );

my $info = get_role_info('Local::Role');

say $info->{name};          # Local::Role
say $info->{type};          # Role::Tiny
say for @{$info->{api}};    # bar
                            # foo

DESCRIPTION

This module allows you to retrieve a hashref of information about a given role. The following role implementations are supported:

• Moose::Role

• Mouse::Role

• Moo::Role

• Role::Tiny

• Role::Basic

• p5-mop-redux

Functions

get_role_info($package_name)

Returns a hashref of information about a role; returns undef if the package does not appear to be a role. Attempts to load the package using Module::Runtime if it's not already loaded.

The hashref may contain the following keys:

• name - the package name of the role

• type - the role implementation used by the role

• api - an arrayref of method names required/provided by the role

• provides and requires - the same as api, but split into lists of methods provided and required by the role

• meta - a metaobject for the role (e.g. a Moose::Meta::Role object). This key may be absent if the role implementation does not provide a metaobject

This function may be exported, but is not exported by default.

does_role($thing, $role)

Returns a boolean indicating if $thing does role $role. $thing can be an object, a class name, or a role name.

This should mostly give the same answers as $thing->DOES($role), but may be slightly more reliable in some cross-implementation (i.e. Moose roles consuming Moo roles) cases.

This function may be exported, but is not exported by default.

Methods

If you do not wish to export the functions provided by Role::Inspector, you may call them as a class methods:

my $info = Role::Inspector->get_role_info($package_name);

$thing->blah() if Role::Inspector->does_role($thing, $role);

Extending Role::Inspector

Role::Inspector::learn { BLOCK }

In the unlikely situation that you have to deal with some other role implementation that Role::Inspector doesn't know about, you can teach it:

use Role::Inspector qw( learn );

learn {
   my $r = shift;
   return unless My::Implementation::is_role($r);
   return {
      name     => $r,
      type     => 'My::Implementation',
      provides => [ sort(@{My::Implementation::provides($r)}) ],
      requires => [ sort(@{My::Implementation::requires($r)}) ],
   };
};

An alternative way to do this is:

push @Role::Inspector::SCANNERS, sub {
   my $r = shift;
   ...;
};

You can do the push thing without having loaded Role::Inspector. This makes it suitable for doing inside My::Implementation itself, without introducing an additional dependency on Role::Inspector.

Note that if you don't provide all of provides, requires, and api, Role::Inspector will attempt to guess the missing parts.

CAVEATS

• It is difficult to distinguish between Moo::Role and Role::Tiny roles. (The distinction is not often important anyway.) Thus sometimes the type for a Moo::Role may say "Role::Tiny".

• The way that Role::Basic roles are detected and introspected is a bit dodgy, relying on undocumented methods.

• Where Moose or Mouse roles define attributes, those attributes tend to result in accessor methods being generated. However neither of these frameworks provides a decent way of figuring out which accessor methods will result from composing the role with the class.

  Role::Inspector does its damnedest to figure out the list of likely methods, but (especially in the case of unusual attribute traits) may get things wrong from time to time.

BUGS

Please report any bugs to http://rt.cpan.org/Dist/Display.html?Queue=Role-Inspector.

SEE ALSO

Class::Inspector.

AUTHOR

Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE

This software is copyright (c) 2014 by Toby Inkster.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

DISCLAIMER OF WARRANTIES

THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.