Perl::Critic::Policy::RegularExpressions::ProhibitSingleCharAlternation - Use C<[abc]> instead of C<a|b|c>.

Perl-Critic documentation Contained in the Perl-Critic distribution.

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NAME

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Perl::Critic::Policy::RegularExpressions::ProhibitSingleCharAlternation - Use [abc] instead of a|b|c.

AFFILIATION

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This Policy is part of the core Perl::Critic distribution.

DESCRIPTION

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Character classes (like [abc]) are significantly faster than single character alternations (like (?:a|b|c)). This policy complains if you have more than one instance of a single character in an alternation. So (?:a|the) is allowed, but (?:a|e|i|o|u) is not.

NOTE: Perl 5.10 (not released as of this writing) has major regexp optimizations which may mitigate the performance penalty of alternations, which will be rewritten behind the scenes as something like character classes. Consequently, if you are deploying exclusively on 5.10, yo might consider ignoring this policy.

CONFIGURATION

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This Policy is not configurable except for the standard options.

CREDITS

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Initial development of this policy was supported by a grant from the Perl Foundation.

AUTHOR

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Chris Dolan <cdolan@cpan.org>

COPYRIGHT

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Copyright (c) 2007-2011 Chris Dolan. Many rights reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. The full text of this license can be found in the LICENSE file included with this module

Perl-Critic documentation Contained in the Perl-Critic distribution. 
##############################################################################
#      $URL: http://perlcritic.tigris.org/svn/perlcritic/trunk/distributions/Perl-Critic/lib/Perl/Critic/Policy/RegularExpressions/ProhibitSingleCharAlternation.pm $
#     $Date: 2011-05-15 16:34:46 -0500 (Sun, 15 May 2011) $
#   $Author: clonezone $
# $Revision: 4078 $
##############################################################################

package Perl::Critic::Policy::RegularExpressions::ProhibitSingleCharAlternation;

use 5.006001;
use strict;
use warnings;

use Carp;
use English qw(-no_match_vars);
use List::MoreUtils qw(all);
use Readonly;

use Perl::Critic::Utils qw{ :booleans :characters :severities };
use base 'Perl::Critic::Policy';

our $VERSION = '1.116';

#-----------------------------------------------------------------------------

Readonly::Scalar my $EXPL => [265];

#-----------------------------------------------------------------------------

sub supported_parameters { return qw()                    }
sub default_severity     { return $SEVERITY_LOWEST        }
sub default_themes       { return qw( core pbp performance ) }
sub applies_to           { return qw(PPI::Token::Regexp::Match
                                     PPI::Token::Regexp::Substitute
                                     PPI::Token::QuoteLike::Regexp) }

#-----------------------------------------------------------------------------

sub violates {
    my ( $self, $elem, $document ) = @_;

    # optimization: don't bother parsing the regexp if there are no pipes
    return if $elem !~ m/[|]/xms;

    my $re = $document->ppix_regexp_from_element( $elem ) or return;
    $re->failures() and return;

    my @violations;
    foreach my $node ( @{ $re->find_parents( sub {
                return $_[1]->isa( 'PPIx::Regexp::Token::Operator' )
                && $_[1]->content() eq q<|>;
            } ) || [] } ) {

        my @singles;
        my @alternative;
        foreach my $kid ( $node->children() ) {
            if ( $kid->isa( 'PPIx::Regexp::Token::Operator' )
                && $kid->content() eq q<|>
            ) {
                @alternative == 1
                    and $alternative[0]->isa( 'PPIx::Regexp::Token::Literal' )
                    and push @singles, map { $_->content() } @alternative;
                @alternative = ();
            } elsif ( $kid->significant() ) {
                push @alternative, $kid;
            }
        }
        @alternative == 1
            and $alternative[0]->isa( 'PPIx::Regexp::Token::Literal' )
            and push @singles, map { $_->content() } @alternative;

        if ( 1 < @singles ) {
            my $description =
                  'Use ['
                . join( $EMPTY, @singles )
                . '] instead of '
                . join q<|>, @singles;
            push @violations, $self->violation( $description, $EXPL, $elem );
        }
    }

    return @violations;
}

1;

__END__

#-----------------------------------------------------------------------------


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