Perl::Critic::Policy::RegularExpressions::RequireExtendedFormatting - Always use the C</x> modifier with regular expressions.

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

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NAME

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Perl::Critic::Policy::RegularExpressions::RequireExtendedFormatting - Always use the /x modifier with regular expressions.

AFFILIATION

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

DESCRIPTION

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Extended regular expression formatting allows you mix whitespace and comments into the pattern, thus making them much more readable.

    # Match a single-quoted string efficiently...

    m{'[^\\']*(?:\\.[^\\']*)*'};  #Huh?

    # Same thing with extended format...

    m{
        '           # an opening single quote
        [^\\']      # any non-special chars (i.e. not backslash or single quote)
        (?:         # then all of...
            \\ .    #    any explicitly backslashed char
            [^\\']* #    followed by an non-special chars
        )*          # ...repeated zero or more times
        '           # a closing single quote
    }x;

CONFIGURATION

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You might find that putting a /x on short regular expressions to be excessive. An exception can be made for them by setting minimum_regex_length_to_complain_about to the minimum match length you'll allow without a /x. The length only counts the regular expression, not the braces or operators.

    [RegularExpressions::RequireExtendedFormatting]
    minimum_regex_length_to_complain_about = 5

    $num =~ m<(\d+)>;              # ok, only 5 characters
    $num =~ m<\d\.(\d+)>;          # not ok, 9 characters

This option defaults to 0.

Because using /x on a regex which has whitespace in it can make it harder to read (you have to escape all that innocent whitespace), by default, you can have a regular expression that only contains whitespace and word characters without the modifier. If you want to restrict this, turn on the strict option.

    [RegularExpressions::RequireExtendedFormatting]
    strict = 1

    $string =~ m/Basset hounds got long ears/;  # no longer ok

This option defaults to false.

NOTES

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For common regular expressions like e-mail addresses, phone numbers, dates, etc., have a look at the Regexp::Common module. Also, be cautions about slapping modifier flags onto existing regular expressions, as they can drastically alter their meaning. See http://www.perlmonks.org/?node_id=484238 for an interesting discussion on the effects of blindly modifying regular expression flags.

TO DO

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Add an exemption for regular expressions that contain \Q at the front and don't use \E until the very end, if at all.

AUTHOR

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Jeffrey Ryan Thalhammer <jeff@imaginative-software.com>

COPYRIGHT

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Copyright (c) 2005-2011 Imaginative Software Systems. All 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/RequireExtendedFormatting.pm $
#     $Date: 2011-05-15 16:34:46 -0500 (Sun, 15 May 2011) $
#   $Author: clonezone $
# $Revision: 4078 $
##############################################################################

package Perl::Critic::Policy::RegularExpressions::RequireExtendedFormatting;

use 5.006001;
use strict;
use warnings;
use Readonly;

use Perl::Critic::Utils qw{ :severities };

use base 'Perl::Critic::Policy';

our $VERSION = '1.116';

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

Readonly::Scalar my $DESC => q{Regular expression without "/x" flag};
Readonly::Scalar my $EXPL => [ 236 ];

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

sub supported_parameters {
    return (
        {
            name               => 'minimum_regex_length_to_complain_about',
            description        =>
                q<The number of characters that a regular expression must contain before this policy will complain.>,
            behavior           => 'integer',
            default_string     => '0',
            integer_minimum    => 0,
        },
        {
            name               => 'strict',
            description        =>
                q<Should regexes that only contain whitespace and word characters be complained about?>,
            behavior           => 'boolean',
            default_string     => '0',
        },
    );
}

sub default_severity     { return $SEVERITY_MEDIUM           }
sub default_themes       { return qw< core pbp maintenance > }
sub applies_to           {
    return qw<
        PPI::Token::Regexp::Match
        PPI::Token::Regexp::Substitute
        PPI::Token::QuoteLike::Regexp
    >;
}

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

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

    my $match = $elem->get_match_string();
    return if length $match <= $self->{_minimum_regex_length_to_complain_about};
    return if not $self->{_strict} and $match =~ m< \A [\s\w]* \z >xms;

    my %mods = $elem->get_modifiers();
    if ( not $mods{x} ) {
        return $self->violation( $DESC, $EXPL, $elem );
    }

    return; # ok!;
}

1;

__END__

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


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