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#      $URL: http://perlcritic.tigris.org/svn/perlcritic/trunk/distributions/Perl-Critic/lib/Perl/Critic/Policy/RegularExpressions/RequireExtendedFormatting.pm $
#     $Date: 2009-03-01 17:40:39 -0600 (Sun, 01 Mar 2009) $
#   $Author: clonezone $
# $Revision: 3205 $
##############################################################################
package Perl::Critic::Policy::RegularExpressions::RequireExtendedFormatting;
use 5.006001;
use strict;
use warnings;
use Readonly;
use Perl::Critic::Utils qw{ :severities };
use Perl::Critic::Utils::PPIRegexp qw{ get_modifiers get_match_string };
use base 'Perl::Critic::Policy';
our $VERSION = '1.097_002';
#-----------------------------------------------------------------------------
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 $match = get_match_string($elem);
    return if length $match <= $self->{_minimum_regex_length_to_complain_about};
    return if not $self->{_strict} and $match =~ m< \A [\s\w]* \z >xms;
    my %mods = get_modifiers($elem);
    if ( not $mods{x} ) {
        return $self->violation( $DESC, $EXPL, $elem );
    }
    return; # ok!;
}
1;
__END__
#-----------------------------------------------------------------------------
HideShow 97 lines of Pod
=pod
=head1 NAME
Perl::Critic::Policy::RegularExpressions::RequireExtendedFormatting - Always use the C</x> modifier with regular expressions.
=head1 AFFILIATION
This Policy is part of the core L<Perl::Critic|Perl::Critic>
distribution.
=head1 DESCRIPTION
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;
=head1 CONFIGURATION
You might find that putting a C</x> on short regular expressions to be
excessive.  An exception can be made for them by setting
C<minimum_regex_length_to_complain_about> to the minimum match length
you'll allow without a C</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 C</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 C<strict> option.
    [RegularExpressions::RequireExtendedFormatting]
    strict = 1
    $string =~ m/Basset hounds got long ears/;  # no longer ok
This option defaults to false.
=head1 NOTES
For common regular expressions like e-mail addresses, phone numbers,
dates, etc., have a look at the L<Regexp::Common|Regexp::Common> module.
Also, be cautions about slapping modifier flags onto existing regular
expressions, as they can drastically alter their meaning.  See
L<http://www.perlmonks.org/?node_id=484238> for an interesting
discussion on the effects of blindly modifying regular expression
flags.
=head1 TO DO
Add an exemption for regular expressions that contain C<\Q> at the
front and don't use C<\E> until the very end, if at all.
=head1 AUTHOR
Jeffrey Ryan Thalhammer  <thaljef@cpan.org>
=head1 COPYRIGHT
Copyright (c) 2005-2009 Jeffrey Ryan Thalhammer. 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.
=cut
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