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package Perl::Critic::Policy::RegularExpressions::ProhibitUselessTopic;
use 5.010;
use strict;
use warnings;
use Readonly;
use Perl::Critic::Utils qw{ :severities :classification :ppi hashify };
use parent 'Perl::Critic::Policy';
our $VERSION = '1.156';
## no critic ( ValuesAndExpressions::RequireInterpolationOfMetachars )
## The numerous $_ variables make false positives.
Readonly::Scalar my $DESC => q{Useless use of $_};
Readonly::Scalar my $EXPL => q{$_ should be omitted when matching a regular expression};
sub supported_parameters { return () }
sub default_severity { return $SEVERITY_LOW }
sub default_themes { return qw( core ) }
sub applies_to { return 'PPI::Token::Magic' }
sub violates {
my ( $self, $elem, undef ) = @_;
if ( $elem->content eq q{$_} ) {
# Is there an op following the $_ ?
my $op_node = $elem->snext_sibling;
if ( $op_node && $op_node->isa('PPI::Token::Operator') ) {
# If the op is a regex match, then we have an unnecessary $_ .
state $is_regex_op = { hashify( qw( =~ !~ ) ) };
if ( $is_regex_op->{$op_node->content} ) {
my $target_node = $op_node->snext_sibling;
if ( $target_node && ($target_node->isa('PPI::Token::Regexp') || $target_node->isa('PPI::Token::QuoteLike::Regexp')) ) {
return $self->violation( $DESC, $EXPL, $elem );
}
}
}
}
return;
}
1;
__END__
=pod
=head1 NAME
Perl::Critic::Policy::RegularExpressions::ProhibitUselessTopic - Don't use $_ to match against regexes.
=head1 AFFILIATION
This Policy is part of the L<Perl::Critic|Perl::Critic> distribution.
=head1 DESCRIPTION
It is not necessary to specify the topic variable C<$_> when matching
against a regular expression.
Match or substitution operations are performed against variables, such as:
$x =~ /foo/;
$x =~ s/foo/bar/;
$x =~ tr/a-mn-z/n-za-m/;
If a variable is not specified, the match is against C<$_>.
# These are identical.
/foo/;
$_ =~ /foo/;
# These are identical.
s/foo/bar/;
$_ =~ s/foo/bar/;
# These are identical.
tr/a-mn-z/n-za-m/;
$_ =~ tr/a-mn-z/n-za-m/;
This applies to negative matching as well.
# These are identical
if ( $_ !~ /DEBUG/ ) { ...
if ( !/DEBUG ) { ...
Including the C<$_ =~> or C<$_ !~> is unnecessary, adds complexity,
and is not idiomatic Perl.
=head1 CONFIGURATION
This Policy is not configurable except for the standard options.
=head1 AUTHOR
Andy Lester <andy@petdance.com>
=head1 COPYRIGHT
Copyright (c) 2013-2023 Andy Lester <andy@petdance.com>
This library is free software; you can redistribute it and/or modify it
under the terms of the Artistic License 2.0.
=cut
# Local Variables:
# mode: cperl
# cperl-indent-level: 4
# fill-column: 78
# indent-tabs-mode: nil
# c-indentation-style: bsd
# End:
# ex: set ts=8 sts=4 sw=4 tw=78 ft=perl expandtab shiftround :
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