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package Perl::Critic::Policy::RegularExpressions::ProhibitFixedStringMatches;
use 5.010001;
use strict;
use warnings;
use Readonly;
use Perl::Critic::Utils qw( :severities );
use parent 'Perl::Critic::Policy';
our $VERSION = '1.156';
#-----------------------------------------------------------------------------
Readonly::Scalar my $DESC => q{Use 'eq' or hash instead of fixed-pattern regexps};
Readonly::Scalar my $EXPL => [271,272];
#-----------------------------------------------------------------------------
sub supported_parameters { return qw() }
sub default_severity { return $SEVERITY_LOW }
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, $doc ) = @_;
my $re = $elem->get_match_string();
# only flag regexps that are anchored front and back
if ($re =~ m{\A \s*
(\\A|\^) # front anchor == $1
(.*?)
(\\z|\$) # end anchor == $2
\s* \z}xms) {
my ($front_anchor, $words, $end_anchor) = ($1, $2, $3);
# If it's a multiline match, then end-of-line anchors don't represent the whole string
if ($front_anchor eq q{^} || $end_anchor eq q{$}) {
my $regexp = $doc->ppix_regexp_from_element( $elem )
or return;
return if $regexp->modifier_asserted( 'm' );
}
# check for grouping and optional alternation. Grouping may or may not capture
if ($words =~ m{\A \s*
[(] # start group
(?:[?]:)? # optional non-capturing indicator
\s* (.*?) \s* # interior of group
[)] # end of group
\s* \z}xms) {
$words = $1;
$words =~ s/[|]//gxms; # ignore alternation inside of parens -- just look at words
}
# Regexps that contain metachars are not fixed strings
return if $words =~ m/[\\#\$()*+.?\@\[\]^{|}]/xms;
return $self->violation( $DESC, $EXPL, $elem );
} else {
return; # OK
}
}
1;
__END__
#-----------------------------------------------------------------------------
=pod
=head1 NAME
Perl::Critic::Policy::RegularExpressions::ProhibitFixedStringMatches - Use C<eq> or hash instead of fixed-pattern regexps.
=head1 AFFILIATION
This Policy is part of the core L<Perl::Critic|Perl::Critic>
distribution.
=head1 DESCRIPTION
A regular expression that matches just a fixed set of constant strings
is wasteful of performance and is hard on maintainers. It is much
more readable and often faster to use C<eq> or a hash to match such
strings.
# Bad
my $is_file_function = $token =~ m/\A (?: open | close | read ) \z/xms;
# Faster and more readable
my $is_file_function = $token eq 'open' ||
$token eq 'close' ||
$token eq 'read';
For larger numbers of strings, a hash is superior:
# Bad
my $is_perl_keyword =
$token =~ m/\A (?: chomp | chop | chr | crypt | hex | index
lc | lcfirst | length | oct | ord | ... ) \z/xms;
# Better
Readonly::Hash my %PERL_KEYWORDS => map {$_ => 1} qw(
chomp chop chr crypt hex index lc lcfirst length oct ord ...
);
my $is_perl_keyword = $PERL_KEYWORD{$token};
Conway also suggests using C<lc()> instead of a case-insensitive match.
=head2 VARIANTS
This policy detects both grouped and non-grouped strings. The
grouping may or may not be capturing. The grouped body may or may not
be alternating. C<\A> and C<\z> are always considered anchoring which
C<^> and C<$> are considered anchoring is the C<m> regexp option is
not in use. Thus, all of these are violations:
m/^foo$/;
m/\A foo \z/x;
m/\A foo \z/xm;
m/\A(foo)\z/;
m/\A(?:foo)\z/;
m/\A(foo|bar)\z/;
m/\A(?:foo|bar)\z/;
Furthermore, this policy detects violations in C<m//>, C<s///> and
C<qr//> constructs, as you would expect.
=head1 CONFIGURATION
This Policy is not configurable except for the standard options.
=head1 CREDITS
Initial development of this policy was supported by a grant from the
Perl Foundation.
=head1 AUTHOR
Chris Dolan <cdolan@cpan.org>
=head1 COPYRIGHT
Copyright (c) 2007-2023 Chris Dolan
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
# 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 :
|
