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##############################################################################
#      $URL: http://perlcritic.tigris.org/svn/perlcritic/trunk/distributions/Perl-Critic/lib/Perl/Critic/Policy/Variables/RequireLocalizedPunctuationVars.pm $
#     $Date: 2009-06-27 20:02:58 -0400 (Sat, 27 Jun 2009) $
#   $Author: clonezone $
# $Revision: 3373 $
##############################################################################
package Perl::Critic::Policy::Variables::RequireLocalizedPunctuationVars;
use 5.006001;
use strict;
use warnings;
use Readonly;
use Perl::Critic::Utils qw{ :severities :classification $EMPTY hashify};
use base 'Perl::Critic::Policy';
our $VERSION = '1.099_002';
#-----------------------------------------------------------------------------
Readonly::Scalar my $PACKAGE_RX => qr/::/xms;
Readonly::Hash   my %EXCEPTIONS => hashify(qw(
    $_
    $ARG
    @_
));
Readonly::Scalar my $DESC => q{Magic variable "%s" should be assigned as "local"};
Readonly::Scalar my $EXPL => [ 81, 82 ];
#-----------------------------------------------------------------------------
sub supported_parameters {
    return (
        {
            name            => 'allow',
            description     =>
                q<Global variables to exclude from this policy.>,
            default_string  => $EMPTY,
            behavior        => 'string list',
            list_always_present_values => [ qw< $_ $ARG @_ > ],
        },
    );
}
sub default_severity     { return $SEVERITY_HIGH             }
sub default_themes       { return qw(core pbp bugs)          }
sub applies_to           { return 'PPI::Token::Operator'     }
#-----------------------------------------------------------------------------
sub violates {
    my ( $self, $elem, undef ) = @_;
    return if $elem->content() ne q{=};
    my $destination = $elem->sprevious_sibling;
    return if !$destination;  # huh? assignment in void context??
    while ($destination->isa('PPI::Structure::Subscript')) {
        $destination = $destination->sprevious_sibling()
            or return;
    }
    if (my $var = $self->_is_non_local_magic_dest($destination)) {
       return $self->violation( sprintf( $DESC, $var ), $EXPL, $elem );
    }
    return;  # OK
}
sub _is_non_local_magic_dest {
    my ($self, $elem) = @_;
    # Quick exit if in good form
    my $modifier = $elem->sprevious_sibling;
    return
        if
                $modifier
            &&  $modifier->isa('PPI::Token::Word')
            &&  ($modifier->content() eq 'local' || $modifier->content() eq 'my');
    # Implementation note: Can't rely on PPI::Token::Magic,
    # unfortunately, because we need English too
    if ($elem->isa('PPI::Token::Symbol')) {
        return $self->_is_magic_var($elem) ? $elem : undef;
    }
    elsif (
            $elem->isa('PPI::Structure::List')
        or  $elem->isa('PPI::Statement::Expression')
    ) {
        for my $child ($elem->schildren) {
            my $var = $self->_is_non_local_magic_dest($child);
            return $var if $var;
        }
    }
    return;
}
#-----------------------------------------------------------------------------
sub _is_magic_var {
    my ($self, $elem) = @_;
    my $variable_name = $elem->symbol();
    return if $self->{_allow}{$variable_name};
    return 1 if $elem->isa('PPI::Token::Magic'); # optimization(?), and helps with PPI 1.118 carat bug
    return if not is_perl_global( $elem );
    return 1;
}
1;
__END__
#-----------------------------------------------------------------------------
HideShow 92 lines of Pod
=pod
=head1 NAME
Perl::Critic::Policy::Variables::RequireLocalizedPunctuationVars - Magic variables should be assigned as "local".
=head1 AFFILIATION
This Policy is part of the core L<Perl::Critic|Perl::Critic>
distribution.
=head1 DESCRIPTION
Punctuation variables (and their English.pm equivalents) are global
variables.  Messing with globals is dangerous in a complex program as
it can lead to very subtle and hard to fix bugs.  If you must change a
magic variable in a non-trivial program, do it in a local scope.
For example, to slurp a filehandle into a scalar, it's common to set
the record separator to undef instead of a newline.  If you choose to
do this (instead of using L<File::Slurp|File::Slurp>!) then be sure to
localize the global and change it for as short a time as possible.
    # BAD:
    $/ = undef;
    my $content = <$fh>;
    # BETTER:
    my $content;
    {
        local $/ = undef;
        $content = <$fh>;
    }
    # A popular idiom:
    my $content = do { local $/ = undef; <$fh> };
This policy also allows the use of C<my>.  Perl prevents using C<my>
with "proper" punctuation variables, but allows C<$a>, C<@ARGV>, the
names declared by L<English|English>, etc.  This is not a good coding
practice, however it is not the concern of this specific policy to
complain about that.
There are exemptions for C<$_> and C<@_>, and the English equivalent
C<$ARG>.
=head1 CONFIGURATION
You can configure your own exemptions using the C<allow> option:
    [Variables::RequireLocalizedPunctuationVars]
    allow = @ARGV $ARGV
These are added to the default exemptions.
=head1 CAVEATS
The current PPI (v1.118) has a bug where $^ variables absorb following
whitespace by mistake.  This makes it harder to spot those as magic
variables.  Hopefully this will be fixed by PPI 1.200.  In the
meantime, we have a workaround in this module.
Additionally, PPI v1.118 fails to recognize %! and %^H as magic
variables.  PPI instead sees the "%" as a modulus operator.  We have
no workaround for that bug right now.
=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) 2007-2009 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.
=cut
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