File Coverage

blib/lib/Perl/Critic/Policy/InputOutput/ProhibitTwoArgOpen.pm

Criterion	Covered	Total	%
statement	34	34	100.0
branch	10	10	100.0
condition	8	9	88.8
subroutine	12	12	100.0
pod	4	5	80.0
total	68	70	97.1

package Perl::Critic::Policy::InputOutput::ProhibitTwoArgOpen;

use 5.010001;
use strict;
use warnings;

use Readonly;

use version;

use Perl::Critic::Utils qw{ :severities :classification :ppi };
use parent 'Perl::Critic::Policy';

our $VERSION = '1.148';

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

Readonly::Scalar my $FORK_HANDLES_RX => qr/\A (?: -[|] | [|]- ) \z/xms;
Readonly::Scalar my $DESC => q{Two-argument "open" used};
Readonly::Scalar my $EXPL => [ 207 ];

Readonly::Scalar my $MINIMUM_VERSION => version->new(5.006);

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

sub supported_parameters { return ()                         }
sub default_severity     { return $SEVERITY_HIGHEST          }
sub default_themes       { return qw(core pbp bugs security certrule) }
sub applies_to           { return 'PPI::Token::Word'         }

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

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

    return if $elem->content() ne 'open';
    return if ! is_function_call($elem);

    my $version = $document->highest_explicit_perl_version();
    return if $version and $version < $MINIMUM_VERSION;

    my @args = parse_arg_list($elem);

    if ( scalar @args <= 2 ) {
        return if @args == 2
               && $args[1]->[0]->isa( 'PPI::Token::Quote' )
               && $args[1]->[0]->string() =~ $FORK_HANDLES_RX;
        return $self->violation( $DESC, $EXPL, $elem );
    }

    return; # ok!
}

1;

__END__

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

=pod

=for stopwords perlipc

=head1 NAME

Perl::Critic::Policy::InputOutput::ProhibitTwoArgOpen - Write C<< open $fh, q{<}, $filename; >> instead of C<< open $fh, "<$filename"; >>.

=head1 AFFILIATION

This Policy is part of the core L<Perl::Critic|Perl::Critic>
distribution.


=head1 DESCRIPTION

The three-argument form of C<open> (introduced in Perl 5.6) prevents
subtle bugs that occur when the filename starts with funny characters
like '>' or '<'.  The L<IO::File|IO::File> module provides a nice
object-oriented interface to filehandles, which I think is more
elegant anyway.

  open( $fh, '>output.txt' );          # not ok
  open( $fh, q{>}, 'output.txt' );     # ok

  use IO::File;
  my $fh = IO::File->new( 'output.txt', q{>} ); # even better!

It's also more explicitly clear to define the input mode of the file,
as in the difference between these two:

  open( $fh, 'foo.txt' );       # BAD: Reader must think what default mode is
  open( $fh, '<', 'foo.txt' );  # GOOD: Reader can see open mode

There is also a one-argument form of C<open> which retrieves the expression to
open from the global variable with the same name as the handle, but this has
the same problems as the two-argument form, and adds in more ambiguity.

  our $FH = '<foo.txt';
  open( FH ); # not ok

This policy will not complain if the file explicitly states that it is
compatible with a version of perl prior to 5.6 via an include
statement, e.g. by having C<require 5.005> in it.


=head1 CONFIGURATION

This Policy is not configurable except for the standard options.


=head1 NOTES

There is one case in which you are forced to use the two-argument form of
open: when doing a safe pipe open, as described in L<perlipc|perlipc>.

=head1 SEE ALSO

L<IO::Handle|IO::Handle>

L<IO::File|IO::File>

=head1 AUTHOR

Jeffrey Ryan Thalhammer <[e-mail]>

=head1 COPYRIGHT

Copyright (c) 2005-2021 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.

=cut

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