package Perl::Critic::Policy::BuiltinFunctions::ProhibitStringyEval;

use 5.006001;
use strict;
use warnings;

use Readonly;

use PPI::Document;

use Perl::Critic::Utils qw{ :booleans :severities :classification :ppi $SCOLON };
use base 'Perl::Critic::Policy';

our $VERSION = '1.134';

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

Readonly::Scalar my $DESC => q{Expression form of "eval"};
Readonly::Scalar my $EXPL => [ 161 ];

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

sub supported_parameters {
    return (
        {
            name           => 'allow_includes',
            description    => q<Allow eval of "use" and "require" strings.>,
            default_string => '0',
            behavior       => 'boolean',
        },
    );
}
sub default_severity     { return $SEVERITY_HIGHEST   }
sub default_themes       { return qw( core pbp bugs certrule ) }
sub applies_to           { return 'PPI::Token::Word'  }

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

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

    return if $elem->content() ne 'eval';
    return if not is_function_call($elem);

    my $argument = first_arg($elem);
    return if not $argument;
    return if $argument->isa('PPI::Structure::Block');
    return if
        $self->{_allow_includes} and _string_eval_is_an_include($argument);

    return $self->violation( $DESC, $EXPL, $elem );
}

sub _string_eval_is_an_include {
    my ($eval_argument) = @_;

    return if not $eval_argument->isa('PPI::Token::Quote');

    my $string = $eval_argument->string();
    my $document;

    eval { $document = PPI::Document->new(\$string); 1 }
        or return;

    my @statements = $document->schildren;

    return if @statements > 2;
    my $include = $statements[0];
    return if not defined $include; # RT 60179
    return if not $include->isa('PPI::Statement::Include');
    return if $include->type() eq 'no';

    if (
            $eval_argument->isa('PPI::Token::Quote::Single')
        or  $eval_argument->isa('PPI::Token::Quote::Literal')
    ) {
        # Don't allow funky inclusion of arbitrary code (note we do allow
        # interpolated values in interpolating strings because they can't
        # entirely screw with the syntax).
        return if $include->find('PPI::Token::Symbol');
    }

    return $TRUE if @statements == 1;

    my $follow_on = $statements[1];
    return if not $follow_on->isa('PPI::Statement');

    my @follow_on_components = $follow_on->schildren();

    return if @follow_on_components > 2;
    return if not $follow_on_components[0]->isa('PPI::Token::Number');
    return $TRUE if @follow_on_components == 1;

    return $follow_on_components[1]->content() eq $SCOLON;
}


1;

__END__

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

=pod

=for stopwords SIGNES

=head1 NAME

Perl::Critic::Policy::BuiltinFunctions::ProhibitStringyEval - Write C<eval { my $foo; bar($foo) }> instead of C<eval "my $foo; bar($foo);">.


=head1 AFFILIATION

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


=head1 DESCRIPTION

The string form of C<eval> is recompiled every time it is executed,
whereas the block form is only compiled once.  Also, the string form
doesn't give compile-time warnings.

    eval "print $foo";        # not ok
    eval {print $foo};        # ok


=head1 CONFIGURATION

There is an C<allow_includes> boolean option for this Policy.  If set, then
strings that look like they only include a single "use" or "require" statement
(with the possible following statement that consists of a single number) are
allowed.  With this option set, the following are flagged as indicated:

    eval 'use Foo';             # ok
    eval 'require Foo';         # ok
    eval "use $thingy;";        # ok
    eval "require $thingy;";    # ok
    eval "use $thingy; 1;";     # ok
    eval "require $thingy; 1;"; # ok

    eval 'use Foo; blah;';      # still not ok
    eval 'require Foo; 2; 1;';  # still not ok
    eval 'use $thingy;';        # still not ok
    eval 'no Foo';              # still not ok

If you don't understand why the number is allowed, see
L<Perl::Critic::Policy::ErrorHandling::RequireCheckingReturnValueOfEval|Perl::Critic::Policy::ErrorHandling::RequireCheckingReturnValueOfEval>.

This option inspired by Ricardo SIGNES'
L<Perl::Critic::Policy::Lax::ProhibitStringyEval::ExceptForRequire|Perl::Critic::Policy::Lax::ProhibitStringyEval::ExceptForRequire>.


=head1 SEE ALSO

L<Perl::Critic::Policy::BuiltInFunctions::RequireBlockGrep|Perl::Critic::Policy::BuiltInFunctions::RequireBlockGrep>

L<Perl::Critic::Policy::BuiltInFunctions::RequireBlockMap|Perl::Critic::Policy::BuiltInFunctions::RequireBlockMap>


=head1 AUTHOR

Jeffrey Ryan Thalhammer <jeff@imaginative-software.com>


=head1 COPYRIGHT

Copyright (c) 2005-2011 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.  The full text of this license
can be found in the LICENSE file included with this module.

=cut

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