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lib/App/PerlNitpick/Rule/RewriteWithAssignmentOperators.pm  view on Meta::CPAN

package App::PerlNitpick::Rule::RewriteWithAssignmentOperators;
use Moose;
use PPI::Document;
use PPI::Token::Whitespace;

no Moose;

use constant IS_REWRITABLE => { map { $_ => 1 } (
    '*', '/', '%', 'x', '+', '-', '.',
    '//', '||',
    '|', '&', '^',
    '|.', '&.', '^.',
    '<<', '>>'
) };

sub is_rewritable {
    my ($op) = @_;
    return IS_REWRITABLE->{$op};
}

sub _trim_whitespace {
    my ($elem) = @_;

    my $e = $elem->next_sibling;
    while (! $e->significant) {
        $e->remove;
        $e = $elem->next_sibling;
    }
}

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

    my @found = grep {
        # Find a statement that looks like $x = $x + $y;
        my $c0 = $_->schild(0);  # $x
        my $c1 = $_->schild(1);  # =
        my $c2 = $_->schild(2);  # $x
        my $c3 = $_->schild(3);  # +
        my $c4 = $_->schild(4);  # $y
        my $c5 = $_->schild(5);  # ;

        ($c1->isa('PPI::Token::Operator') && $c1->content eq '=') &&
        ($c5->isa('PPI::Token::Structure') && $c5->content eq ';') &&
        ($c3->isa('PPI::Token::Operator') && is_rewritable($c3->content)) &&
        ($c0->isa('PPI::Token::Symbol') && $c0->raw_type eq '$' &&
         $c2->isa('PPI::Token::Symbol') && $c2->raw_type eq '$' &&
         $c0->content eq $c2->content)
    } grep {
        $_->schildren == 6
    } @{ $document->find('PPI::Statement') ||[] };

    return $document unless @found;

    for my $statement (@found) {
        my @child = $statement->schildren;

        my $assigment_operator = PPI::Token::Operator->new($child[3]->content . $child[1]->content);

        $child[3]->remove;

        _trim_whitespace($child[2]);
        $child[2]->remove;

        $child[2]->remove;
        $child[1]->insert_after($assigment_operator);
        $child[1]->remove;
    }

    return $document;
}

1;

__END__

=head1 DESCRIPTION

This rule rewrites those assignments that alter a single varible with itself.
For example, this one:

    $x = $x + 2;

Is rewritten with the C<+=> assignment operator, as:

    $x += 2;

=cut