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# Copyright 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2019, 2021 Kevin Ryde
# Perl-Critic-Pulp is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by the
# Free Software Foundation; either version 3, or (at your option) any later
# version.
#
# Perl-Critic-Pulp is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
# for more details.
#
# You should have received a copy of the GNU General Public License along
# with Perl-Critic-Pulp. If not, see <http://www.gnu.org/licenses/>.
# eg.
# perlcritic -s ProhibitArrayAssignAref /usr/lib/perl5/Template/Test.pm
package Perl::Critic::Policy::ValuesAndExpressions::ProhibitArrayAssignAref;
use 5.006;
use strict;
use warnings;
use base 'Perl::Critic::Policy';
use Perl::Critic::Utils;
use Perl::Critic::Pulp;
# uncomment this to run the ### lines
#use Smart::Comments;
our $VERSION = 100;
use constant supported_parameters => ();
use constant default_severity => $Perl::Critic::Utils::SEVERITY_MEDIUM;
use constant default_themes => qw(pulp bugs);
use constant applies_to => ('PPI::Token::Symbol',
'PPI::Token::Cast');
sub violates {
my ($self, $elem, $document) = @_;
($elem->isa('PPI::Token::Cast') ? $elem->content : $elem->raw_type)
eq '@' or return;
### ProhibitArrayAssignAref: $elem->content
my $thing = 'Array';
for (;;) {
$elem = $elem->snext_sibling || return;
last if $elem->isa('PPI::Token::Operator');
### skip: ref $elem
# @foo[1,2] gives the [1,2] as a PPI::Structure::Subscript
# @{foo()}[1,2] gives the [1,2] as a PPI::Structure::Constructor
# the latter is probably wrong (as of PPI 1.215)
if ($elem->isa('PPI::Structure::Subscript')
|| $elem->isa('PPI::Structure::Constructor')) {
if ($elem->start eq '[') {
$thing = 'Array slice';
} elsif ($elem->start eq '{') {
$thing = 'Hash slice';
}
}
}
### $thing
### operator: $elem->content
$elem eq '=' or return;
$elem = $elem->snext_sibling || return;
($elem->isa('PPI::Structure::Constructor') && $elem->start eq '[')
or return;
return $self->violation
("$thing assigned a [] arrayref, should it be a () list ?",
'', $elem);
}
1;
__END__
=for stopwords Ryde arrayref parens Derefs Dereferences
=head1 NAME
Perl::Critic::Policy::ValuesAndExpressions::ProhibitArrayAssignAref - don't assign an anonymous arrayref to an array
=head1 DESCRIPTION
This policy is part of the L<C<Perl::Critic::Pulp>|Perl::Critic::Pulp>
add-on. It asks you not to assign an anonymous arrayref to an array
@array = [ 1, 2, 3 ]; # bad
The idea is that it's rather unclear whether an arrayref is intended, or
might have meant to be a list like
@array = ( 1, 2, 3 );
This policy is under the "bugs" theme (see L<Perl::Critic/POLICY THEMES>)
for the chance C<[]> is a mistake, and since even if it's correct it will
likely make anyone reading it wonder.
A single arrayref can still be assigned to an array, but with parens to make
it clear,
@array = ( [1,2,3] ); # ok
Dereferences or array and hash slices (see L<perldata/Slices>) are
recognised as an array target and treated similarly,
@$ref = [1,2,3]; # bad assign to deref
@{$ref} = [1,2,3]; # bad assign to deref
@x[1,2,3] = ['a','b','c']; # bad assign to array slice
@x{'a','b'} = [1,2]; # bad assign to hash slice
=head2 List Assignment Parens
This policy is not a blanket requirement for C<()> parens on array
assignments. It's normal and unambiguous to have a function call or C<grep>
etc without parens.
@array = foo(); # ok
@array = grep {/\.txt$/} @array; # ok
The only likely problem from lack of parens in such cases is that the C<,>
comma operator has lower precedence than C<=> (see L<perlop>), so something
like
@array = 1,2,3; # oops, not a list
means
@array = (1);
2;
3;
Normally the remaining literals in void context provoke a warning from Perl
itself.
An intentional single element assignment is quite common as a statement, for
instance
@ISA = 'My::Parent::Class'; # ok
And for reference the range operator precedence is high enough,
@array = 1..10; # ok
But of course parens are needed if concatenating some disjoint ranges with
the comma operator,
@array = (1..5, 10..15); # parens needed
The C<qw> form gives a list too
@array = qw(a b c); # ok
=head1 SEE ALSO
L<Perl::Critic>,
L<Perl::Critic::Pulp>
=head1 HOME PAGE
http://user42.tuxfamily.org/perl-critic-pulp/index.html
=head1 COPYRIGHT
Copyright 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2019, 2021 Kevin Ryde
Perl-Critic-Pulp is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.
Perl-Critic-Pulp is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
more details.
You should have received a copy of the GNU General Public License along with
Perl-Critic-Pulp. If not, see <http://www.gnu.org/licenses>.
=cut
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