NAME

Perl::Critic::Policy::Variables::ProhibitPackageVars - Eliminate globals declared with "our" or "use vars".

AFFILIATION

This Policy is part of the core Perl::Critic distribution.

DESCRIPTION

Conway suggests avoiding package variables completely, because they expose your internals to other packages. Never use a package variable when a lexical variable will suffice. If your package needs to keep some dynamic state, consider using an object or closures to keep the state private.

This policy assumes that you're using "strict vars" so that naked variable declarations are not package variables by default. Thus, it complains you declare a variable with "our" or "use vars", or if you make reference to variable with a fully-qualified package name.

    $Some::Package::foo = 1;    # not ok
    our $foo            = 1;    # not ok
    use vars '$foo';            # not ok
    $foo = 1;                   # not allowed by 'strict'
    local $foo = 1;             # bad taste, but technically ok.
    use vars '$FOO';            # ok, because it's ALL CAPS
    my $foo = 1;                # ok

In practice though, its not really practical to prohibit all package variables. Common variables like $VERSION and @EXPORT need to be global, as do any variables that you want to Export. To work around this, the Policy overlooks any variables that are in ALL_CAPS. This forces you to put all your exported variables in ALL_CAPS too, which seems to be the usual practice anyway.

CONFIGURATION

There is room for exceptions. Some modules, like the core File::Find module, use package variables as their only interface, and others like Data::Dumper use package variables as their most common interface. These module can be specified from your .perlcriticrc file, and the policy will ignore them.

    [Variables::ProhibitPackageVars]
    packages = Data::Dumper File::Find FindBin Log::Log4perl

This is the default setting. Using "packages =" will override these defaults.

You can also add packages to the defaults like so:

    [Variables::ProhibitPackageVars]
    add_packages = My::Package

You can add package "main" to the list of packages, but that will only OK variables explicitly in the "main" package.

AUTHOR

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

COPYRIGHT

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.

2023-01-15