NAME¶
Perl::Critic::Policy::Variables::ProhibitEvilVariables - Ban variables that
aren't blessed by your shop.
AFFILIATION¶
This Policy is part of the core Perl::Critic distribution.
DESCRIPTION¶
Use this policy if you wish to prohibit the use of specific variables. These may
be global variables warned against in "perlvar", or just variables
whose names you do not like.
CONFIGURATION¶
The set of prohibited variables is configurable via the "variables"
and "variables_file" options.
The value of "variables" should be a string of space-delimited, fully
qualified variable names and/or regular expressions. An example of prohibiting
two specific variables in a
.perlcriticrc file:
[Variables::ProhibitEvilVariables]
variables = $[ $^S $SIG{__DIE__}
If you prohibit an array or hash (e.g. @INC), use of elements of the array or
hash will be prohibited as well. If you specify a subscripted variable (e.g.
$SIG{__DIE__}), only the literal subscript specified will be detected. The
above <.perlcritic> file, for example, will cause "perlcritic
(1)" to detect "$SIG{__DIE__} = \&foo", but not
my $foo = '__DIE__';
$SIG{$foo} = \&foo;
Regular expressions are identified by values beginning and ending with slashes.
Any variable with a name that matches "m/pattern/sm" will be
forbidden. For example:
[Variables::ProhibitEvilVariables]
variables = /acme/
would cause all variables that match "m/acme/" to be forbidden. If you
want a case-blind check, you can use (?i: ... ). For example
[Variables::ProhibitEvilVariables]
variables = /(?i:acme)/
forbids variables that match "m/acme/smi".
In addition, you can override the default message ("Prohibited variable
"
variable" used") with your own, in order to give
suggestions for alternative action. To do so, put your message in curly braces
after the variable name or regular expression. Like this:
[Variables::ProhibitEvilVariables]
variables = $[ {Found use of $[. Program to base index 0 instead}
If your message contains curly braces, you can enclose it in parentheses, angle
brackets, or square brackets instead.
Similarly, the "variables_file" option gives the name of a file
containing specifications for prohibited variables. Only one variable
specification is allowed per line and comments start with an octothorp and run
to end of line; no curly braces are necessary for delimiting messages:
$[ # Prohibit the "$[" variable and use the default message.
# Prohibit the "$^S" variable and give a replacement message.
$^S Having to think about $^S in exception handlers is just wrong
# Use a regular expression.
/acme/ No coyotes allowed.
By default, there are no prohibited variables, although I can think of a few
that should be. See "perldoc perlvar" for a few suggestions.
RESTRICTIONS¶
Variables of the form "${^foo}" are not recognized by PPI as of
version 1.206. When PPI recognizes these, this policy will Just Work for them
too.
Only direct references to prohibited variables and literal subscripts will be
recognized. For example, if you prohibit $[, the first line in
my $foo = \$[;
$$foo = 1;
will be flagged as a violation, but not the second, even though the second, in
fact, assigns to $[. Similarly, if you prohibit $SIG{__DIE__}, this policy
will not recognize
my $foo = '__DIE__';
$SIG{$foo} = sub {warn 'I cannot die!'};
as an assignment to $SIG{__DIE__}.
NOTES¶
This policy leans heavily on Perl::Critic::Policy::Modules::ProhibitEvilModules
by Jeffrey Ryan Thalhammer.
AUTHOR¶
Thomas R. Wyant, III
wyant at cpan dot org
COPYRIGHT¶
Copyright (c) 2009-2011 Thomas R. Wyant, III
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.