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.IX Title "Perl::Critic::Policy::ValuesAndExpressions::ProhibitComplexVersion 3pm"
.TH Perl::Critic::Policy::ValuesAndExpressions::ProhibitComplexVersion 3pm 2023-07-26 "perl v5.38.0" "User Contributed Perl Documentation"
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.SH NAME
Perl::Critic::Policy::ValuesAndExpressions::ProhibitComplexVersion \- Prohibit version values from outside the module.
.SH AFFILIATION
.IX Header "AFFILIATION"
This Policy is part of the core Perl::Critic
distribution.
.SH DESCRIPTION
.IX Header "DESCRIPTION"
One tempting way to keep a group of related modules at the same version number
is to have all of them import the version number from a designated module. For
example, module \f(CW\*(C`Foo::Master\*(C'\fR could be the version master for the \f(CW\*(C`Foo\*(C'\fR
package, and all other modules could use its \f(CW$VERSION\fR by
.PP
.Vb 1
\&    use Foo::Master; our $VERSION = $Foo::Master::VERSION;
.Ve
.PP
This turns out not to be a good idea, because all sorts of unintended things
can happen \- anything from unintended version number changes to
denial-of-service attacks (since \f(CW\*(C`Foo::Master\*(C'\fR is executed by the 'use').
.PP
This policy examines statements that assign to \f(CW$VERSION\fR, and declares a
violation under two circumstances: first, if that statement uses a
fully-qualified symbol that did not originate in a package declared in the
file; second if there is a \f(CW\*(C`use\*(C'\fR statement on the same line that makes the
assignment.
.PP
By default, an exception is made for \f(CW\*(C`use version;\*(C'\fR because of its
recommendation by Perl Best Practices. See the \f(CW\*(C`forbid_use_version\*(C'\fR
configuration variable if you do not want an exception made for \f(CW\*(C`use
version;\*(C'\fR.
.SH CONFIGURATION
.IX Header "CONFIGURATION"
The construction
.PP
.Vb 1
\&    use version; our $VERSION = qv(\*(Aq1.2.3\*(Aq);
.Ve
.PP
is exempt from this policy by default, because it is recommended by Perl Best
Practices. Should you wish to identify \f(CW\*(C`use version;\*(C'\fR as a violation, add the
following to your perlcriticrc file:
.PP
.Vb 2
\&    [ValuesAndExpressions::ProhibitComplexVersion]
\&    forbid_use_version = 1
.Ve
.SH CAVEATS
.IX Header "CAVEATS"
This code assumes that the hallmark of a violation is a 'use' on the same line
as the \f(CW$VERSION\fR assignment, because that is the way to have it seen by
ExtUtils::MakeMaker\->\fBparse_version()\fR. Other ways to get
a version value from outside the module can be imagined, and this policy is
currently oblivious to them.
.SH AUTHOR
.IX Header "AUTHOR"
Thomas R. Wyant, III \fIwyant at cpan dot org\fR
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright (c) 2009\-2011 Tom Wyant.
.PP
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.