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.IX Title "Perl::Critic::Policy::Subroutines::ProhibitUnusedPrivateSubroutines 3pm"
.TH Perl::Critic::Policy::Subroutines::ProhibitUnusedPrivateSubroutines 3pm 2023-07-26 "perl v5.38.0" "User Contributed Perl Documentation"
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.SH NAME
Perl::Critic::Policy::Subroutines::ProhibitUnusedPrivateSubroutines \- Prevent unused private subroutines.
.SH AFFILIATION
.IX Header "AFFILIATION"
This Policy is part of the core Perl::Critic
distribution.
.SH DESCRIPTION
.IX Header "DESCRIPTION"
By convention Perl authors (like authors in many other languages)
indicate private methods and variables by inserting a leading
underscore before the identifier.  This policy catches such subroutines
which are not used in the file which declares them.
.PP
This module defines a 'use' of a subroutine as a subroutine or method call to
it (other than from inside the subroutine itself), a reference to it (i.e.
\&\f(CW\*(C`my $foo = \e&_foo\*(C'\fR), a \f(CW\*(C`goto\*(C'\fR to it outside the subroutine itself (i.e.
\&\f(CW\*(C`goto &_foo\*(C'\fR), or the use of the subroutine's name as an even-numbered
argument to \f(CW\*(C`use overload\*(C'\fR.
.SH CONFIGURATION
.IX Header "CONFIGURATION"
You can define what a private subroutine name looks like by specifying
a regular expression for the \f(CW\*(C`private_name_regex\*(C'\fR option in your
\&\fI.perlcriticrc\fR:
.PP
.Vb 2
\&    [Subroutines::ProhibitUnusedPrivateSubroutines]
\&    private_name_regex = _(?!_)\ew+
.Ve
.PP
The above example is a way of saying that subroutines that start with
a double underscore are not considered to be private.  (Perl::Critic,
in its implementation, uses leading double underscores to indicate a
distribution-private subroutine \-\- one that is allowed to be invoked by
other Perl::Critic modules, but not by anything outside of
Perl::Critic.)
.PP
You can configure additional subroutines to accept by specifying them
in a space-delimited list to the \f(CW\*(C`allow\*(C'\fR option:
.PP
.Vb 2
\&    [Subroutines::ProhibitUnusedPrivateSubroutines]
\&    allow = _bar _baz
.Ve
.PP
These are added to the default list of exemptions from this policy. So the
above allows \f(CW\*(C`sub _bar {}\*(C'\fR and \f(CW\*(C`sub _baz {}\*(C'\fR, even if they are not
referred to in the module that defines them.
.PP
You can allow a whole class or subroutine names by defining a regular
expression that matches allowed names.
.PP
.Vb 2
\&    [Subroutines::ProhibitUnusedPrivateSubroutines]
\&    allow_name_regex = _build_\ew+
.Ve
.PP
You can configure this policy not to check private subroutines declared in a
file that uses one or more particular named modules.  This allows you to, for
example, exclude unused private subroutine checking in classes that are roles.
.PP
.Vb 2
\&    [Subroutines::ProhibitUnusedPrivateSubroutines]
\&    skip_when_using = Moose::Role Moo::Role Role::Tiny
.Ve
.SH HISTORY
.IX Header "HISTORY"
This policy is derived from
Perl::Critic::Policy::Subroutines::ProtectPrivateSubs,
which looks at the other side of the problem.
.SH BUGS
.IX Header "BUGS"
Does not forbid \f(CW\*(C`sub Foo::_foo{}\*(C'\fR because it does not know (and can not
assume) what is in the \f(CW\*(C`Foo\*(C'\fR package.
.PP
Does not respect the scope caused by multiple packages in the same file.  For
example a file:
.PP
.Vb 2
\&    package Foo;
\&    sub _is_private { print "A private sub!"; }
\&
\&    package Bar;
\&    _is_private();
.Ve
.PP
Will not trigger a violation even though \f(CW\*(C`Foo::_is_private\*(C'\fR is not called.
Similarly, \f(CW\*(C`skip_when_using\*(C'\fR currently works on a \fIfile\fR level, not on a
\&\fIpackage scope\fR level.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Perl::Critic::Policy::Subroutines::ProtectPrivateSubs.
.SH AUTHOR
.IX Header "AUTHOR"
Chris Dolan <cdolan@cpan.org>
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright (c) 2009\-2021 Thomas R. Wyant, III.
.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.