NAME

   Exporter::ConditionalSubs

VERSION

   version v1.11.0

SYNOPSIS

   Allows subroutines to be conditionally exported. If the condition is
   satisfied, the subroutine will be exported as usual. But if not, the
   subroutine will be replaced with a stub that gets optimized away by the
   compiler. When stubbed out, not even the arguments to the subroutine
   will get evaluated.

   This allows for e.g. assertion-like behavior, where subroutine calls
   can be left in the code but effectively ignored under certain
   conditions.

   First create a module that ISA Exporter::ConditionalSubs:

       package My::Assertions;

       require Exporter::ConditionalSubs;
       our @ISA = qw( Exporter::ConditionalSubs );

       our @EXPORT    = ();
       our @EXPORT_OK = qw( _assert_non_empty );

       sub _assert_non_empty
       {
           carp "Found empty value" unless length(shift // '') > 0;
       }

   Then, specify an -if or -unless condition when useing that module:

       package My::App;

       use My::Assertions qw( _assert_non_empty ), -if => $ENV{DEBUG};

       use My::MoreAssertions -unless => $ENV{RUNTIME} eq 'prod';

       # Coderefs work too:
       use My::OtherAssertions -if => sub { ... some logic ... };

       _assert_non_empty($foo);    # this subroutine call might be a no-op

   This is a subclass of Exporter and works just like it, with the
   addition of support for the -if and -unless import arguments.

NAME

   Exporter::ConditionalSubs - Conditionally export subroutines

VERSION

   Version 1.01

SUBROUTINES

import

   Works like the Exporter import() function, except that it checks for an
   optional -if or -unless import arg, followed by either a boolean, or a
   coderef that returns true/false.

   If the condition evaluates to true for -if, or false for -unless, then
   any subs are exported as-is. Otherwise, any subs in @EXPORT_OK are
   replaced with stubs that get optimized away by the compiler (with one
   exception - see "CAVEATS" below).

   You can specify either -if or -unless, but not both. Croaks if both are
   specified, or if you specify the same option more than once.

CAVEATS

   This module uses B::CallChecker and B::Generate under the covers to
   optimize away the exported subroutines. Loading one or the other of
   those modules can potentially break test coverage metrics generated by
   Devel::Cover in mysterious ways.

   To avoid this problem, subroutines are never optimized away if
   Devel::Cover is in use, and are always exported as-is regardless of any
   -if or -unless conditions. (You probably want Devel::Cover to assess
   the coverage of your real exported subroutines in any case.)

SEE ALSO

   Exporter

   B::CallChecker

   B::Generate

AUTHOR

   Larry Leszczynski, <larryl at cpan.org>

BUGS

   Please report any bugs or feature requests at:
   https://github.com/GrantStreetGroup/Exporter-ConditionalSubs

SUPPORT

   You can find documentation for this module with the perldoc command.

       perldoc Exporter::ConditionalSubs

   You can also look for information at:

     * GitHub

     https://github.com/GrantStreetGroup/Exporter-ConditionalSubs

     * MetaCPAN

     https://metacpan.org/pod/Exporter::ConditionalSubs

     * AnnoCPAN, Annotated CPAN documentation

     http://annocpan.org/dist/Exporter-ConditionalSubs

     * CPAN Ratings

     http://cpanratings.perl.org/d/Exporter-ConditionalSubs

AUTHOR

   Larry Leszczynski, <larryl at cpan.org>

ACKNOWLEDGEMENTS

   Thanks to Grant Street Group http://www.grantstreet.com for funding
   development of this code.

   Thanks to Tom Christiansen (<[email protected]>) for help with the
   symbol table hackery.

   Thanks to Zefram (<[email protected]>) for the pointer to his Debug::Show
   hackery.

LICENSE AND COPYRIGHT

   Copyright 2015 Grant Street Group

   This program is free software; you can redistribute it and/or modify it
   under the terms of the the Artistic License (2.0). You may obtain a
   copy of the full license at:

   http://www.perlfoundation.org/artistic_license_2_0

   Any use, modification, and distribution of the Standard or Modified
   Versions is governed by this Artistic License. By using, modifying or
   distributing the Package, you accept this license. Do not use, modify,
   or distribute the Package, if you do not accept this license.

   If your Modified Version has been derived from a Modified Version made
   by someone other than you, you are nevertheless required to ensure that
   your Modified Version complies with the requirements of this license.

   This license does not grant you the right to use any trademark, service
   mark, tradename, or logo of the Copyright Holder.

   This license includes the non-exclusive, worldwide, free-of-charge
   patent license to make, have made, use, offer to sell, sell, import and
   otherwise transfer the Package with respect to any patent claims
   licensable by the Copyright Holder that are necessarily infringed by
   the Package. If you institute patent litigation (including a
   cross-claim or counterclaim) against any party alleging that the
   Package constitutes direct or contributory patent infringement, then
   this Artistic License to you shall terminate on the date that such
   litigation is filed.

   Disclaimer of Warranty: THE PACKAGE IS PROVIDED BY THE COPYRIGHT HOLDER
   AND CONTRIBUTORS "AS IS' AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES.
   THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
   PURPOSE, OR NON-INFRINGEMENT ARE DISCLAIMED TO THE EXTENT PERMITTED BY
   YOUR LOCAL LAW. UNLESS REQUIRED BY LAW, NO COPYRIGHT HOLDER OR
   CONTRIBUTOR WILL BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, OR
   CONSEQUENTIAL DAMAGES ARISING IN ANY WAY OUT OF THE USE OF THE PACKAGE,
   EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

AUTHOR

   Grant Street Group <[email protected]>

COPYRIGHT AND LICENSE

   This software is Copyright (c) 2015 - 2020 by Grant Street Group.

   This is free software, licensed under:

     The Artistic License 2.0 (GPL Compatible)

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