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 (<tchrist@perl.com>) for help with the
    symbol table hackery.

    Thanks to Zefram (<zefram@fysh.org>) 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 <developers@grantstreet.com>

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)

