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Man Pages


Manual Reference Pages  -  DEVEL::HIDE (3)

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NAME

Devel::Hide - Forces the unavailability of specified Perl modules (for testing)

CONTENTS

SYNOPSIS



    use Devel::Hide qw(Module/ToHide.pm);
    require Module::ToHide; # fails

    use Devel::Hide qw(Test::Pod Test::Pod::Coverage);
    require Test::More; # ok
    use Test::Pod 1.18; # fails



Other common usage patterns:



    $ perl -MDevel::Hide=Module::ToHide Makefile.PL

    bash$ PERL5OPT=MDevel::Hide
    bash$ DEVEL_HIDE_PM=Module::Which Test::Pod
    bash$ export PERL5OPT DEVEL_HIDE_PM
    bash$ perl Makefile.PL



outputs (like blib)



    Devel::Hide hides Module::Which, Test::Pod, etc.



DESCRIPTION

Given a list of Perl modules/filenames, this module makes require and use statements fail (no matter the specified files/modules are installed or not).

They die with a message like:



    Cant locate Module/ToHide.pm (hidden)



The original intent of this module is to allow Perl developers to test for alternative behavior when some modules are not available. In a Perl installation, where many modules are already installed, there is a chance to screw things up because you take for granted things that may not be there in other machines.

For example, to test if your distribution does the right thing when a module is missing, you can do



    perl -MDevel::Hide=Test::Pod Makefile.PL



forcing Test::Pod to not be found (whether it is installed or not).

Another use case is to force a module which can choose between two requisites to use the one which is not the default. For example, XML::Simple needs a parser module and may use XML::Parser or XML::SAX (preferring the latter). If you have both of them installed, it will always try XML::SAX. But you can say:



    perl -MDevel::Hide=XML::SAX script_which_uses_xml_simple.pl



NOTE. This module does not use Carp. As said before, denial dies.

This module is pretty trivial. It uses a code reference in @INC to get rid of specific modules during require - denying they can be successfully loaded and stopping the search before they have a chance to be found.

There are three alternative ways to include modules in the hidden list:
o setting @Devel::Hide::HIDDEN
o environment variable DEVEL_HIDE_PM
o import()
Optionally, you can propagate the list of hidden modules to your process’ child processes, by passing ’-from:children’ as the first option when you use() this module. This works by populating PERL5OPT, and is incompatible with Taint mode, as explained in perlrun.

    CAVEATS

There is some interaction between lib and this module



    use Devel::Hide qw(Module/ToHide.pm);
    use lib qw(my_lib);



In this case, ’my_lib’ enters the include path before the Devel::Hide hook and if Module/ToHide.pm is found in ’my_lib’, it succeeds.

Also for modules that were loaded before Devel::Hide, require and use succeeds.

Since 0.0005, Devel::Hide warns about modules already loaded.



    $ perl -MDevel::Hide=Devel::Hide -e 
    Devel::Hide: Too late to hide Devel/Hide.pm



    EXPORTS

Nothing is exported.

ENVIRONMENT VARIABLES

DEVEL_HIDE_PM - if defined, the list of modules is added
to the list of hidden modules

DEVEL_HIDE_VERBOSE - on by default. If off, supresses
the initial message which shows the list of hidden modules
in effect

PERL5OPT - used if you specify ’-from:children’

SEE ALSO

perldoc -f require

Test::Without::Module

BUGS

Please report bugs via CPAN RT <http://rt.cpan.org/NoAuth/Bugs.html?Dist=Devel-Hide>.

AUTHORS

Adriano R. Ferreira, <ferreira@cpan.org>

with contributions from David Cantrell <dcantrell@cpan.org>

COPYRIGHT AND LICENSE

Copyright (C) 2005-2007 by Adriano R. Ferreira

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

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perl v5.20.3 DEVEL::HIDE (3) 2013-01-28

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