Devel::Hide(3pm) User Contributed Perl Documentation Devel::Hide(3pm)
NAME
Devel::Hide - Forces the unavailability of specified Perl modules (for testing)
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:
Can't 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 <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.
perl v5.12.4 2007-11-15 Devel::Hide(3pm)