1Devel::Hide(3)        User Contributed Perl Documentation       Devel::Hide(3)
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NAME

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

10           use Devel::Hide qw(Module/ToHide.pm);
11           require Module::ToHide; # fails
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13           use Devel::Hide qw(Test::Pod Test::Pod::Coverage);
14           require Test::More; # ok
15           use Test::Pod 1.18; # fails
16
17       Other common usage patterns:
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19           $ perl -MDevel::Hide=Module::ToHide Makefile.PL
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21           bash$ PERL5OPT=MDevel::Hide
22           bash$ DEVEL_HIDE_PM='Module::Which Test::Pod'
23           bash$ export PERL5OPT DEVEL_HIDE_PM
24           bash$ perl Makefile.PL
25
26       outputs (like blib)
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28           Devel::Hide hides Module::Which, Test::Pod, etc.
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DESCRIPTION

31       Given a list of Perl modules/filenames, this module makes "require" and
32       "use" statements fail (no matter the specified files/modules are
33       installed or not).
34
35       They die with a message like:
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37           Can't locate Module/ToHide.pm (hidden)
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39       The original intent of this module is to allow Perl developers to test
40       for alternative behavior when some modules are not available. In a Perl
41       installation, where many modules are already installed, there is a
42       chance to screw things up because you take for granted things that may
43       not be there in other machines.
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45       For example, to test if your distribution does the right thing when a
46       module is missing, you can do
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48           perl -MDevel::Hide=Test::Pod Makefile.PL
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50       forcing "Test::Pod" to not be found (whether it is installed or not).
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52       Another use case is to force a module which can choose between two
53       requisites to use the one which is not the default.  For example,
54       "XML::Simple" needs a parser module and may use "XML::Parser" or
55       "XML::SAX" (preferring the latter).  If you have both of them
56       installed, it will always try "XML::SAX".  But you can say:
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58           perl -MDevel::Hide=XML::SAX script_which_uses_xml_simple.pl
59
60       NOTE. This module does not use Carp. As said before, denial dies.
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62       This module is pretty trivial. It uses a code reference in @INC to get
63       rid of specific modules during require - denying they can be
64       successfully loaded and stopping the search before they have a chance
65       to be found.
66
67       There are three alternative ways to include modules in the hidden list:
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69       ·   setting @Devel::Hide::HIDDEN
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71       ·   environment variable DEVEL_HIDE_PM
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73       ·   import()
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75       Optionally, you can propagate the list of hidden modules to your
76       process' child processes, by passing '-from:children' as the first
77       option when you use() this module. This works by populating "PERL5OPT",
78       and is incompatible with Taint mode, as explained in perlrun.
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80   CAVEATS
81       There is some interaction between "lib" and this module
82
83           use Devel::Hide qw(Module/ToHide.pm);
84           use lib qw(my_lib);
85
86       In this case, 'my_lib' enters the include path before the Devel::Hide
87       hook and if Module/ToHide.pm is found in 'my_lib', it succeeds.
88
89       Also for modules that were loaded before Devel::Hide, "require" and
90       "use" succeeds.
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92       Since 0.0005, Devel::Hide warns about modules already loaded.
93
94           $ perl -MDevel::Hide=Devel::Hide -e ''
95           Devel::Hide: Too late to hide Devel/Hide.pm
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97   EXPORTS
98       Nothing is exported.
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ENVIRONMENT VARIABLES

101       DEVEL_HIDE_PM - if defined, the list of modules is added
102          to the list of hidden modules
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104       DEVEL_HIDE_VERBOSE - on by default. If off, suppresses
105          the initial message which shows the list of hidden modules
106          in effect
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108       PERL5OPT - used if you specify '-from:children'
109

SEE ALSO

111       "perldoc -f require"
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113       Test::Without::Module
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BUGS

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

120       Adriano R. Ferreira, <ferreira@cpan.org>
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122       with contributions from David Cantrell <dcantrell@cpan.org>
123

125       Copyright (C) 2005-2007, 2018 by Adriano R. Ferreira
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127       This library is free software; you can redistribute it and/or modify it
128       under the same terms as Perl itself.
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132perl v5.28.1                      2018-06-15                    Devel::Hide(3)
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