1Devel::Hide(3) User Contributed Perl Documentation Devel::Hide(3)
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6 Devel::Hide - Forces the unavailability of specified Perl modules (for
7 testing)
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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
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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
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26 outputs (like blib)
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28 Devel::Hide hides Module::Which, Test::Pod, etc.
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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).
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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
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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.
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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
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83 use Devel::Hide qw(Module/ToHide.pm);
84 use lib qw(my_lib);
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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.
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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.
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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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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'
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111 "perldoc -f require"
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113 Test::Without::Module
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116 Please report bugs via CPAN RT
117 <http://rt.cpan.org/NoAuth/Bugs.html?Dist=Devel-Hide>.
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120 Adriano R. Ferreira, <ferreira@cpan.org>
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122 with contributions from David Cantrell <dcantrell@cpan.org>
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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)