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.\" ========================================================================
.\"
.IX Title "Module::Want 3"
.TH Module::Want 3 "2016-08-24" "perl v5.16.3" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
Module::Want \- Check @INC once for modules that you want but may not have
.SH "VERSION"
.IX Header "VERSION"
This document describes Module::Want version 0.6
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&    use Module::Want;
\&
\&    if (have_mod(\*(AqEncode\*(Aq)) {
\&        ... use Encode::whatever ...
\&    }
\&    else {
\&        ... use Encode:: alternative ...
\&    }
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Sometimes you want to lazy load a module for use in, say, a loop or function. First you do the eval-require but then realize if the module is not available it will re-search \f(CW@INC\fR each time. So then you add a lexical boolean to your eval and do the same simple logic all over the place. On and on it goes :)
.PP
This module encapsulates that logic so that \fIhave_mod()\fR is like eval { require X; 1 } but if the module can't be loaded it will remember that fact and not look in \f(CW@INC\fR again on subsequent calls.
.PP
For example, this searches \f(CW@INC\fR for X.pm every iteration of the loop:
.PP
.Vb 8
\&    while( ... ) {
\&        if (eval { require X; 1 }) {
\&            ... use X code ...
\&        }
\&        else {
\&            ... do X\-alternative code ...
\&        }
\&    }
.Ve
.PP
This searches \f(CW@INC\fR for X.pm once:
.PP
.Vb 8
\&    while( ... ) {
\&        if (have_mod(\*(AqX\*(Aq)) {
\&            ... use X code ...
\&        }
\&        else {
\&            ... do X\-alternative code ...
\&        }
\&    }
.Ve
.PP
Additionally, it will not trip the sig die handler. That prevents a benign eval from tripping a potentially fatal sig handler. (i.e. another step you'd have to do manually with the straight eval form.)
.SH "INTERFACE"
.IX Header "INTERFACE"
\&\fIimport()\fR puts \fIhave_mod()\fR into the caller's name space.
.SS "\fIhave_mod()\fP"
.IX Subsection "have_mod()"
Takes the name space to \fIrequire()\fR if we have not tried already.
.PP
Returns true if it could be loaded. False otherwise.
.PP
You can give it a second true argument to skip using the value from the last time it was called and re-try \fIrequire()\fRing it.
.PP
.Vb 3
\&   if (!have_mod(\*(AqX\*(Aq)) {
\&       # do some things to try and ger X available 
\&   }
\&   
\&   if (have_mod(\*(AqX\*(Aq,1)) {
\&       # sweet we have it now!
\&   }
.Ve
.SS "\fIimport()\fP"
.IX Subsection "import()"
You can \fIuse()\fR it with a list to call \fIhave_mod()\fR on:
.PP
.Vb 1
\&   use Module::Want qw(X Y Z); # calls have_mod(\*(AqX\*(Aq), have_mod(\*(AqY\*(Aq), and have_mod(\*(AqZ\*(Aq)
.Ve
.SS "Utility functions"
.IX Subsection "Utility functions"
These aren't the real reasons for this module but they've proven useful when you're doing things that would require \fIhave_mod()\fR so here they are:
.PP
They can all be exported thusly:
.PP
.Vb 1
\&    use Module::Want qw(is_ns);
.Ve
.PP
For an entire suite if name space utilities see Module::Util and friends.
.PP
\fIis_ns($ns)\fR
.IX Subsection "is_ns($ns)"
.PP
Boolean of if '$ns' is a proper name space or not.
.PP
.Vb 6
\&    if(is_ns($ns)) {
\&        ... use $ns as a module/class name ...
\&    }
\&    else {
\&       ... "invalid input please try again" prompt ...
\&    }
.Ve
.PP
\fI\fIget_ns_regexp()\fI\fR
.IX Subsection "get_ns_regexp()"
.PP
Returns a quoted Regexp that matches a name space for use in your regexes.
.PP
\fIget_all_use_require_in_text($text)\fR
.IX Subsection "get_all_use_require_in_text($text)"
.PP
This will return a list of all name spaces being \fIuse()\fRd or \fIrequire()\fRd in perlish looking \f(CW$text\fR.
.PP
It will also return ones being \fIeval()\fRd in.
.PP
It is very simplistic (e.g. it may or may not return use/require statements that are in comments, it will match verbiage in a here doc that start w/ XuseX) so if it does not fit your needs you'll need to try a \s-1PPI\s0 based solution (I have Perl::DependList on my radar that does just that.).
.PP
\fIget_inc_key($ns)\fR
.IX Subsection "get_inc_key($ns)"
.PP
Returns what \f(CW$ns\fR's key in \f(CW%INC\fR would be (if is_ns($ns) of course)
.PP
.Vb 8
\&    if (my $inc_key =  get_inc_key($ns)) {
\&        if (exists $INC{$inc_key}) {
\&           ... in %INC ...
\&        }
\&        else {
\&            ... not in %INC ...
\&        }    
\&    }
.Ve
.PP
\&\f(CW%INC\fR keys are always unix format so don't panic
.PP
If I've been misinformed of that fact then please let me know, thanks
.PP
get_relative_path_of_ns($ns)
.IX Subsection "get_relative_path_of_ns($ns)"
.PP
Alias of \*(L"get_inc_key($ns)\*(R" whose name indicates a different intent.
.PP
\fIget_clean_ns($ns)\fR
.IX Subsection "get_clean_ns($ns)"
.PP
Takes \f(CW$ns\fR, trims leading and trailing whitespace and turns ' into ::, and returns the cleaned copy.
.PP
normalize_ns($ns)
.IX Subsection "normalize_ns($ns)"
.PP
Alias of \*(L"get_clean_ns($ns)\*(R" whose name indicates a different intent.
.PP
\fIns2distname($ns)\fR
.IX Subsection "ns2distname($ns)"
.PP
Turns the given name space into a distribution name.
.PP
e.g. Foo::Bar::Baz becomes Foo-Bar-Baz
.PP
\fIdistname2ns($distname)\fR
.IX Subsection "distname2ns($distname)"
.PP
Turns the given distribution name into a name space.
.PP
e.g. Foo-Bar-Baz becomes Foo::Bar::Baz
.PP
\fIget_inc_path_via_have_mod($ns)\fR
.IX Subsection "get_inc_path_via_have_mod($ns)"
.PP
Return the \f(CW%INC\fR entryXs value if we have_mod($ns);
.PP
\fIsearch_inc_paths($ns)\fR
.IX Subsection "search_inc_paths($ns)"
.PP
Without loading the module, search for \f(CW$ns\fR in \f(CW@INC\fR.
.PP
In scalar context returns the first path it is found in, in list context returns all paths it is found in.
.PP
.Vb 2
\&    my $first_path_it_is_in = search_inc_paths($ns);
\&    my @all_paths_it_is_in  = search_inc_paths($ns);
.Ve
.PP
By default it returns the path it is in without the module-name part of the path. A second true argument will return the entire path.
.PP
.Vb 1
\&    my $abs_path_of_pm_file = search_inc_paths($ns,1);
.Ve
.SH "DIAGNOSTICS"
.IX Header "DIAGNOSTICS"
.ie n .IP """Invalid Namespace""" 4
.el .IP "\f(CWInvalid Namespace\fR" 4
.IX Item "Invalid Namespace"
The argument to \fIhave_mod()\fR is not a name space
.SH "CONFIGURATION AND ENVIRONMENT"
.IX Header "CONFIGURATION AND ENVIRONMENT"
Module::Want requires no configuration files or environment variables.
.SH "DEPENDENCIES"
.IX Header "DEPENDENCIES"
None.
.SH "INCOMPATIBILITIES"
.IX Header "INCOMPATIBILITIES"
None reported.
.SH "BUGS AND LIMITATIONS"
.IX Header "BUGS AND LIMITATIONS"
No bugs have been reported.
.PP
Please report any bugs or feature requests to
\&\f(CW\*(C`bug\-module\-want@rt.cpan.org\*(C'\fR, or through the web interface at
<http://rt.cpan.org>.
.SH "AUTHOR"
.IX Header "AUTHOR"
Daniel Muey  \f(CW\*(C`<http://drmuey.com/cpan_contact.pl>\*(C'\fR
.SH "LICENCE AND COPYRIGHT"
.IX Header "LICENCE AND COPYRIGHT"
Copyright (c) 2010, Daniel Muey \f(CW\*(C`<http://drmuey.com/cpan_contact.pl>\*(C'\fR. All rights reserved.
.PP
This module is free software; you can redistribute it and/or
modify it under the same terms as Perl itself. See perlartistic.
.SH "DISCLAIMER OF WARRANTY"
.IX Header "DISCLAIMER OF WARRANTY"
\&\s-1BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN
OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
PROVIDE THE SOFTWARE \*(L"AS IS\*(R" WITHOUT WARRANTY OF ANY KIND, EITHER
EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH
YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
NECESSARY SERVICING, REPAIR, OR CORRECTION.\s0
.PP
\&\s-1IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE
LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL,
OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE
THE SOFTWARE \s0(\s-1INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING
RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A
FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE\s0), \s-1EVEN IF
SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
SUCH DAMAGES.\s0