++ed by:
DBR DCPETROV DOHERTY KEEDI TMUELLER

6 PAUSE user(s)
4 non-PAUSE user(s).

Toby Inkster

NAME

Syntax::Collector - collect a bundle of modules into one

SYNOPSIS

In lib/Example/ProjectX/Syntax.pm

   package Example::ProjectX::Syntax;
   
   use 5.010;
   our $VERSION = 1;
   
   use Syntax::Collector q/
      use strict 0;
      use warnings 0;
      use feature 0 ':5.10';
      use Scalar::Util 1.21 qw(blessed);
   /;
   
   1;
   __END__

In projectx.pl:

   #!/usr/bin/perl
   
   use Example::ProjectX::Database;
   use Example::ProjectX::Syntax 1;
   # strict, warnings, feature ':5.10', etc are now enabled!
   
   say "Welcome to ProjectX";

DESCRIPTION

Perl is such a flexible language that the language itself can be extended from within. (Though much of the more interesting stuff needs XS hooks like Devel::Declare.)

One problem with this is that it often requires a lot of declarations at the top of your code, loading various syntax extensions. The syntax module on CPAN addresses this somewhat by allowing you to load a bunch of features in one line, provided each syntax feature implements the necessary API:

   use syntax qw/io maybe perform/;

However this introduces problems of its own. If we look at the code above, it is non-obvious that it requires Syntax::Feature::Io, Syntax::Feature::Maybe and Syntax::Feature::Perform, which makes it difficult for automated tools such as Module::Install to automatically calculate your code's dependencies.

Syntax::Collector to the rescue!

   package Example::ProjectX::Syntax;
   use 5.010;
   use Syntax::Collector q/
   use strict 0;
   use warnings 0;
   use feature 0 ':5.10';
   use Scalar::Util 1.21 qw(blessed);
   /;

When you use Syntax::Collector, you provide a list of modules to "collect" into a single package (notice the q/.../). This list of modules looks like a big string of Perl code that is going to be passed to eval, but don't let that fool you - it is not.

Each line must conform to the following pattern:

   (use|no) MODULENAME VERSION (OTHERSTUFF)? ;

(Actually hash comments, and blank lines are also allowed.) The semantics of all that is pretty much what you'd expect, except that when MODULENAME begins with "Syntax::Feature::" it's treated with some DWIMmery, and install is called instead of import. Note that VERSION is required, but if you don't care which version of a module you use, it's fine to set VERSION to 0. (Yes, VERSION is even required for pragmata.)

Now, you ask... why stuff all that structured data into a string, and parse it out again? Because to naive lexical analysis (e.g. Module::Install) it really looks like a bunch of "use" lines, and not just a single quoted string. This helps tools calculate the dependencies of your collection; and thus the dependencies of other code that uses your collection.

As well as providing an import method for your collection, Syntax::Collector also provides a modules method, which can be called to find out which modules a collection includes. Called in list context, it returns a list. Called in scalar context, it returns a reference to a { module => version } hash.

Exporting

Syntax::Collector will also make your class inherit from Exporter::Tiny so that in addition to collecting up a bunch of features from other modules, your syntax collection can also export its own functions.

   package Example::ProjectX::Syntax;
   
   use 5.010;
   our $VERSION = 1;
   
   use Syntax::Collector q/
     use strict 0;
     use warnings 0;
     use feature 0 ':5.10';
     use Scalar::Util 1.21 qw(blessed);
   /;
   
   our @EXPORT = qw( foo bar );
   
   sub foo { ... }
   
   1;
   __END__

Import Options

Modules importing your syntax collection can suppress particular lines:

   use Example::ProjectX::Syntax qw( -warnings );

Or provide alternative import options:

   use Example::ProjectX::Syntax
      '-Scalar::Util' => [qw/ blessed refaddr /];

See also Exporter::Tiny.

BUGS

Please report any bugs to http://rt.cpan.org/Dist/Display.html?Queue=Syntax-Collector.

SEE ALSO

Exporter::Tiny.

AUTHOR

Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE

This software is copyright (c) 2012 by Toby Inkster.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

DISCLAIMER OF WARRANTIES

THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.




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