Steven Haryanto

NAME

Perinci::Exporter - Metadata-aware Exporter

VERSION

version 0.04

SYNOPSIS

 package YourModule;
 # most of the time, you only need to do this
 use Perinci::Exporter;

DESCRIPTION

Perinci::Exporter is an exporter which can utilize information from Rinci metadata. If your package has Rinci metadata, consider using this exporter for convenience and flexibility.

Features of this module:

  • List exportable routines from Rinci metadata

    All functions which have metadata are assumed to be exportable, so you do not have to list them again via @EXPORT or @EXPORT_OK.

  • Read tags from Rinci metadata

    The exporter can read tags from your function metadata. You do not have to define export tags again.

  • Export to different name

    See the 'as', 'prefix', 'suffix' import options of the install_import() function.

  • Export wrapped function

    This allows importer to get additional/modified behavior. See Perinci::Sub::Wrapper for more about wrapping.

  • Export differently wrapped function to different importers

    See some examples in "FAQ".

  • Warn/bail on clash with existing function

    For testing or safety precaution.

  • Read @EXPORT and @EXPORT_OK

    Perinci::Exporter reads these two package variables, so it is quite compatible with Exporter and Exporter::Lite. In fact, it is basically the same as Exporter::Lite if you do not have any metadata for your functions.

EXPORTING

Most of the time, to set up exporter, you only need to just use() it in your module:

 package YourModule;
 use Perinci::Exporter;

Perinci::Exporter will install an import() routine for your package. If you need to pass some exporting options:

 use Perinci::Exporter default_exports=>[qw/foo bar/], ...;

See install_import() for more details.

IMPORTING

Default exports. Your module users can import functions in a variety of ways. The simplest form is:

 use YourModule;

which by default will export all functions marked with :default tags. For example:

 package YourModule;
 use Perinci::Exporter;
 our %SPEC;
 $SPEC{f1} = { v=>1.1, tags=>[qw/default a/] };
 sub   f1    { ... }
 $SPEC{f2} = { v=>1.1, tags=>[qw/default a b/] };
 sub   f2    { ... }
 $SPEC{f3} = { v=>1.1, tags=>[qw/b c/] };
 sub   f3    { ... }
 1;

YourModule will by default export f1 and f2. If there are no functions tagged with default, there will be no default exports. You can also supply the list of default functions via the default_exports argument:

 use Perinci::Exporter default_exports => [qw/f1 f2/];

or via the @EXPORT package variable, like in Exporter.

Exporting individual functions. Users can import individual functions:

 use YourModule qw(f1 f2);

Each function can have import options, specified in a hashref:

 use YourModule f1 => {wrap=>0}, f2=>{as=>'bar', args_as=>'array'};
 # imports f1, bar

Exporting groups of functions by tags. Users can import groups of individual functions using tags. Tags are collected from function metadata, and written with a : prefix (to differentiate them from function names). Each tag can also have import options:

 use YourModule 'f3', ':a' => {prefix => 'a_'}; # imports f3, a_f1, a_f2

Some tags are defined automatically: :default, :all.

Exporting to a different name. As can be seen from previous examples, the 'as' and 'prefix' (and also 'suffix') import options can be used to import subroutines using into a different name.

Bailing on name clashes. By default, importing will override existing names in the target package. To warn about this, users can set '-on_clash' to 'bail':

 use YourModule 'f1', f2=>{as=>'f1'}, -on_clash=>'bail'; # dies, imports clash

 use YourModule 'f1', -on_clash=>'bail'; # dies, f1 already exists
 sub f1 { ... }

Customizing wrapping options. Users can specify custom wrapping options when importing functions. The wrapping will then be done just for them (as opposed to wrapped functions which are wrapped using default options, which will be shared among all importers not requesting custom wrapping). See some examples in "FAQ".

See do_export() for more details.

FUNCTIONS

install_import(%args)

The routine which installs the import() routine to caller package.

Arguments:

  • into => STR (default: caller package)

    Explicitly set target package to install the import() routine to.

  • caller_level => INT (default: 0)

    If into is not set, caller package will be used. The default is to use caller(0), but the caller level can be set using this argument.

  • default_exports => ARRAY

    Default symbols to export.

    You can also set default exports by setting @EXPORT.

  • extra_exports => ARRAY

    Other symbols to export (other than the ones having metadata and those specified with default_exports and @EXPORT).

    You can also set default exports by setting @EXPORT_OK.

  • default_wrap => BOOL (default: 1)

    Whether wrap subroutines by default.

  • default_on_clash => STR (default: 'force')

    What to do when clash of symbols happen.

do_export($expopts, @args)

The routine which implements the exporting. Will be called from the import() routine. $expopts is a hashref containing exporter options, constructed by install_import(). @args is the same as arguments passed during import: a sequence of function name or tag name (prefixed with :), function/tag name and export option (hashref), or option (prefixed with -).

Example:

 do_export('f1', ':tag1', f2 => {import option...}, -option => ...);

Import options:

  • as => STR

    Export a function to a new name. Will die if new name is invalid. Inapplicable for tags.

    Example:

     use YourModule func => {as => 'f'};
  • prefix => STR

    Export function/tag with a prefix. Will die on invalid prefix.

    Example:

     use YourModule ':default' => {prefix => 'your_'};

    This means, foo, bar, etc. will be exported as your_foo, your_bar, etc.

  • suffix => STR

    Export function/tag with a prefix. Will die on invalid suffix.

    Example:

     use YourModule ':default' => {suffix => '_s'};

    This means, foo, bar, etc. will be exported as foo_s, bar_s, etc.

  • wrap => 0 | 1 | HASH (default: from install_import()'s default_wrap)

    The default is export the wrapped functions. Can be set this to 0 to disable wrapping, or a hash containing custom wrap arguments (to be passed to Perinci::Sub::Wrapper's wrap_sub()).

    Examples:

     use YourModule foo => {}; # export wrapped, with default wrap options
     use YourModule foo => {wrap=>0}; # export unwrapped
     use YourModule foo => {args_as=>'array'}; # export with custom wrap

    Note that when set to 0, the exported function might already be wrapped anyway, e.g. when your module uses embedded wrapping (see Dist::Zilla::Plugin::Rinci::Wrap) or wrap its subroutines manually.

    Also note that wrapping will not be done if subroutine does not have metadata.

  • convert => HASH

    This is a shortcut for specifying:

     wrap => { convert => HASH }
  • args_as => STR

    This is a shortcut for specifying:

     wrap => { convert => { args_as => STR } }
  • result_naked => BOOL

    This is a shortcut for specifying:

     wrap => { convert => { result_naked => BOOL } }
  • curry => STR

    This is a shortcut for specifying:

     wrap => { convert => { curry => STR } }

Options:

  • -on_clash => 'force' | 'bail' (default: from install_import()'s default_on_clash)

    If importer tries to import 'foo' when it already exists, the default is to force importing, without any warnings, like Exporter. Alternatively, you can also bail (dies), which can be more reliable/safe.

  • -prefix => STR

    Like prefix import option, but to apply to all exports.

  • -suffix => STR

    Like suffix import option, but to apply to all exports.

FAQ

Why use this module as my exporter?

If you are fine with Exporter, Exporter::Lite, or Sub::Exporter, then you probably won't need this module.

This module is particularly useful if your subs have Rinci metadata, in which case you'll get some nice features. Some examples of the things you can do with this exporter:

  • Change calling style from argument to positional

     use YourModule func => {args_as=>'array'};

    Then instead of:

     func(a => 1, b => 2);

    your function is called with positional arguments:

     func(1, 2);

    Note: this requires that the function's argument spec puts the 'pos' information. For example:

     $SPEC{func} = {
         v => 1.1,
         args => {
             a => { pos=>0 },
             b => { pos=>1 },
         }
     };
  • Set timeout

     use YourModule ':all' => {wrap=>{convert=>{timeout=>10}}};

    This means all exported functions will be limited to 10s of execution time.

    Note: Perinci::Sub::property::timeout is needed for this.

  • Set retry

     use YourModule ':default' => {wrap=>{convert=>{retry=>3}}};

    This means all exported functions can autoretry up to 3 times.

    Note: Perinci::Sub::property::retry is needed for this.

  • Currying

    Sub::Exporter supports this. Perinci::Exporter does too:

     use YourModule f => {as=>'f_a10', wrap=>{convert=>{curry=>{a=>10}}}};

    This means:

     f_a10();             # equivalent to f(a=>10)
     f_a10(b=>20, c=>30); # equivalent to f(a=>10, b=>20, c=>30)
     f_a10(a=>5);         # error, a is already set

    Note: Perinci::Sub::property::curry is needed for this.

What happens to functions that do not have metadata?

They can still be exported if you list them in @EXPORT or @EXPORT_OK.

TODO/IDEAS

  • Support combining tags?

     use YourModule qw(not(:tag1));
     use YourModule qw(and(:tag1,:tag2));
     use YourModule qw(or(:tag1,and(:tag2,:tag3)));
  • Export variables, etc.

SEE ALSO

Perinci

Perinci::Sub::Wrapper

HOMEPAGE

Please visit the project's homepage at https://metacpan.org/release/Perinci-Exporter.

SOURCE

Source repository is at https://github.com/sharyanto/perl-Perinci-Exporter.

BUGS

Please report any bugs or feature requests on the bugtracker website https://rt.cpan.org/Public/Dist/Display.html?Name=Perinci-Exporter

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.

AUTHOR

Steven Haryanto <stevenharyanto@gmail.com>

COPYRIGHT AND LICENSE

This software is copyright (c) 2014 by Steven Haryanto.

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




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