namespace::clean - Keep imports and functions out of your namespace

SYNOPSIS
DESCRIPTION
METHODS
IMPLEMENTATION DETAILS
SEE ALSO
THANKS
AUTHORS
COPYRIGHT AND LICENSE

SYNOPSIS

package Foo;
use warnings;
use strict;

use Carp qw(croak);   # 'croak' will be removed

sub bar { 23 }        # 'bar' will be removed

# remove all previously defined functions
use namespace::clean;

sub baz { bar() }     # 'baz' still defined, 'bar' still bound

# begin to collection function names from here again
no namespace::clean;

sub quux { baz() }    # 'quux' will be removed

# remove all functions defined after the 'no' unimport
use namespace::clean;

# Will print: 'No', 'No', 'Yes' and 'No'
print +(__PACKAGE__->can('croak') ? 'Yes' : 'No'), "\n";
print +(__PACKAGE__->can('bar')   ? 'Yes' : 'No'), "\n";
print +(__PACKAGE__->can('baz')   ? 'Yes' : 'No'), "\n";
print +(__PACKAGE__->can('quux')  ? 'Yes' : 'No'), "\n";

1;

DESCRIPTION

Keeping packages clean

When you define a function, or import one, into a Perl package, it will naturally also be available as a method. This does not per se cause problems, but it can complicate subclassing and, for example, plugin classes that are included via multiple inheritance by loading them as base classes.

The namespace::clean pragma will remove all previously declared or imported symbols at the end of the current package's compile cycle. Functions called in the package itself will still be bound by their name, but they won't show up as methods on your class or instances.

By unimporting via no you can tell namespace::clean to start collecting functions for the next use namespace::clean; specification.

You can use the -except flag to tell namespace::clean that you don't want it to remove a certain function or method. A common use would be a module exporting an import method along with some functions:

use ModuleExportingImport;
use namespace::clean -except => [qw( import )];

If you just want to -except a single sub, you can pass it directly. For more than one value you have to use an array reference.

Late binding caveat

Note that the technique used by this module relies on perl having resolved all names to actual code references during the compilation of a scope. While this is almost always what the interpreter does, there are some exceptions, notably the sort SUBNAME style of the sort built-in invocation. The following example will not work, because sort does not try to resolve the function name to an actual code reference until runtime.

use MyApp::Utils 'my_sorter';
use namespace::clean;

my @sorted = sort my_sorter @list;

You need to work around this by forcing a compile-time resolution like so:

use MyApp::Utils 'my_sorter';
use namespace::clean;

my $my_sorter_cref = \&my_sorter;

my @sorted = sort $my_sorter_cref @list;

Explicitly removing functions when your scope is compiled

It is also possible to explicitly tell namespace::clean what packages to remove when the surrounding scope has finished compiling. Here is an example:

package Foo;
use strict;

# blessed NOT available

sub my_class {
    use Scalar::Util qw( blessed );
    use namespace::clean qw( blessed );

    # blessed available
    return blessed shift;
}

# blessed NOT available

Moose

When using namespace::clean together with Moose you want to keep the installed meta method. So your classes should look like:

package Foo;
use Moose;
use namespace::clean -except => 'meta';
...

Same goes for Moose::Role.

Cleaning other packages

You can tell namespace::clean that you want to clean up another package instead of the one importing. To do this you have to pass in the -cleanee option like this:

package My::MooseX::namespace::clean;
use strict;

use namespace::clean (); # no cleanup, just load

sub import {
    namespace::clean->import(
      -cleanee => scalar(caller),
      -except  => 'meta',
    );
}

If you don't care about namespace::cleans discover-and--except logic, and just want to remove subroutines, try "clean_subroutines".

METHODS

clean_subroutines

This exposes the actual subroutine-removal logic.

namespace::clean->clean_subroutines($cleanee, qw( subA subB ));

will remove subA and subB from $cleanee. Note that this will remove the subroutines immediately and not wait for scope end. If you want to have this effect at a specific time (e.g. namespace::clean acts on scope compile end) it is your responsibility to make sure it runs at that time.

import

Makes a snapshot of the current defined functions and installs a B::Hooks::EndOfScope hook in the current scope to invoke the cleanups.

unimport

This method will be called when you do a

no namespace::clean;

It will start a new section of code that defines functions to clean up.

get_class_store

This returns a reference to a hash in a passed package containing information about function names included and excluded from removal.

get_functions

Takes a class as argument and returns all currently defined functions in it as a hash reference with the function name as key and a typeglob reference to the symbol as value.

IMPLEMENTATION DETAILS

This module works through the effect that a

delete $SomePackage::{foo};

will remove the foo symbol from $SomePackage for run time lookups (e.g., method calls) but will leave the entry alive to be called by already resolved names in the package itself. namespace::clean will restore and therefor in effect keep all glob slots that aren't CODE.

A test file has been added to the perl core to ensure that this behaviour will be stable in future releases.

Just for completeness sake, if you want to remove the symbol completely, use undef instead.

THANKS

Many thanks to Matt S Trout for the inspiration on the whole idea.

AUTHORS

Robert 'phaylon' Sedlacek <[email protected]>
Florian Ragwitz <[email protected]>
Jesse Luehrs <[email protected]>
Peter Rabbitson <[email protected]>
Father Chrysostomos <[email protected]>

COPYRIGHT AND LICENSE

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