oracular (3) namespace::clean.3pm.gz
NAME
namespace::clean - Keep imports and functions out of your namespace
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 $my_sorter_cref @list;
Explicitly removing functions when your scope is compiled
It is also possible to explicitly tell "namespace::clean" what packages to remove when the surrounding
scope has finished compiling. Here is an example:
package Foo;
use strict;
# blessed NOT available
sub my_class {
use Scalar::Util qw( blessed );
use namespace::clean qw( blessed );
# blessed available
return blessed shift;
}
# blessed NOT available
Moose
When using "namespace::clean" together with Moose you want to keep the installed "meta" method. So your
classes should look like:
package Foo;
use Moose;
use namespace::clean -except => 'meta';
...
Same goes for Moose::Role.
Cleaning other packages
You can tell "namespace::clean" that you want to clean up another package instead of the one importing.
To do this you have to pass in the "-cleanee" option like this:
package My::MooseX::namespace::clean;
use strict;
use namespace::clean (); # no cleanup, just load
sub import {
namespace::clean->import(
-cleanee => scalar(caller),
-except => 'meta',
);
}
If you don't care about "namespace::clean"s discover-and-"-except" logic, and just want to remove
subroutines, try "clean_subroutines".
METHODS
clean_subroutines
This exposes the actual subroutine-removal logic.
namespace::clean->clean_subroutines($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.
SEE ALSO
B::Hooks::EndOfScope
THANKS
Many thanks to Matt S Trout for the inspiration on the whole idea.
AUTHORS
• Robert 'phaylon' Sedlacek <rs@474.at> • Florian Ragwitz <rafl@debian.org> • Jesse Luehrs <doy@tozt.net> • Peter Rabbitson <ribasushi@cpan.org> • Father Chrysostomos <sprout@cpan.org>
COPYRIGHT AND LICENSE
This software is copyright (c) 2011 by "AUTHORS"
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5
programming language system itself.