package namespace::clean;
=head1 NAME
namespace::clean - Keep imports and functions out of your namespace
=cut
use warnings;
use strict;
use vars qw( $VERSION $STORAGE_VAR );
use Symbol qw( qualify_to_ref );
use Filter::EOF;
=head1 VERSION
0.05
=cut
$VERSION = 0.05;
$STORAGE_VAR = '__NAMESPACE_CLEAN_STORAGE';
=head1 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;
=head1 DESCRIPTION
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 C<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 C<no> you can tell C<namespace::clean> to start
collecting functions for the next C<use namespace::clean;> specification.
You can use the C<-except> flag to tell C<namespace::clean> that you
don't want it to remove a certain function or method. A common use would
be a module exporting an C<import> method along with some functions:
use ModuleExportingImport;
use namespace::clean -except => [qw( import )];
If you just want to C<-except> a single sub, you can pass it directly.
For more than one value you have to use an array reference.
=head1 METHODS
You shouldn't need to call any of these. Just C<use> the package at the
appropriate place.
=cut
=head2 import
Makes a snapshot of the current defined functions and registers a
L<Filter::EOF> cleanup routine to remove those symbols at the end
of the compile-time.
=cut
sub import {
my ($pragma, %args) = @_;
# calling class, all current functions and our storage
my $cleanee = caller;
my $functions = $pragma->get_functions($cleanee);
my $store = $pragma->get_class_store($cleanee);
# except parameter can be array ref or single value
my %except = map {( $_ => 1 )} (
$args{ -except }
? ( ref $args{ -except } eq 'ARRAY' ? @{ $args{ -except } } : $args{ -except } )
: ()
);
# register symbols for removal, if they have a CODE entry
for my $f (keys %$functions) {
next if $except{ $f };
next unless $functions->{ $f }
and *{ $functions->{ $f } }{CODE};
$store->{remove}{ $f } = 1;
}
# register EOF handler on first call to import
unless ($store->{handler_is_installed}) {
Filter::EOF->on_eof_call(sub {
SYMBOL:
for my $f (keys %{ $store->{remove} }) {
# ignore already removed symbols
next SYMBOL if $store->{exclude}{ $f };
no strict 'refs';
# keep original value to restore non-code slots
local *__tmp = *{ ${ "${cleanee}::" }{ $f } };
delete ${ "${cleanee}::" }{ $f };
SLOT:
# restore non-code slots to symbol
for my $t (qw( SCALAR ARRAY HASH IO FORMAT )) {
next SLOT unless defined *__tmp{ $t };
*{ "${cleanee}::$f" } = *__tmp{ $t };
}
}
});
$store->{handler_is_installed} = 1;
}
return 1;
}
=head2 unimport
This method will be called when you do a
no namespace::clean;
It will start a new section of code that defines functions to clean up.
=cut
sub unimport {
my ($pragma) = @_;
# the calling class, the current functions and our storage
my $cleanee = caller;
my $functions = $pragma->get_functions($cleanee);
my $store = $pragma->get_class_store($cleanee);
# register all unknown previous functions as excluded
for my $f (keys %$functions) {
next if $store->{remove}{ $f }
or $store->{exclude}{ $f };
$store->{exclude}{ $f } = 1;
}
return 1;
}
=head2 get_class_store
This returns a reference to a hash in a passed package containing
information about function names included and excluded from removal.
=cut
sub get_class_store {
my ($pragma, $class) = @_;
no strict 'refs';
return \%{ "${class}::${STORAGE_VAR}" };
}
=head2 get_functions
Takes a class as argument and returns all currently defined functions
in it as a hash reference with the function name as key and a typeglob
reference to the symbol as value.
=cut
sub get_functions {
my ($pragma, $class) = @_;
return {
map { @$_ } # key => value
grep { *{ $_->[1] }{CODE} } # only functions
map { [$_, qualify_to_ref( $_, $class )] } # get globref
grep { $_ !~ /::$/ } # no packages
do { no strict 'refs'; keys %{ "${class}::" } } # symbol entries
};
}
=head1 IMPLEMENTATION DETAILS
This module works through the effect that a
delete $SomePackage::{foo};
will remove the C<foo> symbol from C<$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. C<namespace::clean> will
restore and therefor in effect keep all glob slots that aren't C<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 C<undef> instead.
=head1 SEE ALSO
L<Filter::EOF>
=head1 AUTHOR AND COPYRIGHT
Robert 'phaylon' Sedlacek C<E<lt>rs@474.atE<gt>>, with many thanks to
Matt S Trout for the inspiration on the whole idea.
=head1 LICENSE
This program is free software; you can redistribute it and/or modify
it under the same terms as perl itself.
=cut
1;