1 package namespace::clean;
5 namespace::clean - Keep imports and functions out of your namespace
12 use vars qw( $VERSION $STORAGE_VAR $SCOPE_HOOK_KEY $SCOPE_EXPLICIT );
13 use Symbol qw( qualify_to_ref );
14 use B::Hooks::EndOfScope;
23 $STORAGE_VAR = '__NAMESPACE_CLEAN_STORAGE';
31 use Carp qw(croak); # 'croak' will be removed
33 sub bar { 23 } # 'bar' will be removed
35 # remove all previously defined functions
38 sub baz { bar() } # 'baz' still defined, 'bar' still bound
40 # begin to collection function names from here again
43 sub quux { baz() } # 'quux' will be removed
45 # remove all functions defined after the 'no' unimport
48 # Will print: 'No', 'No', 'Yes' and 'No'
49 print +(__PACKAGE__->can('croak') ? 'Yes' : 'No'), "\n";
50 print +(__PACKAGE__->can('bar') ? 'Yes' : 'No'), "\n";
51 print +(__PACKAGE__->can('baz') ? 'Yes' : 'No'), "\n";
52 print +(__PACKAGE__->can('quux') ? 'Yes' : 'No'), "\n";
58 =head2 Keeping packages clean
60 When you define a function, or import one, into a Perl package, it will
61 naturally also be available as a method. This does not per se cause
62 problems, but it can complicate subclassing and, for example, plugin
63 classes that are included via multiple inheritance by loading them as
66 The C<namespace::clean> pragma will remove all previously declared or
67 imported symbols at the end of the current package's compile cycle.
68 Functions called in the package itself will still be bound by their
69 name, but they won't show up as methods on your class or instances.
71 By unimporting via C<no> you can tell C<namespace::clean> to start
72 collecting functions for the next C<use namespace::clean;> specification.
74 You can use the C<-except> flag to tell C<namespace::clean> that you
75 don't want it to remove a certain function or method. A common use would
76 be a module exporting an C<import> method along with some functions:
78 use ModuleExportingImport;
79 use namespace::clean -except => [qw( import )];
81 If you just want to C<-except> a single sub, you can pass it directly.
82 For more than one value you have to use an array reference.
84 =head2 Explicitely removing functions when your scope is compiled
86 It is also possible to explicitely tell C<namespace::clean> what packages
87 to remove when the surrounding scope has finished compiling. Here is an
93 # blessed NOT available
96 use Scalar::Util qw( blessed );
97 use namespace::clean qw( blessed );
100 return blessed shift;
103 # blessed NOT available
107 When using C<namespace::clean> together with L<Moose> you want to keep
108 the installed C<meta> method. So your classes should look like:
112 use namespace::clean -except => 'meta';
115 Same goes for L<Moose::Role>.
119 You shouldn't need to call any of these. Just C<use> the package at the
126 Makes a snapshot of the current defined functions and installs a
127 L<B::Hooks::EndOfScope> hook in the current scope to invoke the cleanups.
131 my $RemoveSubs = sub {
137 # ignore already removed symbols
138 next SYMBOL if $store->{exclude}{ $f };
141 # keep original value to restore non-code slots
142 { no warnings 'uninitialized'; # fix possible unimports
143 local *__tmp = *{ ${ "${cleanee}::" }{ $f } };
144 delete ${ "${cleanee}::" }{ $f };
148 # restore non-code slots to symbol
149 for my $t (qw( SCALAR ARRAY HASH IO FORMAT )) {
150 next SLOT unless defined *__tmp{ $t };
151 *{ "${cleanee}::$f" } = *__tmp{ $t };
157 my ($pragma, @args) = @_;
159 my (%args, $is_explicit);
160 if (@args and $args[0] =~ /^\-/) {
168 my $cleanee = caller;
171 $RemoveSubs->($cleanee, {}, @args);
176 # calling class, all current functions and our storage
177 my $functions = $pragma->get_functions($cleanee);
178 my $store = $pragma->get_class_store($cleanee);
180 # except parameter can be array ref or single value
181 my %except = map {( $_ => 1 )} (
183 ? ( ref $args{ -except } eq 'ARRAY' ? @{ $args{ -except } } : $args{ -except } )
187 # register symbols for removal, if they have a CODE entry
188 for my $f (keys %$functions) {
189 next if $except{ $f };
190 next unless $functions->{ $f }
191 and *{ $functions->{ $f } }{CODE};
192 $store->{remove}{ $f } = 1;
195 # register EOF handler on first call to import
196 unless ($store->{handler_is_installed}) {
198 $RemoveSubs->($cleanee, $store, keys %{ $store->{remove} });
200 $store->{handler_is_installed} = 1;
209 This method will be called when you do a
213 It will start a new section of code that defines functions to clean up.
220 # the calling class, the current functions and our storage
221 my $cleanee = caller;
222 my $functions = $pragma->get_functions($cleanee);
223 my $store = $pragma->get_class_store($cleanee);
225 # register all unknown previous functions as excluded
226 for my $f (keys %$functions) {
227 next if $store->{remove}{ $f }
228 or $store->{exclude}{ $f };
229 $store->{exclude}{ $f } = 1;
235 =head2 get_class_store
237 This returns a reference to a hash in a passed package containing
238 information about function names included and excluded from removal.
242 sub get_class_store {
243 my ($pragma, $class) = @_;
245 return \%{ "${class}::${STORAGE_VAR}" };
250 Takes a class as argument and returns all currently defined functions
251 in it as a hash reference with the function name as key and a typeglob
252 reference to the symbol as value.
257 my ($pragma, $class) = @_;
260 map { @$_ } # key => value
261 grep { *{ $_->[1] }{CODE} } # only functions
262 map { [$_, qualify_to_ref( $_, $class )] } # get globref
263 grep { $_ !~ /::$/ } # no packages
264 do { no strict 'refs'; keys %{ "${class}::" } } # symbol entries
268 =head1 IMPLEMENTATION DETAILS
270 This module works through the effect that a
272 delete $SomePackage::{foo};
274 will remove the C<foo> symbol from C<$SomePackage> for run time lookups
275 (e.g., method calls) but will leave the entry alive to be called by
276 already resolved names in the package itself. C<namespace::clean> will
277 restore and therefor in effect keep all glob slots that aren't C<CODE>.
279 A test file has been added to the perl core to ensure that this behaviour
280 will be stable in future releases.
282 Just for completeness sake, if you want to remove the symbol completely,
283 use C<undef> instead.
287 L<B::Hooks::EndOfScope>
289 =head1 AUTHOR AND COPYRIGHT
291 Robert 'phaylon' Sedlacek C<E<lt>rs@474.atE<gt>>, with many thanks to
292 Matt S Trout for the inspiration on the whole idea.
296 This program is free software; you can redistribute it and/or modify
297 it under the same terms as perl itself.
302 'Danger! Laws of Thermodynamics may not apply.'