1 package namespace::clean;
2 # ABSTRACT: Keep imports and functions out of your namespace
7 use vars qw( $STORAGE_VAR );
8 use Sub::Name 0.04 qw(subname);
9 use Sub::Identify 0.04 qw(sub_fullname);
10 use Package::Stash 0.03;
11 use B::Hooks::EndOfScope 0.07;
13 $STORAGE_VAR = '__NAMESPACE_CLEAN_STORAGE';
21 use Carp qw(croak); # 'croak' will be removed
23 sub bar { 23 } # 'bar' will be removed
25 # remove all previously defined functions
28 sub baz { bar() } # 'baz' still defined, 'bar' still bound
30 # begin to collection function names from here again
33 sub quux { baz() } # 'quux' will be removed
35 # remove all functions defined after the 'no' unimport
38 # Will print: 'No', 'No', 'Yes' and 'No'
39 print +(__PACKAGE__->can('croak') ? 'Yes' : 'No'), "\n";
40 print +(__PACKAGE__->can('bar') ? 'Yes' : 'No'), "\n";
41 print +(__PACKAGE__->can('baz') ? 'Yes' : 'No'), "\n";
42 print +(__PACKAGE__->can('quux') ? 'Yes' : 'No'), "\n";
48 =head2 Keeping packages clean
50 When you define a function, or import one, into a Perl package, it will
51 naturally also be available as a method. This does not per se cause
52 problems, but it can complicate subclassing and, for example, plugin
53 classes that are included via multiple inheritance by loading them as
56 The C<namespace::clean> pragma will remove all previously declared or
57 imported symbols at the end of the current package's compile cycle.
58 Functions called in the package itself will still be bound by their
59 name, but they won't show up as methods on your class or instances.
61 By unimporting via C<no> you can tell C<namespace::clean> to start
62 collecting functions for the next C<use namespace::clean;> specification.
64 You can use the C<-except> flag to tell C<namespace::clean> that you
65 don't want it to remove a certain function or method. A common use would
66 be a module exporting an C<import> method along with some functions:
68 use ModuleExportingImport;
69 use namespace::clean -except => [qw( import )];
71 If you just want to C<-except> a single sub, you can pass it directly.
72 For more than one value you have to use an array reference.
74 =head2 Explicitely removing functions when your scope is compiled
76 It is also possible to explicitely tell C<namespace::clean> what packages
77 to remove when the surrounding scope has finished compiling. Here is an
83 # blessed NOT available
86 use Scalar::Util qw( blessed );
87 use namespace::clean qw( blessed );
93 # blessed NOT available
97 When using C<namespace::clean> together with L<Moose> you want to keep
98 the installed C<meta> method. So your classes should look like:
102 use namespace::clean -except => 'meta';
105 Same goes for L<Moose::Role>.
107 =head2 Cleaning other packages
109 You can tell C<namespace::clean> that you want to clean up another package
110 instead of the one importing. To do this you have to pass in the C<-cleanee>
113 package My::MooseX::namespace::clean;
116 use namespace::clean (); # no cleanup, just load
119 namespace::clean->import(
120 -cleanee => scalar(caller),
125 If you don't care about C<namespace::clean>s discover-and-C<-except> logic, and
126 just want to remove subroutines, try L</clean_subroutines>.
128 =method clean_subroutines
130 This exposes the actual subroutine-removal logic.
132 namespace::clean->clean_subroutines($cleanee, qw( subA subB ));
134 will remove C<subA> and C<subB> from C<$cleanee>. Note that this will remove the
135 subroutines B<immediately> and not wait for scope end. If you want to have this
136 effect at a specific time (e.g. C<namespace::clean> acts on scope compile end)
137 it is your responsibility to make sure it runs at that time.
141 my $RemoveSubs = sub {
145 my $cleanee_stash = Package::Stash->new($cleanee);
146 my $deleted_stash = Package::Stash->new("namespace::clean::deleted::$cleanee");
149 my $variable = "&$f";
150 # ignore already removed symbols
151 next SYMBOL if $store->{exclude}{ $f };
153 next SYMBOL unless $cleanee_stash->has_package_symbol($variable);
155 if (ref(\$cleanee_stash->namespace->{$f}) eq 'GLOB') {
156 # convince the Perl debugger to work
157 # it assumes that sub_fullname($sub) can always be used to find the CV again
158 # since we are deleting the glob where the subroutine was originally
159 # defined, that assumption no longer holds, so we need to move it
160 # elsewhere and point the CV's name to the new glob.
161 my $sub = $cleanee_stash->get_package_symbol($variable);
162 if ( sub_fullname($sub) eq ($cleanee_stash->name . "::$f") ) {
163 my $new_fq = $deleted_stash->name . "::$f";
164 subname($new_fq, $sub);
165 $deleted_stash->add_package_symbol($variable, $sub);
169 $cleanee_stash->remove_package_symbol($variable);
173 sub clean_subroutines {
174 my ($nc, $cleanee, @subs) = @_;
175 $RemoveSubs->($cleanee, {}, @subs);
180 Makes a snapshot of the current defined functions and installs a
181 L<B::Hooks::EndOfScope> hook in the current scope to invoke the cleanups.
186 my ($pragma, @args) = @_;
188 my (%args, $is_explicit);
193 if ($args[0] =~ /^\-/) {
194 my $key = shift @args;
195 my $value = shift @args;
196 $args{ $key } = $value;
204 my $cleanee = exists $args{ -cleanee } ? $args{ -cleanee } : scalar caller;
207 $RemoveSubs->($cleanee, {}, @args);
212 # calling class, all current functions and our storage
213 my $functions = $pragma->get_functions($cleanee);
214 my $store = $pragma->get_class_store($cleanee);
215 my $stash = Package::Stash->new($cleanee);
217 # except parameter can be array ref or single value
218 my %except = map {( $_ => 1 )} (
220 ? ( ref $args{ -except } eq 'ARRAY' ? @{ $args{ -except } } : $args{ -except } )
224 # register symbols for removal, if they have a CODE entry
225 for my $f (keys %$functions) {
226 next if $except{ $f };
227 next unless $stash->has_package_symbol("&$f");
228 $store->{remove}{ $f } = 1;
231 # register EOF handler on first call to import
232 unless ($store->{handler_is_installed}) {
234 $RemoveSubs->($cleanee, $store, keys %{ $store->{remove} });
236 $store->{handler_is_installed} = 1;
245 This method will be called when you do a
249 It will start a new section of code that defines functions to clean up.
254 my ($pragma, %args) = @_;
256 # the calling class, the current functions and our storage
257 my $cleanee = exists $args{ -cleanee } ? $args{ -cleanee } : scalar caller;
258 my $functions = $pragma->get_functions($cleanee);
259 my $store = $pragma->get_class_store($cleanee);
261 # register all unknown previous functions as excluded
262 for my $f (keys %$functions) {
263 next if $store->{remove}{ $f }
264 or $store->{exclude}{ $f };
265 $store->{exclude}{ $f } = 1;
271 =method get_class_store
273 This returns a reference to a hash in a passed package containing
274 information about function names included and excluded from removal.
278 sub get_class_store {
279 my ($pragma, $class) = @_;
280 my $stash = Package::Stash->new($class);
281 return $stash->get_package_symbol("%$STORAGE_VAR");
284 =method get_functions
286 Takes a class as argument and returns all currently defined functions
287 in it as a hash reference with the function name as key and a typeglob
288 reference to the symbol as value.
293 my ($pragma, $class) = @_;
295 my $stash = Package::Stash->new($class);
297 map { $_ => $stash->get_package_symbol("&$_") }
298 $stash->list_all_package_symbols('CODE')
302 =head1 IMPLEMENTATION DETAILS
304 This module works through the effect that a
306 delete $SomePackage::{foo};
308 will remove the C<foo> symbol from C<$SomePackage> for run time lookups
309 (e.g., method calls) but will leave the entry alive to be called by
310 already resolved names in the package itself. C<namespace::clean> will
311 restore and therefor in effect keep all glob slots that aren't C<CODE>.
313 A test file has been added to the perl core to ensure that this behaviour
314 will be stable in future releases.
316 Just for completeness sake, if you want to remove the symbol completely,
317 use C<undef> instead.
321 L<B::Hooks::EndOfScope>
325 Many thanks to Matt S Trout for the inspiration on the whole idea.
330 'Danger! Laws of Thermodynamics may not apply.'