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1 | package namespace::clean; |
2 | |
3 | =head1 NAME |
4 | |
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5 | namespace::clean - Keep imports and functions out of your namespace |
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6 | |
7 | =cut |
8 | |
9 | use warnings; |
10 | use strict; |
11 | |
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12 | use vars qw( $VERSION $STORAGE_VAR $SCOPE_HOOK_KEY $SCOPE_EXPLICIT ); |
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13 | use Symbol qw( qualify_to_ref gensym ); |
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14 | use B::Hooks::EndOfScope; |
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15 | use Sub::Identify qw(sub_fullname); |
16 | use Sub::Name qw(subname); |
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17 | |
18 | =head1 VERSION |
19 | |
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20 | 0.13 |
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21 | |
22 | =cut |
23 | |
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24 | $VERSION = '0.13'; |
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25 | $STORAGE_VAR = '__NAMESPACE_CLEAN_STORAGE'; |
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26 | |
27 | =head1 SYNOPSIS |
28 | |
29 | package Foo; |
30 | use warnings; |
31 | use strict; |
32 | |
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33 | use Carp qw(croak); # 'croak' will be removed |
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34 | |
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35 | sub bar { 23 } # 'bar' will be removed |
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36 | |
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37 | # remove all previously defined functions |
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38 | use namespace::clean; |
39 | |
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40 | sub baz { bar() } # 'baz' still defined, 'bar' still bound |
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41 | |
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42 | # begin to collection function names from here again |
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43 | no namespace::clean; |
44 | |
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45 | sub quux { baz() } # 'quux' will be removed |
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46 | |
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47 | # remove all functions defined after the 'no' unimport |
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48 | use namespace::clean; |
49 | |
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50 | # Will print: 'No', 'No', 'Yes' and 'No' |
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51 | print +(__PACKAGE__->can('croak') ? 'Yes' : 'No'), "\n"; |
52 | print +(__PACKAGE__->can('bar') ? 'Yes' : 'No'), "\n"; |
53 | print +(__PACKAGE__->can('baz') ? 'Yes' : 'No'), "\n"; |
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54 | print +(__PACKAGE__->can('quux') ? 'Yes' : 'No'), "\n"; |
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55 | |
56 | 1; |
57 | |
58 | =head1 DESCRIPTION |
59 | |
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60 | =head2 Keeping packages clean |
61 | |
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62 | When you define a function, or import one, into a Perl package, it will |
63 | naturally also be available as a method. This does not per se cause |
64 | problems, but it can complicate subclassing and, for example, plugin |
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65 | classes that are included via multiple inheritance by loading them as |
66 | base classes. |
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67 | |
68 | The C<namespace::clean> pragma will remove all previously declared or |
69 | imported symbols at the end of the current package's compile cycle. |
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70 | Functions called in the package itself will still be bound by their |
71 | name, but they won't show up as methods on your class or instances. |
72 | |
73 | By unimporting via C<no> you can tell C<namespace::clean> to start |
74 | collecting functions for the next C<use namespace::clean;> specification. |
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75 | |
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76 | You can use the C<-except> flag to tell C<namespace::clean> that you |
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77 | don't want it to remove a certain function or method. A common use would |
78 | be a module exporting an C<import> method along with some functions: |
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79 | |
80 | use ModuleExportingImport; |
81 | use namespace::clean -except => [qw( import )]; |
82 | |
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83 | If you just want to C<-except> a single sub, you can pass it directly. |
84 | For more than one value you have to use an array reference. |
85 | |
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86 | =head2 Explicitely removing functions when your scope is compiled |
87 | |
88 | It is also possible to explicitely tell C<namespace::clean> what packages |
89 | to remove when the surrounding scope has finished compiling. Here is an |
90 | example: |
91 | |
92 | package Foo; |
93 | use strict; |
94 | |
95 | # blessed NOT available |
96 | |
97 | sub my_class { |
98 | use Scalar::Util qw( blessed ); |
99 | use namespace::clean qw( blessed ); |
100 | |
101 | # blessed available |
102 | return blessed shift; |
103 | } |
104 | |
105 | # blessed NOT available |
106 | |
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107 | =head2 Moose |
108 | |
109 | When using C<namespace::clean> together with L<Moose> you want to keep |
110 | the installed C<meta> method. So your classes should look like: |
111 | |
112 | package Foo; |
113 | use Moose; |
114 | use namespace::clean -except => 'meta'; |
115 | ... |
116 | |
117 | Same goes for L<Moose::Role>. |
118 | |
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119 | =head2 Cleaning other packages |
120 | |
121 | You can tell C<namespace::clean> that you want to clean up another package |
122 | instead of the one importing. To do this you have to pass in the C<-cleanee> |
123 | option like this: |
124 | |
125 | package My::MooseX::namespace::clean; |
126 | use strict; |
127 | |
128 | use namespace::clean (); # no cleanup, just load |
129 | |
130 | sub import { |
131 | namespace::clean->import( |
132 | -cleanee => scalar(caller), |
133 | -except => 'meta', |
134 | ); |
135 | } |
136 | |
137 | If you don't care about C<namespace::clean>s discover-and-C<-except> logic, and |
138 | just want to remove subroutines, try L</clean_subroutines>. |
139 | |
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140 | =head1 METHODS |
141 | |
142 | You shouldn't need to call any of these. Just C<use> the package at the |
143 | appropriate place. |
144 | |
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145 | =cut |
146 | |
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147 | =head2 clean_subroutines |
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148 | |
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149 | This exposes the actual subroutine-removal logic. |
150 | |
151 | namespace::clean->clean_subroutines($cleanee, qw( subA subB )); |
152 | |
153 | will remove C<subA> and C<subB> from C<$cleanee>. Note that this will remove the |
154 | subroutines B<immediately> and not wait for scope end. If you want to have this |
155 | effect at a specific time (e.g. C<namespace::clean> acts on scope compile end) |
156 | it is your responsibility to make sure it runs at that time. |
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157 | |
158 | =cut |
159 | |
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160 | my $RemoveSubs = sub { |
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161 | |
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162 | my $cleanee = shift; |
163 | my $store = shift; |
164 | SYMBOL: |
165 | for my $f (@_) { |
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166 | my $fq = "${cleanee}::$f"; |
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167 | |
168 | # ignore already removed symbols |
169 | next SYMBOL if $store->{exclude}{ $f }; |
170 | no strict 'refs'; |
171 | |
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172 | next SYMBOL unless exists ${ "${cleanee}::" }{ $f }; |
173 | |
174 | if (ref(\${ "${cleanee}::" }{ $f }) eq 'GLOB') { |
175 | # convince the Perl debugger to work |
176 | # it assumes that sub_fullname($sub) can always be used to find the CV again |
177 | # since we are deleting the glob where the subroutine was originally |
178 | # defined, that assumption no longer holds, so we need to move it |
179 | # elsewhere and point the CV's name to the new glob. |
180 | my $sub = \&$fq; |
181 | if ( sub_fullname($sub) eq $fq ) { |
182 | my $new_fq = "namespace::clean::deleted::$fq"; |
183 | subname($new_fq, $sub); |
184 | *{$new_fq} = $sub; |
185 | } |
186 | |
187 | local *__tmp; |
188 | |
189 | # keep original value to restore non-code slots |
190 | { no warnings 'uninitialized'; # fix possible unimports |
191 | *__tmp = *{ ${ "${cleanee}::" }{ $f } }; |
192 | delete ${ "${cleanee}::" }{ $f }; |
193 | } |
194 | |
195 | SLOT: |
196 | # restore non-code slots to symbol. |
197 | # omit the FORMAT slot, since perl erroneously puts it into the |
198 | # SCALAR slot of the new glob. |
199 | for my $t (qw( SCALAR ARRAY HASH IO )) { |
200 | next SLOT unless defined *__tmp{ $t }; |
201 | *{ "${cleanee}::$f" } = *__tmp{ $t }; |
202 | } |
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203 | } |
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204 | else { |
205 | # A non-glob in the stash is assumed to stand for some kind |
206 | # of function. So far they all do, but the core might change |
207 | # this some day. Watch perl5-porters. |
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208 | delete ${ "${cleanee}::" }{ $f }; |
209 | } |
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210 | } |
211 | }; |
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212 | |
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213 | sub clean_subroutines { |
214 | my ($nc, $cleanee, @subs) = @_; |
215 | $RemoveSubs->($cleanee, {}, @subs); |
216 | } |
217 | |
218 | =head2 import |
219 | |
220 | Makes a snapshot of the current defined functions and installs a |
221 | L<B::Hooks::EndOfScope> hook in the current scope to invoke the cleanups. |
222 | |
223 | =cut |
224 | |
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225 | sub import { |
226 | my ($pragma, @args) = @_; |
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227 | |
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228 | my (%args, $is_explicit); |
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229 | |
230 | ARG: |
231 | while (@args) { |
232 | |
233 | if ($args[0] =~ /^\-/) { |
234 | my $key = shift @args; |
235 | my $value = shift @args; |
236 | $args{ $key } = $value; |
237 | } |
238 | else { |
239 | $is_explicit++; |
240 | last ARG; |
241 | } |
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242 | } |
243 | |
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244 | my $cleanee = exists $args{ -cleanee } ? $args{ -cleanee } : scalar caller; |
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245 | if ($is_explicit) { |
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246 | on_scope_end { |
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247 | $RemoveSubs->($cleanee, {}, @args); |
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248 | }; |
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249 | } |
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250 | else { |
251 | |
252 | # calling class, all current functions and our storage |
253 | my $functions = $pragma->get_functions($cleanee); |
254 | my $store = $pragma->get_class_store($cleanee); |
255 | |
256 | # except parameter can be array ref or single value |
257 | my %except = map {( $_ => 1 )} ( |
258 | $args{ -except } |
259 | ? ( ref $args{ -except } eq 'ARRAY' ? @{ $args{ -except } } : $args{ -except } ) |
260 | : () |
261 | ); |
262 | |
263 | # register symbols for removal, if they have a CODE entry |
264 | for my $f (keys %$functions) { |
265 | next if $except{ $f }; |
266 | next unless $functions->{ $f } |
267 | and *{ $functions->{ $f } }{CODE}; |
268 | $store->{remove}{ $f } = 1; |
269 | } |
270 | |
271 | # register EOF handler on first call to import |
272 | unless ($store->{handler_is_installed}) { |
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273 | on_scope_end { |
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274 | $RemoveSubs->($cleanee, $store, keys %{ $store->{remove} }); |
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275 | }; |
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276 | $store->{handler_is_installed} = 1; |
277 | } |
278 | |
279 | return 1; |
280 | } |
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281 | } |
282 | |
283 | =head2 unimport |
284 | |
285 | This method will be called when you do a |
286 | |
287 | no namespace::clean; |
288 | |
289 | It will start a new section of code that defines functions to clean up. |
290 | |
291 | =cut |
292 | |
293 | sub unimport { |
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294 | my ($pragma, %args) = @_; |
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295 | |
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296 | # the calling class, the current functions and our storage |
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297 | my $cleanee = exists $args{ -cleanee } ? $args{ -cleanee } : scalar caller; |
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298 | my $functions = $pragma->get_functions($cleanee); |
299 | my $store = $pragma->get_class_store($cleanee); |
300 | |
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301 | # register all unknown previous functions as excluded |
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302 | for my $f (keys %$functions) { |
303 | next if $store->{remove}{ $f } |
304 | or $store->{exclude}{ $f }; |
305 | $store->{exclude}{ $f } = 1; |
306 | } |
307 | |
308 | return 1; |
309 | } |
310 | |
311 | =head2 get_class_store |
312 | |
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313 | This returns a reference to a hash in a passed package containing |
314 | information about function names included and excluded from removal. |
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315 | |
316 | =cut |
317 | |
318 | sub get_class_store { |
319 | my ($pragma, $class) = @_; |
320 | no strict 'refs'; |
321 | return \%{ "${class}::${STORAGE_VAR}" }; |
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322 | } |
323 | |
324 | =head2 get_functions |
325 | |
326 | Takes a class as argument and returns all currently defined functions |
327 | in it as a hash reference with the function name as key and a typeglob |
328 | reference to the symbol as value. |
329 | |
330 | =cut |
331 | |
332 | sub get_functions { |
333 | my ($pragma, $class) = @_; |
334 | |
335 | return { |
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336 | map { @$_ } # key => value |
337 | grep { *{ $_->[1] }{CODE} } # only functions |
338 | map { [$_, qualify_to_ref( $_, $class )] } # get globref |
339 | grep { $_ !~ /::$/ } # no packages |
340 | do { no strict 'refs'; keys %{ "${class}::" } } # symbol entries |
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341 | }; |
342 | } |
343 | |
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344 | =head1 BUGS |
345 | |
346 | C<namespace::clean> will clobber any formats that have the same name as |
347 | a deleted sub. This is due to a bug in perl that makes it impossible to |
348 | re-assign the FORMAT ref into a new glob. |
349 | |
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350 | =head1 IMPLEMENTATION DETAILS |
351 | |
352 | This module works through the effect that a |
353 | |
354 | delete $SomePackage::{foo}; |
355 | |
356 | will remove the C<foo> symbol from C<$SomePackage> for run time lookups |
357 | (e.g., method calls) but will leave the entry alive to be called by |
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358 | already resolved names in the package itself. C<namespace::clean> will |
359 | restore and therefor in effect keep all glob slots that aren't C<CODE>. |
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360 | |
361 | A test file has been added to the perl core to ensure that this behaviour |
362 | will be stable in future releases. |
363 | |
364 | Just for completeness sake, if you want to remove the symbol completely, |
365 | use C<undef> instead. |
366 | |
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367 | =head1 SEE ALSO |
368 | |
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369 | L<B::Hooks::EndOfScope> |
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370 | |
371 | =head1 AUTHOR AND COPYRIGHT |
372 | |
373 | Robert 'phaylon' Sedlacek C<E<lt>rs@474.atE<gt>>, with many thanks to |
374 | Matt S Trout for the inspiration on the whole idea. |
375 | |
376 | =head1 LICENSE |
377 | |
378 | This program is free software; you can redistribute it and/or modify |
379 | it under the same terms as perl itself. |
380 | |
381 | =cut |
382 | |
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383 | no warnings; |
384 | 'Danger! Laws of Thermodynamics may not apply.' |