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1 | package namespace::clean; |
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2 | # ABSTRACT: Keep imports and functions out of your namespace |
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3 | |
4 | use warnings; |
5 | use strict; |
6 | |
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7 | use vars qw( $STORAGE_VAR $SCOPE_HOOK_KEY $SCOPE_EXPLICIT ); |
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; |
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12 | |
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13 | $STORAGE_VAR = '__NAMESPACE_CLEAN_STORAGE'; |
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14 | |
15 | =head1 SYNOPSIS |
16 | |
17 | package Foo; |
18 | use warnings; |
19 | use strict; |
20 | |
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21 | use Carp qw(croak); # 'croak' will be removed |
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22 | |
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23 | sub bar { 23 } # 'bar' will be removed |
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24 | |
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25 | # remove all previously defined functions |
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26 | use namespace::clean; |
27 | |
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28 | sub baz { bar() } # 'baz' still defined, 'bar' still bound |
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29 | |
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30 | # begin to collection function names from here again |
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31 | no namespace::clean; |
32 | |
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33 | sub quux { baz() } # 'quux' will be removed |
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34 | |
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35 | # remove all functions defined after the 'no' unimport |
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36 | use namespace::clean; |
37 | |
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38 | # Will print: 'No', 'No', 'Yes' and 'No' |
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39 | print +(__PACKAGE__->can('croak') ? 'Yes' : 'No'), "\n"; |
40 | print +(__PACKAGE__->can('bar') ? 'Yes' : 'No'), "\n"; |
41 | print +(__PACKAGE__->can('baz') ? 'Yes' : 'No'), "\n"; |
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42 | print +(__PACKAGE__->can('quux') ? 'Yes' : 'No'), "\n"; |
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43 | |
44 | 1; |
45 | |
46 | =head1 DESCRIPTION |
47 | |
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48 | =head2 Keeping packages clean |
49 | |
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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 |
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53 | classes that are included via multiple inheritance by loading them as |
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54 | base classes. |
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55 | |
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. |
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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. |
60 | |
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. |
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63 | |
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64 | You can use the C<-except> flag to tell C<namespace::clean> that you |
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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: |
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67 | |
68 | use ModuleExportingImport; |
69 | use namespace::clean -except => [qw( import )]; |
70 | |
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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. |
73 | |
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74 | =head2 Explicitely removing functions when your scope is compiled |
75 | |
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 |
78 | example: |
79 | |
80 | package Foo; |
81 | use strict; |
82 | |
83 | # blessed NOT available |
84 | |
85 | sub my_class { |
86 | use Scalar::Util qw( blessed ); |
87 | use namespace::clean qw( blessed ); |
88 | |
89 | # blessed available |
90 | return blessed shift; |
91 | } |
92 | |
93 | # blessed NOT available |
94 | |
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95 | =head2 Moose |
96 | |
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: |
99 | |
100 | package Foo; |
101 | use Moose; |
102 | use namespace::clean -except => 'meta'; |
103 | ... |
104 | |
105 | Same goes for L<Moose::Role>. |
106 | |
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107 | =head2 Cleaning other packages |
108 | |
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> |
111 | option like this: |
112 | |
113 | package My::MooseX::namespace::clean; |
114 | use strict; |
115 | |
116 | use namespace::clean (); # no cleanup, just load |
117 | |
118 | sub import { |
119 | namespace::clean->import( |
120 | -cleanee => scalar(caller), |
121 | -except => 'meta', |
122 | ); |
123 | } |
124 | |
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>. |
127 | |
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128 | =method clean_subroutines |
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129 | |
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130 | This exposes the actual subroutine-removal logic. |
131 | |
132 | namespace::clean->clean_subroutines($cleanee, qw( subA subB )); |
133 | |
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. |
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138 | |
139 | =cut |
140 | |
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141 | my $RemoveSubs = sub { |
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142 | |
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143 | my $cleanee = shift; |
144 | my $store = shift; |
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145 | my $cleanee_stash = Package::Stash->new($cleanee); |
146 | my $deleted_stash = Package::Stash->new("namespace::clean::deleted::$cleanee"); |
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147 | SYMBOL: |
148 | for my $f (@_) { |
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149 | my $variable = "&$f"; |
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150 | # ignore already removed symbols |
151 | next SYMBOL if $store->{exclude}{ $f }; |
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152 | |
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153 | next SYMBOL unless $cleanee_stash->has_package_symbol($variable); |
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154 | |
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155 | if (ref(\$cleanee_stash->namespace->{$f}) eq 'GLOB') { |
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156 | # convince the Perl debugger to work |
157 | # it assumes that sub_fullname($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. |
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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"; |
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164 | subname($new_fq, $sub); |
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165 | $deleted_stash->add_package_symbol($variable, $sub); |
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166 | } |
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167 | } |
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168 | |
169 | $cleanee_stash->remove_package_symbol($variable); |
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170 | } |
171 | }; |
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172 | |
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173 | sub clean_subroutines { |
174 | my ($nc, $cleanee, @subs) = @_; |
175 | $RemoveSubs->($cleanee, {}, @subs); |
176 | } |
177 | |
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178 | =method import |
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179 | |
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. |
182 | |
183 | =cut |
184 | |
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185 | sub import { |
186 | my ($pragma, @args) = @_; |
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187 | |
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188 | my (%args, $is_explicit); |
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189 | |
190 | ARG: |
191 | while (@args) { |
192 | |
193 | if ($args[0] =~ /^\-/) { |
194 | my $key = shift @args; |
195 | my $value = shift @args; |
196 | $args{ $key } = $value; |
197 | } |
198 | else { |
199 | $is_explicit++; |
200 | last ARG; |
201 | } |
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202 | } |
203 | |
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204 | my $cleanee = exists $args{ -cleanee } ? $args{ -cleanee } : scalar caller; |
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205 | if ($is_explicit) { |
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206 | on_scope_end { |
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207 | $RemoveSubs->($cleanee, {}, @args); |
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208 | }; |
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209 | } |
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210 | else { |
211 | |
212 | # calling class, all current functions and our storage |
213 | my $functions = $pragma->get_functions($cleanee); |
214 | my $store = $pragma->get_class_store($cleanee); |
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215 | my $stash = Package::Stash->new($cleanee); |
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216 | |
217 | # except parameter can be array ref or single value |
218 | my %except = map {( $_ => 1 )} ( |
219 | $args{ -except } |
220 | ? ( ref $args{ -except } eq 'ARRAY' ? @{ $args{ -except } } : $args{ -except } ) |
221 | : () |
222 | ); |
223 | |
224 | # register symbols for removal, if they have a CODE entry |
225 | for my $f (keys %$functions) { |
226 | next if $except{ $f }; |
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227 | next unless $stash->has_package_symbol("&$f"); |
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228 | $store->{remove}{ $f } = 1; |
229 | } |
230 | |
231 | # register EOF handler on first call to import |
232 | unless ($store->{handler_is_installed}) { |
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233 | on_scope_end { |
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234 | $RemoveSubs->($cleanee, $store, keys %{ $store->{remove} }); |
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235 | }; |
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236 | $store->{handler_is_installed} = 1; |
237 | } |
238 | |
239 | return 1; |
240 | } |
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241 | } |
242 | |
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243 | =method unimport |
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244 | |
245 | This method will be called when you do a |
246 | |
247 | no namespace::clean; |
248 | |
249 | It will start a new section of code that defines functions to clean up. |
250 | |
251 | =cut |
252 | |
253 | sub unimport { |
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254 | my ($pragma, %args) = @_; |
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255 | |
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256 | # the calling class, the current functions and our storage |
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257 | my $cleanee = exists $args{ -cleanee } ? $args{ -cleanee } : scalar caller; |
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258 | my $functions = $pragma->get_functions($cleanee); |
259 | my $store = $pragma->get_class_store($cleanee); |
260 | |
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261 | # register all unknown previous functions as excluded |
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262 | for my $f (keys %$functions) { |
263 | next if $store->{remove}{ $f } |
264 | or $store->{exclude}{ $f }; |
265 | $store->{exclude}{ $f } = 1; |
266 | } |
267 | |
268 | return 1; |
269 | } |
270 | |
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271 | =method get_class_store |
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272 | |
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273 | This returns a reference to a hash in a passed package containing |
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274 | information about function names included and excluded from removal. |
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275 | |
276 | =cut |
277 | |
278 | sub get_class_store { |
279 | my ($pragma, $class) = @_; |
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280 | my $stash = Package::Stash->new($class); |
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281 | return $stash->get_package_symbol("%$STORAGE_VAR"); |
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282 | } |
283 | |
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284 | =method get_functions |
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285 | |
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. |
289 | |
290 | =cut |
291 | |
292 | sub get_functions { |
293 | my ($pragma, $class) = @_; |
294 | |
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295 | my $stash = Package::Stash->new($class); |
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296 | return { |
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297 | map { $_ => $stash->get_package_symbol("&$_") } |
298 | $stash->list_all_package_symbols('CODE') |
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299 | }; |
300 | } |
301 | |
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302 | =head1 IMPLEMENTATION DETAILS |
303 | |
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304 | This module works through the effect that a |
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305 | |
306 | delete $SomePackage::{foo}; |
307 | |
308 | will remove the C<foo> symbol from C<$SomePackage> for run time lookups |
309 | (e.g., method calls) but will leave the entry alive to be called by |
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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>. |
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312 | |
313 | A test file has been added to the perl core to ensure that this behaviour |
314 | will be stable in future releases. |
315 | |
316 | Just for completeness sake, if you want to remove the symbol completely, |
317 | use C<undef> instead. |
318 | |
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319 | =head1 SEE ALSO |
320 | |
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321 | L<B::Hooks::EndOfScope> |
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322 | |
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323 | =head1 THANKS |
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324 | |
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325 | Many thanks to Matt S Trout for the inspiration on the whole idea. |
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326 | |
327 | =cut |
328 | |
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329 | no warnings; |
330 | 'Danger! Laws of Thermodynamics may not apply.' |