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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 ); |
14 | use Scope::Guard; |
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15 | |
16 | =head1 VERSION |
17 | |
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18 | 0.08 |
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19 | |
20 | =cut |
21 | |
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22 | $VERSION = 0.08; |
23 | $STORAGE_VAR = '__NAMESPACE_CLEAN_STORAGE'; |
24 | $SCOPE_HOOK_KEY = 'namespace_clean_SCOPING'; |
25 | $SCOPE_EXPLICIT = 'namespace_clean_EXPLICIT'; |
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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 | =head1 METHODS |
120 | |
121 | You shouldn't need to call any of these. Just C<use> the package at the |
122 | appropriate place. |
123 | |
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124 | =cut |
125 | |
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126 | =head2 import |
127 | |
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128 | Makes a snapshot of the current defined functions and installs a |
129 | L<Scope::Guard> in the current scope to invoke the cleanups. |
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130 | |
131 | =cut |
132 | |
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133 | my $RemoveSubs = sub { |
134 | my $cleanee = shift; |
135 | my $store = shift; |
136 | SYMBOL: |
137 | for my $f (@_) { |
138 | |
139 | # ignore already removed symbols |
140 | next SYMBOL if $store->{exclude}{ $f }; |
141 | no strict 'refs'; |
142 | |
143 | # keep original value to restore non-code slots |
144 | { no warnings 'uninitialized'; # fix possible unimports |
145 | local *__tmp = *{ ${ "${cleanee}::" }{ $f } }; |
146 | delete ${ "${cleanee}::" }{ $f }; |
147 | } |
148 | |
149 | SLOT: |
150 | # restore non-code slots to symbol |
151 | for my $t (qw( SCALAR ARRAY HASH IO FORMAT )) { |
152 | next SLOT unless defined *__tmp{ $t }; |
153 | *{ "${cleanee}::$f" } = *__tmp{ $t }; |
154 | } |
155 | } |
156 | }; |
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157 | |
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158 | sub import { |
159 | my ($pragma, @args) = @_; |
160 | $^H |= 0x120000; |
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161 | |
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162 | my (%args, $is_explicit); |
163 | if (@args and $args[0] =~ /^\-/) { |
164 | %args = @args; |
165 | @args = (); |
166 | } |
167 | elsif (@args) { |
168 | $is_explicit++; |
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169 | } |
170 | |
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171 | my $cleanee = caller; |
172 | if ($is_explicit) { |
173 | $^H{ $SCOPE_EXPLICIT } = Scope::Guard->new(sub { |
174 | $RemoveSubs->($cleanee, {}, @args); |
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175 | }); |
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176 | } |
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177 | else { |
178 | |
179 | # calling class, all current functions and our storage |
180 | my $functions = $pragma->get_functions($cleanee); |
181 | my $store = $pragma->get_class_store($cleanee); |
182 | |
183 | # except parameter can be array ref or single value |
184 | my %except = map {( $_ => 1 )} ( |
185 | $args{ -except } |
186 | ? ( ref $args{ -except } eq 'ARRAY' ? @{ $args{ -except } } : $args{ -except } ) |
187 | : () |
188 | ); |
189 | |
190 | # register symbols for removal, if they have a CODE entry |
191 | for my $f (keys %$functions) { |
192 | next if $except{ $f }; |
193 | next unless $functions->{ $f } |
194 | and *{ $functions->{ $f } }{CODE}; |
195 | $store->{remove}{ $f } = 1; |
196 | } |
197 | |
198 | # register EOF handler on first call to import |
199 | unless ($store->{handler_is_installed}) { |
200 | $^H{ $SCOPE_HOOK_KEY } = Scope::Guard->new(sub { |
201 | $RemoveSubs->($cleanee, $store, keys %{ $store->{remove} }); |
202 | }); |
203 | $store->{handler_is_installed} = 1; |
204 | } |
205 | |
206 | return 1; |
207 | } |
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208 | } |
209 | |
210 | =head2 unimport |
211 | |
212 | This method will be called when you do a |
213 | |
214 | no namespace::clean; |
215 | |
216 | It will start a new section of code that defines functions to clean up. |
217 | |
218 | =cut |
219 | |
220 | sub unimport { |
221 | my ($pragma) = @_; |
222 | |
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223 | # the calling class, the current functions and our storage |
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224 | my $cleanee = caller; |
225 | my $functions = $pragma->get_functions($cleanee); |
226 | my $store = $pragma->get_class_store($cleanee); |
227 | |
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228 | # register all unknown previous functions as excluded |
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229 | for my $f (keys %$functions) { |
230 | next if $store->{remove}{ $f } |
231 | or $store->{exclude}{ $f }; |
232 | $store->{exclude}{ $f } = 1; |
233 | } |
234 | |
235 | return 1; |
236 | } |
237 | |
238 | =head2 get_class_store |
239 | |
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240 | This returns a reference to a hash in a passed package containing |
241 | information about function names included and excluded from removal. |
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242 | |
243 | =cut |
244 | |
245 | sub get_class_store { |
246 | my ($pragma, $class) = @_; |
247 | no strict 'refs'; |
248 | return \%{ "${class}::${STORAGE_VAR}" }; |
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249 | } |
250 | |
251 | =head2 get_functions |
252 | |
253 | Takes a class as argument and returns all currently defined functions |
254 | in it as a hash reference with the function name as key and a typeglob |
255 | reference to the symbol as value. |
256 | |
257 | =cut |
258 | |
259 | sub get_functions { |
260 | my ($pragma, $class) = @_; |
261 | |
262 | return { |
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263 | map { @$_ } # key => value |
264 | grep { *{ $_->[1] }{CODE} } # only functions |
265 | map { [$_, qualify_to_ref( $_, $class )] } # get globref |
266 | grep { $_ !~ /::$/ } # no packages |
267 | do { no strict 'refs'; keys %{ "${class}::" } } # symbol entries |
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268 | }; |
269 | } |
270 | |
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271 | =head1 IMPLEMENTATION DETAILS |
272 | |
273 | This module works through the effect that a |
274 | |
275 | delete $SomePackage::{foo}; |
276 | |
277 | will remove the C<foo> symbol from C<$SomePackage> for run time lookups |
278 | (e.g., method calls) but will leave the entry alive to be called by |
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279 | already resolved names in the package itself. C<namespace::clean> will |
280 | restore and therefor in effect keep all glob slots that aren't C<CODE>. |
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281 | |
282 | A test file has been added to the perl core to ensure that this behaviour |
283 | will be stable in future releases. |
284 | |
285 | Just for completeness sake, if you want to remove the symbol completely, |
286 | use C<undef> instead. |
287 | |
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288 | =head1 SEE ALSO |
289 | |
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290 | L<Scope::Guard> |
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291 | |
292 | =head1 AUTHOR AND COPYRIGHT |
293 | |
294 | Robert 'phaylon' Sedlacek C<E<lt>rs@474.atE<gt>>, with many thanks to |
295 | Matt S Trout for the inspiration on the whole idea. |
296 | |
297 | =head1 LICENSE |
298 | |
299 | This program is free software; you can redistribute it and/or modify |
300 | it under the same terms as perl itself. |
301 | |
302 | =cut |
303 | |
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304 | no warnings; |
305 | 'Danger! Laws of Thermodynamics may not apply.' |