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1 | package Package::Variant; |
2 | |
3 | use strictures 1; |
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4 | use Module::Runtime qw(require_module module_notional_filename); |
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5 | use Carp qw(croak); |
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6 | |
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7 | our $VERSION = '1.002000'; # 1.2.0 |
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8 | |
9 | $VERSION = eval $VERSION; |
10 | |
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11 | our %Variable; |
12 | |
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13 | my $sanitize_importing = sub { |
14 | my ($me, $spec) = @_; |
15 | return [] |
16 | unless defined $spec; |
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17 | my @specced = |
18 | not(ref $spec) |
19 | ? ($spec) |
20 | : (ref($spec) eq 'ARRAY') |
21 | ? (@$spec) |
22 | : (ref($spec) eq 'HASH') |
23 | ? (map { |
24 | croak qq{The import argument list for '$_' is not an array ref} |
25 | unless ref($spec->{$_}) eq 'ARRAY'; |
26 | ($_ => $spec->{$_}); |
27 | } sort keys %$spec) |
28 | : croak q{The 'importing' option has to be either a hash or array ref}; |
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29 | my @imports; |
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30 | my $arg_count = 1; |
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31 | while (@specced) { |
32 | my $key = shift @specced; |
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33 | croak qq{Value $arg_count in 'importing' is not a package string}, |
34 | $arg_count |
35 | unless defined($key) and not(ref $key); |
36 | $arg_count++; |
37 | my $import_args = |
38 | (not(@specced) or (defined($specced[0]) and not ref($specced[0]))) |
39 | ? [] |
40 | : (ref($specced[0]) eq 'ARRAY') |
41 | ? do { $arg_count++; shift @specced } |
42 | : croak( |
43 | qq{Value $arg_count for package '$key' in 'importing' is not} |
44 | . qq{ a package string or array ref} |
45 | ); |
46 | push @imports, [$key, $import_args]; |
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47 | } |
48 | return \@imports; |
49 | }; |
50 | |
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51 | my $sub_namer = eval { |
52 | require Sub::Name; sub { shift if @_ > 2; Sub::Name::subname(@_) } |
53 | } || sub { $_[-1] }; |
54 | |
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55 | sub import { |
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56 | my $variable = caller; |
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57 | my $me = shift; |
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58 | my $last = (split '::', $variable)[-1]; |
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59 | my $anon = 'A000'; |
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60 | my %args = @_; |
61 | no strict 'refs'; |
62 | $Variable{$variable} = { |
63 | anon => $anon, |
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64 | args => { |
65 | %args, |
66 | importing => $me->$sanitize_importing($args{importing}), |
67 | }, |
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68 | subs => { |
69 | map +($_ => sub {}), @{$args{subs}||[]}, |
70 | }, |
71 | }; |
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72 | *{"${variable}::import"} = sub { |
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73 | my $target = caller; |
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74 | my (undef, %arg) = @_; |
75 | my $as = defined($arg{as}) ? $arg{as} : $last; |
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76 | no strict 'refs'; |
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77 | *{"${target}::${as}"} = sub { |
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78 | $me->build_variant_of($variable, @_); |
79 | }; |
80 | }; |
81 | my $subs = $Variable{$variable}{subs}; |
82 | foreach my $name (keys %$subs) { |
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83 | *{"${variable}::${name}"} = sub { |
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84 | goto &{$subs->{$name}} |
85 | }; |
86 | } |
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87 | *{"${variable}::install"} = sub { |
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88 | goto &{$Variable{$variable}{install}}; |
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89 | }; |
90 | *{"${variable}::build_variant"} = sub { |
91 | shift; |
92 | $me->build_variant_of($variable, @_); |
93 | }; |
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94 | } |
95 | |
96 | sub build_variant_of { |
97 | my ($me, $variable, @args) = @_; |
98 | my $variant_name = "${variable}::_Variant_".++$Variable{$variable}{anon}; |
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99 | my $build = "package $variant_name;\n"; |
100 | my $importing = $Variable{$variable}{args}{importing}; |
101 | foreach my $i (0 .. $#$importing) { |
102 | my $pkg = $importing->[$i][0]; |
103 | $build .= "use $pkg \@{\$importing->[$i][1]};\n"; |
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104 | } |
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105 | my $subs = $Variable{$variable}{subs}; |
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106 | my $builder = sub { |
107 | local @{$subs}{keys %$subs} = map $variant_name->can($_), keys %$subs; |
108 | local $Variable{$variable}{install} = sub { |
109 | my $full_name = "${variant_name}::".shift; |
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110 | |
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111 | my $ref = $sub_namer->($full_name, @_); |
112 | |
113 | no strict 'refs'; |
114 | *$full_name = $ref; |
115 | }; |
116 | $variable->make_variant($variant_name, @args); |
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117 | }; |
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118 | $build .= "BEGIN { \$builder->() }\n1;\n"; |
119 | eval $build or die $@; |
120 | $INC{module_notional_filename($variant_name)} = '(built by Package::Variant)'; |
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121 | return $variant_name; |
122 | } |
123 | |
124 | 1; |
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125 | |
126 | __END__ |
127 | |
128 | =head1 NAME |
129 | |
130 | Package::Variant - Parameterizable packages |
131 | |
132 | =head1 SYNOPSIS |
133 | |
134 | # declaring a variable Moo role |
135 | package My::Role::ObjectAttr; |
136 | use strictures 1; |
137 | use Package::Variant |
138 | # what modules to 'use' |
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139 | importing => ['Moo::Role'], |
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140 | # proxied subroutines |
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141 | subs => [ qw(has around before after with) ], |
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142 | |
143 | sub make_variant { |
144 | my ($class, $target_package, %arguments) = @_; |
145 | # access arguments |
146 | my $name = $arguments{name}; |
147 | # use proxied 'has' to add an attribute |
148 | has $name => (is => 'lazy'); |
149 | # install a builder method |
150 | install "_build_${name}" => sub { |
151 | return $arguments{class}->new; |
152 | }; |
153 | } |
154 | |
155 | # using the role |
156 | package My::Class::WithObjectAttr; |
157 | use strictures 1; |
158 | use Moo; |
159 | use My::Role::ObjectAttr; |
160 | |
161 | with ObjectAttr(name => 'some_obj', class => 'Some::Class'); |
162 | |
163 | # using our class |
164 | my $obj = My::Class::WithObjectAttr->new; |
165 | $obj->some_obj; # returns a Some::Class instance |
166 | |
167 | =head1 DESCRIPTION |
168 | |
169 | This module allows you to build packages that return different variations |
170 | depending on what parameters are given. |
171 | |
172 | Users of your package will receive a subroutine able to take parameters |
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173 | and return the name of a suitable variant package. The implementation does |
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174 | not care about what kind of package it builds. |
175 | |
176 | =head2 Declaring a variable package |
177 | |
178 | There are two important parts to creating a variable package. You first |
179 | have to give C<Package::Variant> some basic information about what kind of |
180 | package you want to provide, and how. The second part is implementing a |
181 | method receiving the user's arguments and generating your variants. |
182 | |
183 | =head3 Setting up the environment for building variations |
184 | |
185 | When you C<use Package::Variant>, you pass along some arguments that |
186 | describe how you intend to build your variations. |
187 | |
188 | use Package::Variant |
189 | importing => { $package => \@import_arguments, ... }, |
190 | subs => [ @proxied_subroutine_names ]; |
191 | |
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192 | The L</importing> option needs to be a hash or array reference with |
193 | package names to be C<use>d as keys, and array references containing the |
194 | import arguments as values. These packages will be imported into every new |
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195 | variant, and need to set up every declarative subroutine you require to |
196 | build your variable package. The next option will allow you to use these |
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197 | functions. See L</importing> for more options. You can omit empty import |
198 | argument lists when passing an array reference. |
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199 | |
200 | The L</subs> option is an array reference of subroutine names that are |
201 | exported by the packages specified with L</importing>. These subroutines |
202 | will be proxied from your declaration package to the variant to be |
203 | generated. |
204 | |
205 | With L</importing> initializing your package and L</subs> declaring what |
206 | subroutines you want to use to build a variant, you can now write a |
207 | L</make_variant> method building your variants. |
208 | |
209 | =head3 Declaring a method to produce variants |
210 | |
211 | Every time a user requests a new variant a method named L</make_variant> |
212 | will be called with the name of the target package and the arguments from |
213 | the user. |
214 | |
215 | It can then use the proxied subroutines declared with L</subs> to |
216 | customize the new package. An L</install> subroutine is exported as well |
217 | allowing you to dynamically install methods into the new package. If these |
218 | options aren't flexible enough, you can use the passed name of the new |
219 | package to do any other kind of customizations. |
220 | |
221 | sub make_variant { |
222 | my ($class, $target, @arguments) = @_; |
223 | # ... |
224 | # customization goes here |
225 | # ... |
226 | } |
227 | |
228 | When the method is finished, the user will receive the name of the new |
229 | package variant you just set up. |
230 | |
231 | =head2 Using variable packages |
232 | |
233 | After your variable package is L<created|/Declaring a variable package> |
234 | your users can get a variant generating subroutine by simply importing |
235 | your package. |
236 | |
237 | use My::Variant; |
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238 | my $new_variant_package = Variant(@variant_arguments); |
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239 | |
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240 | The package is now fully initialized and used. You can import the |
241 | subroutine under a different name by specifying an C<as> argument. |
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242 | |
243 | =head2 Dynamic creation of variant packages |
244 | |
245 | For regular uses, the L<normal import|/Using variable packages> provides |
246 | more than enough flexibility. However, if you want to create variations of |
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247 | dynamically determined packages, you can use the L</build_variant_of> |
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248 | method. |
249 | |
250 | You can use this to create variations of other packages and pass arguments |
251 | on to them to allow more modular and extensible variations. |
252 | |
253 | =head1 OPTIONS |
254 | |
255 | These are the options that can be passed when importing |
256 | C<Package::Variant>. They describe the environment in which the variants |
257 | are created. |
258 | |
259 | use Package::Variant |
260 | importing => { $package => \@import_arguments, ... }, |
261 | subs => [ @proxied_subroutines ]; |
262 | |
263 | =head2 importing |
264 | |
265 | This option is a hash reference mapping package names to array references |
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266 | containing import arguments. The packages will be imported with the given |
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267 | arguments by every variation before the L</make_variant> method is asked |
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268 | to create the package (this is done using L<Import::Into>). |
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269 | |
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270 | If import order is important to you, you can also pass the C<importing> |
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271 | arguments as a flat array reference: |
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272 | |
273 | use Package::Variant |
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274 | importing => [ 'PackageA', 'PackageB' ]; |
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275 | |
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276 | # same as |
277 | use Package::Variant |
278 | importing => [ 'PackageA' => [], 'PackageB' => [] ]; |
279 | |
280 | # or |
281 | use Package::Variant |
282 | importing => { 'PackageA' => [], 'PackageB' => [] }; |
283 | |
284 | The import method will be called even if the list of import arguments is |
285 | empty or not specified, |
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286 | |
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287 | If you just want to import a single package's default exports, you can |
288 | also pass a string instead: |
289 | |
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290 | use Package::Variant importing => 'Package'; |
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291 | |
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292 | =head2 subs |
293 | |
294 | An array reference of strings listing the names of subroutines that should |
295 | be proxied. These subroutines are expected to be installed into the new |
296 | variant package by the modules imported with L</importing>. Subroutines |
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297 | with the same name will be available in your declaration package, and will |
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298 | proxy through to the newly created package when used within |
299 | L</make_variant>. |
300 | |
301 | =head1 VARIABLE PACKAGE METHODS |
302 | |
303 | These are methods on the variable package you declare when you import |
304 | C<Package::Variant>. |
305 | |
306 | =head2 make_variant |
307 | |
308 | Some::Variant::Package->make_variant( $target, @arguments ); |
309 | |
310 | B<You need to provide this method.> This method will be called for every |
311 | new variant of your package. This method should use the subroutines |
312 | declared in L</subs> to customize the new variant package. |
313 | |
314 | This is a class method receiving the C<$target> package and the |
315 | C<@arguments> defining the requested variant. |
316 | |
317 | =head2 import |
318 | |
319 | use Some::Variant::Package; |
320 | my $variant_package = Package( @arguments ); |
321 | |
322 | This method is provided for you. It will allow a user to C<use> your |
323 | package and receive a subroutine taking C<@arguments> defining the variant |
324 | and returning the name of the newly created variant package. |
325 | |
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326 | The following options can be specified when importing: |
327 | |
328 | =over |
329 | |
330 | =item * B<as> |
331 | |
332 | use Some::Variant::Package as => 'Foo'; |
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333 | my $variant_package = Foo(@arguments); |
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334 | |
335 | Exports the generator subroutine under a different name than the default. |
336 | |
337 | =back |
338 | |
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339 | =head2 build_variant |
340 | |
341 | use Some::Variant::Package (); |
342 | my $variant_package = Some::Variant::Package->build_variant( @arguments ); |
343 | |
344 | This method is provided for you. It will generate a variant package |
345 | and return its name, just like the generator sub provided by |
346 | L</import>. This allows you to avoid importing anything into the |
347 | consuming package. |
348 | |
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349 | =head1 C<Package::Variant> METHODS |
350 | |
351 | These methods are available on C<Package::Variant> itself. |
352 | |
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353 | =head2 build_variant_of |
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354 | |
355 | my $variant_package = Package::Variant |
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356 | ->build_variant_of($variable_package, @arguments); |
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357 | |
358 | This is the dynamic method of creating new variants. It takes the |
359 | C<$variable_package>, which is a pre-declared variable package, and a set |
360 | of C<@arguments> passed to the package to generate a new |
361 | C<$variant_package>, which will be returned. |
362 | |
363 | =head2 import |
364 | |
365 | use Package::Variant @options; |
366 | |
367 | Sets up the environment in which you declare the variants of your |
368 | packages. See L</OPTIONS> for details on the available options and |
369 | L</EXPORTS> for a list of exported subroutines. |
370 | |
371 | =head1 EXPORTS |
372 | |
373 | Additionally to the proxies for subroutines provided in L</subs>, the |
374 | following exports will be available in your variable package: |
375 | |
376 | =head2 install |
377 | |
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378 | install($method_name, $code_reference); |
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379 | |
380 | Installs a method with the given C<$method_name> into the newly created |
381 | variant package. The C<$code_reference> will be used as the body for the |
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382 | method, and if L<Sub::Name> is available the coderef will be named. If you |
383 | want to name it something else, then use: |
384 | |
385 | install($method_name, $name_to_use, $code_reference); |
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386 | |
387 | =head1 AUTHOR |
388 | |
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389 | mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk> |
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390 | |
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391 | =head1 CONTRIBUTORS |
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392 | |
5b1d922a |
393 | phaylon - Robert Sedlacek (cpan:PHAYLON) <r.sedlacek@shadowcat.co.uk> |
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394 | |
39c3689b |
395 | haarg - Graham Knop (cpan:HAARG) <haarg@haarg.org> |
396 | |
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397 | =head1 COPYRIGHT |
398 | |
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399 | Copyright (c) 2010-2012 the C<Package::Variant> L</AUTHOR> and |
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400 | L</CONTRIBUTORS> as listed above. |
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401 | |
402 | =head1 LICENSE |
403 | |
404 | This library is free software and may be distributed under the same |
405 | terms as perl itself. |
406 | |
407 | =cut |