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1 | package Import::Into; |
2 | |
3 | use strict; |
4 | use warnings FATAL => 'all'; |
5 | |
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6 | our $VERSION = '1.001001'; # 1.1.1 |
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7 | |
324e7017 |
8 | sub _prelude { |
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9 | my $target = shift; |
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10 | my ($package, $file, $line, $level) |
11 | = ref $target ? @{$target}{qw(package filename line)} |
12 | : $target =~ /[^0-9]/ ? ($target) |
13 | : (undef, undef, undef, $target); |
14 | if (defined $level) { |
15 | my ($p, $fn, $ln) = caller($level + 2); |
16 | $package ||= $p; |
17 | $file ||= $fn; |
18 | $line ||= $ln; |
19 | } |
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20 | qq{package $package;\n} |
ac6d2081 |
21 | . ($file ? "#line $line \"$file\"\n" : '') |
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22 | } |
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23 | |
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24 | sub _make_action { |
25 | my ($action, $target) = @_; |
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26 | my $version = ref $target && $target->{version}; |
27 | my $ver_check = $version ? '$_[0]->VERSION($version);' : ''; |
28 | eval _prelude($target).qq{sub { $ver_check shift->$action(\@_) }} |
5f5f09b1 |
29 | or die "Failed to build action sub to ${action} for ${target}: $@"; |
30 | } |
31 | |
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32 | sub import::into { |
33 | my ($class, $target, @args) = @_; |
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34 | _make_action(import => $target)->($class, @args); |
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35 | } |
36 | |
37 | sub unimport::out_of { |
38 | my ($class, $target, @args) = @_; |
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39 | _make_action(unimport => $target)->($class, @args); |
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40 | } |
41 | |
42 | 1; |
43 | |
44 | =head1 NAME |
45 | |
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46 | Import::Into - import packages into other packages |
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47 | |
48 | =head1 SYNOPSIS |
49 | |
50 | package My::MultiExporter; |
51 | |
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52 | use Import::Into; |
53 | |
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54 | use Thing1 (); |
55 | use Thing2 (); |
56 | |
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57 | # simple |
58 | sub import { |
59 | Thing1->import::into(scalar caller); |
60 | } |
61 | |
62 | # multiple |
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63 | sub import { |
64 | my $target = caller; |
65 | Thing1->import::into($target); |
66 | Thing2->import::into($target, qw(import arguments)); |
67 | } |
68 | |
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69 | # by level |
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70 | sub import { |
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71 | Thing1->import::into(1); |
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72 | } |
73 | |
074eb8db |
74 | # with exporter |
8c17b6f8 |
75 | use base qw(Exporter); |
8c17b6f8 |
76 | sub import { |
77 | shift->export_to_level(1); |
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78 | Thing1->import::into(1); |
8c17b6f8 |
79 | } |
80 | |
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81 | # no My::MultiExporter == no Thing1 |
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82 | sub unimport { |
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83 | Thing1->unimport::out_of(scalar caller); |
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84 | } |
85 | |
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86 | You don't need to do anything more clever than this provided you |
87 | document that people wanting to re-export your module should also be using |
88 | L<Import::Into>. |
89 | |
90 | Note: You do B<not> need to make ayny changes to Thing1 to be able to call |
91 | C<import::into> on it. This is a global method, and is callable on any |
92 | package (and in fact on any object as well, although it's rarer that you'd |
93 | want to do that). |
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94 | |
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95 | =head1 DESCRIPTION |
96 | |
97 | Writing exporters is a pain. Some use L<Exporter>, some use L<Sub::Exporter>, |
98 | some use L<Moose::Exporter>, some use L<Exporter::Declare> ... and some things |
99 | are pragmas. |
100 | |
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101 | Exporting on someone else's behalf is harder. The exporters don't provide a |
102 | consistent API for this, and pragmas need to have their import method called |
103 | directly, since they effect the current unit of compilation. |
104 | |
105 | C<Import::Into> provides global methods to make this painless. |
106 | |
107 | =head1 METHODS |
108 | |
109 | =head2 $package->import::into( $target, @arguments ); |
110 | |
111 | A global method, callable on any package. Imports the given package into |
112 | C<$target>. C<@arguments> are passed along to the package's import method. |
113 | |
114 | C<$target> can be an package name to export to, an integer for the caller level to export to, or a hashref with the following options: |
115 | |
116 | =over 4 |
117 | |
118 | =item package |
119 | |
120 | The target package to export to. |
121 | |
122 | =item filename |
123 | |
124 | The apparent filename to export to. Some exporting modules, such as L<autodie> or L<strictures>, care about the filename they are being imported to. |
125 | |
126 | =item line |
127 | |
128 | The apparent line number to export to. To be combined with the C<filename> option. |
129 | |
130 | =item level |
131 | |
132 | The caller level to export to. This will automatically populate the C<package>, C<filename>, and C<line> options, making it the easiest most constent option. |
133 | |
134 | =item version |
135 | |
136 | A version number to check for the module. The equivalent of specifying the version number on a C<use> line. |
137 | |
138 | =back |
139 | |
140 | =head2 $package->unimport::out_of( $target, @arguments ); |
141 | |
142 | Equivalent to C<import::into>, but dispatches to C<$package>'s C<unimport> method instead of C<import>. |
143 | |
144 | =head1 WHY USE THIS MODULE |
145 | |
146 | The APIs for exporting modules aren't consistent. L<Exporter> subclasses |
147 | provide export_to_level, but if they overrode their import method all bets |
148 | are off. L<Sub::Exporter> provides an into parameter but figuring out |
149 | something used it isn't trivial. Pragmas need to have their C<import> method |
150 | called directly since they affect the current unit of compilation. |
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151 | |
152 | It's ... annoying. |
153 | |
154 | However, there is an approach that actually works for all of these types. |
155 | |
156 | eval "package $target; use $thing;" |
157 | |
158 | will work for anything checking caller, which is everything except pragmas. |
159 | But it doesn't work for pragmas - pragmas need: |
160 | |
161 | $thing->import; |
162 | |
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163 | because they're designed to affect the code currently being compiled - so |
164 | within an eval, that's the scope of the eval itself, not the module that |
165 | just C<use>d you - so |
166 | |
167 | sub import { |
168 | eval "use strict;" |
169 | } |
170 | |
171 | doesn't do what you wanted, but |
172 | |
173 | sub import { |
174 | strict->import; |
175 | } |
176 | |
177 | will apply L<strict> to the calling file correctly. |
178 | |
179 | Of course, now you have two new problems - first, that you still need to |
180 | know if something's a pragma, and second that you can't use either of |
181 | these approaches alone on something like L<Moose> or L<Moo> that's both |
182 | an exporter and a pragma. |
183 | |
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184 | So, a solution for that is: |
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185 | |
186 | my $sub = eval "package $target; sub { shift->import(\@_) }"; |
187 | $sub->($thing, @import_args); |
188 | |
189 | which means that import is called from the right place for pragmas to take |
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190 | effect, and from the right package for caller checking to work - and so |
191 | behaves correctly for all types of exporter, for pragmas, and for hybrids. |
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192 | |
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193 | Additionally, some import routines check the filename they are being imported |
194 | to. This can be dealt with by generating a L<#line directive|perlsyn/Plain |
195 | Old Comments (Not!)> in the eval, which will change what C<caller> reports for |
196 | the filename when called in the importer. The filename and line number to use |
197 | in the directive then need to be fetched using C<caller>: |
198 | |
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199 | my ($target, $file, $line) = caller(1); |
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200 | my $sub = eval qq{ |
201 | package $target; |
202 | #line $line "$file" |
203 | sub { shift->import(\@_) } |
204 | }; |
205 | $sub->($thing, @import_args); |
206 | |
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207 | Remembering all this, however, is excessively irritating. So I wrote a module |
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208 | so I didn't have to anymore. Loading L<Import::Into> creates a global method |
209 | C<import::into> which you can call on any package to import it into another |
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210 | package. So now you can simply write: |
211 | |
212 | use Import::Into; |
213 | |
214 | $thing->import::into($target, @import_args); |
215 | |
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216 | This works because of how perl resolves method calls - a call to a simple |
217 | method name is resolved against the package of the class or object, so |
218 | |
219 | $thing->method_name(@args); |
220 | |
221 | is roughly equivalent to: |
222 | |
223 | my $code_ref = $thing->can('method_name'); |
224 | $code_ref->($thing, @args); |
225 | |
226 | while if a C<::> is found, the lookup is made relative to the package name |
227 | (i.e. everything before the last C<::>) so |
228 | |
229 | $thing->Package::Name::method_name(@args); |
230 | |
231 | is roughly equivalent to: |
232 | |
233 | my $code_ref = Package::Name->can('method_name'); |
234 | $code_ref->($thing, @args); |
235 | |
236 | So since L<Import::Into> defines a method C<into> in package C<import> |
237 | the syntax reliably calls that. |
238 | |
239 | For more craziness of this order, have a look at the article I wrote at |
240 | L<http://shadow.cat/blog/matt-s-trout/madness-with-methods> which covers |
241 | coderef abuse and the C<${\...}> syntax. |
242 | |
243 | Final note: You do still need to ensure that you already loaded C<$thing> - if |
244 | you're receiving this from a parameter, I recommend using L<Module::Runtime>: |
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245 | |
246 | use Import::Into; |
247 | use Module::Runtime qw(use_module); |
248 | |
249 | use_module($thing)->import::into($target, @import_args); |
250 | |
251 | And that's it. |
252 | |
95ecfed2 |
253 | =head1 ACKNOWLEDGEMENTS |
254 | |
255 | Thanks to Getty for asking "how can I get C<< use strict; use warnings; >> |
256 | turned on for all consumers of my code?" and then "why is this not a |
257 | module?!". |
258 | |
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259 | =head1 AUTHOR |
260 | |
261 | mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk> |
262 | |
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263 | =head1 CONTRIBUTORS |
264 | |
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265 | haarg - Graham Knop (cpan:HAARG) <haarg@haarg.org> |
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266 | |
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267 | =head1 COPYRIGHT |
268 | |
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269 | Copyright (c) 2012 the Import::Into L</AUTHOR> and L</CONTRIBUTORS> |
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270 | as listed above. |
271 | |
272 | =head1 LICENSE |
273 | |
274 | This library is free software and may be distributed under the same terms |
275 | as perl itself. |