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1 | package Import::Into; |
2 | |
3 | use strict; |
4 | use warnings FATAL => 'all'; |
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5 | use Module::Runtime; |
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6 | |
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7 | our $VERSION = '1.002002'; # 1.2.2 |
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8 | |
324e7017 |
9 | sub _prelude { |
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10 | my $target = shift; |
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11 | my ($package, $file, $line, $level) |
12 | = ref $target ? @{$target}{qw(package filename line)} |
13 | : $target =~ /[^0-9]/ ? ($target) |
14 | : (undef, undef, undef, $target); |
15 | if (defined $level) { |
16 | my ($p, $fn, $ln) = caller($level + 2); |
17 | $package ||= $p; |
18 | $file ||= $fn; |
19 | $line ||= $ln; |
20 | } |
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21 | qq{package $package;\n} |
ac6d2081 |
22 | . ($file ? "#line $line \"$file\"\n" : '') |
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23 | } |
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24 | |
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25 | sub _make_action { |
26 | my ($action, $target) = @_; |
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27 | my $version = ref $target && $target->{version}; |
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28 | my $ver_check = $version ? ', $version' : ''; |
29 | eval _prelude($target) |
30 | . qq{sub { Module::Runtime::use_module( shift$ver_check )->$action(\@_) }} |
5f5f09b1 |
31 | or die "Failed to build action sub to ${action} for ${target}: $@"; |
32 | } |
33 | |
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34 | sub import::into { |
35 | my ($class, $target, @args) = @_; |
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36 | _make_action(import => $target)->($class, @args); |
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37 | } |
38 | |
39 | sub unimport::out_of { |
40 | my ($class, $target, @args) = @_; |
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41 | _make_action(unimport => $target)->($class, @args); |
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42 | } |
43 | |
44 | 1; |
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45 | |
46 | __END__ |
47 | |
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48 | =head1 NAME |
49 | |
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50 | Import::Into - import packages into other packages |
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51 | |
52 | =head1 SYNOPSIS |
53 | |
54 | package My::MultiExporter; |
55 | |
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56 | use Import::Into; |
57 | |
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58 | # simple |
59 | sub import { |
60 | Thing1->import::into(scalar caller); |
61 | } |
62 | |
63 | # multiple |
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64 | sub import { |
65 | my $target = caller; |
66 | Thing1->import::into($target); |
67 | Thing2->import::into($target, qw(import arguments)); |
68 | } |
69 | |
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70 | # by level |
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71 | sub import { |
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72 | Thing1->import::into(1); |
8c17b6f8 |
73 | } |
74 | |
074eb8db |
75 | # with exporter |
8c17b6f8 |
76 | use base qw(Exporter); |
8c17b6f8 |
77 | sub import { |
78 | shift->export_to_level(1); |
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79 | Thing1->import::into(1); |
8c17b6f8 |
80 | } |
81 | |
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82 | # no My::MultiExporter == no Thing1 |
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83 | sub unimport { |
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84 | Thing1->unimport::out_of(scalar caller); |
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85 | } |
86 | |
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87 | People wanting to re-export your module should also be using L<Import::Into>. |
88 | Any exporter or pragma will work seamlessly. |
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89 | |
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90 | Note: You do B<not> need to make any changes to Thing1 to be able to call |
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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( $target, @arguments ); |
110 | |
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111 | A global method, callable on any package. Loads and imports the given package |
112 | into C<$target>. C<@arguments> are passed along to the package's import method. |
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113 | |
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114 | C<$target> can be an package name to export to, an integer for the |
115 | caller level to export to, or a hashref with the following options: |
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116 | |
117 | =over 4 |
118 | |
119 | =item package |
120 | |
121 | The target package to export to. |
122 | |
123 | =item filename |
124 | |
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125 | The apparent filename to export to. Some exporting modules, such as |
126 | L<autodie> or L<strictures>, care about the filename they are being imported |
127 | to. |
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128 | |
129 | =item line |
130 | |
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131 | The apparent line number to export to. To be combined with the C<filename> |
132 | option. |
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133 | |
134 | =item level |
135 | |
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136 | The caller level to export to. This will automatically populate the |
137 | C<package>, C<filename>, and C<line> options, making it the easiest most |
138 | constent option. |
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139 | |
140 | =item version |
141 | |
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142 | A version number to check for the module. The equivalent of specifying the |
143 | version number on a C<use> line. |
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144 | |
145 | =back |
146 | |
147 | =head2 $package->unimport::out_of( $target, @arguments ); |
148 | |
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149 | Equivalent to C<import::into>, but dispatches to C<$package>'s C<unimport> |
150 | method instead of C<import>. |
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151 | |
152 | =head1 WHY USE THIS MODULE |
153 | |
154 | The APIs for exporting modules aren't consistent. L<Exporter> subclasses |
155 | provide export_to_level, but if they overrode their import method all bets |
156 | are off. L<Sub::Exporter> provides an into parameter but figuring out |
157 | something used it isn't trivial. Pragmas need to have their C<import> method |
158 | called directly since they affect the current unit of compilation. |
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159 | |
160 | It's ... annoying. |
161 | |
162 | However, there is an approach that actually works for all of these types. |
163 | |
164 | eval "package $target; use $thing;" |
165 | |
166 | will work for anything checking caller, which is everything except pragmas. |
167 | But it doesn't work for pragmas - pragmas need: |
168 | |
169 | $thing->import; |
170 | |
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171 | because they're designed to affect the code currently being compiled - so |
172 | within an eval, that's the scope of the eval itself, not the module that |
173 | just C<use>d you - so |
174 | |
175 | sub import { |
176 | eval "use strict;" |
177 | } |
178 | |
179 | doesn't do what you wanted, but |
180 | |
181 | sub import { |
182 | strict->import; |
183 | } |
184 | |
185 | will apply L<strict> to the calling file correctly. |
186 | |
187 | Of course, now you have two new problems - first, that you still need to |
188 | know if something's a pragma, and second that you can't use either of |
189 | these approaches alone on something like L<Moose> or L<Moo> that's both |
190 | an exporter and a pragma. |
191 | |
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192 | So, a solution for that is: |
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193 | |
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194 | use Module::Runtime; |
195 | my $sub = eval "package $target; sub { use_module(shift)->import(\@_) }"; |
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196 | $sub->($thing, @import_args); |
197 | |
198 | which means that import is called from the right place for pragmas to take |
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199 | effect, and from the right package for caller checking to work - and so |
200 | behaves correctly for all types of exporter, for pragmas, and for hybrids. |
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201 | |
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202 | Additionally, some import routines check the filename they are being imported |
203 | to. This can be dealt with by generating a L<#line directive|perlsyn/Plain |
204 | Old Comments (Not!)> in the eval, which will change what C<caller> reports for |
205 | the filename when called in the importer. The filename and line number to use |
206 | in the directive then need to be fetched using C<caller>: |
207 | |
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208 | my ($target, $file, $line) = caller(1); |
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209 | my $sub = eval qq{ |
210 | package $target; |
211 | #line $line "$file" |
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212 | sub { use_module(shift)->import(\@_) } |
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213 | }; |
214 | $sub->($thing, @import_args); |
215 | |
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216 | And you need to switch between these implementations depending on if you are |
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217 | targeting a specific package, or something in your call stack. |
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218 | |
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219 | Remembering all this, however, is excessively irritating. So I wrote a module |
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220 | so I didn't have to anymore. Loading L<Import::Into> creates a global method |
221 | C<import::into> which you can call on any package to import it into another |
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222 | package. So now you can simply write: |
223 | |
224 | use Import::Into; |
225 | |
226 | $thing->import::into($target, @import_args); |
227 | |
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228 | This works because of how perl resolves method calls - a call to a simple |
229 | method name is resolved against the package of the class or object, so |
230 | |
231 | $thing->method_name(@args); |
232 | |
233 | is roughly equivalent to: |
234 | |
235 | my $code_ref = $thing->can('method_name'); |
236 | $code_ref->($thing, @args); |
237 | |
238 | while if a C<::> is found, the lookup is made relative to the package name |
239 | (i.e. everything before the last C<::>) so |
240 | |
241 | $thing->Package::Name::method_name(@args); |
242 | |
243 | is roughly equivalent to: |
244 | |
245 | my $code_ref = Package::Name->can('method_name'); |
246 | $code_ref->($thing, @args); |
247 | |
248 | So since L<Import::Into> defines a method C<into> in package C<import> |
249 | the syntax reliably calls that. |
250 | |
251 | For more craziness of this order, have a look at the article I wrote at |
252 | L<http://shadow.cat/blog/matt-s-trout/madness-with-methods> which covers |
253 | coderef abuse and the C<${\...}> syntax. |
254 | |
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255 | And that's it. |
256 | |
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257 | =head1 SEE ALSO |
258 | |
259 | I gave a lightning talk on this module (and L<curry> and L<Safe::Isa>) at |
260 | L<YAPC::NA 2013|https://www.youtube.com/watch?v=wFXWV2yY7gE&t=46m05s>. |
261 | |
95ecfed2 |
262 | =head1 ACKNOWLEDGEMENTS |
263 | |
264 | Thanks to Getty for asking "how can I get C<< use strict; use warnings; >> |
265 | turned on for all consumers of my code?" and then "why is this not a |
266 | module?!". |
267 | |
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268 | =head1 AUTHOR |
269 | |
270 | mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk> |
271 | |
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272 | =head1 CONTRIBUTORS |
273 | |
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274 | haarg - Graham Knop (cpan:HAARG) <haarg@haarg.org> |
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275 | |
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276 | Mithaldu - Christian Walde (cpan:MITHALDU) <walde.christian@gmail.com> |
277 | |
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278 | =head1 COPYRIGHT |
279 | |
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280 | Copyright (c) 2012 the Import::Into L</AUTHOR> and L</CONTRIBUTORS> |
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281 | as listed above. |
282 | |
283 | =head1 LICENSE |
284 | |
285 | This library is free software and may be distributed under the same terms |
286 | as perl itself. |
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287 | |
288 | =cut |