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1 | package Import::Into; |
2 | |
3 | use strict; |
4 | use warnings FATAL => 'all'; |
5 | |
35faefa4 |
6 | our $VERSION = '1.001001'; # 1.1.1 |
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7 | |
324e7017 |
8 | sub _prelude { |
10074211 |
9 | my $target = shift; |
568eef3e |
10 | my ($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 | } |
324e7017 |
20 | qq{package $package;\n} |
ac6d2081 |
21 | . ($file ? "#line $line \"$file\"\n" : '') |
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22 | } |
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23 | |
5f5f09b1 |
24 | sub _make_action { |
25 | my ($action, $target) = @_; |
568eef3e |
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}: $@"; |
30 | } |
31 | |
2afb5246 |
32 | sub import::into { |
33 | my ($class, $target, @args) = @_; |
5f5f09b1 |
34 | _make_action(import => $target)->($class, @args); |
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35 | } |
36 | |
37 | sub unimport::out_of { |
38 | my ($class, $target, @args) = @_; |
5f5f09b1 |
39 | _make_action(unimport => $target)->($class, @args); |
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40 | } |
41 | |
42 | 1; |
43 | |
44 | =head1 NAME |
45 | |
46 | Import::Into - import packages into other packages |
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 (); |
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56 | use Thing3 (); |
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57 | |
58 | sub import { |
59 | my $target = caller; |
60 | Thing1->import::into($target); |
61 | Thing2->import::into($target, qw(import arguments)); |
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62 | Thing3->import::into(1); # import to level |
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63 | } |
64 | |
8c17b6f8 |
65 | Note: you don't need to do anything more clever than this provided you |
66 | document that people wanting to re-export your module should also be using |
67 | L<Import::Into>. In fact, for a single module you can simply do: |
68 | |
69 | sub import { |
70 | ... |
71 | Thing1->import::into(scalar caller); |
72 | } |
73 | |
74 | Notably, this works: |
75 | |
76 | use base qw(Exporter); |
77 | |
78 | sub import { |
79 | shift->export_to_level(1); |
80 | Thing1->import::into(scalar caller); |
81 | } |
82 | |
aa5ad642 |
83 | Note 2: You do B<not> need to do anything to Thing1 to be able to call |
84 | C<import::into> on it. This is a global method, and is callable on any |
85 | package (and in fact on any object as well, although it's rarer that you'd |
86 | want to do that). |
87 | |
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88 | If you provide C<import::into> with an integer instead of a package name, it |
89 | will be used as the number of stack frames to skip to find where to export to. |
90 | This has the advantage of preserving the apparent filename and line number |
91 | being exported to, which some modules (L<autodie>, L<strictures>) check. |
92 | |
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93 | Finally, we also provide an C<unimport::out_of> to allow the exporting of the |
94 | effect of C<no>: |
95 | |
c501842c |
96 | # unimport::out_of was added in 1.1.0 (1.001000) |
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97 | sub unimport { |
98 | Moose->unimport::out_of(scalar caller); # no MyThing == no Moose |
99 | } |
100 | |
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101 | If how and why this all works is of interest to you, please read on to the |
102 | description immediately below. |
103 | |
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104 | =head1 DESCRIPTION |
105 | |
106 | Writing exporters is a pain. Some use L<Exporter>, some use L<Sub::Exporter>, |
107 | some use L<Moose::Exporter>, some use L<Exporter::Declare> ... and some things |
108 | are pragmas. |
109 | |
110 | If you want to re-export other things, you have to know which is which. |
111 | L<Exporter> subclasses provide export_to_level, but if they overrode their |
112 | import method all bets are off. L<Sub::Exporter> provides an into parameter |
113 | but figuring out something used it isn't trivial. Pragmas need to have |
114 | their C<import> method called directly since they affect the current unit of |
115 | compilation. |
116 | |
117 | It's ... annoying. |
118 | |
119 | However, there is an approach that actually works for all of these types. |
120 | |
121 | eval "package $target; use $thing;" |
122 | |
123 | will work for anything checking caller, which is everything except pragmas. |
124 | But it doesn't work for pragmas - pragmas need: |
125 | |
126 | $thing->import; |
127 | |
8c17b6f8 |
128 | because they're designed to affect the code currently being compiled - so |
129 | within an eval, that's the scope of the eval itself, not the module that |
130 | just C<use>d you - so |
131 | |
132 | sub import { |
133 | eval "use strict;" |
134 | } |
135 | |
136 | doesn't do what you wanted, but |
137 | |
138 | sub import { |
139 | strict->import; |
140 | } |
141 | |
142 | will apply L<strict> to the calling file correctly. |
143 | |
144 | Of course, now you have two new problems - first, that you still need to |
145 | know if something's a pragma, and second that you can't use either of |
146 | these approaches alone on something like L<Moose> or L<Moo> that's both |
147 | an exporter and a pragma. |
148 | |
ba1c5bf0 |
149 | So, a solution for that is: |
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150 | |
151 | my $sub = eval "package $target; sub { shift->import(\@_) }"; |
152 | $sub->($thing, @import_args); |
153 | |
154 | which means that import is called from the right place for pragmas to take |
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155 | effect, and from the right package for caller checking to work - and so |
156 | behaves correctly for all types of exporter, for pragmas, and for hybrids. |
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157 | |
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158 | Additionally, some import routines check the filename they are being imported |
159 | to. This can be dealt with by generating a L<#line directive|perlsyn/Plain |
160 | Old Comments (Not!)> in the eval, which will change what C<caller> reports for |
161 | the filename when called in the importer. The filename and line number to use |
162 | in the directive then need to be fetched using C<caller>: |
163 | |
995d8262 |
164 | my ($target, $file, $line) = caller(1); |
ba1c5bf0 |
165 | my $sub = eval qq{ |
166 | package $target; |
167 | #line $line "$file" |
168 | sub { shift->import(\@_) } |
169 | }; |
170 | $sub->($thing, @import_args); |
171 | |
e0ff3439 |
172 | Remembering all this, however, is excessively irritating. So I wrote a module |
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173 | so I didn't have to anymore. Loading L<Import::Into> creates a global method |
174 | C<import::into> which you can call on any package to import it into another |
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175 | package. So now you can simply write: |
176 | |
177 | use Import::Into; |
178 | |
179 | $thing->import::into($target, @import_args); |
180 | |
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181 | This works because of how perl resolves method calls - a call to a simple |
182 | method name is resolved against the package of the class or object, so |
183 | |
184 | $thing->method_name(@args); |
185 | |
186 | is roughly equivalent to: |
187 | |
188 | my $code_ref = $thing->can('method_name'); |
189 | $code_ref->($thing, @args); |
190 | |
191 | while if a C<::> is found, the lookup is made relative to the package name |
192 | (i.e. everything before the last C<::>) so |
193 | |
194 | $thing->Package::Name::method_name(@args); |
195 | |
196 | is roughly equivalent to: |
197 | |
198 | my $code_ref = Package::Name->can('method_name'); |
199 | $code_ref->($thing, @args); |
200 | |
201 | So since L<Import::Into> defines a method C<into> in package C<import> |
202 | the syntax reliably calls that. |
203 | |
204 | For more craziness of this order, have a look at the article I wrote at |
205 | L<http://shadow.cat/blog/matt-s-trout/madness-with-methods> which covers |
206 | coderef abuse and the C<${\...}> syntax. |
207 | |
208 | Final note: You do still need to ensure that you already loaded C<$thing> - if |
209 | you're receiving this from a parameter, I recommend using L<Module::Runtime>: |
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210 | |
211 | use Import::Into; |
212 | use Module::Runtime qw(use_module); |
213 | |
214 | use_module($thing)->import::into($target, @import_args); |
215 | |
216 | And that's it. |
217 | |
95ecfed2 |
218 | =head1 ACKNOWLEDGEMENTS |
219 | |
220 | Thanks to Getty for asking "how can I get C<< use strict; use warnings; >> |
221 | turned on for all consumers of my code?" and then "why is this not a |
222 | module?!". |
223 | |
2afb5246 |
224 | =head1 AUTHOR |
225 | |
226 | mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk> |
227 | |
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228 | =head1 CONTRIBUTORS |
229 | |
93bb9005 |
230 | haarg - Graham Knop (cpan:HAARG) <haarg@haarg.org> |
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231 | |
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232 | =head1 COPYRIGHT |
233 | |
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234 | Copyright (c) 2012 the Import::Into L</AUTHOR> and L</CONTRIBUTORS> |
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235 | as listed above. |
236 | |
237 | =head1 LICENSE |
238 | |
239 | This library is free software and may be distributed under the same terms |
240 | as perl itself. |