Commit | Line | Data |
2afb5246 |
1 | package Import::Into; |
2 | |
3 | use strict; |
4 | use warnings FATAL => 'all'; |
5 | |
35faefa4 |
6 | our $VERSION = '1.001001'; # 1.1.1 |
2afb5246 |
7 | |
8 | my %importers; |
9 | |
10074211 |
10 | sub _importer { |
11 | my $target = shift; |
ac6d2081 |
12 | my ($package, $file, $line) = $target =~ /[^0-9]/ ? ($target) : caller($target + 1); |
13 | my $code = qq{package $package;\n} |
14 | . ($file ? "#line $line \"$file\"\n" : '') |
15 | . 'sub { my $m = splice @_, 1, 1; shift->$m(@_) };'."\n"; |
16 | my $sub = \(eval $code |
17 | or die "Couldn't build importer for $package: $@"); |
18 | $importers{$target} = $sub |
19 | unless $file; |
20 | $sub; |
10074211 |
21 | } |
10074211 |
22 | |
2afb5246 |
23 | sub import::into { |
24 | my ($class, $target, @args) = @_; |
10074211 |
25 | $class->${_importer($target)}(import => @args); |
26 | } |
27 | |
28 | sub unimport::out_of { |
29 | my ($class, $target, @args) = @_; |
30 | $class->${_importer($target)}(unimport => @args); |
2afb5246 |
31 | } |
32 | |
33 | 1; |
34 | |
35 | =head1 NAME |
36 | |
37 | Import::Into - import packages into other packages |
38 | |
39 | =head1 SYNOPSIS |
40 | |
41 | package My::MultiExporter; |
42 | |
e0ff3439 |
43 | use Import::Into; |
44 | |
2afb5246 |
45 | use Thing1 (); |
46 | use Thing2 (); |
47 | |
48 | sub import { |
49 | my $target = caller; |
50 | Thing1->import::into($target); |
51 | Thing2->import::into($target, qw(import arguments)); |
52 | } |
53 | |
8c17b6f8 |
54 | Note: you don't need to do anything more clever than this provided you |
55 | document that people wanting to re-export your module should also be using |
56 | L<Import::Into>. In fact, for a single module you can simply do: |
57 | |
58 | sub import { |
59 | ... |
60 | Thing1->import::into(scalar caller); |
61 | } |
62 | |
63 | Notably, this works: |
64 | |
65 | use base qw(Exporter); |
66 | |
67 | sub import { |
68 | shift->export_to_level(1); |
69 | Thing1->import::into(scalar caller); |
70 | } |
71 | |
aa5ad642 |
72 | Note 2: You do B<not> need to do anything to Thing1 to be able to call |
73 | C<import::into> on it. This is a global method, and is callable on any |
74 | package (and in fact on any object as well, although it's rarer that you'd |
75 | want to do that). |
76 | |
10074211 |
77 | Finally, we also provide an C<unimport::out_of> to allow the exporting of the |
78 | effect of C<no>: |
79 | |
c501842c |
80 | # unimport::out_of was added in 1.1.0 (1.001000) |
10074211 |
81 | sub unimport { |
82 | Moose->unimport::out_of(scalar caller); # no MyThing == no Moose |
83 | } |
84 | |
aa5ad642 |
85 | If how and why this all works is of interest to you, please read on to the |
86 | description immediately below. |
87 | |
e0ff3439 |
88 | =head1 DESCRIPTION |
89 | |
90 | Writing exporters is a pain. Some use L<Exporter>, some use L<Sub::Exporter>, |
91 | some use L<Moose::Exporter>, some use L<Exporter::Declare> ... and some things |
92 | are pragmas. |
93 | |
94 | If you want to re-export other things, you have to know which is which. |
95 | L<Exporter> subclasses provide export_to_level, but if they overrode their |
96 | import method all bets are off. L<Sub::Exporter> provides an into parameter |
97 | but figuring out something used it isn't trivial. Pragmas need to have |
98 | their C<import> method called directly since they affect the current unit of |
99 | compilation. |
100 | |
101 | It's ... annoying. |
102 | |
103 | However, there is an approach that actually works for all of these types. |
104 | |
105 | eval "package $target; use $thing;" |
106 | |
107 | will work for anything checking caller, which is everything except pragmas. |
108 | But it doesn't work for pragmas - pragmas need: |
109 | |
110 | $thing->import; |
111 | |
8c17b6f8 |
112 | because they're designed to affect the code currently being compiled - so |
113 | within an eval, that's the scope of the eval itself, not the module that |
114 | just C<use>d you - so |
115 | |
116 | sub import { |
117 | eval "use strict;" |
118 | } |
119 | |
120 | doesn't do what you wanted, but |
121 | |
122 | sub import { |
123 | strict->import; |
124 | } |
125 | |
126 | will apply L<strict> to the calling file correctly. |
127 | |
128 | Of course, now you have two new problems - first, that you still need to |
129 | know if something's a pragma, and second that you can't use either of |
130 | these approaches alone on something like L<Moose> or L<Moo> that's both |
131 | an exporter and a pragma. |
132 | |
133 | So, the complete solution is: |
e0ff3439 |
134 | |
135 | my $sub = eval "package $target; sub { shift->import(\@_) }"; |
136 | $sub->($thing, @import_args); |
137 | |
138 | which means that import is called from the right place for pragmas to take |
8c17b6f8 |
139 | effect, and from the right package for caller checking to work - and so |
140 | behaves correctly for all types of exporter, for pragmas, and for hybrids. |
e0ff3439 |
141 | |
142 | Remembering all this, however, is excessively irritating. So I wrote a module |
aa5ad642 |
143 | so I didn't have to anymore. Loading L<Import::Into> creates a global method |
144 | C<import::into> which you can call on any package to import it into another |
e0ff3439 |
145 | package. So now you can simply write: |
146 | |
147 | use Import::Into; |
148 | |
149 | $thing->import::into($target, @import_args); |
150 | |
aa5ad642 |
151 | This works because of how perl resolves method calls - a call to a simple |
152 | method name is resolved against the package of the class or object, so |
153 | |
154 | $thing->method_name(@args); |
155 | |
156 | is roughly equivalent to: |
157 | |
158 | my $code_ref = $thing->can('method_name'); |
159 | $code_ref->($thing, @args); |
160 | |
161 | while if a C<::> is found, the lookup is made relative to the package name |
162 | (i.e. everything before the last C<::>) so |
163 | |
164 | $thing->Package::Name::method_name(@args); |
165 | |
166 | is roughly equivalent to: |
167 | |
168 | my $code_ref = Package::Name->can('method_name'); |
169 | $code_ref->($thing, @args); |
170 | |
171 | So since L<Import::Into> defines a method C<into> in package C<import> |
172 | the syntax reliably calls that. |
173 | |
174 | For more craziness of this order, have a look at the article I wrote at |
175 | L<http://shadow.cat/blog/matt-s-trout/madness-with-methods> which covers |
176 | coderef abuse and the C<${\...}> syntax. |
177 | |
178 | Final note: You do still need to ensure that you already loaded C<$thing> - if |
179 | you're receiving this from a parameter, I recommend using L<Module::Runtime>: |
e0ff3439 |
180 | |
181 | use Import::Into; |
182 | use Module::Runtime qw(use_module); |
183 | |
184 | use_module($thing)->import::into($target, @import_args); |
185 | |
186 | And that's it. |
187 | |
95ecfed2 |
188 | =head1 ACKNOWLEDGEMENTS |
189 | |
190 | Thanks to Getty for asking "how can I get C<< use strict; use warnings; >> |
191 | turned on for all consumers of my code?" and then "why is this not a |
192 | module?!". |
193 | |
2afb5246 |
194 | =head1 AUTHOR |
195 | |
196 | mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk> |
197 | |
e0ff3439 |
198 | =head1 CONTRIBUTORS |
199 | |
200 | None yet - maybe this software is perfect! (ahahahahahahahahaha) |
201 | |
2afb5246 |
202 | =head1 COPYRIGHT |
203 | |
aa5ad642 |
204 | Copyright (c) 2012 the Import::Into L</AUTHOR> and L</CONTRIBUTORS> |
2afb5246 |
205 | as listed above. |
206 | |
207 | =head1 LICENSE |
208 | |
209 | This library is free software and may be distributed under the same terms |
210 | as perl itself. |