use strict;
use warnings FATAL => 'all';
-our $VERSION = '1.0';
+our $VERSION = '1.001001'; # 1.1.1
+
+sub _prelude {
+ my $target = shift;
+ my ($package, $file, $line)
+ = $target =~ /[^0-9]/ ? ($target) : caller($target + 2);
+ qq{package $package;\n}
+ . ($file ? "#line $line \"$file\"\n" : '')
+}
-my %importers;
+sub _make_action {
+ my ($action, $target) = @_;
+ eval _prelude($target).qq{sub { shift->$action(\@_) }}
+ or die "Failed to build action sub to ${action} for ${target}: $@";
+}
sub import::into {
my ($class, $target, @args) = @_;
- $class->${\(
- $importers{$target} ||= eval qq{
- package $target;
- sub { shift->import(\@_) };
- } or die "Couldn't build importer for $target: $@"
- )}(@args);
+ _make_action(import => $target)->($class, @args);
+}
+
+sub unimport::out_of {
+ my ($class, $target, @args) = @_;
+ _make_action(unimport => $target)->($class, @args);
}
1;
package My::MultiExporter;
+ use Import::Into;
+
use Thing1 ();
use Thing2 ();
+ use Thing3 ();
sub import {
my $target = caller;
Thing1->import::into($target);
Thing2->import::into($target, qw(import arguments));
+ Thing3->import::into(1); # import to level
+ }
+
+Note: you don't need to do anything more clever than this provided you
+document that people wanting to re-export your module should also be using
+L<Import::Into>. In fact, for a single module you can simply do:
+
+ sub import {
+ ...
+ Thing1->import::into(scalar caller);
+ }
+
+Notably, this works:
+
+ use base qw(Exporter);
+
+ sub import {
+ shift->export_to_level(1);
+ Thing1->import::into(scalar caller);
+ }
+
+Note 2: You do B<not> need to do anything to Thing1 to be able to call
+C<import::into> on it. This is a global method, and is callable on any
+package (and in fact on any object as well, although it's rarer that you'd
+want to do that).
+
+If you provide C<import::into> with an integer instead of a package name, it
+will be used as the number of stack frames to skip to find where to export to.
+This has the advantage of preserving the apparent filename and line number
+being exported to, which some modules (L<autodie>, L<strictures>) check.
+
+Finally, we also provide an C<unimport::out_of> to allow the exporting of the
+effect of C<no>:
+
+ # unimport::out_of was added in 1.1.0 (1.001000)
+ sub unimport {
+ Moose->unimport::out_of(scalar caller); # no MyThing == no Moose
+ }
+
+If how and why this all works is of interest to you, please read on to the
+description immediately below.
+
+=head1 DESCRIPTION
+
+Writing exporters is a pain. Some use L<Exporter>, some use L<Sub::Exporter>,
+some use L<Moose::Exporter>, some use L<Exporter::Declare> ... and some things
+are pragmas.
+
+If you want to re-export other things, you have to know which is which.
+L<Exporter> subclasses provide export_to_level, but if they overrode their
+import method all bets are off. L<Sub::Exporter> provides an into parameter
+but figuring out something used it isn't trivial. Pragmas need to have
+their C<import> method called directly since they affect the current unit of
+compilation.
+
+It's ... annoying.
+
+However, there is an approach that actually works for all of these types.
+
+ eval "package $target; use $thing;"
+
+will work for anything checking caller, which is everything except pragmas.
+But it doesn't work for pragmas - pragmas need:
+
+ $thing->import;
+
+because they're designed to affect the code currently being compiled - so
+within an eval, that's the scope of the eval itself, not the module that
+just C<use>d you - so
+
+ sub import {
+ eval "use strict;"
}
+doesn't do what you wanted, but
+
+ sub import {
+ strict->import;
+ }
+
+will apply L<strict> to the calling file correctly.
+
+Of course, now you have two new problems - first, that you still need to
+know if something's a pragma, and second that you can't use either of
+these approaches alone on something like L<Moose> or L<Moo> that's both
+an exporter and a pragma.
+
+So, a solution for that is:
+
+ my $sub = eval "package $target; sub { shift->import(\@_) }";
+ $sub->($thing, @import_args);
+
+which means that import is called from the right place for pragmas to take
+effect, and from the right package for caller checking to work - and so
+behaves correctly for all types of exporter, for pragmas, and for hybrids.
+
+Additionally, some import routines check the filename they are being imported
+to. This can be dealt with by generating a L<#line directive|perlsyn/Plain
+Old Comments (Not!)> in the eval, which will change what C<caller> reports for
+the filename when called in the importer. The filename and line number to use
+in the directive then need to be fetched using C<caller>:
+
+ my ($target, $file, $line) = caller(1);
+ my $sub = eval qq{
+ package $target;
+ #line $line "$file"
+ sub { shift->import(\@_) }
+ };
+ $sub->($thing, @import_args);
+
+Remembering all this, however, is excessively irritating. So I wrote a module
+so I didn't have to anymore. Loading L<Import::Into> creates a global method
+C<import::into> which you can call on any package to import it into another
+package. So now you can simply write:
+
+ use Import::Into;
+
+ $thing->import::into($target, @import_args);
+
+This works because of how perl resolves method calls - a call to a simple
+method name is resolved against the package of the class or object, so
+
+ $thing->method_name(@args);
+
+is roughly equivalent to:
+
+ my $code_ref = $thing->can('method_name');
+ $code_ref->($thing, @args);
+
+while if a C<::> is found, the lookup is made relative to the package name
+(i.e. everything before the last C<::>) so
+
+ $thing->Package::Name::method_name(@args);
+
+is roughly equivalent to:
+
+ my $code_ref = Package::Name->can('method_name');
+ $code_ref->($thing, @args);
+
+So since L<Import::Into> defines a method C<into> in package C<import>
+the syntax reliably calls that.
+
+For more craziness of this order, have a look at the article I wrote at
+L<http://shadow.cat/blog/matt-s-trout/madness-with-methods> which covers
+coderef abuse and the C<${\...}> syntax.
+
+Final note: You do still need to ensure that you already loaded C<$thing> - if
+you're receiving this from a parameter, I recommend using L<Module::Runtime>:
+
+ use Import::Into;
+ use Module::Runtime qw(use_module);
+
+ use_module($thing)->import::into($target, @import_args);
+
+And that's it.
+
+=head1 ACKNOWLEDGEMENTS
+
+Thanks to Getty for asking "how can I get C<< use strict; use warnings; >>
+turned on for all consumers of my code?" and then "why is this not a
+module?!".
+
=head1 AUTHOR
mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>
+=head1 CONTRIBUTORS
+
+haarg - Graham Knop (cpan:HAARG) <haarg@haarg.org>
+
=head1 COPYRIGHT
-Copyright (c) 2010-2011 the Import::Into L</AUTHOR> and L</CONTRIBUTORS>
+Copyright (c) 2012 the Import::Into L</AUTHOR> and L</CONTRIBUTORS>
as listed above.
=head1 LICENSE
projects / p5sagit/Import-Into.git / blobdiff