6 $Verbose = 0 unless $Verbose;
12 # First make import warnings look like they're coming from the "use".
13 local $SIG{__WARN__} = sub {
15 $text =~ s/ at \S*Exporter.pm line \d+.*\n//;
16 local $Carp::CarpLevel = 1; # ignore package calling us too.
19 local $SIG{__DIE__} = sub {
20 Carp::croak("$_[0]Illegal null symbol in \@${1}::EXPORT")
21 if $_[0] =~ /^Unable to create sub named "(.*?)::"/;
24 my($pkg, $callpkg, @imports) = @_;
25 my($type, $sym, $oops);
26 *exports = *{"${pkg}::EXPORT"};
30 grep(s/^&//, @exports);
31 @exports{@exports} = (1) x @exports;
32 my $ok = \@{"${pkg}::EXPORT_OK"};
35 @exports{@$ok} = (1) x @$ok;
39 if ($imports[0] =~ m#^[/!:]#){
40 my $tagsref = \%{"${pkg}::EXPORT_TAGS"};
43 my($remove, $spec, @names, @allexports);
44 # negated first item implies starting with default set:
45 unshift @imports, ':DEFAULT' if $imports[0] =~ m/^!/;
46 foreach $spec (@imports){
47 $remove = $spec =~ s/^!//;
50 if ($spec eq 'DEFAULT'){
53 elsif ($tagdata = $tagsref->{$spec}) {
57 warn qq["$spec" is not defined in %${pkg}::EXPORT_TAGS];
62 elsif ($spec =~ m:^/(.*)/$:){
64 @allexports = keys %exports unless @allexports; # only do keys once
65 @names = grep(/$patn/, @allexports); # not anchored by default
68 @names = ($spec); # is a normal symbol name
71 warn "Import ".($remove ? "del":"add").": @names "
75 foreach $sym (@names) { delete $imports{$sym} }
78 @imports{@names} = (1) x @names;
81 @imports = keys %imports;
84 foreach $sym (@imports) {
85 if (!$exports{$sym}) {
87 $pkg->require_version($sym);
88 # If the version number was the only thing specified
89 # then we should act as if nothing was specified:
94 # We need a way to emulate 'use Foo ()' but still
95 # allow an easy version check: "use Foo 1.23, ''";
96 if (@imports == 2 and !$imports[1]) {
100 } elsif ($sym !~ s/^&// || !$exports{$sym}) {
101 warn qq["$sym" is not exported by the $pkg module];
106 Carp::croak("Can't continue after import errors") if $oops;
112 *fail = *{"${pkg}::EXPORT_FAIL"};
115 # Build cache of symbols. Optimise the lookup by adding
116 # barewords twice... both with and without a leading &.
117 # (Technique could be applied to %exports cache at cost of memory)
118 my @expanded = map { /^\w/ ? ($_, '&'.$_) : $_ } @fail;
119 warn "${pkg}::EXPORT_FAIL cached: @expanded" if $Verbose;
120 @fail{@expanded} = (1) x @expanded;
123 foreach $sym (@imports) { push(@failed, $sym) if $fail{$sym} }
125 @failed = $pkg->export_fail(@failed);
126 foreach $sym (@failed) {
127 warn qq["$sym" is not implemented by the $pkg module ],
128 "on this architecture";
130 Carp::croak("Can't continue after import errors") if @failed;
134 warn "Importing into $callpkg from $pkg: ",
135 join(", ",sort @imports) if $Verbose;
137 foreach $sym (@imports) {
138 # shortcut for the common case of no type character
139 (*{"${callpkg}::$sym"} = \&{"${pkg}::$sym"}, next)
140 unless $sym =~ s/^(\W)//;
142 *{"${callpkg}::$sym"} =
143 $type eq '&' ? \&{"${pkg}::$sym"} :
144 $type eq '$' ? \${"${pkg}::$sym"} :
145 $type eq '@' ? \@{"${pkg}::$sym"} :
146 $type eq '%' ? \%{"${pkg}::$sym"} :
147 $type eq '*' ? *{"${pkg}::$sym"} :
148 Carp::croak("Can't export symbol: $type$sym");
154 my $callpkg = caller($ExportLevel);
155 export $pkg, $callpkg, @_;
162 my($pkg, $var, $syms) = @_;
164 *export_tags = \%{"${pkg}::EXPORT_TAGS"};
165 push(@{"${pkg}::$var"},
166 map { $export_tags{$_} ? @{$export_tags{$_}} : scalar(++$nontag,$_) }
167 (@$syms) ? @$syms : keys %export_tags);
168 # This may change to a die one day
169 Carp::carp("Some names are not tags") if $nontag and $^W;
172 sub export_tags { _push_tags((caller)[0], "EXPORT", \@_) }
173 sub export_ok_tags { _push_tags((caller)[0], "EXPORT_OK", \@_) }
182 sub require_version {
183 my($self, $wanted) = @_;
184 my $pkg = ref $self || $self;
185 my $version = ${"${pkg}::VERSION"};
186 if (!$version or $version < $wanted) {
187 $version ||= "(undef)";
188 my $file = $INC{"$pkg.pm"};
189 $file &&= " ($file)";
190 Carp::croak("$pkg $wanted required--this is only version $version$file")
197 # A simple self test harness. Change 'require Carp' to 'use Carp ()' for testing.
198 # package main; eval(join('',<DATA>)) or die $@ unless caller;
201 $INC{'Exporter.pm'} = 1;
203 @EXPORT = qw(A1 A2 A3 A4 A5);
204 @EXPORT_OK = qw(B1 B2 B3 B4 B5);
205 %EXPORT_TAGS = (T1=>[qw(A1 A2 B1 B2)], T2=>[qw(A1 A2 B3 B4)], T3=>[qw(X3)]);
206 @EXPORT_FAIL = qw(B4);
207 Exporter::export_ok_tags('T3', 'unknown_tag');
209 map { "Test::$_" } @_ # edit symbols just as an example
213 $Exporter::Verbose = 1;
215 #import Test qw(X3); # export ok via export_ok_tags()
216 #import Test qw(:T1 !A2 /5/ !/3/ B5);
217 import Test qw(:T2 !B4);
218 import Test qw(:T2); # should fail
223 Exporter - Implements default import method for modules
227 In module ModuleName.pm:
233 @EXPORT = qw(...); # symbols to export by default
234 @EXPORT_OK = qw(...); # symbols to export on request
235 %EXPORT_TAGS = tag => [...]; # define names for sets of symbols
237 In other files which wish to use ModuleName:
239 use ModuleName; # import default symbols into my package
241 use ModuleName qw(...); # import listed symbols into my package
243 use ModuleName (); # do not import any symbols
247 The Exporter module implements a default C<import> method which
248 many modules choose inherit rather than implement their own.
250 Perl automatically calls the C<import> method when processing a
251 C<use> statement for a module. Modules and C<use> are documented
252 in L<perlfunc> and L<perlmod>. Understanding the concept of
253 modules and how the C<use> statement operates is important to
254 understanding the Exporter.
256 =head2 Selecting What To Export
258 Do B<not> export method names!
260 Do B<not> export anything else by default without a good reason!
262 Exports pollute the namespace of the module user. If you must export
263 try to use @EXPORT_OK in preference to @EXPORT and avoid short or
264 common symbol names to reduce the risk of name clashes.
266 Generally anything not exported is still accessible from outside the
267 module using the ModuleName::item_name (or $blessed_ref->method)
268 syntax. By convention you can use a leading underscore on names to
269 informally indicate that they are 'internal' and not for public use.
271 (It is actually possible to get private functions by saying:
273 my $subref = sub { ... };
276 But there's no way to call that directly as a method, since a method
277 must have a name in the symbol table.)
279 As a general rule, if the module is trying to be object oriented
280 then export nothing. If it's just a collection of functions then
281 @EXPORT_OK anything but use @EXPORT with caution.
283 Other module design guidelines can be found in L<perlmod>.
285 =head2 Specialised Import Lists
287 If the first entry in an import list begins with !, : or / then the
288 list is treated as a series of specifications which either add to or
289 delete from the list of names to import. They are processed left to
290 right. Specifications are in the form:
292 [!]name This name only
293 [!]:DEFAULT All names in @EXPORT
294 [!]:tag All names in $EXPORT_TAGS{tag} anonymous list
295 [!]/pattern/ All names in @EXPORT and @EXPORT_OK which match
297 A leading ! indicates that matching names should be deleted from the
298 list of names to import. If the first specification is a deletion it
299 is treated as though preceded by :DEFAULT. If you just want to import
300 extra names in addition to the default set you will still need to
301 include :DEFAULT explicitly.
303 e.g., Module.pm defines:
305 @EXPORT = qw(A1 A2 A3 A4 A5);
306 @EXPORT_OK = qw(B1 B2 B3 B4 B5);
307 %EXPORT_TAGS = (T1 => [qw(A1 A2 B1 B2)], T2 => [qw(A1 A2 B3 B4)]);
309 Note that you cannot use tags in @EXPORT or @EXPORT_OK.
310 Names in EXPORT_TAGS must also appear in @EXPORT or @EXPORT_OK.
312 An application using Module can say something like:
314 use Module qw(:DEFAULT :T2 !B3 A3);
316 Other examples include:
318 use Socket qw(!/^[AP]F_/ !SOMAXCONN !SOL_SOCKET);
319 use POSIX qw(:errno_h :termios_h !TCSADRAIN !/^EXIT/);
321 Remember that most patterns (using //) will need to be anchored
322 with a leading ^, e.g., C</^EXIT/> rather than C</EXIT/>.
324 You can say C<BEGIN { $Exporter::Verbose=1 }> to see how the
325 specifications are being processed and what is actually being imported
328 =head2 Module Version Checking
330 The Exporter module will convert an attempt to import a number from a
331 module into a call to $module_name->require_version($value). This can
332 be used to validate that the version of the module being used is
333 greater than or equal to the required version.
335 The Exporter module supplies a default require_version method which
336 checks the value of $VERSION in the exporting module.
338 Since the default require_version method treats the $VERSION number as
339 a simple numeric value it will regard version 1.10 as lower than
340 1.9. For this reason it is strongly recommended that you use numbers
341 with at least two decimal places, e.g., 1.09.
343 =head2 Managing Unknown Symbols
345 In some situations you may want to prevent certain symbols from being
346 exported. Typically this applies to extensions which have functions
347 or constants that may not exist on some systems.
349 The names of any symbols that cannot be exported should be listed
350 in the C<@EXPORT_FAIL> array.
352 If a module attempts to import any of these symbols the Exporter will
353 will give the module an opportunity to handle the situation before
354 generating an error. The Exporter will call an export_fail method
355 with a list of the failed symbols:
357 @failed_symbols = $module_name->export_fail(@failed_symbols);
359 If the export_fail method returns an empty list then no error is
360 recorded and all the requested symbols are exported. If the returned
361 list is not empty then an error is generated for each symbol and the
362 export fails. The Exporter provides a default export_fail method which
363 simply returns the list unchanged.
365 Uses for the export_fail method include giving better error messages
366 for some symbols and performing lazy architectural checks (put more
367 symbols into @EXPORT_FAIL by default and then take them out if someone
368 actually tries to use them and an expensive check shows that they are
369 usable on that platform).
371 =head2 Tag Handling Utility Functions
373 Since the symbols listed within %EXPORT_TAGS must also appear in either
374 @EXPORT or @EXPORT_OK, two utility functions are provided which allow
375 you to easily add tagged sets of symbols to @EXPORT or @EXPORT_OK:
377 %EXPORT_TAGS = (foo => [qw(aa bb cc)], bar => [qw(aa cc dd)]);
379 Exporter::export_tags('foo'); # add aa, bb and cc to @EXPORT
380 Exporter::export_ok_tags('bar'); # add aa, cc and dd to @EXPORT_OK
382 Any names which are not tags are added to @EXPORT or @EXPORT_OK
383 unchanged but will trigger a warning (with C<-w>) to avoid misspelt tags
384 names being silently added to @EXPORT or @EXPORT_OK. Future versions
385 may make this a fatal error.