6 # We go to a lot of trouble not to 'require Carp' at file scope,
7 # because Carp requires Exporter, and something has to give.
11 $Verbose = 0 unless $Verbose;
15 # First make import warnings look like they're coming from the "use".
16 local $SIG{__WARN__} = sub {
18 if ($text =~ s/ at \S*Exporter.pm line \d+.*\n//) {
20 local $Carp::CarpLevel = 1; # ignore package calling us too.
27 local $SIG{__DIE__} = sub {
29 local $Carp::CarpLevel = 1; # ignore package calling us too.
30 Carp::croak("$_[0]Illegal null symbol in \@${1}::EXPORT")
31 if $_[0] =~ /^Unable to create sub named "(.*?)::"/;
34 my($pkg, $callpkg, @imports) = @_;
35 my($type, $sym, $oops);
36 *exports = *{"${pkg}::EXPORT"};
40 grep(s/^&//, @exports);
41 @exports{@exports} = (1) x @exports;
42 my $ok = \@{"${pkg}::EXPORT_OK"};
45 @exports{@$ok} = (1) x @$ok;
49 if ($imports[0] =~ m#^[/!:]#){
50 my $tagsref = \%{"${pkg}::EXPORT_TAGS"};
53 my($remove, $spec, @names, @allexports);
54 # negated first item implies starting with default set:
55 unshift @imports, ':DEFAULT' if $imports[0] =~ m/^!/;
56 foreach $spec (@imports){
57 $remove = $spec =~ s/^!//;
60 if ($spec eq 'DEFAULT'){
63 elsif ($tagdata = $tagsref->{$spec}) {
67 warn qq["$spec" is not defined in %${pkg}::EXPORT_TAGS];
72 elsif ($spec =~ m:^/(.*)/$:){
74 @allexports = keys %exports unless @allexports; # only do keys once
75 @names = grep(/$patn/, @allexports); # not anchored by default
78 @names = ($spec); # is a normal symbol name
81 warn "Import ".($remove ? "del":"add").": @names "
85 foreach $sym (@names) { delete $imports{$sym} }
88 @imports{@names} = (1) x @names;
91 @imports = keys %imports;
94 foreach $sym (@imports) {
95 if (!$exports{$sym}) {
97 $pkg->require_version($sym);
98 # If the version number was the only thing specified
99 # then we should act as if nothing was specified:
104 # We need a way to emulate 'use Foo ()' but still
105 # allow an easy version check: "use Foo 1.23, ''";
106 if (@imports == 2 and !$imports[1]) {
110 } elsif ($sym !~ s/^&// || !$exports{$sym}) {
111 warn qq["$sym" is not exported by the $pkg module];
118 Carp::croak("Can't continue after import errors");
125 *fail = *{"${pkg}::EXPORT_FAIL"};
128 # Build cache of symbols. Optimise the lookup by adding
129 # barewords twice... both with and without a leading &.
130 # (Technique could be applied to %exports cache at cost of memory)
131 my @expanded = map { /^\w/ ? ($_, '&'.$_) : $_ } @fail;
132 warn "${pkg}::EXPORT_FAIL cached: @expanded" if $Verbose;
133 @fail{@expanded} = (1) x @expanded;
136 foreach $sym (@imports) { push(@failed, $sym) if $fail{$sym} }
138 @failed = $pkg->export_fail(@failed);
139 foreach $sym (@failed) {
140 warn qq["$sym" is not implemented by the $pkg module ],
141 "on this architecture";
145 Carp::croak("Can't continue after import errors");
150 warn "Importing into $callpkg from $pkg: ",
151 join(", ",sort @imports) if $Verbose;
153 foreach $sym (@imports) {
154 # shortcut for the common case of no type character
155 (*{"${callpkg}::$sym"} = \&{"${pkg}::$sym"}, next)
156 unless $sym =~ s/^(\W)//;
158 *{"${callpkg}::$sym"} =
159 $type eq '&' ? \&{"${pkg}::$sym"} :
160 $type eq '$' ? \${"${pkg}::$sym"} :
161 $type eq '@' ? \@{"${pkg}::$sym"} :
162 $type eq '%' ? \%{"${pkg}::$sym"} :
163 $type eq '*' ? *{"${pkg}::$sym"} :
164 do { require Carp; Carp::croak("Can't export symbol: $type$sym") };
170 my $callpkg = caller($ExportLevel);
171 export $pkg, $callpkg, @_;
178 my($pkg, $var, $syms) = @_;
180 *export_tags = \%{"${pkg}::EXPORT_TAGS"};
181 push(@{"${pkg}::$var"},
182 map { $export_tags{$_} ? @{$export_tags{$_}} : scalar(++$nontag,$_) }
183 (@$syms) ? @$syms : keys %export_tags);
184 if ($nontag and $^W) {
185 # This may change to a die one day
187 Carp::carp("Some names are not tags");
191 sub export_tags { _push_tags((caller)[0], "EXPORT", \@_) }
192 sub export_ok_tags { _push_tags((caller)[0], "EXPORT_OK", \@_) }
202 sub require_version {
203 my($self, $wanted) = @_;
204 my $pkg = ref $self || $self;
205 my $version = ${"${pkg}::VERSION"};
206 if (!$version or $version < $wanted) {
207 $version ||= "(undef)";
208 my $file = $INC{"$pkg.pm"};
209 $file &&= " ($file)";
211 Carp::croak("$pkg $wanted required--this is only version $version$file")
218 # A simple self test harness. Change 'require Carp' to 'use Carp ()' for testing.
219 # package main; eval(join('',<DATA>)) or die $@ unless caller;
222 $INC{'Exporter.pm'} = 1;
224 @EXPORT = qw(A1 A2 A3 A4 A5);
225 @EXPORT_OK = qw(B1 B2 B3 B4 B5);
226 %EXPORT_TAGS = (T1=>[qw(A1 A2 B1 B2)], T2=>[qw(A1 A2 B3 B4)], T3=>[qw(X3)]);
227 @EXPORT_FAIL = qw(B4);
228 Exporter::export_ok_tags('T3', 'unknown_tag');
230 map { "Test::$_" } @_ # edit symbols just as an example
234 $Exporter::Verbose = 1;
236 #import Test qw(X3); # export ok via export_ok_tags()
237 #import Test qw(:T1 !A2 /5/ !/3/ B5);
238 import Test qw(:T2 !B4);
239 import Test qw(:T2); # should fail
244 Exporter - Implements default import method for modules
248 In module ModuleName.pm:
254 @EXPORT = qw(...); # symbols to export by default
255 @EXPORT_OK = qw(...); # symbols to export on request
256 %EXPORT_TAGS = tag => [...]; # define names for sets of symbols
258 In other files which wish to use ModuleName:
260 use ModuleName; # import default symbols into my package
262 use ModuleName qw(...); # import listed symbols into my package
264 use ModuleName (); # do not import any symbols
268 The Exporter module implements a default C<import> method which
269 many modules choose to inherit rather than implement their own.
271 Perl automatically calls the C<import> method when processing a
272 C<use> statement for a module. Modules and C<use> are documented
273 in L<perlfunc> and L<perlmod>. Understanding the concept of
274 modules and how the C<use> statement operates is important to
275 understanding the Exporter.
277 =head2 Selecting What To Export
279 Do B<not> export method names!
281 Do B<not> export anything else by default without a good reason!
283 Exports pollute the namespace of the module user. If you must export
284 try to use @EXPORT_OK in preference to @EXPORT and avoid short or
285 common symbol names to reduce the risk of name clashes.
287 Generally anything not exported is still accessible from outside the
288 module using the ModuleName::item_name (or $blessed_ref-E<gt>method)
289 syntax. By convention you can use a leading underscore on names to
290 informally indicate that they are 'internal' and not for public use.
292 (It is actually possible to get private functions by saying:
294 my $subref = sub { ... };
297 But there's no way to call that directly as a method, since a method
298 must have a name in the symbol table.)
300 As a general rule, if the module is trying to be object oriented
301 then export nothing. If it's just a collection of functions then
302 @EXPORT_OK anything but use @EXPORT with caution.
304 Other module design guidelines can be found in L<perlmod>.
306 =head2 Specialised Import Lists
308 If the first entry in an import list begins with !, : or / then the
309 list is treated as a series of specifications which either add to or
310 delete from the list of names to import. They are processed left to
311 right. Specifications are in the form:
313 [!]name This name only
314 [!]:DEFAULT All names in @EXPORT
315 [!]:tag All names in $EXPORT_TAGS{tag} anonymous list
316 [!]/pattern/ All names in @EXPORT and @EXPORT_OK which match
318 A leading ! indicates that matching names should be deleted from the
319 list of names to import. If the first specification is a deletion it
320 is treated as though preceded by :DEFAULT. If you just want to import
321 extra names in addition to the default set you will still need to
322 include :DEFAULT explicitly.
324 e.g., Module.pm defines:
326 @EXPORT = qw(A1 A2 A3 A4 A5);
327 @EXPORT_OK = qw(B1 B2 B3 B4 B5);
328 %EXPORT_TAGS = (T1 => [qw(A1 A2 B1 B2)], T2 => [qw(A1 A2 B3 B4)]);
330 Note that you cannot use tags in @EXPORT or @EXPORT_OK.
331 Names in EXPORT_TAGS must also appear in @EXPORT or @EXPORT_OK.
333 An application using Module can say something like:
335 use Module qw(:DEFAULT :T2 !B3 A3);
337 Other examples include:
339 use Socket qw(!/^[AP]F_/ !SOMAXCONN !SOL_SOCKET);
340 use POSIX qw(:errno_h :termios_h !TCSADRAIN !/^EXIT/);
342 Remember that most patterns (using //) will need to be anchored
343 with a leading ^, e.g., C</^EXIT/> rather than C</EXIT/>.
345 You can say C<BEGIN { $Exporter::Verbose=1 }> to see how the
346 specifications are being processed and what is actually being imported
349 =head2 Module Version Checking
351 The Exporter module will convert an attempt to import a number from a
352 module into a call to $module_name-E<gt>require_version($value). This can
353 be used to validate that the version of the module being used is
354 greater than or equal to the required version.
356 The Exporter module supplies a default require_version method which
357 checks the value of $VERSION in the exporting module.
359 Since the default require_version method treats the $VERSION number as
360 a simple numeric value it will regard version 1.10 as lower than
361 1.9. For this reason it is strongly recommended that you use numbers
362 with at least two decimal places, e.g., 1.09.
364 =head2 Managing Unknown Symbols
366 In some situations you may want to prevent certain symbols from being
367 exported. Typically this applies to extensions which have functions
368 or constants that may not exist on some systems.
370 The names of any symbols that cannot be exported should be listed
371 in the C<@EXPORT_FAIL> array.
373 If a module attempts to import any of these symbols the Exporter
374 will give the module an opportunity to handle the situation before
375 generating an error. The Exporter will call an export_fail method
376 with a list of the failed symbols:
378 @failed_symbols = $module_name->export_fail(@failed_symbols);
380 If the export_fail method returns an empty list then no error is
381 recorded and all the requested symbols are exported. If the returned
382 list is not empty then an error is generated for each symbol and the
383 export fails. The Exporter provides a default export_fail method which
384 simply returns the list unchanged.
386 Uses for the export_fail method include giving better error messages
387 for some symbols and performing lazy architectural checks (put more
388 symbols into @EXPORT_FAIL by default and then take them out if someone
389 actually tries to use them and an expensive check shows that they are
390 usable on that platform).
392 =head2 Tag Handling Utility Functions
394 Since the symbols listed within %EXPORT_TAGS must also appear in either
395 @EXPORT or @EXPORT_OK, two utility functions are provided which allow
396 you to easily add tagged sets of symbols to @EXPORT or @EXPORT_OK:
398 %EXPORT_TAGS = (foo => [qw(aa bb cc)], bar => [qw(aa cc dd)]);
400 Exporter::export_tags('foo'); # add aa, bb and cc to @EXPORT
401 Exporter::export_ok_tags('bar'); # add aa, cc and dd to @EXPORT_OK
403 Any names which are not tags are added to @EXPORT or @EXPORT_OK
404 unchanged but will trigger a warning (with C<-w>) to avoid misspelt tags
405 names being silently added to @EXPORT or @EXPORT_OK. Future versions
406 may make this a fatal error.