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undo changes to Exporter.pm from #2312
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1package Exporter;
2
748a9306 3require 5.001;
8990e307 4
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5#
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.
8#
9
a0d0e21e 10$ExportLevel = 0;
c07a80fd 11$Verbose = 0 unless $Verbose;
748a9306 12
a0d0e21e 13sub export {
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14
15 # First make import warnings look like they're coming from the "use".
16 local $SIG{__WARN__} = sub {
17 my $text = shift;
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18 if ($text =~ s/ at \S*Exporter.pm line \d+.*\n//) {
19 require Carp;
20 local $Carp::CarpLevel = 1; # ignore package calling us too.
21 Carp::carp($text);
22 }
23 else {
24 warn $text;
25 }
748a9306 26 };
4633a7c4 27 local $SIG{__DIE__} = sub {
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28 require Carp;
29 local $Carp::CarpLevel = 1; # ignore package calling us too.
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30 Carp::croak("$_[0]Illegal null symbol in \@${1}::EXPORT")
31 if $_[0] =~ /^Unable to create sub named "(.*?)::"/;
32 };
748a9306 33
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34 my($pkg, $callpkg, @imports) = @_;
35 my($type, $sym, $oops);
36 *exports = *{"${pkg}::EXPORT"};
37
8990e307 38 if (@imports) {
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39 if (!%exports) {
40 grep(s/^&//, @exports);
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41 @exports{@exports} = (1) x @exports;
42 my $ok = \@{"${pkg}::EXPORT_OK"};
43 if (@$ok) {
44 grep(s/^&//, @$ok);
45 @exports{@$ok} = (1) x @$ok;
a0d0e21e 46 }
8990e307 47 }
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48
49 if ($imports[0] =~ m#^[/!:]#){
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50 my $tagsref = \%{"${pkg}::EXPORT_TAGS"};
51 my $tagdata;
52 my %imports;
2b5b2650 53 my($remove, $spec, @names, @allexports);
748a9306 54 # negated first item implies starting with default set:
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55 unshift @imports, ':DEFAULT' if $imports[0] =~ m/^!/;
56 foreach $spec (@imports){
57 $remove = $spec =~ s/^!//;
748a9306 58
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59 if ($spec =~ s/^://){
60 if ($spec eq 'DEFAULT'){
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61 @names = @exports;
62 }
2b5b2650 63 elsif ($tagdata = $tagsref->{$spec}) {
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64 @names = @$tagdata;
65 }
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66 else {
67 warn qq["$spec" is not defined in %${pkg}::EXPORT_TAGS];
68 ++$oops;
69 next;
70 }
71 }
72 elsif ($spec =~ m:^/(.*)/$:){
73 my $patn = $1;
74 @allexports = keys %exports unless @allexports; # only do keys once
75 @names = grep(/$patn/, @allexports); # not anchored by default
748a9306 76 }
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77 else {
78 @names = ($spec); # is a normal symbol name
79 }
80
81 warn "Import ".($remove ? "del":"add").": @names "
82 if $Verbose;
748a9306 83
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84 if ($remove) {
85 foreach $sym (@names) { delete $imports{$sym} }
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86 }
87 else {
2b5b2650 88 @imports{@names} = (1) x @names;
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89 }
90 }
91 @imports = keys %imports;
92 }
93
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94 foreach $sym (@imports) {
95 if (!$exports{$sym}) {
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96 if ($sym =~ m/^\d/) {
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:
100 if (@imports == 1) {
101 @imports = @exports;
102 last;
103 }
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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 !$imports[1]) {
107 @imports = ();
108 last;
109 }
e50aee73 110 } elsif ($sym !~ s/^&// || !$exports{$sym}) {
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111 require Carp;
112 Carp::carp(qq["$sym" is not exported by the $pkg module]);
8990e307 113 $oops++;
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114 }
115 }
116 }
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117 if ($oops) {
118 require Carp;
119 Carp::croak("Can't continue after import errors");
120 }
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121 }
122 else {
123 @imports = @exports;
124 }
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125
126 *fail = *{"${pkg}::EXPORT_FAIL"};
127 if (@fail) {
128 if (!%fail) {
129 # Build cache of symbols. Optimise the lookup by adding
130 # barewords twice... both with and without a leading &.
131 # (Technique could be applied to %exports cache at cost of memory)
132 my @expanded = map { /^\w/ ? ($_, '&'.$_) : $_ } @fail;
133 warn "${pkg}::EXPORT_FAIL cached: @expanded" if $Verbose;
134 @fail{@expanded} = (1) x @expanded;
135 }
136 my @failed;
137 foreach $sym (@imports) { push(@failed, $sym) if $fail{$sym} }
138 if (@failed) {
139 @failed = $pkg->export_fail(@failed);
140 foreach $sym (@failed) {
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141 require Carp;
142 Carp::carp(qq["$sym" is not implemented by the $pkg module ],
143 "on this architecture");
2b5b2650 144 }
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145 if (@failed) {
146 require Carp;
147 Carp::croak("Can't continue after import errors");
148 }
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149 }
150 }
151
c07a80fd 152 warn "Importing into $callpkg from $pkg: ",
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153 join(", ",sort @imports) if $Verbose;
154
8990e307 155 foreach $sym (@imports) {
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156 # shortcut for the common case of no type character
157 (*{"${callpkg}::$sym"} = \&{"${pkg}::$sym"}, next)
158 unless $sym =~ s/^(\W)//;
159 $type = $1;
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160 *{"${callpkg}::$sym"} =
161 $type eq '&' ? \&{"${pkg}::$sym"} :
162 $type eq '$' ? \${"${pkg}::$sym"} :
163 $type eq '@' ? \@{"${pkg}::$sym"} :
164 $type eq '%' ? \%{"${pkg}::$sym"} :
165 $type eq '*' ? *{"${pkg}::$sym"} :
68dc0745 166 do { require Carp; Carp::croak("Can't export symbol: $type$sym") };
8990e307 167 }
2b5b2650 168}
8990e307 169
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170sub export_to_level
171{
172 my $pkg = shift;
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173 my ($level, $junk) = (shift, shift); # need to get rid of first arg
174 # we know it already.
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175 my $callpkg = caller($level);
176 $pkg->export($callpkg, @_);
177}
178
a0d0e21e 179sub import {
748a9306 180 my $pkg = shift;
2b5b2650 181 my $callpkg = caller($ExportLevel);
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182 export $pkg, $callpkg, @_;
183}
184
2b5b2650 185
84902520 186
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187# Utility functions
188
189sub _push_tags {
190 my($pkg, $var, $syms) = @_;
191 my $nontag;
c07a80fd 192 *export_tags = \%{"${pkg}::EXPORT_TAGS"};
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193 push(@{"${pkg}::$var"},
194 map { $export_tags{$_} ? @{$export_tags{$_}} : scalar(++$nontag,$_) }
195 (@$syms) ? @$syms : keys %export_tags);
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196 if ($nontag and $^W) {
197 # This may change to a die one day
198 require Carp;
199 Carp::carp("Some names are not tags");
200 }
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201}
202
203sub export_tags { _push_tags((caller)[0], "EXPORT", \@_) }
204sub export_ok_tags { _push_tags((caller)[0], "EXPORT_OK", \@_) }
205
206
207# Default methods
208
209sub export_fail {
a45ab7f6 210 my $self = shift;
2b5b2650 211 @_;
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212}
213
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214sub require_version {
215 my($self, $wanted) = @_;
216 my $pkg = ref $self || $self;
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217 my $version = ${"${pkg}::VERSION"};
218 if (!$version or $version < $wanted) {
219 $version ||= "(undef)";
220 my $file = $INC{"$pkg.pm"};
221 $file &&= " ($file)";
68dc0745 222 require Carp;
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223 Carp::croak("$pkg $wanted required--this is only version $version$file")
224 }
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225 $version;
226}
227
8990e307 2281;
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229
230# A simple self test harness. Change 'require Carp' to 'use Carp ()' for testing.
231# package main; eval(join('',<DATA>)) or die $@ unless caller;
232__END__
233package Test;
234$INC{'Exporter.pm'} = 1;
235@ISA = qw(Exporter);
236@EXPORT = qw(A1 A2 A3 A4 A5);
237@EXPORT_OK = qw(B1 B2 B3 B4 B5);
238%EXPORT_TAGS = (T1=>[qw(A1 A2 B1 B2)], T2=>[qw(A1 A2 B3 B4)], T3=>[qw(X3)]);
239@EXPORT_FAIL = qw(B4);
240Exporter::export_ok_tags('T3', 'unknown_tag');
241sub export_fail {
242 map { "Test::$_" } @_ # edit symbols just as an example
243}
244
245package main;
246$Exporter::Verbose = 1;
247#import Test;
248#import Test qw(X3); # export ok via export_ok_tags()
249#import Test qw(:T1 !A2 /5/ !/3/ B5);
250import Test qw(:T2 !B4);
251import Test qw(:T2); # should fail
2521;
253
254=head1 NAME
255
256Exporter - Implements default import method for modules
257
258=head1 SYNOPSIS
259
260In module ModuleName.pm:
261
262 package ModuleName;
263 require Exporter;
264 @ISA = qw(Exporter);
265
266 @EXPORT = qw(...); # symbols to export by default
267 @EXPORT_OK = qw(...); # symbols to export on request
268 %EXPORT_TAGS = tag => [...]; # define names for sets of symbols
269
270In other files which wish to use ModuleName:
271
272 use ModuleName; # import default symbols into my package
273
274 use ModuleName qw(...); # import listed symbols into my package
275
276 use ModuleName (); # do not import any symbols
277
278=head1 DESCRIPTION
279
280The Exporter module implements a default C<import> method which
68dc0745 281many modules choose to inherit rather than implement their own.
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282
283Perl automatically calls the C<import> method when processing a
284C<use> statement for a module. Modules and C<use> are documented
285in L<perlfunc> and L<perlmod>. Understanding the concept of
286modules and how the C<use> statement operates is important to
287understanding the Exporter.
288
289=head2 Selecting What To Export
290
291Do B<not> export method names!
292
293Do B<not> export anything else by default without a good reason!
294
295Exports pollute the namespace of the module user. If you must export
296try to use @EXPORT_OK in preference to @EXPORT and avoid short or
297common symbol names to reduce the risk of name clashes.
298
299Generally anything not exported is still accessible from outside the
1fef88e7 300module using the ModuleName::item_name (or $blessed_ref-E<gt>method)
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301syntax. By convention you can use a leading underscore on names to
302informally indicate that they are 'internal' and not for public use.
303
304(It is actually possible to get private functions by saying:
305
306 my $subref = sub { ... };
307 &$subref;
308
309But there's no way to call that directly as a method, since a method
310must have a name in the symbol table.)
311
312As a general rule, if the module is trying to be object oriented
313then export nothing. If it's just a collection of functions then
314@EXPORT_OK anything but use @EXPORT with caution.
315
316Other module design guidelines can be found in L<perlmod>.
317
318=head2 Specialised Import Lists
319
320If the first entry in an import list begins with !, : or / then the
321list is treated as a series of specifications which either add to or
322delete from the list of names to import. They are processed left to
323right. Specifications are in the form:
324
325 [!]name This name only
326 [!]:DEFAULT All names in @EXPORT
327 [!]:tag All names in $EXPORT_TAGS{tag} anonymous list
328 [!]/pattern/ All names in @EXPORT and @EXPORT_OK which match
329
330A leading ! indicates that matching names should be deleted from the
331list of names to import. If the first specification is a deletion it
332is treated as though preceded by :DEFAULT. If you just want to import
333extra names in addition to the default set you will still need to
334include :DEFAULT explicitly.
335
336e.g., Module.pm defines:
337
338 @EXPORT = qw(A1 A2 A3 A4 A5);
339 @EXPORT_OK = qw(B1 B2 B3 B4 B5);
340 %EXPORT_TAGS = (T1 => [qw(A1 A2 B1 B2)], T2 => [qw(A1 A2 B3 B4)]);
341
342 Note that you cannot use tags in @EXPORT or @EXPORT_OK.
343 Names in EXPORT_TAGS must also appear in @EXPORT or @EXPORT_OK.
344
345An application using Module can say something like:
346
347 use Module qw(:DEFAULT :T2 !B3 A3);
348
349Other examples include:
350
351 use Socket qw(!/^[AP]F_/ !SOMAXCONN !SOL_SOCKET);
352 use POSIX qw(:errno_h :termios_h !TCSADRAIN !/^EXIT/);
353
354Remember that most patterns (using //) will need to be anchored
355with a leading ^, e.g., C</^EXIT/> rather than C</EXIT/>.
356
357You can say C<BEGIN { $Exporter::Verbose=1 }> to see how the
358specifications are being processed and what is actually being imported
359into modules.
360
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361=head2 Exporting without using Export's import method
362
363Exporter has a special method, 'export_to_level' which is used in situations
364where you can't directly call Export's import method. The export_to_level
365method looks like:
366
367MyPackage->export_to_level($where_to_export, @what_to_export);
368
369where $where_to_export is an integer telling how far up the calling stack
370to export your symbols, and @what_to_export is an array telling what
371symbols *to* export (usually this is @_).
372
373For example, suppose that you have a module, A, which already has an
374import function:
375
376package A;
377
378@ISA = qw(Exporter);
379@EXPORT_OK = qw ($b);
380
381sub import
382{
383 $A::b = 1; # not a very useful import method
384}
385
386and you want to Export symbol $A::b back to the module that called
387package A. Since Exporter relies on the import method to work, via
388inheritance, as it stands Exporter::import() will never get called.
389Instead, say the following:
390
391package A;
392@ISA = qw(Exporter);
393@EXPORT_OK = qw ($b);
394
395sub import
396{
397 $A::b = 1;
398 A->export_to_level(1, @_);
399}
400
401This will export the symbols one level 'above' the current package - ie: to
402the program or module that used package A.
403
404Note: Be careful not to modify '@_' at all before you call export_to_level
405- or people using your package will get very unexplained results!
406
407
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408=head2 Module Version Checking
409
410The Exporter module will convert an attempt to import a number from a
1fef88e7 411module into a call to $module_name-E<gt>require_version($value). This can
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412be used to validate that the version of the module being used is
413greater than or equal to the required version.
414
415The Exporter module supplies a default require_version method which
416checks the value of $VERSION in the exporting module.
417
418Since the default require_version method treats the $VERSION number as
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419a simple numeric value it will regard version 1.10 as lower than
4201.9. For this reason it is strongly recommended that you use numbers
421with at least two decimal places, e.g., 1.09.
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422
423=head2 Managing Unknown Symbols
424
425In some situations you may want to prevent certain symbols from being
426exported. Typically this applies to extensions which have functions
427or constants that may not exist on some systems.
428
429The names of any symbols that cannot be exported should be listed
430in the C<@EXPORT_FAIL> array.
431
7a2e2cd6 432If a module attempts to import any of these symbols the Exporter
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433will give the module an opportunity to handle the situation before
434generating an error. The Exporter will call an export_fail method
435with a list of the failed symbols:
436
437 @failed_symbols = $module_name->export_fail(@failed_symbols);
438
439If the export_fail method returns an empty list then no error is
440recorded and all the requested symbols are exported. If the returned
441list is not empty then an error is generated for each symbol and the
442export fails. The Exporter provides a default export_fail method which
443simply returns the list unchanged.
444
445Uses for the export_fail method include giving better error messages
446for some symbols and performing lazy architectural checks (put more
447symbols into @EXPORT_FAIL by default and then take them out if someone
448actually tries to use them and an expensive check shows that they are
449usable on that platform).
450
451=head2 Tag Handling Utility Functions
452
453Since the symbols listed within %EXPORT_TAGS must also appear in either
454@EXPORT or @EXPORT_OK, two utility functions are provided which allow
455you to easily add tagged sets of symbols to @EXPORT or @EXPORT_OK:
456
457 %EXPORT_TAGS = (foo => [qw(aa bb cc)], bar => [qw(aa cc dd)]);
458
459 Exporter::export_tags('foo'); # add aa, bb and cc to @EXPORT
460 Exporter::export_ok_tags('bar'); # add aa, cc and dd to @EXPORT_OK
461
462Any names which are not tags are added to @EXPORT or @EXPORT_OK
d5e40bcc 463unchanged but will trigger a warning (with C<-w>) to avoid misspelt tags
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464names being silently added to @EXPORT or @EXPORT_OK. Future versions
465may make this a fatal error.
466
467=cut