package Exporter;
-=head1 Comments
-
-If the first entry in an import list begins with !, : or / then the
-list is treated as a series of specifications which either add to or
-delete from the list of names to import. They are processed left to
-right. Specifications are in the form:
-
- [!]name This name only
- [!]:DEFAULT All names in @EXPORT
- [!]:tag All names in $EXPORT_TAGS{tag} anonymous list
- [!]/pattern/ All names in @EXPORT and @EXPORT_OK which match
-
-A leading ! indicates that matching names should be deleted from the
-list of names to import. If the first specification is a deletion it
-is treated as though preceded by :DEFAULT. If you just want to import
-extra names in addition to the default set you will still need to
-include :DEFAULT explicitly.
-
-e.g., Module.pm defines:
-
- @EXPORT = qw(A1 A2 A3 A4 A5);
- @EXPORT_OK = qw(B1 B2 B3 B4 B5);
- %EXPORT_TAGS = (T1 => [qw(A1 A2 B1 B2)], T2 => [qw(A1 A2 B3 B4)]);
-
- Note that you cannot use tags in @EXPORT or @EXPORT_OK.
- Names in EXPORT_TAGS must also appear in @EXPORT or @EXPORT_OK.
-
-Application says:
-
- use Module qw(:DEFAULT :T2 !B3 A3);
- use Socket qw(!/^[AP]F_/ !SOMAXCONN !SOL_SOCKET);
- use POSIX qw(/^S_/ acos asin atan /^E/ !/^EXIT/);
-
-You can set C<$Exporter::Verbose=1;> to see how the specifications are
-being processed and what is actually being imported into modules.
-
-=head2 Module Version Checking
-
-The Exporter module will convert an attempt to import a number from a
-module into a call to $module_name->require_version($value). This can
-be used to validate that the version of the module being used is
-greater than or equal to the required version.
-
-The Exporter module supplies a default require_version method which
-checks the value of $VERSION in the exporting module.
-
-=cut
-
require 5.001;
-$ExportLevel = 0;
-$Verbose = 0;
+#
+# We go to a lot of trouble not to 'require Carp' at file scope,
+# because Carp requires Exporter, and something has to give.
+#
-require Carp;
+$ExportLevel = 0;
+$Verbose = 0 unless $Verbose;
sub export {
# First make import warnings look like they're coming from the "use".
local $SIG{__WARN__} = sub {
my $text = shift;
- $text =~ s/ at \S*Exporter.pm line \d+.\n//;
- local $Carp::CarpLevel = 1; # ignore package calling us too.
- Carp::carp($text);
+ if ($text =~ s/ at \S*Exporter.pm line \d+.*\n//) {
+ require Carp;
+ local $Carp::CarpLevel = 1; # ignore package calling us too.
+ Carp::carp($text);
+ }
+ else {
+ warn $text;
+ }
};
local $SIG{__DIE__} = sub {
+ require Carp;
+ local $Carp::CarpLevel = 1; # ignore package calling us too.
Carp::croak("$_[0]Illegal null symbol in \@${1}::EXPORT")
if $_[0] =~ /^Unable to create sub named "(.*?)::"/;
};
- my $pkg = shift;
- my $callpkg = shift;
- my @imports = @_;
- my($type, $sym);
- *exports = \@{"${pkg}::EXPORT"};
+ my($pkg, $callpkg, @imports) = @_;
+ my($type, $sym, $oops);
+ *exports = *{"${pkg}::EXPORT"};
+
if (@imports) {
- my $oops;
- *exports = \%{"${pkg}::EXPORT"};
if (!%exports) {
grep(s/^&//, @exports);
- @exports{@exports} = (1) x @exports;
- foreach $extra (@{"${pkg}::EXPORT_OK"}) {
- $exports{$extra} = 1;
+ @exports{@exports} = (1) x @exports;
+ my $ok = \@{"${pkg}::EXPORT_OK"};
+ if (@$ok) {
+ grep(s/^&//, @$ok);
+ @exports{@$ok} = (1) x @$ok;
}
}
if ($imports[0] =~ m#^[/!:]#){
- my(@allexports) = keys %exports;
my $tagsref = \%{"${pkg}::EXPORT_TAGS"};
my $tagdata;
my %imports;
+ my($remove, $spec, @names, @allexports);
# negated first item implies starting with default set:
- unshift(@imports, ':DEFAULT') if $imports[0] =~ m/^!/;
- foreach (@imports){
- my(@names);
- my($mode,$spec) = m/^(!)?(.*)/;
- $mode = '+' unless defined $mode;
-
- @names = ($spec); # default, maybe overridden below
+ unshift @imports, ':DEFAULT' if $imports[0] =~ m/^!/;
+ foreach $spec (@imports){
+ $remove = $spec =~ s/^!//;
- if ($spec =~ m:^/(.*)/$:){
- my $patn = $1;
- @names = grep(/$patn/, @allexports); # XXX anchor by default?
- }
- elsif ($spec =~ m#^:(.*)# and $tagsref){
- if ($1 eq 'DEFAULT'){
+ if ($spec =~ s/^://){
+ if ($spec eq 'DEFAULT'){
@names = @exports;
}
- elsif ($tagsref and $tagdata = $tagsref->{$1}) {
+ elsif ($tagdata = $tagsref->{$spec}) {
@names = @$tagdata;
}
+ else {
+ warn qq["$spec" is not defined in %${pkg}::EXPORT_TAGS];
+ ++$oops;
+ next;
+ }
+ }
+ elsif ($spec =~ m:^/(.*)/$:){
+ my $patn = $1;
+ @allexports = keys %exports unless @allexports; # only do keys once
+ @names = grep(/$patn/, @allexports); # not anchored by default
+ }
+ else {
+ @names = ($spec); # is a normal symbol name
}
- warn "Import Mode $mode, Spec $spec, Names @names\n" if $Verbose;
- if ($mode eq '!') {
- map {delete $imports{$_}} @names; # delete @imports{@names} would be handy :-)
+ warn "Import ".($remove ? "del":"add").": @names "
+ if $Verbose;
+
+ if ($remove) {
+ foreach $sym (@names) { delete $imports{$sym} }
}
else {
- @imports{@names} = (1) x @names;
+ @imports{@names} = (1) x @names;
}
}
@imports = keys %imports;
@imports = @exports;
last;
}
+ # We need a way to emulate 'use Foo ()' but still
+ # allow an easy version check: "use Foo 1.23, ''";
+ if (@imports == 2 and !$imports[1]) {
+ @imports = ();
+ last;
+ }
} elsif ($sym !~ s/^&// || !$exports{$sym}) {
- warn qq["$sym" is not exported by the $pkg module ],
- "at $callfile line $callline\n";
+ warn qq["$sym" is not exported by the $pkg module];
$oops++;
- next;
}
}
}
- Carp::croak("Can't continue with import errors.\n") if $oops;
+ if ($oops) {
+ require Carp;
+ Carp::croak("Can't continue after import errors");
+ }
}
else {
@imports = @exports;
}
- warn "Importing from $pkg into $callpkg: ",
- join(", ",@imports),"\n" if ($Verbose && @imports);
+
+ *fail = *{"${pkg}::EXPORT_FAIL"};
+ if (@fail) {
+ if (!%fail) {
+ # Build cache of symbols. Optimise the lookup by adding
+ # barewords twice... both with and without a leading &.
+ # (Technique could be applied to %exports cache at cost of memory)
+ my @expanded = map { /^\w/ ? ($_, '&'.$_) : $_ } @fail;
+ warn "${pkg}::EXPORT_FAIL cached: @expanded" if $Verbose;
+ @fail{@expanded} = (1) x @expanded;
+ }
+ my @failed;
+ foreach $sym (@imports) { push(@failed, $sym) if $fail{$sym} }
+ if (@failed) {
+ @failed = $pkg->export_fail(@failed);
+ foreach $sym (@failed) {
+ warn qq["$sym" is not implemented by the $pkg module ],
+ "on this architecture";
+ }
+ if (@failed) {
+ require Carp;
+ Carp::croak("Can't continue after import errors");
+ }
+ }
+ }
+
+ warn "Importing into $callpkg from $pkg: ",
+ join(", ",sort @imports) if $Verbose;
+
foreach $sym (@imports) {
- $type = '&';
- $type = $1 if $sym =~ s/^(\W)//;
+ # shortcut for the common case of no type character
+ (*{"${callpkg}::$sym"} = \&{"${pkg}::$sym"}, next)
+ unless $sym =~ s/^(\W)//;
+ $type = $1;
*{"${callpkg}::$sym"} =
$type eq '&' ? \&{"${pkg}::$sym"} :
$type eq '$' ? \${"${pkg}::$sym"} :
$type eq '@' ? \@{"${pkg}::$sym"} :
$type eq '%' ? \%{"${pkg}::$sym"} :
$type eq '*' ? *{"${pkg}::$sym"} :
- warn "Can't export symbol: $type$sym\n";
+ do { require Carp; Carp::croak("Can't export symbol: $type$sym") };
}
-};
+}
sub import {
- local ($callpkg, $callfile, $callline) = caller($ExportLevel);
my $pkg = shift;
+ my $callpkg = caller($ExportLevel);
export $pkg, $callpkg, @_;
}
-sub export_tags {
- my ($pkg) = caller;
- *tags = \%{"${pkg}::EXPORT_TAGS"};
- push(@{"${pkg}::EXPORT"},
- map {$tags{$_} ? @{$tags{$_}} : $_} @_ ? @_ : keys %tags);
+
+# Utility functions
+
+sub _push_tags {
+ my($pkg, $var, $syms) = @_;
+ my $nontag;
+ *export_tags = \%{"${pkg}::EXPORT_TAGS"};
+ push(@{"${pkg}::$var"},
+ map { $export_tags{$_} ? @{$export_tags{$_}} : scalar(++$nontag,$_) }
+ (@$syms) ? @$syms : keys %export_tags);
+ if ($nontag and $^W) {
+ # This may change to a die one day
+ require Carp;
+ Carp::carp("Some names are not tags");
+ }
+}
+
+sub export_tags { _push_tags((caller)[0], "EXPORT", \@_) }
+sub export_ok_tags { _push_tags((caller)[0], "EXPORT_OK", \@_) }
+
+
+# Default methods
+
+sub export_fail {
+ my $self = shift;
+ @_;
}
sub require_version {
my($self, $wanted) = @_;
my $pkg = ref $self || $self;
- my $version = ${"${pkg}::VERSION"} || "(undef)";
- Carp::croak("$pkg $wanted required--this is only version $version")
- if $version < $wanted;
+ my $version = ${"${pkg}::VERSION"};
+ if (!$version or $version < $wanted) {
+ $version ||= "(undef)";
+ my $file = $INC{"$pkg.pm"};
+ $file &&= " ($file)";
+ require Carp;
+ Carp::croak("$pkg $wanted required--this is only version $version$file")
+ }
$version;
}
1;
+
+# A simple self test harness. Change 'require Carp' to 'use Carp ()' for testing.
+# package main; eval(join('',<DATA>)) or die $@ unless caller;
+__END__
+package Test;
+$INC{'Exporter.pm'} = 1;
+@ISA = qw(Exporter);
+@EXPORT = qw(A1 A2 A3 A4 A5);
+@EXPORT_OK = qw(B1 B2 B3 B4 B5);
+%EXPORT_TAGS = (T1=>[qw(A1 A2 B1 B2)], T2=>[qw(A1 A2 B3 B4)], T3=>[qw(X3)]);
+@EXPORT_FAIL = qw(B4);
+Exporter::export_ok_tags('T3', 'unknown_tag');
+sub export_fail {
+ map { "Test::$_" } @_ # edit symbols just as an example
+}
+
+package main;
+$Exporter::Verbose = 1;
+#import Test;
+#import Test qw(X3); # export ok via export_ok_tags()
+#import Test qw(:T1 !A2 /5/ !/3/ B5);
+import Test qw(:T2 !B4);
+import Test qw(:T2); # should fail
+1;
+
+=head1 NAME
+
+Exporter - Implements default import method for modules
+
+=head1 SYNOPSIS
+
+In module ModuleName.pm:
+
+ package ModuleName;
+ require Exporter;
+ @ISA = qw(Exporter);
+
+ @EXPORT = qw(...); # symbols to export by default
+ @EXPORT_OK = qw(...); # symbols to export on request
+ %EXPORT_TAGS = tag => [...]; # define names for sets of symbols
+
+In other files which wish to use ModuleName:
+
+ use ModuleName; # import default symbols into my package
+
+ use ModuleName qw(...); # import listed symbols into my package
+
+ use ModuleName (); # do not import any symbols
+
+=head1 DESCRIPTION
+
+The Exporter module implements a default C<import> method which
+many modules choose to inherit rather than implement their own.
+
+Perl automatically calls the C<import> method when processing a
+C<use> statement for a module. Modules and C<use> are documented
+in L<perlfunc> and L<perlmod>. Understanding the concept of
+modules and how the C<use> statement operates is important to
+understanding the Exporter.
+
+=head2 Selecting What To Export
+
+Do B<not> export method names!
+
+Do B<not> export anything else by default without a good reason!
+
+Exports pollute the namespace of the module user. If you must export
+try to use @EXPORT_OK in preference to @EXPORT and avoid short or
+common symbol names to reduce the risk of name clashes.
+
+Generally anything not exported is still accessible from outside the
+module using the ModuleName::item_name (or $blessed_ref-E<gt>method)
+syntax. By convention you can use a leading underscore on names to
+informally indicate that they are 'internal' and not for public use.
+
+(It is actually possible to get private functions by saying:
+
+ my $subref = sub { ... };
+ &$subref;
+
+But there's no way to call that directly as a method, since a method
+must have a name in the symbol table.)
+
+As a general rule, if the module is trying to be object oriented
+then export nothing. If it's just a collection of functions then
+@EXPORT_OK anything but use @EXPORT with caution.
+
+Other module design guidelines can be found in L<perlmod>.
+
+=head2 Specialised Import Lists
+
+If the first entry in an import list begins with !, : or / then the
+list is treated as a series of specifications which either add to or
+delete from the list of names to import. They are processed left to
+right. Specifications are in the form:
+
+ [!]name This name only
+ [!]:DEFAULT All names in @EXPORT
+ [!]:tag All names in $EXPORT_TAGS{tag} anonymous list
+ [!]/pattern/ All names in @EXPORT and @EXPORT_OK which match
+
+A leading ! indicates that matching names should be deleted from the
+list of names to import. If the first specification is a deletion it
+is treated as though preceded by :DEFAULT. If you just want to import
+extra names in addition to the default set you will still need to
+include :DEFAULT explicitly.
+
+e.g., Module.pm defines:
+
+ @EXPORT = qw(A1 A2 A3 A4 A5);
+ @EXPORT_OK = qw(B1 B2 B3 B4 B5);
+ %EXPORT_TAGS = (T1 => [qw(A1 A2 B1 B2)], T2 => [qw(A1 A2 B3 B4)]);
+
+ Note that you cannot use tags in @EXPORT or @EXPORT_OK.
+ Names in EXPORT_TAGS must also appear in @EXPORT or @EXPORT_OK.
+
+An application using Module can say something like:
+
+ use Module qw(:DEFAULT :T2 !B3 A3);
+
+Other examples include:
+
+ use Socket qw(!/^[AP]F_/ !SOMAXCONN !SOL_SOCKET);
+ use POSIX qw(:errno_h :termios_h !TCSADRAIN !/^EXIT/);
+
+Remember that most patterns (using //) will need to be anchored
+with a leading ^, e.g., C</^EXIT/> rather than C</EXIT/>.
+
+You can say C<BEGIN { $Exporter::Verbose=1 }> to see how the
+specifications are being processed and what is actually being imported
+into modules.
+
+=head2 Module Version Checking
+
+The Exporter module will convert an attempt to import a number from a
+module into a call to $module_name-E<gt>require_version($value). This can
+be used to validate that the version of the module being used is
+greater than or equal to the required version.
+
+The Exporter module supplies a default require_version method which
+checks the value of $VERSION in the exporting module.
+
+Since the default require_version method treats the $VERSION number as
+a simple numeric value it will regard version 1.10 as lower than
+1.9. For this reason it is strongly recommended that you use numbers
+with at least two decimal places, e.g., 1.09.
+
+=head2 Managing Unknown Symbols
+
+In some situations you may want to prevent certain symbols from being
+exported. Typically this applies to extensions which have functions
+or constants that may not exist on some systems.
+
+The names of any symbols that cannot be exported should be listed
+in the C<@EXPORT_FAIL> array.
+
+If a module attempts to import any of these symbols the Exporter will
+will give the module an opportunity to handle the situation before
+generating an error. The Exporter will call an export_fail method
+with a list of the failed symbols:
+
+ @failed_symbols = $module_name->export_fail(@failed_symbols);
+
+If the export_fail method returns an empty list then no error is
+recorded and all the requested symbols are exported. If the returned
+list is not empty then an error is generated for each symbol and the
+export fails. The Exporter provides a default export_fail method which
+simply returns the list unchanged.
+
+Uses for the export_fail method include giving better error messages
+for some symbols and performing lazy architectural checks (put more
+symbols into @EXPORT_FAIL by default and then take them out if someone
+actually tries to use them and an expensive check shows that they are
+usable on that platform).
+
+=head2 Tag Handling Utility Functions
+
+Since the symbols listed within %EXPORT_TAGS must also appear in either
+@EXPORT or @EXPORT_OK, two utility functions are provided which allow
+you to easily add tagged sets of symbols to @EXPORT or @EXPORT_OK:
+
+ %EXPORT_TAGS = (foo => [qw(aa bb cc)], bar => [qw(aa cc dd)]);
+
+ Exporter::export_tags('foo'); # add aa, bb and cc to @EXPORT
+ Exporter::export_ok_tags('bar'); # add aa, cc and dd to @EXPORT_OK
+
+Any names which are not tags are added to @EXPORT or @EXPORT_OK
+unchanged but will trigger a warning (with C<-w>) to avoid misspelt tags
+names being silently added to @EXPORT or @EXPORT_OK. Future versions
+may make this a fatal error.
+
+=cut
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