X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FExporter.pm;h=adc843b9f5cac78a8849e08aaedd05212c8da29a;hb=4fddf32b02405fe6f8dbd7b7013cd63eb6be0196;hp=ca1ff3547cde603643b9b21271da5dd29eb9cad6;hpb=f06db76b9e41859439aeadb79feb6c603ee741ff;p=p5sagit%2Fp5-mst-13.2.git diff --git a/lib/Exporter.pm b/lib/Exporter.pm index ca1ff35..adc843b 100644 --- a/lib/Exporter.pm +++ b/lib/Exporter.pm @@ -1,6 +1,165 @@ package Exporter; -=head1 Comments +require 5.001; + +$ExportLevel = 0; +$Verbose ||= 0; + +sub export_to_level { + require Exporter::Heavy; + goto &heavy_export_to_level; +} + +sub export { + require Exporter::Heavy; + goto &heavy_export; +} + +sub export_tags { + require Exporter::Heavy; + _push_tags((caller)[0], "EXPORT", \@_); +} + +sub export_ok_tags { + require Exporter::Heavy; + _push_tags((caller)[0], "EXPORT_OK", \@_); +} + +sub import { + my $pkg = shift; + my $callpkg = caller($ExportLevel); + *exports = *{"$pkg\::EXPORT"}; + # We *need* to treat @{"$pkg\::EXPORT_FAIL"} since Carp uses it :-( + *fail = *{"$pkg\::EXPORT_FAIL"}; + return export $pkg, $callpkg, @_ + if $Verbose or $Debug or @fail > 1; + my $args = @_ or @_ = @exports; + + if ($args and not %exports) { + foreach my $sym (@exports, @{"$pkg\::EXPORT_OK"}) { + $sym =~ s/^&//; + $exports{$sym} = 1; + } + } + if ($Verbose or $Debug + or grep {/\W/ or $args and not exists $exports{$_} + or @fail and $_ eq $fail[0] + or (@{"$pkg\::EXPORT_OK"} + and $_ eq ${"$pkg\::EXPORT_OK"}[0])} @_) { + return export $pkg, $callpkg, ($args ? @_ : ()); + } + #local $SIG{__WARN__} = sub {require Carp; goto &Carp::carp}; + local $SIG{__WARN__} = + sub {require Carp; local $Carp::CarpLevel = 1; &Carp::carp}; + foreach $sym (@_) { + # shortcut for the common case of no type character + *{"$callpkg\::$sym"} = \&{"$pkg\::$sym"}; + } +} + +1; + +# A simple self test harness. Change 'require Carp' to 'use Carp ()' for testing. +# package main; eval(join('',)) 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 method which +many modules choose to inherit rather than implement their own. + +Perl automatically calls the C method when processing a +C statement for a module. Modules and C are documented +in L and L. Understanding the concept of +modules and how the C statement operates is important to +understanding the Exporter. + +=head2 How to Export + +The arrays C<@EXPORT> and C<@EXPORT_OK> in a module hold lists of +symbols that are going to be exported into the users name space by +default, or which they can request to be exported, respectively. The +symbols can represent functions, scalars, arrays, hashes, or typeglobs. +The symbols must be given by full name with the exception that the +ampersand in front of a function is optional, e.g. + + @EXPORT = qw(afunc $scalar @array); # afunc is a function + @EXPORT_OK = qw(&bfunc %hash *typeglob); # explicit prefix on &bfunc + +=head2 Selecting What To Export + +Do B export method names! + +Do B 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-Emethod) +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. + +=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 @@ -27,129 +186,127 @@ e.g., Module.pm defines: 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: +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(/^S_/ acos asin atan /^E/ !/^EXIT/); + use POSIX qw(:errno_h :termios_h !TCSADRAIN !/^EXIT/); -You can set C<$Exporter::Verbose=1;> to see how the specifications are -being processed and what is actually being imported into modules. +Remember that most patterns (using //) will need to be anchored +with a leading ^, e.g., C rather than C. -=cut +You can say C to see how the +specifications are being processed and what is actually being imported +into modules. -require 5.001; +=head2 Exporting without using Export's import method -$ExportLevel = 0; -$Verbose = 0; +Exporter has a special method, 'export_to_level' which is used in situations +where you can't directly call Export's import method. The export_to_level +method looks like: -require Carp; +MyPackage->export_to_level($where_to_export, $package, @what_to_export); -sub export { +where $where_to_export is an integer telling how far up the calling stack +to export your symbols, and @what_to_export is an array telling what +symbols *to* export (usually this is @_). The $package argument is +currently unused. - # 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); - }; - - my $pkg = shift; - my $callpkg = shift; - my @imports = @_; - my($type, $sym); - *exports = \@{"${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; - } - } - - if ($imports[0] =~ m#^[/!:]#){ - my(@allexports) = keys %exports; - my $tagsref = \%{"${pkg}::EXPORT_TAGS"}; - my $tagdata; - my %imports; - # 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 - - if ($spec =~ m:^/(.*)/$:){ - my $patn = $1; - @names = grep(/$patn/, @allexports); # XXX anchor by default? - } - elsif ($spec =~ m#^:(.*)# and $tagsref){ - if ($1 eq 'DEFAULT'){ - @names = @exports; - } - elsif ($tagsref and $tagdata = $tagsref->{$1}) { - @names = @$tagdata; - } - } - - warn "Import Mode $mode, Spec $spec, Names @names\n" if $Verbose; - if ($mode eq '!') { - map {delete $imports{$_}} @names; # delete @imports{@names} would be handy :-) - } - else { - @imports{@names} = (1) x @names; - } - } - @imports = keys %imports; - } - - foreach $sym (@imports) { - if (!$exports{$sym}) { - if ($sym !~ s/^&// || !$exports{$sym}) { - warn qq["$sym" is not exported by the $pkg module ], - "at $callfile line $callline\n"; - $oops++; - next; - } - } - } - Carp::croak("Can't continue with import errors.\n") if $oops; - } - else { - @imports = @exports; - } - warn "Importing from $pkg into $callpkg: ", - join(", ",@imports),"\n" if ($Verbose && @imports); - foreach $sym (@imports) { - $type = '&'; - $type = $1 if $sym =~ s/^(\W)//; - *{"${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"; - } -}; +For example, suppose that you have a module, A, which already has an +import function: -sub import { - local ($callpkg, $callfile, $callline) = caller($ExportLevel); - my $pkg = shift; - export $pkg, $callpkg, @_; +package A; + +@ISA = qw(Exporter); +@EXPORT_OK = qw ($b); + +sub import +{ + $A::b = 1; # not a very useful import method } -sub export_tags { - my ($pkg) = caller; - *tags = \%{"${pkg}::EXPORT_TAGS"}; - push(@{"${pkg}::EXPORT"}, - map {$tags{$_} ? @{$tags{$_}} : $_} @_ ? @_ : keys %tags); +and you want to Export symbol $A::b back to the module that called +package A. Since Exporter relies on the import method to work, via +inheritance, as it stands Exporter::import() will never get called. +Instead, say the following: + +package A; +@ISA = qw(Exporter); +@EXPORT_OK = qw ($b); + +sub import +{ + $A::b = 1; + A->export_to_level(1, @_); } -1; +This will export the symbols one level 'above' the current package - ie: to +the program or module that used package A. + +Note: Be careful not to modify '@_' at all before you call export_to_level +- or people using your package will get very unexplained results! + + +=head2 Module Version Checking + +The Exporter module will convert an attempt to import a number from a +module into a call to $module_name-Erequire_version($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 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