X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FExporter.pm;h=343b9fbd17462ccde1998504d3f5c5f2d2e4e5d9;hb=79dd614e1e8c3b0e4ed35016e6971240b606da64;hp=dce6909b187b1f052f217693ccae9a15a72c09b6;hpb=a0d0e21ea6ea90a22318550944fe6cb09ae10cda;p=p5sagit%2Fp5-mst-13.2.git diff --git a/lib/Exporter.pm b/lib/Exporter.pm index dce6909..343b9fb 100644 --- a/lib/Exporter.pm +++ b/lib/Exporter.pm @@ -1,57 +1,377 @@ package Exporter; -require 5.000; +require 5.001; $ExportLevel = 0; +$Verbose = 0 unless $Verbose; + +require Carp; sub export { - my $pack = shift; - my $callpack = shift; - my @imports = @_; - *exports = \@{"${pack}::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); + }; + local $SIG{__DIE__} = sub { + Carp::croak("$_[0]Illegal null symbol in \@${1}::EXPORT") + if $_[0] =~ /^Unable to create sub named "(.*?)::"/; + }; + + my($pkg, $callpkg, @imports) = @_; + my($type, $sym, $oops); + *exports = *{"${pkg}::EXPORT"}; + if (@imports) { - my $oops; - my $type; - *exports = \%{"${pack}::EXPORT"}; if (!%exports) { grep(s/^&//, @exports); - @exports{@exports} = (1) x @exports; - foreach $extra (@{"${pack}::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 $tagsref = \%{"${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 $spec (@imports){ + $remove = $spec =~ s/^!//; + + if ($spec =~ s/^://){ + if ($spec eq 'DEFAULT'){ + @names = @exports; + } + elsif ($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 = ($spec); # is a normal symbol name + } + + warn "Import ".($remove ? "del":"add").": @names " + if $Verbose; + + if ($remove) { + foreach $sym (@names) { delete $imports{$sym} } + } + 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 $pack module ], - "at $callfile line $callline\n"; + if ($sym =~ m/^\d/) { + $pkg->require_version($sym); + # If the version number was the only thing specified + # then we should act as if nothing was specified: + if (@imports == 1) { + @imports = @exports; + last; + } + } elsif ($sym !~ s/^&// || !$exports{$sym}) { + warn qq["$sym" is not exported by the $pkg module]; $oops++; - next; } } } - die "Can't continue with import errors.\n" if $oops; + Carp::croak("Can't continue after import errors") if $oops; } else { @imports = @exports; } + + *fail = *{"${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"; + } + Carp::croak("Can't continue after import errors") if @failed; + } + } + + warn "Importing into $callpkg from $pkg: ", + join(", ",sort @imports) if $Verbose; + foreach $sym (@imports) { - $type = '&'; - $type = $1 if $sym =~ s/^(\W)//; - *{"${callpack}::$sym"} = - $type eq '&' ? \&{"${pack}::$sym"} : - $type eq '$' ? \${"${pack}::$sym"} : - $type eq '@' ? \@{"${pack}::$sym"} : - $type eq '%' ? \%{"${pack}::$sym"} : - $type eq '*' ? *{"${pack}::$sym"} : - warn "Can't export symbol: $type$sym\n"; + # 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"} : + Carp::croak("Can't export symbol: $type$sym"); } -}; +} sub import { - local ($callpack, $callfile, $callline) = caller($ExportLevel); - my $pack = shift; - export $pack, $callpack, @_; + my $pkg = shift; + my $callpkg = caller($ExportLevel); + export $pkg, $callpkg, @_; +} + + +# Utility functions + +sub _push_tags { + my($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); + # This may change to a die one day + Carp::carp("Some names are not tags") if $nontag and $^W; +} + +sub export_tags { _push_tags((caller)[0], "EXPORT", \@_) } +sub export_ok_tags { _push_tags((caller)[0], "EXPORT_OK", \@_) } + + +# Default methods + +sub export_fail { + @_; +} + +sub require_version { + my($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; + $version; } 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 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 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->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. + +=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 rather than C. + +You can say C 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. + +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