X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FMoose%2FExporter.pm;h=b32f30279605d18433f277e3b196971c55d10291;hb=9398581271f50b3d7bf4be076d23e278eee9cbc7;hp=9c333778dceccd5db97e7384d7bbd411f767ec06;hpb=24fb5d6529b0afc6cf9289a2d964ed83f524f1f1;p=gitmo%2FMoose.git diff --git a/lib/Moose/Exporter.pm b/lib/Moose/Exporter.pm index 9c33377..b32f302 100644 --- a/lib/Moose/Exporter.pm +++ b/lib/Moose/Exporter.pm @@ -3,123 +3,948 @@ package Moose::Exporter; use strict; use warnings; +use Class::Load qw(is_class_loaded); use Class::MOP; -use namespace::clean 0.08 (); -use Sub::Exporter; +use List::MoreUtils qw( first_index uniq ); +use Moose::Util::MetaRole; +use Scalar::Util qw(reftype); +use Sub::Exporter 0.980; +use Sub::Name qw(subname); +my %EXPORT_SPEC; -sub get_caller { - # 1 extra level because it's called by import so there's a layer - # of indirection - my $offset = 1; +sub setup_import_methods { + my ( $class, %args ) = @_; - return - ( ref $_[1] && defined $_[1]->{into} ) ? $_[1]->{into} - : ( ref $_[1] && defined $_[1]->{into_level} ) - ? caller( $offset + $_[1]->{into_level} ) - : caller($offset); + $args{exporting_package} ||= caller(); + + $class->build_import_methods( + %args, + install => [qw(import unimport init_meta)] + ); } -my %EXPORT_SPEC; +# A reminder to intrepid Moose hackers +# there may be more than one level of exporter +# don't make doy cry. -- perigrin + sub build_import_methods { - my $class = shift; - my %args = @_; + my ( $class, %args ) = @_; + + my $exporting_package = $args{exporting_package} ||= caller(); - my $exporting_package = caller(); + my $meta_lookup = $args{meta_lookup} || sub { Class::MOP::class_of(shift) }; $EXPORT_SPEC{$exporting_package} = \%args; - my ( $exporter, $exported ) - = $class->_build_exporter( exporting_package => $exporting_package, - %args ); + my @exports_from = $class->_follow_also($exporting_package); + + my $export_recorder = {}; + my $is_reexport = {}; + + my $exports = $class->_make_sub_exporter_params( + [ $exporting_package, @exports_from ], + $export_recorder, + $is_reexport, + $args{meta_lookup}, # so that we don't pass through the default + ); + + my $exporter = $class->_make_exporter( + $exports, + $is_reexport, + $meta_lookup, + ); + + my %methods; + $methods{import} = $class->_make_import_sub( + $exporting_package, + $exporter, + \@exports_from, + $is_reexport, + $meta_lookup, + ); + + $methods{unimport} = $class->_make_unimport_sub( + $exporting_package, + $exports, + $export_recorder, + $is_reexport, + $meta_lookup, + ); + + $methods{init_meta} = $class->_make_init_meta( + $exporting_package, + \%args, + $meta_lookup, + ); + + my $package = Class::MOP::Package->initialize($exporting_package); + for my $to_install ( @{ $args{install} || [] } ) { + my $symbol = '&' . $to_install; + next + unless $methods{$to_install} + && !$package->has_package_symbol($symbol); + $package->add_package_symbol( $symbol, $methods{$to_install} ); + } + + return ( $methods{import}, $methods{unimport}, $methods{init_meta} ); +} + +sub _make_exporter { + my ($class, $exports, $is_reexport, $meta_lookup) = @_; + + return Sub::Exporter::build_exporter( + { + exports => $exports, + groups => { default => [':all'] }, + installer => sub { + my ($arg, $to_export) = @_; + my $meta = $meta_lookup->($arg->{into}); + + goto &Sub::Exporter::default_installer unless $meta; + + # don't overwrite existing symbols with our magically flagged + # version of it if we would install the same sub that's already + # in the importer + + my @filtered_to_export; + my %installed; + for (my $i = 0; $i < @{ $to_export }; $i += 2) { + my ($as, $cv) = @{ $to_export }[$i, $i + 1]; + + next if !ref($as) + && $meta->has_package_symbol('&' . $as) + && $meta->get_package_symbol('&' . $as) == $cv; + + push @filtered_to_export, $as, $cv; + $installed{$as} = 1 unless ref $as; + } + + Sub::Exporter::default_installer($arg, \@filtered_to_export); + + for my $name ( keys %{$is_reexport} ) { + no strict 'refs'; + no warnings 'once'; + next unless exists $installed{$name}; + _flag_as_reexport( \*{ join q{::}, $arg->{into}, $name } ); + } + }, + } + ); +} + +{ + my $seen = {}; + + sub _follow_also { + my $class = shift; + my $exporting_package = shift; + + local %$seen = ( $exporting_package => 1 ); + + return uniq( _follow_also_real($exporting_package) ); + } + + sub _follow_also_real { + my $exporting_package = shift; + + if ( !exists $EXPORT_SPEC{$exporting_package} ) { + my $loaded = is_class_loaded($exporting_package); + + die "Package in also ($exporting_package) does not seem to " + . "use Moose::Exporter" + . ( $loaded ? "" : " (is it loaded?)" ); + } + + my $also = $EXPORT_SPEC{$exporting_package}{also}; + + return unless defined $also; + + my @also = ref $also ? @{$also} : $also; + + for my $package (@also) { + die + "Circular reference in 'also' parameter to Moose::Exporter between $exporting_package and $package" + if $seen->{$package}; + + $seen->{$package} = 1; + } + + return map { $_, _follow_also_real($_) } @also; + } +} + +sub _parse_trait_aliases { + my $class = shift; + my ($package, $aliases) = @_; + + my @ret; + for my $alias (@$aliases) { + my $name; + if (ref($alias)) { + reftype($alias) eq 'ARRAY' + or Moose->throw_error(reftype($alias) . " references are not " + . "valid arguments to the 'trait_aliases' " + . "option"); + + ($alias, $name) = @$alias; + } + else { + ($name = $alias) =~ s/.*:://; + } + push @ret, subname "${package}::${name}" => sub () { $alias }; + } + + return @ret; +} + +sub _make_sub_exporter_params { + my $class = shift; + my $packages = shift; + my $export_recorder = shift; + my $is_reexport = shift; + my $meta_lookup_override = shift; + + my %exports; + my $current_meta_lookup; - my $import = sub { - my $caller = Moose::Exporter->get_caller(@_); + for my $package ( @{$packages} ) { + my $args = $EXPORT_SPEC{$package} + or die "The $package package does not use Moose::Exporter\n"; - # this works because both pragmas set $^H (see perldoc perlvar) - # which affects the current compilation - i.e. the file who use'd - # us - which is why we don't need to do anything special to make - # it affect that file rather than this one (which is already compiled) + $current_meta_lookup = $meta_lookup_override || $args->{meta_lookup}; + $meta_lookup_override = $current_meta_lookup; + + my $meta_lookup = $current_meta_lookup + || sub { Class::MOP::class_of(shift) }; + + for my $name ( @{ $args->{with_meta} } ) { + my $sub = $class->_sub_from_package( $package, $name ) + or next; + + my $fq_name = $package . '::' . $name; + + $exports{$name} = $class->_make_wrapped_sub_with_meta( + $fq_name, + $sub, + $export_recorder, + $meta_lookup, + ) unless exists $exports{$name}; + } + + for my $name ( @{ $args->{with_caller} } ) { + my $sub = $class->_sub_from_package( $package, $name ) + or next; + + my $fq_name = $package . '::' . $name; + + $exports{$name} = $class->_make_wrapped_sub( + $fq_name, + $sub, + $export_recorder, + ) unless exists $exports{$name}; + } + + my @extra_exports = $class->_parse_trait_aliases( + $package, $args->{trait_aliases}, + ); + for my $name ( @{ $args->{as_is} }, @extra_exports ) { + my ( $sub, $coderef_name ); + + if ( ref $name ) { + $sub = $name; + + my $coderef_pkg; + ( $coderef_pkg, $coderef_name ) + = Class::MOP::get_code_info($name); + + if ( $coderef_pkg ne $package ) { + $is_reexport->{$coderef_name} = 1; + } + } + else { + $sub = $class->_sub_from_package( $package, $name ) + or next; + + $coderef_name = $name; + } + + $export_recorder->{$sub} = 1; + + $exports{$coderef_name} = sub { $sub } + unless exists $exports{$coderef_name}; + } + } + + return \%exports; +} + +sub _sub_from_package { + my $sclass = shift; + my $package = shift; + my $name = shift; + + my $sub = do { + no strict 'refs'; + \&{ $package . '::' . $name }; + }; + + return $sub if defined &$sub; + + Carp::cluck "Trying to export undefined sub ${package}::${name}"; + + return; +} + +our $CALLER; + +sub _make_wrapped_sub { + my $self = shift; + my $fq_name = shift; + my $sub = shift; + my $export_recorder = shift; + + # We need to set the package at import time, so that when + # package Foo imports has(), we capture "Foo" as the + # package. This lets other packages call Foo::has() and get + # the right package. This is done for backwards compatibility + # with existing production code, not because this is a good + # idea ;) + return sub { + my $caller = $CALLER; + + my $wrapper = $self->_curry_wrapper( $sub, $fq_name, $caller ); + + my $sub = subname( $fq_name => $wrapper ); + + $export_recorder->{$sub} = 1; + + return $sub; + }; +} + +sub _make_wrapped_sub_with_meta { + my $self = shift; + my $fq_name = shift; + my $sub = shift; + my $export_recorder = shift; + my $meta_lookup = shift; + + return sub { + my $caller = $CALLER; + + my $wrapper = $self->_late_curry_wrapper( + $sub, $fq_name, + $meta_lookup => $caller + ); + + my $sub = subname( $fq_name => $wrapper ); + + $export_recorder->{$sub} = 1; + + return $sub; + }; +} + +sub _curry_wrapper { + my $class = shift; + my $sub = shift; + my $fq_name = shift; + my @extra = @_; + + my $wrapper = sub { $sub->( @extra, @_ ) }; + if ( my $proto = prototype $sub ) { + + # XXX - Perl's prototype sucks. Use & to make set_prototype + # ignore the fact that we're passing "private variables" + &Scalar::Util::set_prototype( $wrapper, $proto ); + } + return $wrapper; +} + +sub _late_curry_wrapper { + my $class = shift; + my $sub = shift; + my $fq_name = shift; + my $extra = shift; + my @ex_args = @_; + + my $wrapper = sub { + + # resolve curried arguments at runtime via this closure + my @curry = ( $extra->(@ex_args) ); + return $sub->( @curry, @_ ); + }; + + if ( my $proto = prototype $sub ) { + + # XXX - Perl's prototype sucks. Use & to make set_prototype + # ignore the fact that we're passing "private variables" + &Scalar::Util::set_prototype( $wrapper, $proto ); + } + return $wrapper; +} + +sub _make_import_sub { + shift; + my $exporting_package = shift; + my $exporter = shift; + my $exports_from = shift; + my $is_reexport = shift; + my $meta_lookup = shift; + + return sub { + + # I think we could use Sub::Exporter's collector feature + # to do this, but that would be rather gross, since that + # feature isn't really designed to return a value to the + # caller of the exporter sub. + # + # Also, this makes sure we preserve backwards compat for + # _get_caller, so it always sees the arguments in the + # expected order. + my $traits; + ( $traits, @_ ) = _strip_traits(@_); + + my $metaclass; + ( $metaclass, @_ ) = _strip_metaclass(@_); + $metaclass + = Moose::Util::resolve_metaclass_alias( 'Class' => $metaclass ) + if defined $metaclass && length $metaclass; + + my $meta_name; + ( $meta_name, @_ ) = _strip_meta_name(@_); + + # Normally we could look at $_[0], but in some weird cases + # (involving goto &Moose::import), $_[0] ends as something + # else (like Squirrel). + my $class = $exporting_package; + + $CALLER = _get_caller(@_); + + # this works because both pragmas set $^H (see perldoc + # perlvar) which affects the current compilation - + # i.e. the file who use'd us - which is why we don't need + # to do anything special to make it affect that file + # rather than this one (which is already compiled) strict->import; warnings->import; - # we should never export to main - if ( $caller eq 'main' ) { - warn - qq{$exporting_package does not export its sugar to the 'main' package.\n}; - return; + my $did_init_meta; + for my $c ( grep { $_->can('init_meta') } $class, @{$exports_from} ) { + + # init_meta can apply a role, which when loaded uses + # Moose::Exporter, which in turn sets $CALLER, so we need + # to protect against that. + local $CALLER = $CALLER; + $c->init_meta( + for_class => $CALLER, + metaclass => $metaclass, + meta_name => $meta_name, + ); + $did_init_meta = 1; } - if ( $exporting_package->can('_init_meta') ) { - $exporting_package->_init_meta( - for_class => $caller, - %{ $args{init_meta_args} || {} } + { + # The metaroles will use Moose::Role, which in turn uses + # Moose::Exporter, which in turn sets $CALLER, so we need + # to protect against that. + local $CALLER = $CALLER; + _apply_metaroles( + $CALLER, + [$class, @$exports_from], + $meta_lookup ); } - goto $exporter; - }; + if ( $did_init_meta && @{$traits} ) { + + # The traits will use Moose::Role, which in turn uses + # Moose::Exporter, which in turn sets $CALLER, so we need + # to protect against that. + local $CALLER = $CALLER; + _apply_meta_traits( $CALLER, $traits, $meta_lookup ); + } + elsif ( @{$traits} ) { + require Moose; + Moose->throw_error( + "Cannot provide traits when $class does not have an init_meta() method" + ); + } - # [12:24] yes. that's horrible. I know. but it should work. - # - # This will hopefully be replaced in the future once - # namespace::clean has an API for it. - my $unimport = sub { - @_ = ( 'namespace::clean', @{ $exported } ); + my ( undef, @args ) = @_; + my $extra = shift @args if ref $args[0] eq 'HASH'; - goto &namespace::clean::import; + $extra ||= {}; + if ( !$extra->{into} ) { + $extra->{into_level} ||= 0; + $extra->{into_level}++; + } + + $class->$exporter( $extra, @args ); }; +} - no strict 'refs'; - *{ $exporting_package . '::import' } = $import; - *{ $exporting_package . '::unimport' } = $unimport; +sub _strip_traits { + my $idx = first_index { ( $_ || '' ) eq '-traits' } @_; + + return ( [], @_ ) unless $idx >= 0 && $#_ >= $idx + 1; + + my $traits = $_[ $idx + 1 ]; + + splice @_, $idx, 2; + + $traits = [$traits] unless ref $traits; + + return ( $traits, @_ ); } -my %EXPORTED; -sub _build_exporter { - my $class = shift; - my %args = @_; +sub _strip_metaclass { + my $idx = first_index { ( $_ || '' ) eq '-metaclass' } @_; - my $exporting_package = $args{exporting_package}; + return ( undef, @_ ) unless $idx >= 0 && $#_ >= $idx + 1; - my @exported_names; - my %exports; - for my $name ( @{ $args{with_caller} } ) { - my $sub = do { no strict 'refs'; \&{ $exporting_package . '::' . $name } }; + my $metaclass = $_[ $idx + 1 ]; - my $wrapped = Class::MOP::subname( - $exporting_package . '::' . $name => sub { $sub->( scalar caller(), @_ ) } ); + splice @_, $idx, 2; - $exports{$name} = sub { $wrapped }; + return ( $metaclass, @_ ); +} - push @exported_names, $name; - } +sub _strip_meta_name { + my $idx = first_index { ( $_ || '' ) eq '-meta_name' } @_; + + return ( 'meta', @_ ) unless $idx >= 0 && $#_ >= $idx + 1; + + my $meta_name = $_[ $idx + 1 ]; + + splice @_, $idx, 2; + + return ( $meta_name, @_ ); +} + +sub _apply_metaroles { + my ($class, $exports_from, $meta_lookup) = @_; + + my $metaroles = _collect_metaroles($exports_from); + my $base_class_roles = delete $metaroles->{base_class_roles}; + + my $meta = $meta_lookup->($class); + # for instance, Moose.pm uses Moose::Util::TypeConstraints + return unless $meta; + + Moose::Util::MetaRole::apply_metaroles( + for => $meta, + %$metaroles, + ) if keys %$metaroles; + + Moose::Util::MetaRole::apply_base_class_roles( + for => $meta, + roles => $base_class_roles, + ) if $meta->isa('Class::MOP::Class') + && $base_class_roles && @$base_class_roles; +} + +sub _collect_metaroles { + my ($exports_from) = @_; + + my @old_style_role_types = map { "${_}_roles" } qw( + metaclass + attribute_metaclass + method_metaclass + wrapped_method_metaclass + instance_metaclass + constructor_class + destructor_class + error_class + ); + + my %class_metaroles; + my %role_metaroles; + my @base_class_roles; + my %old_style_roles; - for my $name ( @{ $args{as_is} } ) { - my $sub; + for my $exporter (@$exports_from) { + my $data = $EXPORT_SPEC{$exporter}; - if ( ref $name ) { - $sub = $name; - $name = ( Class::MOP::get_code_info($name) )[1]; + if (exists $data->{class_metaroles}) { + for my $type (keys %{ $data->{class_metaroles} }) { + push @{ $class_metaroles{$type} ||= [] }, + @{ $data->{class_metaroles}{$type} }; + } + } + + if (exists $data->{role_metaroles}) { + for my $type (keys %{ $data->{role_metaroles} }) { + push @{ $role_metaroles{$type} ||= [] }, + @{ $data->{role_metaroles}{$type} }; + } } - else { - $sub = do { no strict 'refs'; \&{ $exporting_package . '::' . $name } }; - push @exported_names, $name; + if (exists $data->{base_class_roles}) { + push @base_class_roles, @{ $data->{base_class_roles} }; } - $exports{$name} = sub { $sub }; + for my $type (@old_style_role_types) { + if (exists $data->{$type}) { + push @{ $old_style_roles{$type} ||= [] }, + @{ $data->{$type} }; + } + } } - my $exporter = Sub::Exporter::build_exporter( - { - exports => \%exports, - groups => { default => [':all'] } + return { + (keys(%class_metaroles) + ? (class_metaroles => \%class_metaroles) + : ()), + (keys(%role_metaroles) + ? (role_metaroles => \%role_metaroles) + : ()), + (@base_class_roles + ? (base_class_roles => \@base_class_roles) + : ()), + %old_style_roles, + }; +} + +sub _apply_meta_traits { + my ( $class, $traits, $meta_lookup ) = @_; + + return unless @{$traits}; + + my $meta = $meta_lookup->($class); + + my $type = ( split /::/, ref $meta )[-1] + or Moose->throw_error( + 'Cannot determine metaclass type for trait application . Meta isa ' + . ref $meta ); + + my @resolved_traits = map { + ref $_ + ? $_ + : Moose::Util::resolve_metatrait_alias( $type => $_ ) + } @$traits; + + return unless @resolved_traits; + + my %args = ( for => $class ); + + if ( $meta->isa('Moose::Meta::Role') ) { + $args{role_metaroles} = { role => \@resolved_traits }; + } + else { + $args{class_metaroles} = { class => \@resolved_traits }; + } + + Moose::Util::MetaRole::apply_metaroles(%args); +} + +sub _get_caller { + + # 1 extra level because it's called by import so there's a layer + # of indirection + my $offset = 1; + + return + ( ref $_[1] && defined $_[1]->{into} ) ? $_[1]->{into} + : ( ref $_[1] && defined $_[1]->{into_level} ) + ? caller( $offset + $_[1]->{into_level} ) + : caller($offset); +} + +sub _make_unimport_sub { + shift; + my $exporting_package = shift; + my $exports = shift; + my $export_recorder = shift; + my $is_reexport = shift; + my $meta_lookup = shift; + + return sub { + my $caller = scalar caller(); + Moose::Exporter->_remove_keywords( + $caller, + [ keys %{$exports} ], + $export_recorder, + $is_reexport, + ); + }; +} + +sub _remove_keywords { + shift; + my $package = shift; + my $keywords = shift; + my $recorded_exports = shift; + my $is_reexport = shift; + + no strict 'refs'; + + foreach my $name ( @{$keywords} ) { + if ( defined &{ $package . '::' . $name } ) { + my $sub = \&{ $package . '::' . $name }; + + # make sure it is from us + next unless $recorded_exports->{$sub}; + + if ( $is_reexport->{$name} ) { + no strict 'refs'; + next + unless _export_is_flagged( + \*{ join q{::} => $package, $name } ); + } + + # and if it is from us, then undef the slot + delete ${ $package . '::' }{$name}; } - ); + } +} + +# maintain this for now for backcompat +# make sure to return a sub to install in the same circumstances as previously +# but this functionality now happens at the end of ->import +sub _make_init_meta { + shift; + my $class = shift; + my $args = shift; + my $meta_lookup = shift; + + my %old_style_roles; + for my $role ( + map {"${_}_roles"} + qw( + metaclass + attribute_metaclass + method_metaclass + wrapped_method_metaclass + instance_metaclass + constructor_class + destructor_class + error_class + ) + ) { + $old_style_roles{$role} = $args->{$role} + if exists $args->{$role}; + } + + my %base_class_roles; + %base_class_roles = ( roles => $args->{base_class_roles} ) + if exists $args->{base_class_roles}; + + my %new_style_roles = map { $_ => $args->{$_} } + grep { exists $args->{$_} } qw( class_metaroles role_metaroles ); + + return unless %new_style_roles || %old_style_roles || %base_class_roles; + + return sub { }; +} - return $exporter, \@exported_names; +sub import { + strict->import; + warnings->import; } 1; + +# ABSTRACT: make an import() and unimport() just like Moose.pm + +__END__ + +=head1 SYNOPSIS + + package MyApp::Moose; + + use Moose (); + use Moose::Exporter; + + Moose::Exporter->setup_import_methods( + with_meta => [ 'has_rw', 'sugar2' ], + as_is => [ 'sugar3', \&Some::Random::thing ], + also => 'Moose', + ); + + sub has_rw { + my ( $meta, $name, %options ) = @_; + $meta->add_attribute( + $name, + is => 'rw', + %options, + ); + } + + # then later ... + package MyApp::User; + + use MyApp::Moose; + + has 'name'; + has_rw 'size'; + thing; + + no MyApp::Moose; + +=head1 DESCRIPTION + +This module encapsulates the exporting of sugar functions in a +C-like manner. It does this by building custom C and +C methods for your module, based on a spec you provide. + +It also lets you "stack" Moose-alike modules so you can export Moose's sugar +as well as your own, along with sugar from any random C module, as +long as they all use C. This feature exists to let you bundle +a set of MooseX modules into a policy module that developers can use directly +instead of using Moose itself. + +To simplify writing exporter modules, C also imports +C and C into your exporter module, as well as into +modules that use it. + +=head1 METHODS + +This module provides two public methods: + +=over 4 + +=item B<< Moose::Exporter->setup_import_methods(...) >> + +When you call this method, C builds custom C and +C methods for your module. The C method +will export the functions you specify, and can also re-export functions +exported by some other module (like C). If you pass any parameters +for L, the C method will also call +C and +C as needed, after making +sure the metaclass is initialized. + +The C method cleans the caller's namespace of all the exported +functions. This includes any functions you re-export from other +packages. However, if the consumer of your package also imports those +functions from the original package, they will I be cleaned. + +Note that if any of these methods already exist, they will not be +overridden, you will have to use C to get the +coderef that would be installed. + +This method accepts the following parameters: + +=over 8 + +=item * with_meta => [ ... ] + +This list of function I will be wrapped and then exported. The +wrapper will pass the metaclass object for the caller as its first argument. + +Many sugar functions will need to use this metaclass object to do something to +the calling package. + +=item * as_is => [ ... ] + +This list of function names or sub references will be exported as-is. You can +identify a subroutine by reference, which is handy to re-export some other +module's functions directly by reference (C<\&Some::Package::function>). + +If you do export some other package's function, this function will never be +removed by the C method. The reason for this is we cannot know if +the caller I explicitly imported the sub themselves, and therefore wants +to keep it. + +=item * trait_aliases => [ ... ] + +This is a list of package names which should have shortened aliases exported, +similar to the functionality of L. Each element in the list can be +either a package name, in which case the export will be named as the last +namespace component of the package, or an arrayref, whose first element is the +package to alias to, and second element is the alias to export. + +=item * also => $name or \@names + +This is a list of modules which contain functions that the caller +wants to export. These modules must also use C. The +most common use case will be to export the functions from C. +Functions specified by C or C take precedence over +functions exported by modules specified by C, so that a module +can selectively override functions exported by another module. + +C also makes sure all these functions get removed +when C is called. + +=item * meta_lookup => sub { ... } + +This is a function which will be called to provide the metaclass +to be operated upon by the exporter. This is an advanced feature +intended for use by package generator modules in the vein of +L in order to simplify reusing sugar +from other modules that use C. This function is +used, for example, to select the metaclass to bind to functions +that are exported using the C option. + +This function will receive one parameter: the class name into which +the sugar is being exported. The default implementation is: + + sub { Class::MOP::class_of(shift) } + +Accordingly, this function is expected to return a metaclass. + +=back + +You can also provide parameters for C +and C. Specifically, valid parameters +are "class_metaroles", "role_metaroles", and "base_class_roles". + +=item B<< Moose::Exporter->build_import_methods(...) >> + +Returns two code refs, one for C and one for C. + +Accepts the additional C option, which accepts an arrayref of method +names to install into your exporting package. The valid options are C +and C. Calling C is equivalent +to calling C with C<< install => [qw(import unimport)] >> +except that it doesn't also return the methods. + +The C method is built using L. This means that it can +take a hashref of the form C<< { into => $package } >> to specify the package +it operates on. + +Used by C. + +=back + +=head1 IMPORTING AND init_meta + +If you want to set an alternative base object class or metaclass class, see +above for details on how this module can call L for +you. + +If you want to do something that is not supported by this module, simply +define an C method in your class. The C method that +C generates for you will call this method (if it exists). It +will always pass the caller to this method via the C parameter. + +Most of the time, your C method will probably just call C<< +Moose->init_meta >> to do the real work: + + sub init_meta { + shift; # our class name + return Moose->init_meta( @_, metaclass => 'My::Metaclass' ); + } + +=head1 METACLASS TRAITS + +The C method generated by C will allow the +user of your module to specify metaclass traits in a C<-traits> +parameter passed as part of the import: + + use Moose -traits => 'My::Meta::Trait'; + + use Moose -traits => [ 'My::Meta::Trait', 'My::Other::Trait' ]; + +These traits will be applied to the caller's metaclass +instance. Providing traits for an exporting class that does not create +a metaclass for the caller is an error. + +=head1 BUGS + +See L for details on reporting bugs. + +=cut