Moose::Exporter - make an import() and unimport() just like Moose.pm

  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;

  sub init_meta {
      shift; # our class name
      return Moose->init_meta( @_, metaclass => 'My::Metaclass' );
  }

  my ( $import, $unimport, $init_meta ) =
      Moose::Exporter->build_import_methods( ... );

  sub import {
     my $class = shift;

     ...

     $class->$import(...);

     ...
  }

  sub unimport { goto &$unimport }

  sub init_meta {
     my $class = shift;

     ...

     $class->$init_meta(...);

     ...
  }

  use Moose -traits => 'My::Meta::Trait';

  use Moose -traits => [ 'My::Meta::Trait', 'My::Other::Trait' ];

package Moose::Exporter;
BEGIN {
  $Moose::Exporter::AUTHORITY = 'cpan:STEVAN';
}
BEGIN {
  $Moose::Exporter::VERSION = '2.0010';
}

use strict;
use warnings;

use Class::MOP;
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 setup_import_methods {
    my ( $class, %args ) = @_;

    $args{exporting_package} ||= caller();

    $class->build_import_methods(
        %args,
        install => [qw(import unimport init_meta)]
    );
}

sub build_import_methods {
    my ( $class, %args ) = @_;

    my $exporting_package = $args{exporting_package} ||= caller();

    $EXPORT_SPEC{$exporting_package} = \%args;

    my @exports_from = $class->_follow_also($exporting_package);

    my $export_recorder = {};
    my $is_reexport     = {};

    my $exports = $class->_make_sub_exporter_params(
        [ @exports_from, $exporting_package ],
        $export_recorder,
        $is_reexport,
    );

    my $exporter = $class->_make_exporter($exports, $is_reexport);

    my %methods;
    $methods{import} = $class->_make_import_sub(
        $exporting_package,
        $exporter,
        \@exports_from,
        $is_reexport
    );

    $methods{unimport} = $class->_make_unimport_sub(
        $exporting_package,
        $exports,
        $export_recorder,
        $is_reexport
    );

    $methods{init_meta} = $class->_make_init_meta(
        $exporting_package,
        \%args
    );

    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) = @_;

    return Sub::Exporter::build_exporter(
        {
            exports   => $exports,
            groups    => { default => [':all'] },
            installer => sub {
                my ($arg, $to_export) = @_;
                my $meta = Class::MOP::class_of($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 reverse uniq( _follow_also_real($exporting_package) );
    }

    sub _follow_also_real {
        my $exporting_package = shift;

        if ( !exists $EXPORT_SPEC{$exporting_package} ) {
            my $loaded = Class::MOP::is_class_loaded($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 @also, 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 %exports;

    for my $package ( @{$packages} ) {
        my $args = $EXPORT_SPEC{$package}
            or die "The $package package does not use Moose::Exporter\n";

        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,
            );
        }

        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,
            );
        }

        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};
        }
    }

    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;

    return sub {
        my $caller = $CALLER;

        my $wrapper = $self->_late_curry_wrapper(
            $sub, $fq_name,
            sub { Class::MOP::class_of(shift) } => $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;

    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;

        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 ( $did_init_meta && @{$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, $traits );
        }
        elsif ( @{$traits} ) {
            require Moose;
            Moose->throw_error(
                "Cannot provide traits when $class does not have an init_meta() method"
            );
        }

        my ( undef, @args ) = @_;
        my $extra = shift @args if ref $args[0] eq 'HASH';

        $extra ||= {};
        if ( !$extra->{into} ) {
            $extra->{into_level} ||= 0;
            $extra->{into_level}++;
        }

        $class->$exporter( $extra, @args );
    };
}

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, @_ );
}

sub _strip_metaclass {
    my $idx = first_index { ( $_ || '' ) eq '-metaclass' } @_;

    return ( undef, @_ ) unless $idx >= 0 && $#_ >= $idx + 1;

    my $metaclass = $_[ $idx + 1 ];

    splice @_, $idx, 2;

    return ( $metaclass, @_ );
}

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_meta_traits {
    my ( $class, $traits ) = @_;

    return unless @{$traits};

    my $meta = Class::MOP::class_of($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;

    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};
        }
    }
}

sub _make_init_meta {
    shift;
    my $class = shift;
    my $args  = 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 {
        shift;
        my %options = @_;

        return unless Class::MOP::class_of( $options{for_class} );

        if ( %new_style_roles || %old_style_roles ) {
            Moose::Util::MetaRole::apply_metaroles(
                for => $options{for_class},
                %new_style_roles,
                %old_style_roles,
            );
        }

        Moose::Util::MetaRole::apply_base_class_roles(
            for_class => $options{for_class},
            %base_class_roles,
            )
            if Class::MOP::class_of( $options{for_class} )
                ->isa('Moose::Meta::Class');

        return Class::MOP::class_of( $options{for_class} );
    };
}

sub import {
    strict->import;
    warnings->import;
}

1;

# ABSTRACT: make an import() and unimport() just like Moose.pm

__END__