Improve the error message of having a plain reference in 'default'

[gitmo/Class-MOP.git] / lib / Class / MOP / Package.pm

package Class::MOP::Package;

use strict;
use warnings;

use Scalar::Util 'blessed';
use Carp         'confess';

our $VERSION   = '0.08';
our $AUTHORITY = 'cpan:STEVAN';

use base 'Class::MOP::Object';

# creation ...

sub initialize {
    my $class        = shift;
    my $package_name = shift;
    # we hand-construct the class 
    # until we can bootstrap it
    no strict 'refs';
    return bless { 
        '$!package'   => $package_name,
        # NOTE:
        # because of issues with the Perl API 
        # to the typeglob in some versions, we 
        # need to just always grab a new 
        # reference to the hash in the accessor. 
        # Ideally we could just store a ref and 
        # it would Just Work, but oh well :\
        '%!namespace' => \undef,
    } => $class;
}

# Attributes

# NOTE:
# all these attribute readers will be bootstrapped 
# away in the Class::MOP bootstrap section

sub name      { $_[0]->{'$!package'}   }
sub namespace { 
    # NOTE:
    # because of issues with the Perl API 
    # to the typeglob in some versions, we 
    # need to just always grab a new 
    # reference to the hash here. Ideally 
    # we could just store a ref and it would
    # Just Work, but oh well :\    
    no strict 'refs';    
    \%{$_[0]->name . '::'} 
}

# utility methods

{
    my %SIGIL_MAP = (
        '$' => 'SCALAR',
        '@' => 'ARRAY',
        '%' => 'HASH',
        '&' => 'CODE',
    );
    
    sub _deconstruct_variable_name {
        my ($self, $variable) = @_;

        (defined $variable)
            || confess "You must pass a variable name";    

        my $sigil = substr($variable, 0, 1, '');

        (defined $sigil)
            || confess "The variable name must include a sigil";    

        (exists $SIGIL_MAP{$sigil})
            || confess "I do not recognize that sigil '$sigil'";    
        
        return ($variable, $sigil, $SIGIL_MAP{$sigil});
    }
}

# Class attributes

# ... these functions have to touch the symbol table itself,.. yuk

sub add_package_symbol {
    my ($self, $variable, $initial_value) = @_;

    my ($name, $sigil, $type) = $self->_deconstruct_variable_name($variable); 

    no strict 'refs';
    no warnings 'redefine', 'misc';    
    *{$self->name . '::' . $name} = ref $initial_value ? $initial_value : \$initial_value;      
}

sub remove_package_glob {
    my ($self, $name) = @_;
    no strict 'refs';        
    delete ${$self->name . '::'}{$name};     
}

# ... these functions deal with stuff on the namespace level

sub has_package_symbol {
    my ($self, $variable) = @_;

    my ($name, $sigil, $type) = $self->_deconstruct_variable_name($variable); 
    
    return 0 unless exists $self->namespace->{$name};   
    
    # FIXME:
    # For some really stupid reason 
    # a typeglob will have a default
    # value of \undef in the SCALAR 
    # slot, so we need to work around
    # this. Which of course means that 
    # if you put \undef in your scalar
    # then this is broken.

    if (ref($self->namespace->{$name}) eq 'SCALAR') {
        return ($type eq 'CODE' ? 1 : 0);
    }
    elsif ($type eq 'SCALAR') {    
        my $val = *{$self->namespace->{$name}}{$type};
        return defined(${$val}) ? 1 : 0;        
    }
    else {
        defined(*{$self->namespace->{$name}}{$type}) ? 1 : 0;
    }
}

sub get_package_symbol {
    my ($self, $variable) = @_;    

    my ($name, $sigil, $type) = $self->_deconstruct_variable_name($variable); 

    $self->add_package_symbol($variable)
        unless exists $self->namespace->{$name};

    if (ref($self->namespace->{$name}) eq 'SCALAR') {
        if ($type eq 'CODE') {
            no strict 'refs';
            return \&{$self->name.'::'.$name};
        }
        else {
            return undef;
        }
    }
    else {
        return *{$self->namespace->{$name}}{$type};
    }
}

sub remove_package_symbol {
    my ($self, $variable) = @_;

    my ($name, $sigil, $type) = $self->_deconstruct_variable_name($variable); 

    # FIXME:
    # no doubt this is grossly inefficient and 
    # could be done much easier and faster in XS

    my ($scalar, $array, $hash, $code);
    if ($type eq 'SCALAR') {
        $array  = $self->get_package_symbol('@' . $name) if $self->has_package_symbol('@' . $name);
        $hash   = $self->get_package_symbol('%' . $name) if $self->has_package_symbol('%' . $name);     
        $code   = $self->get_package_symbol('&' . $name) if $self->has_package_symbol('&' . $name);     
    }
    elsif ($type eq 'ARRAY') {
        $scalar = $self->get_package_symbol('$' . $name) if $self->has_package_symbol('$' . $name);
        $hash   = $self->get_package_symbol('%' . $name) if $self->has_package_symbol('%' . $name);     
        $code   = $self->get_package_symbol('&' . $name) if $self->has_package_symbol('&' . $name);
    }
    elsif ($type eq 'HASH') {
        $scalar = $self->get_package_symbol('$' . $name) if $self->has_package_symbol('$' . $name);
        $array  = $self->get_package_symbol('@' . $name) if $self->has_package_symbol('@' . $name);        
        $code   = $self->get_package_symbol('&' . $name) if $self->has_package_symbol('&' . $name);      
    }
    elsif ($type eq 'CODE') {
        $scalar = $self->get_package_symbol('$' . $name) if $self->has_package_symbol('$' . $name);
        $array  = $self->get_package_symbol('@' . $name) if $self->has_package_symbol('@' . $name);        
        $hash   = $self->get_package_symbol('%' . $name) if $self->has_package_symbol('%' . $name);        
    }    
    else {
        confess "This should never ever ever happen";
    }
        
    $self->remove_package_glob($name);
    
    $self->add_package_symbol(('$' . $name) => $scalar) if defined $scalar;      
    $self->add_package_symbol(('@' . $name) => $array)  if defined $array;    
    $self->add_package_symbol(('%' . $name) => $hash)   if defined $hash;
    $self->add_package_symbol(('&' . $name) => $code)   if defined $code;            
}

sub list_all_package_symbols {
    my ($self, $type_filter) = @_;
    return keys %{$self->namespace} unless defined $type_filter;
    # NOTE:
    # or we can filter based on 
    # type (SCALAR|ARRAY|HASH|CODE)
    my $namespace = $self->namespace;
    return grep { 
        (ref($namespace->{$_})
            ? (ref($namespace->{$_}) eq 'SCALAR' && $type_filter eq 'CODE')
            : (ref(\$namespace->{$_}) eq 'GLOB'
               && defined(*{$namespace->{$_}}{$type_filter})));
    } keys %{$namespace};
}

1;

__END__

=pod

=head1 NAME 

Class::MOP::Package - Package Meta Object

=head1 DESCRIPTION

This is an abstraction of a Perl 5 package, it is a superclass of
L<Class::MOP::Class> and provides all of the symbol table 
introspection methods.

=head1 METHODS

=over 4

=item B<meta>

Returns a metaclass for this package.

=item B<initialize ($package_name)>

This will initialize a Class::MOP::Package instance which represents 
the package of C<$package_name>.

=item B<name>

This is a read-only attribute which returns the package name for the 
given instance.

=item B<namespace>

This returns a HASH reference to the symbol table. The keys of the 
HASH are the symbol names, and the values are typeglob references.

=item B<add_package_symbol ($variable_name, ?$initial_value)>

Given a C<$variable_name>, which must contain a leading sigil, this 
method will create that variable within the package which houses the 
class. It also takes an optional C<$initial_value>, which must be a 
reference of the same type as the sigil of the C<$variable_name> 
implies.

=item B<get_package_symbol ($variable_name)>

This will return a reference to the package variable in 
C<$variable_name>. 

=item B<has_package_symbol ($variable_name)>

Returns true (C<1>) if there is a package variable defined for 
C<$variable_name>, and false (C<0>) otherwise.

=item B<remove_package_symbol ($variable_name)>

This will attempt to remove the package variable at C<$variable_name>.

=item B<remove_package_glob ($glob_name)>

This will attempt to remove the entire typeglob associated with 
C<$glob_name> from the package. 

=item B<list_all_package_symbols (?$type_filter)>

This will list all the glob names associated with the current package. 
By inspecting the globs returned you can discern all the variables in 
the package.

By passing a C<$type_filter>, you can limit the list to only those 
which match the filter (either SCALAR, ARRAY, HASH or CODE).

=back

=head1 AUTHORS

Stevan Little E<lt>stevan@iinteractive.comE<gt>

=head1 COPYRIGHT AND LICENSE

Copyright 2006-2008 by Infinity Interactive, Inc.

L<http://www.iinteractive.com>

This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.

=cut