Make Meta::Method::Constructor easier to subclass

[gitmo/Moose.git] / lib / Moose / Meta / Method / Constructor.pm

package Moose::Meta::Method::Constructor;

use strict;
use warnings;

use Scalar::Util 'blessed', 'weaken', 'looks_like_number';

our $VERSION   = '0.72';
our $AUTHORITY = 'cpan:STEVAN';

use base 'Moose::Meta::Method',
         'Class::MOP::Method::Generated';

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

    my $meta = $options{metaclass};

    (ref $options{options} eq 'HASH')
        || $class->throw_error("You must pass a hash of options", data => $options{options});

    ($options{package_name} && $options{name})
        || $class->throw_error("You must supply the package_name and name parameters $Class::MOP::Method::UPGRADE_ERROR_TEXT");

    my $self = bless {
        # from our superclass
        'body'          => undef, 
        'package_name'  => $options{package_name},
        'name'          => $options{name},
        # specific to this subclass
        'options'       => $options{options},
        'meta_instance' => $meta->get_meta_instance,
        'attributes'    => [ $meta->compute_all_applicable_attributes ],
        # ...
        'associated_metaclass' => $meta,
    } => $class;

    # we don't want this creating
    # a cycle in the code, if not
    # needed
    weaken($self->{'associated_metaclass'});

    $self->initialize_body;

    return $self;
}

sub can_be_inlined {
    my $self      = shift;
    my $metaclass = $self->associated_metaclass;

    my $expected_class = $self->_expected_constructor_class;

    # If any of our parents have been made immutable, we are okay to
    # inline our own new method. The assumption is that an inlined new
    # method provided by a parent does not actually get used by
    # children anyway.
    for my $meta (
        grep { $_->is_immutable }
        map  { ( ref $metaclass )->initialize($_) }
        grep { $_ ne $expected_class }
        $metaclass->linearized_isa
        ) {
        my $transformer = $meta->get_immutable_transformer;

        # This is actually a false positive if we're in a subclass of
        # this class, _and_ the expected class is not overridden (but
        # should be), and the real expected class is actually
        # immutable itself (see Fey::Object::Table for an example of
        # how this can happen). I'm not sure how to actually handle
        # that case, since it's effectively a bug in the subclass (for
        # not overriding _expected_constructor_class).
        return 1 if $transformer->inlined_constructor;
    }

    if ( my $constructor = $metaclass->find_method_by_name( $self->name ) ) {
        my $class = $self->associated_metaclass->name;

        if ( $constructor->body != $expected_class->can('new') ) {
            my $warning
                = "Not inlining a constructor for $class since it is not"
                . " inheriting the default $expected_class constructor\n"
                . "If you are certain you don't need to inline your"
                . " constructor, specify inline_constructor => 0 in your"
                . " call to $class->meta->make_immutable\n";

            $warning .= " (constructor has method modifiers which would be lost if it were inlined)\n"
                if $constructor->isa('Class::MOP::Method::Wrapped');

            warn $warning;

            return 0;
        }
        else {
            return 1;
        }
    }

    # This would be a rather weird case where we have no constructor
    # in the inheritance chain.
    return 1;
}

# This is here so can_be_inlined can be inherited by MooseX modules.
sub _expected_constructor_class {
    return 'Moose::Object';
}

## accessors

sub options       { (shift)->{'options'}       }
sub meta_instance { (shift)->{'meta_instance'} }
sub attributes    { (shift)->{'attributes'}    }

sub associated_metaclass { (shift)->{'associated_metaclass'} }

## method

# this was changed in 0.41, but broke MooseX::Singleton, so try to catch
# any other code using the original broken spelling
sub intialize_body { $_[0]->throw_error("Please correct the spelling of 'intialize_body' to 'initialize_body'") }

sub _generate_params {
  my ($self, $var, $class_var) = @_;
  "my $var = " . $self->_generate_BUILDARGS($class_var, '@_') . ";\n";
}

sub _generate_instance {
  my ($self, $var, $class_var) = @_;
  "my $var = " . $self->meta_instance->inline_create_instance($class_var) 
               . ";\n";
}

sub _generate_slot_initializers {
    my ($self) = @_;
    return (join ";\n" => map {
        $self->_generate_slot_initializer($_)
    } 0 .. (@{$self->attributes} - 1)) . ";\n";
}

sub initialize_body {
    my $self = shift;
    # TODO:
    # the %options should also include a both
    # a call 'initializer' and call 'SUPER::'
    # options, which should cover approx 90%
    # of the possible use cases (even if it
    # requires some adaption on the part of
    # the author, after all, nothing is free)
    my $source = 'sub {';
    $source .= "\n" . 'my $class = shift;';

    $source .= "\n" . 'return $class->Moose::Object::new(@_)';
    $source .= "\n    if \$class ne '" . $self->associated_metaclass->name 
            .  "';\n";

    $source .= $self->_generate_params('$params', '$class');
    $source .= $self->_generate_instance('$instance', '$class');
    $source .= $self->_generate_slot_initializers;

    $source .= $self->_generate_triggers();
    $source .= ";\n" . $self->_generate_BUILDALL();

    $source .= ";\nreturn \$instance";
    $source .= ";\n" . '}';
    warn $source if $self->options->{debug};

    # We need to check if the attribute ->can('type_constraint')
    # since we may be trying to immutabilize a Moose meta class,
    # which in turn has attributes which are Class::MOP::Attribute
    # objects, rather than Moose::Meta::Attribute. And
    # Class::MOP::Attribute attributes have no type constraints.
    # However we need to make sure we leave an undef value there
    # because the inlined code is using the index of the attributes
    # to determine where to find the type constraint

    my $attrs = $self->attributes;

    my @type_constraints = map {
        $_->can('type_constraint') ? $_->type_constraint : undef
    } @$attrs;

    my @type_constraint_bodies = map {
        defined $_ ? $_->_compiled_type_constraint : undef;
    } @type_constraints;

    my $code = $self->_compile_code(
        code => $source,
        environment => {
            '$meta'  => \$self,
            '$attrs' => \$attrs,
            '@type_constraints' => \@type_constraints,
            '@type_constraint_bodies' => \@type_constraint_bodies,
        },
    ) or $self->throw_error("Could not eval the constructor :\n\n$source\n\nbecause :\n\n$@", error => $@, data => $source );
    
    $self->{'body'} = $code;
}

sub _generate_BUILDARGS {
    my ( $self, $class, $args ) = @_;

    my $buildargs = $self->associated_metaclass->find_method_by_name("BUILDARGS");

    if ( $args eq '@_' and ( !$buildargs or $buildargs->body == \&Moose::Object::BUILDARGS ) ) {
        return join("\n",
            'do {',
            $self->_inline_throw_error('"Single parameters to new() must be a HASH ref"', 'data => $_[0]'),
            '    if scalar @_ == 1 && !( defined $_[0] && ref $_[0] eq q{HASH} );',
            '(scalar @_ == 1) ? {%{$_[0]}} : {@_};',
            '}',
        );
    } else {
        return $class . "->BUILDARGS($args)";
    }
}

sub _generate_BUILDALL {
    my $self = shift;
    my @BUILD_calls;
    foreach my $method (reverse $self->associated_metaclass->find_all_methods_by_name('BUILD')) {
        push @BUILD_calls => '$instance->' . $method->{class} . '::BUILD($params)';
    }
    return join ";\n" => @BUILD_calls;
}

sub _generate_triggers {
    my $self = shift;
    my @trigger_calls;
    foreach my $i (0 .. $#{ $self->attributes }) {
        my $attr = $self->attributes->[$i];
        if ($attr->can('has_trigger') && $attr->has_trigger) {
            if (defined(my $init_arg = $attr->init_arg)) {
                push @trigger_calls => (
                    '(exists $params->{\'' . $init_arg . '\'}) && do {' . "\n    "
                    .   '$attrs->[' . $i . ']->trigger->('
                    .       '$instance, ' 
                    .        $self->meta_instance->inline_get_slot_value(
                                 '$instance',
                                 $attr->name,
                             ) 
                             . ', '
                    .        '$attrs->[' . $i . ']'
                    .   ');'
                    ."\n}"
                );
            } 
        }
    }
    return join ";\n" => @trigger_calls;    
}

sub _generate_slot_initializer {
    my $self  = shift;
    my $index = shift;

    my $attr = $self->attributes->[$index];

    my @source = ('## ' . $attr->name);

    my $is_moose = $attr->isa('Moose::Meta::Attribute'); # XXX FIXME

    if ($is_moose && defined($attr->init_arg) && $attr->is_required && !$attr->has_default && !$attr->has_builder) {
        push @source => ('(exists $params->{\'' . $attr->init_arg . '\'}) ' .
                        '|| ' . $self->_inline_throw_error('"Attribute (' . $attr->name . ') is required"') .';');
    }

    if (($attr->has_default || $attr->has_builder) && !($is_moose && $attr->is_lazy)) {

        if ( defined( my $init_arg = $attr->init_arg ) ) {
            push @source => 'if (exists $params->{\'' . $init_arg . '\'}) {';
            push @source => ('my $val = $params->{\'' . $init_arg . '\'};');
            push @source => $self->_generate_type_constraint_and_coercion($attr, $index)
                if $is_moose;
            push @source => $self->_generate_slot_assignment($attr, '$val', $index);
            push @source => "} else {";
        }
            my $default;
            if ( $attr->has_default ) {
                $default = $self->_generate_default_value($attr, $index);
            } 
            else {
               my $builder = $attr->builder;
               $default = '$instance->' . $builder;
            }
            
            push @source => '{'; # wrap this to avoid my $val overwrite warnings
            push @source => ('my $val = ' . $default . ';');
            push @source => $self->_generate_type_constraint_and_coercion($attr, $index)
                if $is_moose; 
            push @source => $self->_generate_slot_assignment($attr, '$val', $index);
            push @source => '}'; # close - wrap this to avoid my $val overrite warnings           

        push @source => "}" if defined $attr->init_arg;
    }
    elsif ( defined( my $init_arg = $attr->init_arg ) ) {
        push @source => '(exists $params->{\'' . $init_arg . '\'}) && do {';

            push @source => ('my $val = $params->{\'' . $init_arg . '\'};');
            if ($is_moose && $attr->has_type_constraint) {
                if ($attr->should_coerce && $attr->type_constraint->has_coercion) {
                    push @source => $self->_generate_type_coercion(
                        $attr, 
                        '$type_constraints[' . $index . ']', 
                        '$val', 
                        '$val'
                    );
                }
                push @source => $self->_generate_type_constraint_check(
                    $attr, 
                    '$type_constraint_bodies[' . $index . ']', 
                    '$type_constraints[' . $index . ']',                     
                    '$val'
                );
            }
            push @source => $self->_generate_slot_assignment($attr, '$val', $index);

        push @source => "}";
    }

    return join "\n" => @source;
}

sub _generate_slot_assignment {
    my ($self, $attr, $value, $index) = @_;

    my $source;
    
    if ($attr->has_initializer) {
        $source = (
            '$attrs->[' . $index . ']->set_initial_value($instance, ' . $value . ');'
        );        
    }
    else {
        $source = (
            $self->meta_instance->inline_set_slot_value(
                '$instance',
                $attr->name,
                $value
            ) . ';'
        );        
    }
    
    my $is_moose = $attr->isa('Moose::Meta::Attribute'); # XXX FIXME        

    if ($is_moose && $attr->is_weak_ref) {
        $source .= (
            "\n" .
            $self->meta_instance->inline_weaken_slot_value(
                '$instance',
                $attr->name
            ) .
            ' if ref ' . $value . ';'
        );
    }

    return $source;
}

sub _generate_type_constraint_and_coercion {
    my ($self, $attr, $index) = @_;
    
    return unless $attr->has_type_constraint;
    
    my @source;
    if ($attr->should_coerce && $attr->type_constraint->has_coercion) {
        push @source => $self->_generate_type_coercion(
            $attr,
            '$type_constraints[' . $index . ']',
            '$val',
            '$val'
        );
    }
    push @source => $self->_generate_type_constraint_check(
        $attr,
        ('$type_constraint_bodies[' . $index . ']'),
        ('$type_constraints[' . $index . ']'),            
        '$val'
    );
    return @source;
}

sub _generate_type_coercion {
    my ($self, $attr, $type_constraint_name, $value_name, $return_value_name) = @_;
    return ($return_value_name . ' = ' . $type_constraint_name .  '->coerce(' . $value_name . ');');
}

sub _generate_type_constraint_check {
    my ($self, $attr, $type_constraint_cv, $type_constraint_obj, $value_name) = @_;
    return (
        $self->_inline_throw_error('"Attribute (' # FIXME add 'dad'
        . $attr->name 
        . ') does not pass the type constraint because: " . ' 
        . $type_constraint_obj . '->get_message(' . $value_name . ')')
        . "\n\t unless " .  $type_constraint_cv . '->(' . $value_name . ');'
    );
}

sub _generate_default_value {
    my ($self, $attr, $index) = @_;
    # NOTE:
    # default values can either be CODE refs
    # in which case we need to call them. Or
    # they can be scalars (strings/numbers)
    # in which case we can just deal with them
    # in the code we eval.
    if ($attr->is_default_a_coderef) {
        return '$attrs->[' . $index . ']->default($instance)';
    }
    else {
        return q{"} . quotemeta( $attr->default ) . q{"};
    }
}

1;

__END__

=pod

=head1 NAME

Moose::Meta::Method::Constructor - Method Meta Object for constructors

=head1 DESCRIPTION

This is a subclass of L<Class::MOP::Method> which handles
constructing an appropriate Constructor methods. This is primarily
used in the making of immutable metaclasses, otherwise it is
not particularly useful.

=head1 METHODS

=over 4

=item B<new>

=item B<can_be_inlined>

=item B<attributes>

=item B<meta_instance>

=item B<options>

=item B<initialize_body>

=item B<associated_metaclass>

=back

=head1 AUTHORS

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

=head1 COPYRIGHT AND LICENSE

Copyright 2006-2009 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