package MooseX::UndefTolerant::Constructor;
use Moose::Role;

if ( $Moose::VERSION < 1.9900 ) {
    around('_generate_slot_initializer', sub {
        my $orig = shift;
        my $self = shift;

        # note the key in the params may not match the attr name.
        my $key_name = $self->_attributes->[$_[0]]->init_arg;

        # insert a line of code at the start of the initializer,
        # clearing the param if it's undefined.

        if (defined $key_name)
        {
            # leave the value unscathed if the attribute's type constraint can
            # handle undef (or doesn't have one, which implicitly means it can)
            my $type_constraint = $self->_attributes->[$_[0]]->type_constraint;
            if ($type_constraint and not $type_constraint->check(undef))
            {
                my $tolerant_code =
                    qq# delete \$params->{'$key_name'} unless # .
                    qq# exists \$params->{'$key_name'} && defined \$params->{'$key_name'};\n#;

                return $tolerant_code . $self->$orig(@_);
            }
        }

        return $self->$orig(@_);
});

no Moose::Role;
1;
