Ticket #3654: bug.cc

#include <boost/optional.hpp>
#include <boost/python.hpp>
#include <boost/python/detail/wrap_python.hpp>
#include <string>

template <typename T, typename TfromPy>
struct object_from_python
{
  object_from_python() {
    boost::python::converter::registry::insert
      (&TfromPy::convertible, &TfromPy::construct,
       boost::python::type_id<T>());
  }
};

template <typename T, typename TtoPy, typename TfromPy>
struct register_python_conversion
{
  register_python_conversion() {
    boost::python::to_python_converter<T, TtoPy>();
    object_from_python<T, TfromPy>();
  }
};

template <typename T>
struct register_optional_to_python : public boost::noncopyable
{
  struct optional_to_python
  {
    static PyObject * convert(const boost::optional<T>& value)
    {
      return boost::python::incref
        (value ? boost::python::to_python_value<T>()(*value) :
                 boost::python::detail::none());
    }
  };

  struct optional_from_python
  {
    static void * convertible(PyObject * source)
    {
      using namespace boost::python::converter;

      if (source == Py_None)
        return source;

      const registration& converters(registered<T>::converters);

      if (implicit_rvalue_convertible_from_python(source, converters)) {
        rvalue_from_python_stage1_data data =
          rvalue_from_python_stage1(source, converters);
        return rvalue_from_python_stage2(source, data, converters);
      }
      return NULL;
    }

    static void construct(PyObject * source,
                          boost::python::converter::rvalue_from_python_stage1_data * data)
    {
      using namespace boost::python::converter;

      void * const storage =
        reinterpret_cast<rvalue_from_python_storage<T> *>(data)->storage.bytes;

      if (data->convertible == source)      // == None
        new (storage) boost::optional<T>(); // A Boost uninitialized value
      else
        new (storage) boost::optional<T>(*reinterpret_cast<T *>(data->convertible));

      data->convertible = storage;
    }
  };

  explicit register_optional_to_python() {
    register_python_conversion<boost::optional<T>,
                               optional_to_python, optional_from_python>();
  }
};

class amount_t
{
public:
  std::string hello() { return "Hello, world!"; }
};

class annotation_t
{
public:
  boost::optional<amount_t> price;
};

boost::optional<amount_t> py_price(annotation_t& ann) {
  return ann.price;
}

BOOST_PYTHON_MODULE(bug)
{
  using namespace boost::python;

  class_< annotation_t > ("Annotation")
    .add_property("price", make_getter(&annotation_t::price))
    .add_property("price2", py_price)
    ;

  register_optional_to_python<amount_t>();
}