Should datetime.date convert to std::chrono::sys_days rather than std::chrono::sys_time?

[kcajf]

Right now, datetime.date converts to a std::chrono::sys_time with zero hour/minute/second.. component.
This is wrong, because datetime.date represents a calendar date, not a time point. A more suitable conversion would be to std::chrono::sys_days, with the following code:

#pragma once
#include <chrono>

#include <pybind11/chrono.h>
#include <pybind11/pybind11.h>

namespace PYBIND11_NAMESPACE
{
    namespace detail
    {
        template <>
        struct type_caster<std::chrono::sys_days>
        {
        public:

            PYBIND11_TYPE_CASTER(std::chrono::sys_days, const_name("datetime.date"));

            bool load(handle src, bool)
            {
                // Lazy initialise the PyDateTime import
                if (!PyDateTimeAPI)
                {
                    PyDateTime_IMPORT;
                }
                if (PyDate_Check(src.ptr()))
                {
                    uint8_t day = PyDateTime_GET_DAY(src.ptr());
                    uint8_t month = PyDateTime_GET_MONTH(src.ptr());
                    uint16_t year = PyDateTime_GET_YEAR(src.ptr());
                    value = std::chrono::sys_days{std::chrono::year_month_day{
                        std::chrono::year{year}, std::chrono::month{month}, std::chrono::day{day}}};
                    return true;
                }
                else
                {
                    return false;
                }
            }

            static handle
            cast(std::chrono::sys_days src, return_value_policy /* policy */, handle /* parent */)
            {
                // Lazy initialise the PyDateTime import
                if (!PyDateTimeAPI)
                {
                    PyDateTime_IMPORT;
                }
                std::chrono::year_month_day ymd = std::chrono::year_month_day{src};
                return PyDate_FromDate((int)ymd.year(), (uint)ymd.month(), (uint)ymd.day());
            }
        };
    } // namespace detail
} // namespace PYBIND11_NAMESPACE