export_traits_optional.h

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/** @file
 *  @author Bram de Greve (bram@cocamware.com)
 *  @author Tom De Muer (tom@cocamware.com)
 *
 *  *** BEGIN LICENSE INFORMATION ***
 *  
 *  The contents of this file are subject to the Common Public Attribution License 
 *  Version 1.0 (the "License"); you may not use this file except in compliance with 
 *  the License. You may obtain a copy of the License at 
 *  http://lass.sourceforge.net/cpal-license. The License is based on the 
 *  Mozilla Public License Version 1.1 but Sections 14 and 15 have been added to cover 
 *  use of software over a computer network and provide for limited attribution for 
 *  the Original Developer. In addition, Exhibit A has been modified to be consistent 
 *  with Exhibit B.
 *  
 *  Software distributed under the License is distributed on an "AS IS" basis, WITHOUT 
 *  WARRANTY OF ANY KIND, either express or implied. See the License for the specific 
 *  language governing rights and limitations under the License.
 *  
 *  The Original Code is LASS - Library of Assembled Shared Sources.
 *  
 *  The Initial Developer of the Original Code is Bram de Greve and Tom De Muer.
 *  The Original Developer is the Initial Developer.
 *  
 *  All portions of the code written by the Initial Developer are:
 *  Copyright (C) 2022-2025 the Initial Developer.
 *  All Rights Reserved.
 *  
 *  Contributor(s):
 *
 *  Alternatively, the contents of this file may be used under the terms of the 
 *  GNU General Public License Version 2 or later (the GPL), in which case the 
 *  provisions of GPL are applicable instead of those above.  If you wish to allow use
 *  of your version of this file only under the terms of the GPL and not to allow 
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 *  deleting the provisions above and replace them with the notice and other 
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 *  
 *  *** END LICENSE INFORMATION ***
 */
 
#pragma once
 
#include "python_common.h"
#include "export_traits.h"
 
#include <optional>
 
namespace lass
{
namespace python
{
 
/** Uses None to represent a std::optional without value.
 * 
 *  If None is also a valid value for the type T (such as pointers), then it
 *  will be impossible to differentiate between an unset std::optional, and
 *  a set std::optional with a value for None.
 *
 *  @ingroup PyExportTraits
 */
template <typename T>
struct PyExportTraits< std::optional<T> >
{
    static constexpr const char* py_typing = "T | None";
 
    static PyObject* build(const std::optional<T>& value)
    {
        if (!value)
        {
            Py_RETURN_NONE;
        }
        return PyExportTraits<T>::build(*value);
    }
    static int get(PyObject* obj, std::optional<T>& value)
    {
        if (obj == Py_None)
        {
            value.reset();
            return 0;
        }
        T tmp;
        if (PyExportTraits<T>::get(obj, tmp) != 0)
        {
            return 1;
        }
        value = std::move(tmp);
        return 0;
    }
};
 
 
 
/** MaybeNone<std::optional<T>> type-hints a type as `T | MaybeNone`
 * 
 *  @ingroup PyExportTraits
 *  @sa MaybeNone
 *  @sa PyExportTraitsMaybeNone
 */
template <typename T>
struct PyExportTraits< MaybeNone< std::optional<T> > > : public PyExportTraitsMaybeNone< std::optional<T> >
{
};
 
}
}