tests/test_native_enum.cpp

#include <pybind11/native_enum.h>

#include "pybind11_tests.h"

#include <typeindex>

namespace test_native_enum {

// https://en.cppreference.com/w/cpp/language/enum

// enum that takes 16 bits
enum smallenum : std::int16_t { a, b, c };

// color may be red (value 0), yellow (value 1), green (value 20), or blue (value 21)
enum color { red, yellow, green = 20, blue };

// altitude may be altitude::high or altitude::low
enum class altitude : char {
    high = 'h',
    low = 'l', // trailing comma only allowed after CWG518
};

enum class flags_uchar : unsigned char { bit0 = 0x1u, bit1 = 0x2u, bit2 = 0x4u };
enum class flags_uint : unsigned int { bit0 = 0x1u, bit1 = 0x2u, bit2 = 0x4u };

enum class export_values { exv0, exv1 };

enum class member_doc { mem0, mem1, mem2 };

struct class_with_enum {
    enum class in_class { one, two };

    in_class nested_value = in_class::one;
};

// https://github.com/protocolbuffers/protobuf/blob/d70b5c5156858132decfdbae0a1103e6a5cb1345/src/google/protobuf/generated_enum_util.h#L52-L53
template <typename T>
struct is_proto_enum : std::false_type {};

enum some_proto_enum : int { Zero, One };

template <>
struct is_proto_enum<some_proto_enum> : std::true_type {};

enum class func_sig_rendering {};

} // namespace test_native_enum

PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
PYBIND11_NAMESPACE_BEGIN(detail)

// Negate this condition to demonstrate "ambiguous template instantiation" compilation error:
#if defined(PYBIND11_HAS_NATIVE_ENUM)
template <typename ProtoEnumType>
struct type_caster_enum_type_enabled<
    ProtoEnumType,
    enable_if_t<test_native_enum::is_proto_enum<ProtoEnumType>::value>> : std::false_type {};
#endif

// https://github.com/pybind/pybind11_protobuf/blob/a50899c2eb604fc5f25deeb8901eff6231b8b3c0/pybind11_protobuf/enum_type_caster.h#L101-L105
template <typename ProtoEnumType>
struct type_caster<ProtoEnumType,
                   detail::enable_if_t<test_native_enum::is_proto_enum<ProtoEnumType>::value>> {
    static handle
    cast(const ProtoEnumType & /*src*/, return_value_policy /*policy*/, handle /*parent*/) {
        return py::none();
    }

    bool load(handle /*src*/, bool /*convert*/) {
        value = static_cast<ProtoEnumType>(0);
        return true;
    }

    PYBIND11_TYPE_CASTER(ProtoEnumType, const_name<ProtoEnumType>());
};

PYBIND11_NAMESPACE_END(detail)
PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)

TEST_SUBMODULE(native_enum, m) {
    using namespace test_native_enum;

    py::native_enum<smallenum>(m, "smallenum", "enum.IntEnum", "doc smallenum")
        .value("a", smallenum::a)
        .value("b", smallenum::b)
        .value("c", smallenum::c)
        .finalize();

    py::native_enum<color>(m, "color", "enum.IntEnum")
        .value("red", color::red)
        .value("yellow", color::yellow)
        .value("green", color::green)
        .value("blue", color::blue)
        .finalize();

    m.def("bind_altitude", [](const py::module_ &mod) {
        py::native_enum<altitude>(mod, "altitude", "enum.Enum")
            .value("high", altitude::high)
            .value("low", altitude::low)
            .finalize();
    });
    m.def("is_high_altitude", [](altitude alt) { return alt == altitude::high; });
    m.def("get_altitude", []() -> altitude { return altitude::high; });

    py::native_enum<flags_uchar>(m, "flags_uchar", "enum.Flag")
        .value("bit0", flags_uchar::bit0)
        .value("bit1", flags_uchar::bit1)
        .value("bit2", flags_uchar::bit2)
        .finalize();

    py::native_enum<flags_uint>(m, "flags_uint", "enum.IntFlag")
        .value("bit0", flags_uint::bit0)
        .value("bit1", flags_uint::bit1)
        .value("bit2", flags_uint::bit2)
        .finalize();

    py::native_enum<export_values>(m, "export_values", "enum.IntEnum")
        .value("exv0", export_values::exv0)
        .value("exv1", export_values::exv1)
        .export_values()
        .finalize();

    py::native_enum<member_doc>(m, "member_doc", "enum.IntEnum")
        .value("mem0", member_doc::mem0, "docA")
        .value("mem1", member_doc::mem1)
        .value("mem2", member_doc::mem2, "docC")
        .finalize();

    py::class_<class_with_enum> py_class_with_enum(m, "class_with_enum");
    py::native_enum<class_with_enum::in_class>(py_class_with_enum, "in_class", "enum.IntEnum")
        .value("one", class_with_enum::in_class::one)
        .value("two", class_with_enum::in_class::two)
        .finalize();

    py_class_with_enum.def(py::init())
        .def_readwrite("nested_value", &class_with_enum::nested_value);

    m.def("isinstance_color", [](const py::object &obj) { return py::isinstance<color>(obj); });

    m.def("pass_color", [](color e) { return static_cast<int>(e); });
    m.def("return_color", [](int i) { return static_cast<color>(i); });

    m.def("return_color_const_ptr", []() -> const color * {
        static const color test_color = color::red;
        return &test_color;
    });
    m.def("return_color_mutbl_ptr", []() -> color * {
        static color test_color = color::green;
        return &test_color;
    });

    py::native_enum<func_sig_rendering>(m, "func_sig_rendering", "enum.Enum").finalize();
    m.def(
        "pass_and_return_func_sig_rendering",
        [](func_sig_rendering e) { return e; },
        py::arg("e"));

    m.def("pass_some_proto_enum", [](some_proto_enum) { return py::none(); });
    m.def("return_some_proto_enum", []() { return some_proto_enum::Zero; });

#if defined(__MINGW32__)
    m.attr("obj_cast_color_ptr") = "MinGW: dangling pointer to an unnamed temporary may be used "
                                   "[-Werror=dangling-pointer=]";
#elif defined(NDEBUG)
    m.attr("obj_cast_color_ptr") = "NDEBUG disables cast safety check";
#else
    m.def("obj_cast_color_ptr", [](const py::object &obj) { obj.cast<color *>(); });
#endif

    m.def("py_cast_color_handle", [](py::handle obj) {
        // Exercises `if (is_enum_cast && cast_is_temporary_value_reference<T>::value)`
        // in `T cast(const handle &handle)`
        auto e = py::cast<color>(obj);
        return static_cast<int>(e);
    });

    m.def("exercise_import_or_getattr", [](py::module_ &m, const char *native_type_name) {
        enum fake { x };
        py::native_enum<fake>(m, "fake_import_or_getattr", native_type_name)
            .value("x", fake::x)
            .finalize();
    });

    m.def("native_enum_data_missing_finalize_error_message",
          [](const std::string &enum_name_encoded) {
              return py::detail::native_enum_missing_finalize_error_message(enum_name_encoded);
          });

    m.def("native_enum_ctor_malformed_utf8", [](const char *malformed_utf8) {
        enum fake { x };
        py::native_enum<fake>{py::none(), malformed_utf8, "enum.IntEnum"};
    });

    m.def("native_enum_double_finalize", [](py::module_ &m) {
        enum fake { x };
        py::native_enum<fake> ne(m, "fake_native_enum_double_finalize", "enum.IntEnum");
        ne.finalize();
        ne.finalize();
    });

    m.def("native_enum_value_after_finalize", [](py::module_ &m) {
        enum fake { x };
        py::native_enum<fake> ne(m, "fake_native_enum_value_after_finalize", "enum.IntEnum");
        ne.finalize();
        ne.value("x", fake::x);
    });

    m.def("native_enum_value_malformed_utf8", [](const char *malformed_utf8) {
        enum fake { x };
        py::native_enum<fake>(py::none(), "fake", "enum.IntEnum").value(malformed_utf8, fake::x);
    });

    m.def("double_registration_native_enum", [](py::module_ &m) {
        enum fake { x };
        py::native_enum<fake>(m, "fake_double_registration_native_enum", "enum.IntEnum")
            .value("x", fake::x)
            .finalize();
        py::native_enum<fake>(m, "fake_double_registration_native_enum", "enum.Enum");
    });

    m.def("native_enum_name_clash", [](py::module_ &m) {
        enum fake { x };
        py::native_enum<fake>(m, "fake_native_enum_name_clash", "enum.IntEnum")
            .value("x", fake::x)
            .finalize();
    });

    m.def("native_enum_value_name_clash", [](py::module_ &m) {
        enum fake { x };
        py::native_enum<fake>(m, "fake_native_enum_value_name_clash", "enum.IntEnum")
            .value("fake_native_enum_value_name_clash_x", fake::x)
            .export_values()
            .finalize();
    });

    m.def("double_registration_enum_before_native_enum", [](py::module_ &m) {
        enum fake { x };
        py::enum_<fake>(m, "fake_enum_first").value("x", fake::x);
        py::native_enum<fake>(m, "fake_enum_first", "enum.IntEnum").value("x", fake::x).finalize();
    });

    m.def("double_registration_native_enum_before_enum", [](py::module_ &m) {
        enum fake { x };
        py::native_enum<fake>(m, "fake_native_enum_first", "enum.IntEnum")
            .value("x", fake::x)
            .finalize();
        py::enum_<fake>(m, "name_must_be_different_to_reach_desired_code_path");
    });

#if defined(PYBIND11_NEGATE_THIS_CONDITION_FOR_LOCAL_TESTING) && !defined(NDEBUG)
    m.def("native_enum_missing_finalize_failure", []() {
        enum fake { x };
        py::native_enum<fake>(
            py::none(), "fake_native_enum_missing_finalize_failure", "enum.IntEnum")
            .value("x", fake::x)
            // .finalize() missing
            ;
    });
#else
    m.attr("native_enum_missing_finalize_failure") = "For local testing only: terminates process";
#endif
}