Fix missing pythonic type hints for native_enum (#5619)

* fix missing pythonic type hints for native_enum

* Fix __qualname__ in native_enum

* Rename `enum class native` → `func_sig_rendering`. Add to `ENUM_TYPES_AND_MEMBERS`. Move new code around to fit in more organically.

"native" is used in so many places here, it would be very difficult to pin-point where the specific enum type is used.

Similarly, "value" is difficult to pin-point. Changed to "nested_value".

---------

Co-authored-by: Bryn Lloyd <12702862+dyollb@users.noreply.github.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rgrossekunst@nvidia.com>

include/pybind11/detail/native_enum_data.h

@@ -182,6 +182,10 @@ inline void native_enum_data::finalize() {
     if (module_name) {
         py_enum.attr("__module__") = module_name;
     }
+    if (hasattr(parent_scope, "__qualname__")) {
+        const auto parent_qualname = parent_scope.attr("__qualname__").cast<std::string>();
+        py_enum.attr("__qualname__") = str(parent_qualname + "." + enum_name.cast<std::string>());
+    }
     parent_scope.attr(enum_name) = py_enum;
     if (export_values_flag) {
         for (auto member : members) {

include/pybind11/pybind11.h

@@ -160,6 +160,9 @@ inline std::string generate_function_signature(const char *type_caster_name_fiel
                 handle th((PyObject *) tinfo->type);
                 signature += th.attr("__module__").cast<std::string>() + "."
                              + th.attr("__qualname__").cast<std::string>();
+            } else if (auto th = detail::global_internals_native_enum_type_map_get_item(*t)) {
+                signature += th.attr("__module__").cast<std::string>() + "."
+                             + th.attr("__qualname__").cast<std::string>();
             } else if (func_rec->is_new_style_constructor && arg_index == 0) {
                 // A new-style `__init__` takes `self` as `value_and_holder`.
                 // Rewrite it to the proper class type.

tests/test_native_enum.cpp

@@ -29,6 +29,8 @@ 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
@@ -40,6 +42,8 @@ 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)
@@ -124,11 +128,20 @@ TEST_SUBMODULE(native_enum, m) {
         .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); });
 
+    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; });
 

tests/test_native_enum.py

@@ -54,6 +54,8 @@ MEMBER_DOC_MEMBERS = (
     ("mem2", 2),
 )
 
+FUNC_SIG_RENDERING_MEMBERS = ()
+
 ENUM_TYPES_AND_MEMBERS = (
     (m.smallenum, SMALLENUM_MEMBERS),
     (m.color, COLOR_MEMBERS),
@@ -62,6 +64,7 @@ ENUM_TYPES_AND_MEMBERS = (
     (m.flags_uint, FLAGS_UINT_MEMBERS),
     (m.export_values, EXPORT_VALUES_MEMBERS),
     (m.member_doc, MEMBER_DOC_MEMBERS),
+    (m.func_sig_rendering, FUNC_SIG_RENDERING_MEMBERS),
     (m.class_with_enum.in_class, CLASS_WITH_ENUM_IN_CLASS_MEMBERS),
 )
 
@@ -84,11 +87,6 @@ def test_enum_members(enum_type, members):
 def test_pickle_roundtrip(enum_type, members):
     for name, _ in members:
         orig = enum_type[name]
-        if enum_type is m.class_with_enum.in_class:
-            # This is a general pickle limitation.
-            with pytest.raises(pickle.PicklingError):
-                pickle.dumps(orig)
-        else:
         # This only works if __module__ is correct.
         serialized = pickle.dumps(orig)
         restored = pickle.loads(serialized)
@@ -139,7 +137,7 @@ def test_pass_color_success():
 def test_pass_color_fail():
     with pytest.raises(TypeError) as excinfo:
         m.pass_color(None)
-    assert "test_native_enum::color" in str(excinfo.value)
+    assert "pybind11_tests.native_enum.color" in str(excinfo.value)
 
 
 def test_return_color_success():
@@ -155,6 +153,22 @@ def test_return_color_fail():
     assert str(excinfo_cast.value) == str(excinfo_direct.value)
 
 
+def test_property_type_hint():
+    prop = m.class_with_enum.__dict__["nested_value"]
+    assert isinstance(prop, property)
+    assert prop.fget.__doc__.startswith(
+        "(self: pybind11_tests.native_enum.class_with_enum)"
+        " -> pybind11_tests.native_enum.class_with_enum.in_class"
+    )
+
+
+def test_func_sig_rendering():
+    assert m.pass_and_return_func_sig_rendering.__doc__.startswith(
+        "pass_and_return_func_sig_rendering(e: pybind11_tests.native_enum.func_sig_rendering)"
+        " -> pybind11_tests.native_enum.func_sig_rendering"
+    )
+
+
 def test_type_caster_enum_type_enabled_false():
     # This is really only a "does it compile" test.
     assert m.pass_some_proto_enum(None) is None