Fix smart_holder def_readwrite for non-smart-holder member types

Author: virtuald

include/pybind11/pybind11.h

@@ -2013,10 +2013,17 @@ struct property_cpp_function_sh_raw_ptr_member {
 // This prevents disowning of the Python object owning the member.
 template <typename T, typename D>
 struct property_cpp_function_sh_member_held_by_value {
+    static bool use_smart_holder_member_aliasing() {
+        type_info *member_tinfo = get_type_info(typeid(intrinsic_t<D>), /*throw_if_missing=*/false);
+        return member_tinfo != nullptr
+               && member_tinfo->holder_enum_v == holder_enum_t::smart_holder;
+    }
+
     template <typename PM, must_be_member_function_pointer<PM> = 0>
     static cpp_function readonly(PM pm, const handle &hdl) {
         type_info *tinfo = get_type_info(typeid(T), /*throw_if_missing=*/true);
-        if (tinfo->holder_enum_v == holder_enum_t::smart_holder) {
+        if (tinfo->holder_enum_v == holder_enum_t::smart_holder
+            && use_smart_holder_member_aliasing()) {
             return cpp_function(
                 [pm](handle c_hdl) -> std::shared_ptr<typename std::add_const<D>::type> {
                     std::shared_ptr<T> c_sp
@@ -2033,7 +2040,8 @@ struct property_cpp_function_sh_member_held_by_value {
     template <typename PM, must_be_member_function_pointer<PM> = 0>
     static cpp_function read(PM pm, const handle &hdl) {
         type_info *tinfo = get_type_info(typeid(T), /*throw_if_missing=*/true);
-        if (tinfo->holder_enum_v == holder_enum_t::smart_holder) {
+        if (tinfo->holder_enum_v == holder_enum_t::smart_holder
+            && use_smart_holder_member_aliasing()) {
             return cpp_function(
                 [pm](handle c_hdl) -> std::shared_ptr<D> {
                     std::shared_ptr<T> c_sp

tests/test_class_sh_property.cpp

@@ -43,6 +43,23 @@ struct WithConstCharPtrMember {
     const char *const_char_ptr_member = "ConstChar*";
 };
 
+enum class TinyLevel {
+    A = 0,
+    B = 1,
+};
+
+struct HolderWithEnum {
+    TinyLevel level = TinyLevel::A;
+};
+
+struct LegacyThing {
+    int value = 7;
+};
+
+struct HolderWithLegacyMember {
+    LegacyThing legacy;
+};
+
 } // namespace test_class_sh_property
 
 TEST_SUBMODULE(class_sh_property, m) {
@@ -91,4 +108,16 @@ TEST_SUBMODULE(class_sh_property, m) {
     py::classh<WithConstCharPtrMember>(m, "WithConstCharPtrMember")
         .def(py::init<>())
         .def_readonly("const_char_ptr_member", &WithConstCharPtrMember::const_char_ptr_member);
+
+    py::enum_<TinyLevel>(m, "TinyLevel").value("A", TinyLevel::A).value("B", TinyLevel::B);
+
+    py::classh<HolderWithEnum>(m, "HolderWithEnum")
+        .def(py::init<>())
+        .def_readwrite("level", &HolderWithEnum::level);
+
+    py::class_<LegacyThing>(m, "LegacyThing").def(py::init<>()).def_readwrite("value", &LegacyThing::value);
+
+    py::classh<HolderWithLegacyMember>(m, "HolderWithLegacyMember")
+        .def(py::init<>())
+        .def_readwrite("legacy", &HolderWithLegacyMember::legacy);
 }

tests/test_class_sh_property.py

@@ -164,3 +164,36 @@ def test_readonly_char6_member():
 def test_readonly_const_char_ptr_member():
     obj = m.WithConstCharPtrMember()
     assert obj.const_char_ptr_member == "ConstChar*"
+
+
+def test_enum_member_with_smart_holder_def_readwrite():
+    env.check_script_success_in_subprocess(
+        """
+        import gc
+        from pybind11_tests import class_sh_property as m
+
+        obj = m.HolderWithEnum()
+        assert obj.level == m.TinyLevel.A
+        for _ in range(100):
+            v = obj.level
+            assert v == m.TinyLevel.A
+            del v
+        gc.collect()
+        """
+    )
+
+
+def test_non_smart_holder_member_type_with_smart_holder_owner():
+    env.check_script_success_in_subprocess(
+        """
+        import gc
+        from pybind11_tests import class_sh_property as m
+
+        obj = m.HolderWithLegacyMember()
+        for _ in range(1000):
+            v = obj.legacy
+            assert v.value == 7
+            del v
+        gc.collect()
+        """
+    )