Merge pull request #30032 from rwgk/from_python_policies_automatic_reference_fix

`from_python_policies` `automatic_reference` bug fix

Author: rwgk

include/pybind11/detail/common.h

@@ -606,7 +606,8 @@ struct from_python_policies {
         : rvpp(return_value_policy::automatic_reference), convert(true), none(true) {}
 
     // NOLINTNEXTLINE(google-explicit-constructor)
-    from_python_policies(bool convert, bool none = true) : convert(convert), none(none) {}
+    from_python_policies(bool convert, bool none = true)
+        : rvpp(return_value_policy::automatic_reference), convert(convert), none(none) {}
 
     // NOLINTNEXTLINE(google-explicit-constructor)
     from_python_policies(const return_value_policy_pack &rvpp)

tests/test_return_value_policy_pack.cpp

@@ -18,7 +18,8 @@
 #    include <variant>
 #endif
 
-namespace {
+namespace pybind11_tests {
+namespace return_value_policy_pack {
 
 using PairString = std::pair<std::string, std::string>;
 
@@ -223,7 +224,19 @@ int call_virtual_override(const VirtualBase &base, const std::string &which) {
     return -99; // Invalid which.
 }
 
-} // namespace
+struct IntOwner {
+    int val = 3;
+};
+
+int call_callback_pass_int_owner_const_ptr(const std::function<int(const IntOwner *)> &cb) {
+    IntOwner int_owner;
+    return cb(&int_owner) + 500;
+}
+
+} // namespace return_value_policy_pack
+} // namespace pybind11_tests
+
+using namespace pybind11_tests::return_value_policy_pack;
 
 TEST_SUBMODULE(return_value_policy_pack, m) {
     static constexpr auto rvpc = py::return_value_policy::_clif_automatic;
@@ -422,4 +435,8 @@ TEST_SUBMODULE(return_value_policy_pack, m) {
         .def("py_nonp_bs", &VirtualBase::nonp_bs, py::arg("a0"), py::arg("a1"));
 
     m.def("call_virtual_override", call_virtual_override);
+
+    py::class_<IntOwner>(m, "IntOwner").def_readonly("val", &IntOwner::val);
+
+    m.def("call_callback_pass_int_owner_const_ptr", call_callback_pass_int_owner_const_ptr);
 }

tests/test_return_value_policy_pack.py

@@ -328,3 +328,10 @@ def test_virtual_overrides_base(which, expected):
         )
     else:
         assert m.call_virtual_override(b, which) == -expected
+
+
+def test_call_callback_pass_int_owner():
+    def cb(int_owner):
+        return int_owner.val + 40
+
+    assert m.call_callback_pass_int_owner_const_ptr(cb) == 543