cast.h return_value_policy_override _clif_automatic (#4364)

Author: rwgk

include/pybind11/cast.h

@@ -1042,6 +1042,7 @@ struct return_value_policy_override<
                         void>> {
     static return_value_policy policy(return_value_policy p) {
         return !std::is_lvalue_reference<Return>::value && !std::is_pointer<Return>::value
+                       && p != return_value_policy::_clif_automatic
                    ? return_value_policy::move
                    : p;
     }

tests/CMakeLists.txt

@@ -167,6 +167,7 @@ set(PYBIND11_TEST_FILES
     test_operator_overloading
     test_pickling
     test_pytypes
+    test_return_value_policy_override
     test_sequences_and_iterators
     test_smart_ptr
     test_stl

tests/test_return_value_policy_override.cpp

@@ -0,0 +1,82 @@
+#include "pybind11_tests.h"
+
+namespace test_return_value_policy_override {
+
+struct some_type {};
+
+} // namespace test_return_value_policy_override
+
+using test_return_value_policy_override::some_type;
+
+namespace pybind11 {
+namespace detail {
+
+const char *return_value_policy_name(return_value_policy policy) {
+    switch (policy) {
+        case return_value_policy::automatic:
+            return "automatic";
+        case return_value_policy::automatic_reference:
+            return "automatic_reference";
+        case return_value_policy::take_ownership:
+            return "take_ownership";
+        case return_value_policy::copy:
+            return "copy";
+        case return_value_policy::move:
+            return "move";
+        case return_value_policy::reference:
+            return "reference";
+        case return_value_policy::reference_internal:
+            return "reference_internal";
+        case return_value_policy::_return_as_bytes:
+            return "_return_as_bytes";
+        case return_value_policy::_clif_automatic:
+            return "_clif_automatic";
+        default:
+            return "Expected to be unreachable.";
+    }
+};
+
+template <>
+struct type_caster<some_type> : type_caster_base<some_type> {
+
+    static handle cast(some_type &&, return_value_policy policy, handle /*parent*/) {
+        return str(std::string(return_value_policy_name(policy))).release().ptr();
+    }
+
+    static handle cast(some_type *, return_value_policy policy, handle /*parent*/) {
+        return str(std::string(return_value_policy_name(policy))).release().ptr();
+    }
+};
+
+} // namespace detail
+} // namespace pybind11
+
+TEST_SUBMODULE(return_value_policy_override, m) {
+    m.def("return_value_with_default_policy", []() { return some_type(); });
+    m.def(
+        "return_value_with_policy_copy",
+        []() { return some_type(); },
+        py::return_value_policy::copy);
+    m.def(
+        "return_value_with_policy_clif_automatic",
+        []() { return some_type(); },
+        py::return_value_policy::_clif_automatic);
+    m.def("return_pointer_with_default_policy", []() {
+        static some_type value;
+        return &value;
+    });
+    m.def(
+        "return_pointer_with_policy_move",
+        []() {
+            static some_type value;
+            return &value;
+        },
+        py::return_value_policy::move);
+    m.def(
+        "return_pointer_with_policy_clif_automatic",
+        []() {
+            static some_type value;
+            return &value;
+        },
+        py::return_value_policy::_clif_automatic);
+}

tests/test_return_value_policy_override.py

@@ -0,0 +1,13 @@
+from pybind11_tests import return_value_policy_override as m
+
+
+def test_return_value():
+    assert m.return_value_with_default_policy() == "move"
+    assert m.return_value_with_policy_copy() == "move"
+    assert m.return_value_with_policy_clif_automatic() == "_clif_automatic"
+
+
+def test_return_pointer():
+    assert m.return_pointer_with_default_policy() == "automatic"
+    assert m.return_pointer_with_policy_move() == "move"
+    assert m.return_pointer_with_policy_clif_automatic() == "_clif_automatic"