Fold in PR pybind#3970 with #ifdefs

include/pybind11/pytypes.h

@@ -85,7 +85,13 @@ class object_api : public pyobject_tag {
         or `object` subclass causes a call to ``__setitem__``.
     \endrst */
     item_accessor operator[](handle key) const;
-    /// See above (the only difference is that they key is provided as a string literal)
+#define PYBIND11_PR3970
+#ifdef PYBIND11_PR3970
+#    define PYBIND11_PR3970_ITEM_ACCESSOR
+    /// See above (the only difference is that the key's reference is stolen)
+    item_accessor operator[](object &&key) const;
+#endif
+    /// See above (the only difference is that the key is provided as a string literal)
     item_accessor operator[](const char *key) const;
 
     /** \rst
@@ -95,7 +101,12 @@ class object_api : public pyobject_tag {
         or `object` subclass causes a call to ``setattr``.
     \endrst */
     obj_attr_accessor attr(handle key) const;
-    /// See above (the only difference is that they key is provided as a string literal)
+    /// See above (the only difference is that the key's reference is stolen)
+#ifdef PYBIND11_PR3970
+#    define PYBIND11_PR3970_ATTR_ACCESSOR
+    obj_attr_accessor attr(object &&key) const;
+    /// See above (the only difference is that the key is provided as a string literal)
+#endif
     str_attr_accessor attr(const char *key) const;
 
     /** \rst
@@ -676,7 +687,12 @@ class accessor : public object_api<accessor<Policy>> {
     }
     template <typename T>
     void operator=(T &&value) & {
+#ifdef PYBIND11_PR3970
+#    define PYBIND11_PR3970_ENSURE_OBJECT
+        get_cache() = ensure_object(object_or_cast(std::forward<T>(value)));
+#else
         get_cache() = reinterpret_borrow<object>(object_or_cast(std::forward<T>(value)));
+#endif
     }
 
     template <typename T = Policy>
@@ -704,6 +720,11 @@ class accessor : public object_api<accessor<Policy>> {
     }
 
 private:
+#ifdef PYBIND11_PR3970_ENSURE_OBJECT
+    static object ensure_object(object &&o) { return std::move(o); }
+    static object ensure_object(handle h) { return reinterpret_borrow<object>(h); }
+#endif
+
     object &get_cache() const {
         if (!cache) {
             cache = Policy::get(obj, key);
@@ -1703,7 +1724,14 @@ class tuple : public object {
     size_t size() const { return (size_t) PyTuple_Size(m_ptr); }
     bool empty() const { return size() == 0; }
     detail::tuple_accessor operator[](size_t index) const { return {*this, index}; }
+#ifdef PYBIND11_PR3970
+    template <typename T, detail::enable_if_t<detail::is_pyobject<T>::value, int> = 0>
+    detail::item_accessor operator[](T o) const {
+        return object::operator[](std::forward<T>(o));
+    }
+#else
     detail::item_accessor operator[](handle h) const { return object::operator[](h); }
+#endif
     detail::tuple_iterator begin() const { return {*this, 0}; }
     detail::tuple_iterator end() const { return {*this, PyTuple_GET_SIZE(m_ptr)}; }
 };
@@ -1763,7 +1791,14 @@ class sequence : public object {
     }
     bool empty() const { return size() == 0; }
     detail::sequence_accessor operator[](size_t index) const { return {*this, index}; }
+#ifdef PYBIND11_PR3970
+    template <typename T, detail::enable_if_t<detail::is_pyobject<T>::value, int> = 0>
+    detail::item_accessor operator[](T o) const {
+        return object::operator[](std::forward<T>(o));
+    }
+#else
     detail::item_accessor operator[](handle h) const { return object::operator[](h); }
+#endif
     detail::sequence_iterator begin() const { return {*this, 0}; }
     detail::sequence_iterator end() const { return {*this, PySequence_Size(m_ptr)}; }
 };
@@ -1782,7 +1817,14 @@ class list : public object {
     size_t size() const { return (size_t) PyList_Size(m_ptr); }
     bool empty() const { return size() == 0; }
     detail::list_accessor operator[](size_t index) const { return {*this, index}; }
+#ifdef PYBIND11_PR3970
+    template <typename T, detail::enable_if_t<detail::is_pyobject<T>::value, int> = 0>
+    detail::item_accessor operator[](T o) const {
+        return object::operator[](std::forward<T>(o));
+    }
+#else
     detail::item_accessor operator[](handle h) const { return object::operator[](h); }
+#endif
     detail::list_iterator begin() const { return {*this, 0}; }
     detail::list_iterator end() const { return {*this, PyList_GET_SIZE(m_ptr)}; }
     template <typename T>
@@ -2077,6 +2119,12 @@ template <typename D>
 iterator object_api<D>::end() const {
     return iterator::sentinel();
 }
+#ifdef PYBIND11_PR3970_ITEM_ACCESSOR
+template <typename D>
+item_accessor object_api<D>::operator[](object &&key) const {
+    return {derived(), std::move(key)};
+}
+#endif
 template <typename D>
 item_accessor object_api<D>::operator[](handle key) const {
     return {derived(), reinterpret_borrow<object>(key)};
@@ -2085,6 +2133,12 @@ template <typename D>
 item_accessor object_api<D>::operator[](const char *key) const {
     return {derived(), pybind11::str(key)};
 }
+#ifdef PYBIND11_PR3970_ATTR_ACCESSOR
+template <typename D>
+obj_attr_accessor object_api<D>::attr(object &&key) const {
+    return {derived(), std::move(key)};
+}
+#endif
 template <typename D>
 obj_attr_accessor object_api<D>::attr(handle key) const {
     return {derived(), reinterpret_borrow<object>(key)};

tests/test_pytypes.cpp

@@ -300,6 +300,11 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("accessor_moves", []() {
         py::list return_list;
 #ifdef PYBIND11_HANDLE_REF_DEBUG
+#    ifdef PYBIND11_PR3970
+        return_list.append("move");
+#    else
+        return_list.append("copy");
+#    endif
         py::list lst;
         lst.append(0);
         auto list_accessor = lst[0];

tests/test_pytypes.py

@@ -320,7 +320,10 @@ def func(self, x, *args):
 def test_accessor_moves():
     inc_refs = m.accessor_moves()
     if inc_refs:
-        assert inc_refs == [1, 1, 1, 1]
+        if inc_refs[0] == "copy":
+            assert inc_refs == ["copy", 1, 1, 1, 1]
+        else:
+            assert inc_refs == ["move", 1, 0, 1, 0]
     else:
         pytest.skip("Not defined: PYBIND11_HANDLE_REF_DEBUG")