bpo-24766: doc= argument to subclasses of property not handled correctly (GH-2487)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

Lib/test/test_property.py

@@ -463,6 +463,40 @@ class PropertySubclassTests(unittest.TestCase):
         self.assertEqual(p.__doc__, "user")
         self.assertEqual(p2.__doc__, "user")
 
+    @unittest.skipIf(sys.flags.optimize >= 2,
+                     "Docstrings are omitted with -O2 and above")
+    def test_prefer_explicit_doc(self):
+        # Issue 25757: subclasses of property lose docstring
+        self.assertEqual(property(doc="explicit doc").__doc__, "explicit doc")
+        self.assertEqual(PropertySub(doc="explicit doc").__doc__, "explicit doc")
+
+        class Foo:
+            spam = PropertySub(doc="spam explicit doc")
+
+            @spam.getter
+            def spam(self):
+                """ignored as doc already set"""
+                return 1
+
+            def _stuff_getter(self):
+                """ignored as doc set directly"""
+            stuff = PropertySub(doc="stuff doc argument", fget=_stuff_getter)
+
+        #self.assertEqual(Foo.spam.__doc__, "spam explicit doc")
+        self.assertEqual(Foo.stuff.__doc__, "stuff doc argument")
+
+    def test_property_no_doc_on_getter(self):
+        # If a property's getter has no __doc__ then the property's doc should
+        # be None; test that this is consistent with subclasses as well; see
+        # GH-2487
+        class NoDoc:
+            @property
+            def __doc__(self):
+                raise AttributeError
+
+        self.assertEqual(property(NoDoc()).__doc__, None)
+        self.assertEqual(PropertySub(NoDoc()).__doc__, None)
+
     @unittest.skipIf(sys.flags.optimize >= 2,
                      "Docstrings are omitted with -O2 and above")
     def test_property_setter_copies_getter_docstring(self):

Misc/NEWS.d/next/Core and Builtins/2018-10-09-15-14-53.bpo-24766.c_C1Wc.rst

@@ -0,0 +1 @@
+Fix handling of ``doc`` argument to subclasses of ``property``.

Objects/descrobject.c

@@ -1859,22 +1859,9 @@ property_init_impl(propertyobject *self, PyObject *fget, PyObject *fset,
     /* if no docstring given and the getter has one, use that one */
     else if (fget != NULL) {
         int rc = PyObject_GetOptionalAttr(fget, &_Py_ID(__doc__), &prop_doc);
-        if (rc <= 0) {
+        if (rc < 0) {
             return rc;
         }
-        if (!Py_IS_TYPE(self, &PyProperty_Type) &&
-            prop_doc != NULL && prop_doc != Py_None) {
-            // This oddity preserves the long existing behavior of surfacing
-            // an AttributeError when using a dict-less (__slots__) property
-            // subclass as a decorator on a getter method with a docstring.
-            // See PropertySubclassTest.test_slots_docstring_copy_exception.
-            int err = PyObject_SetAttr(
-                        (PyObject *)self, &_Py_ID(__doc__), prop_doc);
-            if (err < 0) {
-                Py_DECREF(prop_doc);  // release our new reference.
-                return -1;
-            }
-        }
         if (prop_doc == Py_None) {
             prop_doc = NULL;
             Py_DECREF(Py_None);
@@ -1902,7 +1889,9 @@ property_init_impl(propertyobject *self, PyObject *fget, PyObject *fset,
         Py_DECREF(prop_doc);
         if (err < 0) {
             assert(PyErr_Occurred());
-            if (PyErr_ExceptionMatches(PyExc_AttributeError)) {
+            if (!self->getter_doc &&
+                PyErr_ExceptionMatches(PyExc_AttributeError))
+            {
                 PyErr_Clear();
                 // https://github.com/python/cpython/issues/98963#issuecomment-1574413319
                 // Python silently dropped this doc assignment through 3.11.