[Python-checkins] gh-98963: Restore the ability to have a dict-less property. (#105262)
JelleZijlstra
webhook-mailer at python.org
Sun Jun 4 23:18:37 EDT 2023
https://github.com/python/cpython/commit/418befd75d4d0d1cba83d8b81e1a7bcc9a65be8e
commit: 418befd75d4d0d1cba83d8b81e1a7bcc9a65be8e
branch: main
author: Gregory P. Smith <greg at krypto.org>
committer: JelleZijlstra <jelle.zijlstra at gmail.com>
date: 2023-06-05T03:18:15Z
summary:
gh-98963: Restore the ability to have a dict-less property. (#105262)
Ignore doc string assignment failures in `property` as has been the
behavior of all past Python releases.
files:
A Misc/NEWS.d/next/Core and Builtins/2023-06-02-17-39-19.gh-issue-98963.J4wJgk.rst
M Lib/test/test_property.py
M Objects/descrobject.c
diff --git a/Lib/test/test_property.py b/Lib/test/test_property.py
index d4bdf50c0192..45aa9e51c06d 100644
--- a/Lib/test/test_property.py
+++ b/Lib/test/test_property.py
@@ -246,16 +246,67 @@ class PropertySubSlots(property):
class PropertySubclassTests(unittest.TestCase):
def test_slots_docstring_copy_exception(self):
- try:
+ # A special case error that we preserve despite the GH-98963 behavior
+ # that would otherwise silently ignore this error.
+ # This came from commit b18500d39d791c879e9904ebac293402b4a7cd34
+ # as part of https://bugs.python.org/issue5890 which allowed docs to
+ # be set via property subclasses in the first place.
+ with self.assertRaises(AttributeError):
class Foo(object):
@PropertySubSlots
def spam(self):
"""Trying to copy this docstring will raise an exception"""
return 1
- except AttributeError:
- pass
- else:
- raise Exception("AttributeError not raised")
+
+ def test_property_with_slots_no_docstring(self):
+ # https://github.com/python/cpython/issues/98963#issuecomment-1574413319
+ class slotted_prop(property):
+ __slots__ = ("foo",)
+
+ p = slotted_prop() # no AttributeError
+ self.assertIsNone(getattr(p, "__doc__", None))
+
+ def undocumented_getter():
+ return 4
+
+ p = slotted_prop(undocumented_getter) # New in 3.12: no AttributeError
+ self.assertIsNone(getattr(p, "__doc__", None))
+
+ @unittest.skipIf(sys.flags.optimize >= 2,
+ "Docstrings are omitted with -O2 and above")
+ def test_property_with_slots_docstring_silently_dropped(self):
+ # https://github.com/python/cpython/issues/98963#issuecomment-1574413319
+ class slotted_prop(property):
+ __slots__ = ("foo",)
+
+ p = slotted_prop(doc="what's up") # no AttributeError
+ self.assertIsNone(p.__doc__)
+
+ def documented_getter():
+ """getter doc."""
+ return 4
+
+ # Historical behavior: A docstring from a getter always raises.
+ # (matches test_slots_docstring_copy_exception above).
+ with self.assertRaises(AttributeError):
+ p = slotted_prop(documented_getter)
+
+ @unittest.skipIf(sys.flags.optimize >= 2,
+ "Docstrings are omitted with -O2 and above")
+ def test_property_with_slots_and_doc_slot_docstring_present(self):
+ # https://github.com/python/cpython/issues/98963#issuecomment-1574413319
+ class slotted_prop(property):
+ __slots__ = ("foo", "__doc__")
+
+ p = slotted_prop(doc="what's up")
+ self.assertEqual("what's up", p.__doc__) # new in 3.12: This gets set.
+
+ def documented_getter():
+ """what's up getter doc?"""
+ return 4
+
+ p = slotted_prop(documented_getter)
+ self.assertEqual("what's up getter doc?", p.__doc__)
@unittest.skipIf(sys.flags.optimize >= 2,
"Docstrings are omitted with -O2 and above")
diff --git a/Misc/NEWS.d/next/Core and Builtins/2023-06-02-17-39-19.gh-issue-98963.J4wJgk.rst b/Misc/NEWS.d/next/Core and Builtins/2023-06-02-17-39-19.gh-issue-98963.J4wJgk.rst
new file mode 100644
index 000000000000..4caadb0875a1
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2023-06-02-17-39-19.gh-issue-98963.J4wJgk.rst
@@ -0,0 +1,4 @@
+Restore the ability for a subclass of :class:`property` to define ``__slots__``
+or otherwise be dict-less by ignoring failures to set a docstring on such a
+class. This behavior had regressed in 3.12beta1. An :exc:`AttributeError`
+where there had not previously been one was disruptive to existing code.
diff --git a/Objects/descrobject.c b/Objects/descrobject.c
index 17c0c85a06c4..72ac47039492 100644
--- a/Objects/descrobject.c
+++ b/Objects/descrobject.c
@@ -1485,7 +1485,10 @@ class property(object):
self.__get = fget
self.__set = fset
self.__del = fdel
- self.__doc__ = doc
+ try:
+ self.__doc__ = doc
+ except AttributeError: # read-only or dict-less class
+ pass
def __get__(self, inst, type=None):
if inst is None:
@@ -1791,6 +1794,19 @@ property_init_impl(propertyobject *self, PyObject *fget, PyObject *fset,
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);
@@ -1806,19 +1822,32 @@ property_init_impl(propertyobject *self, PyObject *fget, PyObject *fset,
if (Py_IS_TYPE(self, &PyProperty_Type)) {
Py_XSETREF(self->prop_doc, prop_doc);
} else {
- /* If this is a property subclass, put __doc__
- in dict of the subclass instance instead,
- otherwise it gets shadowed by __doc__ in the
- class's dict. */
+ /* If this is a property subclass, put __doc__ in the dict
+ or designated slot of the subclass instance instead, otherwise
+ it gets shadowed by __doc__ in the class's dict. */
if (prop_doc == NULL) {
prop_doc = Py_NewRef(Py_None);
}
int err = PyObject_SetAttr(
(PyObject *)self, &_Py_ID(__doc__), prop_doc);
- Py_XDECREF(prop_doc);
- if (err < 0)
- return -1;
+ Py_DECREF(prop_doc);
+ if (err < 0) {
+ assert(PyErr_Occurred());
+ if (PyErr_ExceptionMatches(PyExc_AttributeError)) {
+ PyErr_Clear();
+ // https://github.com/python/cpython/issues/98963#issuecomment-1574413319
+ // Python silently dropped this doc assignment through 3.11.
+ // We preserve that behavior for backwards compatibility.
+ //
+ // If we ever want to deprecate this behavior, only raise a
+ // warning or error when proc_doc is not None so that
+ // property without a specific doc= still works.
+ return 0;
+ } else {
+ return -1;
+ }
+ }
}
return 0;
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