bpo-45356: fix incorrect access of class property in pydoc and inspect

Lib/inspect.py

@@ -486,6 +486,14 @@ def getmembers(object, predicate=None):
 
 Attribute = namedtuple('Attribute', 'name kind defining_class object')
 
+def _is_class_property(cls, name):
+    for base in cls.__mro__:
+        o = base.__dict__.get(name)
+        if isinstance(o, classmethod) and \
+           isinstance(o.__func__, property):
+            return True
+    return False
+
 def classify_class_attrs(cls):
     """Return list of attribute-descriptor tuples.
 
@@ -546,6 +554,8 @@ def classify_class_attrs(cls):
             try:
                 if name == '__dict__':
                     raise Exception("__dict__ is special, don't want the proxy")
+                if _is_class_property(cls, name):
+                    raise Exception("class property")
                 get_obj = getattr(cls, name)
             except Exception as exc:
                 pass

Lib/pydoc.py

@@ -885,6 +885,8 @@ def spill(msg, attrs, predicate):
                 push(msg)
                 for name, kind, homecls, value in ok:
                     try:
+                        if inspect._is_class_property(object, name):
+                            raise Exception("class property")
                         value = getattr(object, name)
                     except Exception:
                         # Some descriptors may meet a failure in their __get__.
@@ -1368,6 +1370,8 @@ def spill(msg, attrs, predicate):
                 push(msg)
                 for name, kind, homecls, value in ok:
                     try:
+                        if inspect._is_class_property(object, name):
+                            raise Exception("class property")
                         value = getattr(object, name)
                     except Exception:
                         # Some descriptors may meet a failure in their __get__.

Lib/test/test_pydoc.py

@@ -514,6 +514,19 @@ class object
                 " |      ... and \\d+ other subclasses")
         self.assertRegex(text, snip)
 
+    def test_classmethod_property(self):
+        # Issue 45356
+        class A:
+            @classmethod
+            @property
+            def a(self):
+                # BaseException because accessor of attributes in pydoc and in
+                # inspect catches Exception
+                raise BaseException
+        class B(A): pass
+        pydoc.render_doc(A)
+        pydoc.render_doc(B)
+
     def test_builtin_with_child(self):
         """Tests help on builtin object which have only child classes.
 

Misc/NEWS.d/next/Library/2021-10-28-22-29-30.bpo-45356.jCCqdb.rst

@@ -0,0 +1,4 @@
+:mod:`pydoc` ``help`` command, :meth:`~pydoc.HTMLDoc.docclass`,
+:meth:`~pydoc.TextDoc.docclass`, and :func:`~inspect.classify_class_attrs`
+will no longer execute the logic of a class property when examining a class
+object that contains such property.