Fix #9607: autodoc: Incorrect base class detection

In case of the descendants of generic class, the value of
obj.__orig_bases__ is incorrect because it returns original base
arguments for the child of the generic class instead of the target
class itself.

This uses obj.__dict__ to get the correct __orig_bases__ information.

CHANGES

@@ -21,6 +21,8 @@ Bugs fixed
 * #9630: autodoc: Failed to build cross references if :confval:`primary_domain`
   is not 'py'
 * #9644: autodoc: Crashed on getting source info from problematic object
+* #9607: autodoc: Incorrect base class detection for the subclasses of the
+  generic class
 * #9630: autosummary: Failed to build summary table if :confval:`primary_domain`
   is not 'py'
 

sphinx/ext/autodoc/__init__.py

@@ -1650,7 +1650,7 @@ class ClassDocumenter(DocstringSignatureMixin, ModuleLevelDocumenter):  # type:
 
         # add inheritance info, if wanted
         if not self.doc_as_attr and self.options.show_inheritance:
-            if hasattr(self.object, '__orig_bases__') and len(self.object.__orig_bases__):
+            if inspect.getorigbases(self.object):
                 # A subclass of generic types
                 # refs: PEP-560 <https://www.python.org/dev/peps/pep-0560/>
                 bases = list(self.object.__orig_bases__)

sphinx/util/inspect.py

@@ -187,6 +187,21 @@ def getmro(obj: Any) -> Tuple[Type, ...]:
         return tuple()
 
 
+def getorigbases(obj: Any) -> Optional[Tuple[Any, ...]]:
+    """Get __orig_bases__ from *obj* safely."""
+    if not inspect.isclass(obj):
+        return None
+
+    # Get __orig_bases__ from obj.__dict__ to avoid accessing the parent's __orig_bases__.
+    # refs: https://github.com/sphinx-doc/sphinx/issues/9607
+    __dict__ = safe_getattr(obj, '__dict__', {})
+    __orig_bases__ = __dict__.get('__orig_bases__')
+    if isinstance(__orig_bases__, tuple) and len(__orig_bases__) > 0:
+        return __orig_bases__
+    else:
+        return None
+
+
 def getslots(obj: Any) -> Optional[Dict]:
     """Get __slots__ attribute of the class as dict.
 

tests/roots/test-ext-autodoc/target/classes.py

@@ -29,6 +29,10 @@ class Quux(List[Union[int, float]]):
     pass
 
 
+class Corge(Quux):
+    pass
+
+
 Alias = Foo
 
 #: docstring

tests/test_ext_autodoc_autoclass.py

@@ -273,6 +273,21 @@ def test_show_inheritance_for_subclass_of_generic_type(app):
     ]
 
 
+@pytest.mark.skipif(sys.version_info < (3, 7), reason='python 3.7+ is required.')
+@pytest.mark.sphinx('html', testroot='ext-autodoc')
+def test_show_inheritance_for_decendants_of_generic_type(app):
+    options = {'show-inheritance': None}
+    actual = do_autodoc(app, 'class', 'target.classes.Corge', options)
+    assert list(actual) == [
+        '',
+        '.. py:class:: Corge(iterable=(), /)',
+        '   :module: target.classes',
+        '',
+        '   Bases: :py:class:`target.classes.Quux`',
+        '',
+    ]
+
+
 @pytest.mark.sphinx('html', testroot='ext-autodoc')
 def test_autodoc_process_bases(app):
     def autodoc_process_bases(app, name, obj, options, bases):