Fix sphinx-doc#8567: autodoc: Instance attributes are incorrectly add…

…ed to Parent class

The instance attributes on subclasses are shown on the document of
parent class unexpectedly because of autodoc modifies `__annotations__`
in place.  This fix creates a copy of `__annotations__` attribute and
attach it to the subclass.

CHANGES

@@ -19,6 +19,7 @@ Bugs fixed
 * #8559: autodoc: AttributeError is raised when using forward-reference type
   annotations
 * #8568: autodoc: TypeError is raised on checking slots attribute
+* #8567: autodoc: Instance attributes are incorrectly added to Parent class
 
 Testing
 --------

sphinx/ext/autodoc/__init__.py

@@ -1856,7 +1856,8 @@ def can_document_member(cls, member: Any, membername: str, isattr: bool, parent:
     def update_annotations(self, parent: Any) -> None:
         """Update __annotations__ to support type_comment and so on."""
         try:
-            annotations = inspect.getannotations(parent)
+            annotations = dict(inspect.getannotations(parent))
+            parent.__annotations__ = annotations
 
             analyzer = ModuleAnalyzer.for_module(self.modname)
             analyzer.analyze()
@@ -2292,7 +2293,8 @@ def isinstanceattribute(self) -> bool:
     def update_annotations(self, parent: Any) -> None:
         """Update __annotations__ to support type_comment and so on."""
         try:
-            annotations = inspect.getannotations(parent)
+            annotations = dict(inspect.getannotations(parent))
+            parent.__annotations__ = annotations
 
             for cls in inspect.getmro(parent):
                 try: