gh-99535: Add test for inheritance of annotations and update documentation (GH-99990)

(cherry picked from commit f5b7b19bf10724d831285fb04e00f763838bd555)

Co-authored-by: MonadChains <monadchains@gmail.com>

diff --git a/Doc/howto/annotations.rst b/Doc/howto/annotations.rst
index 2bc2f2d4c839e2df8d7ae31e4dc95c0923f6e3cd..472069032d6509c432892613d8b405d150ed6866 100644 (file)
--- a/Doc/howto/annotations.rst
+++ b/Doc/howto/annotations.rst
@@ -57,6 +57,12 @@ Accessing The Annotations Dict Of An Object In Python 3.10 And Newer
   newer is to call :func:`getattr` with three arguments,
   for example ``getattr(o, '__annotations__', None)``.
 
+  Before Python 3.10, accessing ``__annotations__`` on a class that
+  defines no annotations but that has a parent class with
+  annotations would return the parent's ``__annotations__``.
+  In Python 3.10 and newer, the child class's annotations
+  will be an empty dict instead.
+
 
 Accessing The Annotations Dict Of An Object In Python 3.9 And Older
 ===================================================================

diff --git a/Doc/library/typing.rst b/Doc/library/typing.rst
index 7fc0aa3a8e62868f413acc8baec454c4a68c892e..a3a6181eba2980bd03184e94d8695da9a0c87ace 100644 (file)
--- a/Doc/library/typing.rst
+++ b/Doc/library/typing.rst
@@ -2767,6 +2767,10 @@ Introspection helpers
    .. versionchanged:: 3.9
       Added ``include_extras`` parameter as part of :pep:`593`.
 
+   .. versionchanged:: 3.10
+      Calling ``get_type_hints()`` on a class no longer returns the annotations
+      of its base classes.
+
    .. versionchanged:: 3.11
       Previously, ``Optional[t]`` was added for function and method annotations
       if a default value equal to ``None`` was set.

diff --git a/Lib/test/test_grammar.py b/Lib/test/test_grammar.py
index da88519862712a7136d6df359d61bcd35bf4ff3b..bcd8d584b0f51b8bf922374233e3ee9d20e6faf1 100644 (file)
--- a/Lib/test/test_grammar.py
+++ b/Lib/test/test_grammar.py
@@ -415,6 +415,28 @@ class GrammarTests(unittest.TestCase):
                 x: int
                 x.y: list = []
 
+    def test_annotations_inheritance(self):
+        # Check that annotations are not inherited by derived classes
+        class A:
+            attr: int
+        class B(A):
+            pass
+        class C(A):
+            attr: str
+        class D:
+            attr2: int
+        class E(A, D):
+            pass
+        class F(C, A):
+            pass
+        self.assertEqual(A.__annotations__, {"attr": int})
+        self.assertEqual(B.__annotations__, {})
+        self.assertEqual(C.__annotations__, {"attr" : str})
+        self.assertEqual(D.__annotations__, {"attr2" : int})
+        self.assertEqual(E.__annotations__, {})
+        self.assertEqual(F.__annotations__, {})
+
+
     def test_var_annot_metaclass_semantics(self):
         class CMeta(type):
             @classmethod