Remove unnecessary hasattr check from TypedDict (python#533)

Co-authored-by: Jelle Zijlstra <[email protected]>

Author: Daraan

CHANGELOG.md

@@ -38,6 +38,10 @@ aliases that have a `Concatenate` special form as their argument.
   Patch by [Daraan](https://github.com/Daraan).
 - Fix error on Python 3.10 when using `typing.Concatenate` and 
   `typing_extensions.Concatenate` together. Patch by [Daraan](https://github.com/Daraan).
+- Backport of CPython PR [#109544](https://github.com/python/cpython/pull/109544)
+  to reflect Python 3.13+ behavior: A value assigned to `__total__` in the class body of a
+  `TypedDict` will be overwritten by the `total` argument of the `TypedDict` constructor.
+  Patch by [Daraan](https://github.com/Daraan), backporting a CPython PR by Jelle Zijlstra.
 
 # Release 4.12.2 (June 7, 2024)
 

src/test_typing_extensions.py

@@ -4237,6 +4237,37 @@ def test_total(self):
         self.assertEqual(Options.__required_keys__, frozenset())
         self.assertEqual(Options.__optional_keys__, {'log_level', 'log_path'})
 
+    def test_total_inherits_non_total(self):
+        class TD1(TypedDict, total=False):
+            a: int
+
+        self.assertIs(TD1.__total__, False)
+
+        class TD2(TD1):
+            b: str
+
+        self.assertIs(TD2.__total__, True)
+
+    def test_total_with_assigned_value(self):
+        class TD(TypedDict):
+            __total__ = "some_value"
+
+        self.assertIs(TD.__total__, True)
+
+        class TD2(TypedDict, total=True):
+            __total__ = "some_value"
+
+        self.assertIs(TD2.__total__, True)
+
+        class TD3(TypedDict, total=False):
+            __total__ = "some value"
+
+        self.assertIs(TD3.__total__, False)
+
+        TD4 = TypedDict('TD4', {'__total__': "some_value"})  # noqa: F821
+        self.assertIs(TD4.__total__, True)
+
+
     def test_optional_keys(self):
         class Point2Dor3D(Point2D, total=False):
             z: int

src/typing_extensions.py

@@ -1029,8 +1029,7 @@ def __new__(cls, name, bases, ns, *, total=True, closed=False):
             tp_dict.__optional_keys__ = frozenset(optional_keys)
             tp_dict.__readonly_keys__ = frozenset(readonly_keys)
             tp_dict.__mutable_keys__ = frozenset(mutable_keys)
-            if not hasattr(tp_dict, '__total__'):
-                tp_dict.__total__ = total
+            tp_dict.__total__ = total
             tp_dict.__closed__ = closed
             tp_dict.__extra_items__ = extra_items_type
             return tp_dict