bpo-46066: Deprecate kwargs syntax for TypedDict definitions (GH-31126)

Closes python/typing#981

https://bugs.python.org/issue46066

Doc/library/typing.rst

@@ -1470,10 +1470,19 @@ These are not used in annotations. They are building blocks for declaring types.
    ``Point2D.__optional_keys__``.
    To allow using this feature with older versions of Python that do not
    support :pep:`526`, ``TypedDict`` supports two additional equivalent
-   syntactic forms::
+   syntactic forms:
+
+   * Using a literal :class:`dict` as the second argument::
+
+      Point2D = TypedDict('Point2D', {'x': int, 'y': int, 'label': str})
+
+   * Using keyword arguments::
 
       Point2D = TypedDict('Point2D', x=int, y=int, label=str)
-      Point2D = TypedDict('Point2D', {'x': int, 'y': int, 'label': str})
+
+   .. deprecated-removed:: 3.11 3.13
+      The keyword-argument syntax is deprecated in 3.11 and will be removed
+      in 3.13. It may also be unsupported by static type checkers.
 
    By default, all keys must be present in a ``TypedDict``. It is possible to
    override this by specifying totality.
@@ -1483,6 +1492,9 @@ These are not used in annotations. They are building blocks for declaring types.
           x: int
           y: int
 
+      # Alternative syntax
+      Point2D = TypedDict('Point2D', {'x': int, 'y': int}, total=False)
+
    This means that a ``Point2D`` ``TypedDict`` can have any of the keys
    omitted. A type checker is only expected to support a literal ``False`` or
    ``True`` as the value of the ``total`` argument. ``True`` is the default,

Lib/test/test_typing.py

@@ -4380,6 +4380,7 @@ class TypedDictTests(BaseTestCase):
         self.assertEqual(Emp.__total__, True)
 
     def test_basics_keywords_syntax(self):
+        with self.assertWarns(DeprecationWarning):
             Emp = TypedDict('Emp', name=str, id=int)
         self.assertIsSubclass(Emp, dict)
         self.assertIsSubclass(Emp, typing.MutableMapping)
@@ -4395,6 +4396,7 @@ class TypedDictTests(BaseTestCase):
         self.assertEqual(Emp.__total__, True)
 
     def test_typeddict_special_keyword_names(self):
+        with self.assertWarns(DeprecationWarning):
             TD = TypedDict("TD", cls=type, self=object, typename=str, _typename=int, fields=list, _fields=dict)
         self.assertEqual(TD.__name__, 'TD')
         self.assertEqual(TD.__annotations__, {'cls': type, 'self': object, 'typename': str, '_typename': int, 'fields': list, '_fields': dict})
@@ -4451,7 +4453,7 @@ class TypedDictTests(BaseTestCase):
 
     def test_pickle(self):
         global EmpD  # pickle wants to reference the class by name
-        EmpD = TypedDict('EmpD', name=str, id=int)
+        EmpD = TypedDict('EmpD', {'name': str, 'id': int})
         jane = EmpD({'name': 'jane', 'id': 37})
         for proto in range(pickle.HIGHEST_PROTOCOL + 1):
             z = pickle.dumps(jane, proto)
@@ -4463,7 +4465,7 @@ class TypedDictTests(BaseTestCase):
             self.assertEqual(EmpDnew({'name': 'jane', 'id': 37}), jane)
 
     def test_optional(self):
-        EmpD = TypedDict('EmpD', name=str, id=int)
+        EmpD = TypedDict('EmpD', {'name': str, 'id': int})
 
         self.assertEqual(typing.Optional[EmpD], typing.Union[None, EmpD])
         self.assertNotEqual(typing.List[EmpD], typing.Tuple[EmpD])

Lib/typing.py

@@ -2569,9 +2569,8 @@ def TypedDict(typename, fields=None, /, *, total=True, **kwargs):
 
     The type info can be accessed via the Point2D.__annotations__ dict, and
     the Point2D.__required_keys__ and Point2D.__optional_keys__ frozensets.
-    TypedDict supports two additional equivalent forms::
+    TypedDict supports an additional equivalent form::
 
-        Point2D = TypedDict('Point2D', x=int, y=int, label=str)
         Point2D = TypedDict('Point2D', {'x': int, 'y': int, 'label': str})
 
     By default, all keys must be present in a TypedDict. It is possible
@@ -2587,14 +2586,22 @@ def TypedDict(typename, fields=None, /, *, total=True, **kwargs):
     the total argument. True is the default, and makes all items defined in the
     class body be required.
 
-    The class syntax is only supported in Python 3.6+, while two other
-    syntax forms work for Python 2.7 and 3.2+
+    The class syntax is only supported in Python 3.6+, while the other
+    syntax form works for Python 2.7 and 3.2+
     """
     if fields is None:
         fields = kwargs
     elif kwargs:
         raise TypeError("TypedDict takes either a dict or keyword arguments,"
                         " but not both")
+    if kwargs:
+        warnings.warn(
+            "The kwargs-based syntax for TypedDict definitions is deprecated "
+            "in Python 3.11, will be removed in Python 3.13, and may not be "
+            "understood by third-party type checkers.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
 
     ns = {'__annotations__': dict(fields)}
     module = _caller()

Misc/ACKS

@@ -1974,6 +1974,7 @@ Arnon Yaari
 Alakshendra Yadav
 Hirokazu Yamamoto
 Masayuki Yamamoto
+Jingchen Ye
 Ka-Ping Yee
 Chi Hsuan Yen
 Jason Yeo

Misc/NEWS.d/next/Library/2022-02-08-16-42-20.bpo-46066.m32Hl0.rst

@@ -0,0 +1,3 @@
+Deprecate kwargs-based syntax for :class:`typing.TypedDict` definitions.
+It had confusing semantics when specifying totality, and was largely unused.
+Patch by Jingchen Ye.