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

Closes python/typing#981

https://bugs.python.org/issue46066

diff --git a/Doc/library/typing.rst b/Doc/library/typing.rst
index 94a46b01a1a8c0312c949026b534b9e62d3aef0e..8240c912c649714fde574ceed31d6cc6595f8d8c 100644 (file)
--- a/Doc/library/typing.rst
+++ b/Doc/library/typing.rst
@@ -1470,11 +1470,20 @@ 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)
       Point2D = TypedDict('Point2D', {'x': int, 'y': int, 'label': str})
 
+   * Using keyword arguments::
+
+      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.
    Usage::
@@ -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,

diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
index 2bb5d61068a78c40374650e8d772c197fb563157..9548a0cab1d1ec3471ddda5276fc0cde9e496caa 100644 (file)
--- a/Lib/test/test_typing.py
+++ b/Lib/test/test_typing.py
@@ -4380,7 +4380,8 @@ class TypedDictTests(BaseTestCase):
         self.assertEqual(Emp.__total__, True)
 
     def test_basics_keywords_syntax(self):
-        Emp = TypedDict('Emp', name=str, id=int)
+        with self.assertWarns(DeprecationWarning):
+            Emp = TypedDict('Emp', name=str, id=int)
         self.assertIsSubclass(Emp, dict)
         self.assertIsSubclass(Emp, typing.MutableMapping)
         self.assertNotIsSubclass(Emp, collections.abc.Sequence)
@@ -4395,7 +4396,8 @@ class TypedDictTests(BaseTestCase):
         self.assertEqual(Emp.__total__, True)
 
     def test_typeddict_special_keyword_names(self):
-        TD = TypedDict("TD", cls=type, self=object, typename=str, _typename=int, fields=list, _fields=dict)
+        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})
         a = TD(cls=str, self=42, typename='foo', _typename=53, fields=[('bar', tuple)], _fields={'baz', set})
@@ -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])

diff --git a/Lib/typing.py b/Lib/typing.py
index 4a8bdf8132861ed65904399292bbfbddceae744f..3233827d816d13842272b7e81ffc74ae39ca2273 100644 (file)
--- a/Lib/typing.py
+++ b/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()

diff --git a/Misc/ACKS b/Misc/ACKS
index 64bd91d7d69053583e303cb8faa70804313318ad..244d7579b25eb383d8907ff2c9c584660a3c232d 100644 (file)
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1974,6 +1974,7 @@ Arnon Yaari
 Alakshendra Yadav
 Hirokazu Yamamoto
 Masayuki Yamamoto
+Jingchen Ye
 Ka-Ping Yee
 Chi Hsuan Yen
 Jason Yeo

diff --git a/Misc/NEWS.d/next/Library/2022-02-08-16-42-20.bpo-46066.m32Hl0.rst b/Misc/NEWS.d/next/Library/2022-02-08-16-42-20.bpo-46066.m32Hl0.rst
new file mode 100644 (file)
index 0000000..d13d942
--- /dev/null
+++ b/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.