require explicit empty sequence for 0-field TypedDict objects

Author: picnixz

Doc/whatsnew/3.15.rst

@@ -118,10 +118,13 @@ Deprecated
 Removed
 =======
 
-module_name
------------
+typing
+------
 
-* TODO
+* Using  ``TypedDict("T")`` or ``TypedDict("T", None)`` to construct
+  :class:`~typing.TypedDict` with zero fields is no more supported.
+  Use ``TypedDict("T", [])`` instead.
+  (Contributed by Bénédikt Tran in :gh:`133823`.)
 
 
 Porting to Python 3.15

Lib/test/test_typing.py

@@ -8904,39 +8904,27 @@ class MultipleGenericBases(GenericParent[int], GenericParent[float]):
         self.assertEqual(CallTypedDict.__orig_bases__, (TypedDict,))
 
     def test_zero_fields_typeddicts(self):
-        T1 = TypedDict("T1", {})
+        T1a = TypedDict("T1a", {})
+        T1b = TypedDict("T1b", [])
+        T1c = TypedDict("T1c", ())
         class T2(TypedDict): pass
         class T3[tvar](TypedDict): pass
         S = TypeVar("S")
         class T4(TypedDict, Generic[S]): pass
 
-        expected_warning = re.escape(
-            "Failing to pass a value for the 'fields' parameter is deprecated "
-            "and will be disallowed in Python 3.15. "
-            "To create a TypedDict class with 0 fields "
-            "using the functional syntax, "
-            "pass an empty dictionary, e.g. `T5 = TypedDict('T5', {})`."
-        )
-        with self.assertWarnsRegex(DeprecationWarning, fr"^{expected_warning}$"):
-            T5 = TypedDict('T5')
-
-        expected_warning = re.escape(
-            "Passing `None` as the 'fields' parameter is deprecated "
-            "and will be disallowed in Python 3.15. "
-            "To create a TypedDict class with 0 fields "
-            "using the functional syntax, "
-            "pass an empty dictionary, e.g. `T6 = TypedDict('T6', {})`."
-        )
-        with self.assertWarnsRegex(DeprecationWarning, fr"^{expected_warning}$"):
-            T6 = TypedDict('T6', None)
-
-        for klass in T1, T2, T3, T4, T5, T6:
+        for klass in T1a, T1b, T1c, T2, T3, T4:
             with self.subTest(klass=klass.__name__):
                 self.assertEqual(klass.__annotations__, {})
                 self.assertEqual(klass.__required_keys__, set())
                 self.assertEqual(klass.__optional_keys__, set())
                 self.assertIsInstance(klass(), dict)
 
+    def test_errors(self):
+        with self.assertRaisesRegex(TypeError, "missing 1 required.*argument"):
+            TypedDict('TD')
+        with self.assertRaisesRegex(TypeError, "object is not iterable"):
+            TypedDict('TD', None)
+
     def test_readonly_inheritance(self):
         class Base1(TypedDict):
             a: ReadOnly[int]

Lib/typing.py

@@ -3198,7 +3198,7 @@ def __subclasscheck__(cls, other):
     __instancecheck__ = __subclasscheck__
 
 
-def TypedDict(typename, fields=_sentinel, /, *, total=True):
+def TypedDict(typename, fields, /, *, total=True):
     """A simple typed namespace. At runtime it is equivalent to a plain dict.
 
     TypedDict creates a dictionary type such that a type checker will expect all
@@ -3253,24 +3253,6 @@ class DatabaseUser(TypedDict):
             username: str      # the "username" key can be changed
 
     """
-    if fields is _sentinel or fields is None:
-        import warnings
-
-        if fields is _sentinel:
-            deprecated_thing = "Failing to pass a value for the 'fields' parameter"
-        else:
-            deprecated_thing = "Passing `None` as the 'fields' parameter"
-
-        example = f"`{typename} = TypedDict({typename!r}, {{{{}}}})`"
-        deprecation_msg = (
-            "{name} is deprecated and will be disallowed in Python {remove}. "
-            "To create a TypedDict class with 0 fields "
-            "using the functional syntax, "
-            "pass an empty dictionary, e.g. "
-        ) + example + "."
-        warnings._deprecated(deprecated_thing, message=deprecation_msg, remove=(3, 15))
-        fields = {}
-
     ns = {'__annotations__': dict(fields)}
     module = _caller()
     if module is not None:

Misc/NEWS.d/next/Library/2025-05-11-08-48-55.gh-issue-133823.F8udQy.rst

@@ -0,0 +1,3 @@
+Remove support for ``TypedDict("T")`` and ``TypedDict("T", None)`` calls for
+constructing :class:`typing.TypedDict` objects with zero fields. Patch by
+Bénédikt Tran.