Make the attribute non-optional and support kwarg compat.

Also reorganize the test cases and add coverage.

Signed-off-by: Zixuan James Li <p359101898@gmail.com>

doc/index.rst

@@ -396,10 +396,10 @@ Special typing primitives
       .. versionadded:: 4.9.0
 
     The experimental ``closed`` keyword argument and the special key
-    ``"__extra_items__"`` proposed in :pep:`728` are supported.
+    ``__extra_items__`` proposed in :pep:`728` are supported.
 
     When ``closed`` is unspecified or ``closed=False`` is given,
-    ``"__extra_items__"`` behave like a regular key. Otherwise, this becomes a
+    ``__extra_items__`` behaves like a regular key. Otherwise, this becomes a
     special key that does not show up in ``__readonly_keys__``,
     ``__mutable_keys__``, ``__required_keys__``, ``__optional_keys``, or
     ``__annotations__``.
@@ -408,16 +408,21 @@ Special typing primitives
 
     .. attribute:: __closed__
 
-        A boolean flag indicating the value of the keyword argument ``closed``
-        on the current ``TypedDict``.
+        A boolean flag indicating whether the current ``TypedDict`` is
+        considered closed. This is not inherited by its subclasses.
 
         .. versionadded:: 4.10.0
 
     .. attribute:: __extra_items__
 
         The type annotation of the extra items allowed on the ``TypedDict``.
-        This attribute does not appear on a TypedDict that has itself and all
-        its bases non-closed.
+        This attribute defaults to ``None`` on a TypedDict that has itself and
+        all its bases non-closed. This default is different from ``type(None)``
+        that represents ``__extra_items__: None`` defined on a closed
+        ``TypedDict``.
+
+        If ``__extra_items__`` is not defined or inherited on a closed
+        ``TypedDict``, this defaults to ``Never``.
 
         .. versionadded:: 4.10.0
 
@@ -455,7 +460,7 @@ Special typing primitives
 
    .. versionchanged:: 4.10.0
 
-      The keyword argument ``closed`` and the special key ``"__extra_items__"``
+      The keyword argument ``closed`` and the special key ``__extra_items__``
       when ``closed=True`` is given were supported.
 
 .. class:: TypeVar(name, *constraints, bound=None, covariant=False,

src/test_typing_extensions.py

@@ -3820,6 +3820,24 @@ class ChildWithInlineAndOptional(Untotal, Inline):
             {'inline': bool, 'untotal': str, 'child': bool},
         )
 
+        class Closed(TypedDict, closed=True):
+            __extra_items__: None
+
+        class Unclosed(TypedDict, closed=False):
+            ...
+
+        class ChildUnclosed(Closed, Unclosed):
+            ...
+
+        self.assertFalse(ChildUnclosed.__closed__)
+        self.assertEqual(ChildUnclosed.__extra_items__, type(None))
+
+        class ChildClosed(Unclosed, Closed):
+            ...
+
+        self.assertFalse(ChildClosed.__closed__)
+        self.assertEqual(ChildClosed.__extra_items__, type(None))
+
         wrong_bases = [
             (One, Regular),
             (Regular, One),
@@ -4219,79 +4237,92 @@ def test_regular_extra_items(self):
         class ExtraReadOnly(TypedDict):
             __extra_items__: ReadOnly[str]
 
-        class ExtraRequired(TypedDict):
-            __extra_items__: Required[str]
-
-        class ExtraNotRequired(TypedDict):
-            __extra_items__: NotRequired[str]
-
         self.assertEqual(ExtraReadOnly.__required_keys__, frozenset({'__extra_items__'}))
         self.assertEqual(ExtraReadOnly.__optional_keys__, frozenset({}))
         self.assertEqual(ExtraReadOnly.__readonly_keys__, frozenset({'__extra_items__'}))
         self.assertEqual(ExtraReadOnly.__mutable_keys__, frozenset({}))
+        self.assertEqual(ExtraReadOnly.__extra_items__, None)
+        self.assertFalse(ExtraReadOnly.__closed__)
+
+        class ExtraRequired(TypedDict):
+            __extra_items__: Required[str]
 
         self.assertEqual(ExtraRequired.__required_keys__, frozenset({'__extra_items__'}))
         self.assertEqual(ExtraRequired.__optional_keys__, frozenset({}))
         self.assertEqual(ExtraRequired.__readonly_keys__, frozenset({}))
         self.assertEqual(ExtraRequired.__mutable_keys__, frozenset({'__extra_items__'}))
+        self.assertEqual(ExtraRequired.__extra_items__, None)
+        self.assertFalse(ExtraRequired.__closed__)
+
+        class ExtraNotRequired(TypedDict):
+            __extra_items__: NotRequired[str]
 
         self.assertEqual(ExtraNotRequired.__required_keys__, frozenset({}))
         self.assertEqual(ExtraNotRequired.__optional_keys__, frozenset({'__extra_items__'}))
         self.assertEqual(ExtraNotRequired.__readonly_keys__, frozenset({}))
         self.assertEqual(ExtraNotRequired.__mutable_keys__, frozenset({'__extra_items__'}))
+        self.assertEqual(ExtraNotRequired.__extra_items__, None)
+        self.assertFalse(ExtraNotRequired.__closed__)
 
     def test_closed_inheritance(self):
         class Base(TypedDict, closed=True):
             __extra_items__: ReadOnly[Union[str, None]]
-
-        class Child(Base):
-            a: int
-            __extra_items__: int
-
-        class GrandChild(Child, closed=True):
-            __extra_items__: str
 
         self.assertEqual(Base.__required_keys__, frozenset({}))
         self.assertEqual(Base.__optional_keys__, frozenset({}))
         self.assertEqual(Base.__readonly_keys__, frozenset({}))
         self.assertEqual(Base.__mutable_keys__, frozenset({}))
+        self.assertEqual(Base.__annotations__, {})
         self.assertEqual(Base.__extra_items__, ReadOnly[Union[str, None]])
+        self.assertTrue(Base.__closed__)
+
+        class Child(Base):
+            a: int
+            __extra_items__: int
 
         self.assertEqual(Child.__required_keys__, frozenset({'a', "__extra_items__"}))
         self.assertEqual(Child.__optional_keys__, frozenset({}))
         self.assertEqual(Child.__readonly_keys__, frozenset({}))
         self.assertEqual(Child.__mutable_keys__, frozenset({'a', "__extra_items__"}))
+        self.assertEqual(Child.__annotations__, {"__extra_items__": int, "a": int})
         self.assertEqual(Child.__extra_items__, ReadOnly[Union[str, None]])
+        self.assertFalse(Child.__closed__)
+
+        class GrandChild(Child, closed=True):
+            __extra_items__: str
 
         self.assertEqual(GrandChild.__required_keys__, frozenset({'a', "__extra_items__"}))
         self.assertEqual(GrandChild.__optional_keys__, frozenset({}))
         self.assertEqual(GrandChild.__readonly_keys__, frozenset({}))
         self.assertEqual(GrandChild.__mutable_keys__, frozenset({'a', "__extra_items__"}))
-        self.assertEqual(GrandChild.__extra_items__, str)
-
-        self.assertEqual(Base.__annotations__, {})
-        self.assertEqual(Child.__annotations__, {"__extra_items__": int, "a": int})
         self.assertEqual(GrandChild.__annotations__, {"__extra_items__": int, "a": int})
-
-        self.assertTrue(Base.__closed__)
-        self.assertFalse(Child.__closed__)
+        self.assertEqual(GrandChild.__extra_items__, str)
         self.assertTrue(GrandChild.__closed__)
 
-    def test_absent_extra_items(self):
+    def test_implicit_extra_items(self):
         class Base(TypedDict):
             a: int
-
+
+        self.assertEqual(Base.__extra_items__, None)
+        self.assertFalse(Base.__closed__)
+
         class ChildA(Base, closed=True):
             ...
 
+        self.assertEqual(ChildA.__extra_items__, Never)
+        self.assertTrue(ChildA.__closed__)
+
         class ChildB(Base, closed=True):
             __extra_items__: None
-
-        self.assertNotIn("__extra_items__", Base.__dict__)
-        self.assertIn("__extra_items__", ChildA.__dict__)
-        self.assertIn("__extra_items__", ChildB.__dict__)
-        self.assertEqual(ChildA.__extra_items__, Never)
+
         self.assertEqual(ChildB.__extra_items__, type(None))
+        self.assertTrue(ChildB.__closed__)
+
+    def test_backwards_compatibility(self):
+        with self.assertWarns(DeprecationWarning):
+            TD = TypedDict("TD", closed=int)
+        self.assertFalse(TD.__closed__)
+        self.assertEqual(TD.__annotations__, {"closed": int})
 
 
 class AnnotatedTests(BaseTestCase):

src/typing_extensions.py

@@ -920,7 +920,7 @@ def __new__(cls, name, bases, ns, *, total=True, closed=False):
             optional_keys = set()
             readonly_keys = set()
             mutable_keys = set()
-            extra_items_type = _marker
+            extra_items_type = None
 
             for base in bases:
                 base_dict = base.__dict__
@@ -930,18 +930,18 @@ def __new__(cls, name, bases, ns, *, total=True, closed=False):
                 optional_keys.update(base_dict.get('__optional_keys__', ()))
                 readonly_keys.update(base_dict.get('__readonly_keys__', ()))
                 mutable_keys.update(base_dict.get('__mutable_keys__', ()))
-                if '__extra_items__' in base_dict:
-                    extra_items_type = base_dict['__extra_items__']
-
-            if closed and extra_items_type is _marker:
+                if (base_extra_items_type := base_dict.get('__extra_items__', None)) is not None:
+                    extra_items_type = base_extra_items_type
+                
+            if closed and extra_items_type is None:
                 extra_items_type = Never
             if closed and "__extra_items__" in own_annotations:
                 annotation_type = own_annotations.pop("__extra_items__")
                 qualifiers = set(_get_typeddict_qualifiers(annotation_type))
                 if Required in qualifiers or NotRequired in qualifiers:
                     raise TypeError(
-                        f"Special key __extra_items__ does not support"
-                        " Required and NotRequired"
+                        "Special key __extra_items__ does not support "
+                        "Required and NotRequired"
                     )
                 extra_items_type = annotation_type
 
@@ -972,8 +972,7 @@ def __new__(cls, name, bases, ns, *, total=True, closed=False):
             if not hasattr(tp_dict, '__total__'):
                 tp_dict.__total__ = total
             tp_dict.__closed__ = closed
-            if extra_items_type is not _marker:
-                tp_dict.__extra_items__ = extra_items_type
+            tp_dict.__extra_items__ = extra_items_type
             return tp_dict
 
         __call__ = dict  # static method
@@ -1047,6 +1046,9 @@ class Point2D(TypedDict):
                 "using the functional syntax, pass an empty dictionary, e.g. "
             ) + example + "."
             warnings.warn(deprecation_msg, DeprecationWarning, stacklevel=2)
+            if closed is not False and closed is not True:
+                kwargs["closed"] = closed
+                closed = False
             fields = kwargs
         elif kwargs:
             raise TypeError("TypedDict takes either a dict or keyword arguments,"