gh-91243: Document Required and NotRequired (GH-93173)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
(cherry picked from commit 711eda7dec)

Co-authored-by: David Foster <david@dafoster.net>

Doc/library/typing.rst

@@ -78,6 +78,8 @@ annotations. These include:
      *Introducing* :data:`TypeVarTuple`
 * :pep:`647`: User-Defined Type Guards
      *Introducing* :data:`TypeGuard`
+* :pep:`655`: Marking individual TypedDict items as required or potentially-missing
+     *Introducing* :data:`Required` and :data:`NotRequired`
 * :pep:`673`: Self type
     *Introducing* :data:`Self`
 * :pep:`675`: Arbitrary Literal String Type
@@ -1022,6 +1024,18 @@ These can be used as types in annotations using ``[]``, each having a unique syn
 
    .. versionadded:: 3.8
 
+.. data:: Required
+
+.. data:: NotRequired
+
+   Special typing constructs that mark individual keys of a :class:`TypedDict`
+   as either required or non-required respectively.
+
+   For more information, see :class:`TypedDict` and
+   :pep:`655` ("Marking individual TypedDict items as required or potentially-missing").
+
+   .. versionadded:: 3.11
+
 .. data:: Annotated
 
    A type, introduced in :pep:`593` (``Flexible function and variable
@@ -1706,8 +1720,21 @@ These are not used in annotations. They are building blocks for declaring types.
       Point2D = TypedDict('Point2D', {'in': int, 'x-y': int})
 
    By default, all keys must be present in a ``TypedDict``. It is possible to
-   override this by specifying totality.
-   Usage::
+   mark individual keys as non-required using :data:`NotRequired`::
+
+      class Point2D(TypedDict):
+          x: int
+          y: int
+          label: NotRequired[str]
+
+      # Alternative syntax
+      Point2D = TypedDict('Point2D', {'x': int, 'y': int, 'label': NotRequired[str]})
+
+   This means that a ``Point2D`` ``TypedDict`` can have the ``label``
+   key omitted.
+
+   It is also possible to mark all keys as non-required by default
+   by specifying a totality of ``False``::
 
       class Point2D(TypedDict, total=False):
           x: int
@@ -1721,6 +1748,21 @@ These are not used in annotations. They are building blocks for declaring types.
    ``True`` as the value of the ``total`` argument. ``True`` is the default,
    and makes all items defined in the class body required.
 
+   Individual keys of a ``total=False`` ``TypedDict`` can be marked as
+   required using :data:`Required`::
+
+      class Point2D(TypedDict, total=False):
+          x: Required[int]
+          y: Required[int]
+          label: str
+
+      # Alternative syntax
+      Point2D = TypedDict('Point2D', {
+          'x': Required[int],
+          'y': Required[int],
+          'label': str
+      }, total=False)
+
    It is possible for a ``TypedDict`` type to inherit from one or more other ``TypedDict`` types
    using the class-based syntax.
    Usage::
@@ -1785,11 +1827,16 @@ These are not used in annotations. They are building blocks for declaring types.
 
       ``Point2D.__required_keys__`` and ``Point2D.__optional_keys__`` return
       :class:`frozenset` objects containing required and non-required keys, respectively.
-      Currently the only way to declare both required and non-required keys in the
-      same ``TypedDict`` is mixed inheritance, declaring a ``TypedDict`` with one value
-      for the ``total`` argument and then inheriting it from another ``TypedDict`` with
-      a different value for ``total``.
-      Usage::
+
+      Keys marked with :data:`Required` will always appear in ``__required_keys__``
+      and keys marked with :data:`NotRequired` will always appear in ``__optional_keys__``.
+
+      For backwards compatibility with Python 3.10 and below,
+      it is also possible to use inheritance to declare both required and
+      non-required keys in the same ``TypedDict`` . This is done by declaring a
+      ``TypedDict`` with one value for the ``total`` argument and then
+      inheriting from it in another ``TypedDict`` with a different value for
+      ``total``::
 
          >>> class Point2D(TypedDict, total=False):
          ...     x: int
@@ -1807,6 +1854,10 @@ These are not used in annotations. They are building blocks for declaring types.
 
    .. versionadded:: 3.8
 
+   .. versionchanged:: 3.11
+      Added support for marking individual keys as :data:`Required` or :data:`NotRequired`.
+      See :pep:`655`.
+
    .. versionchanged:: 3.11
       Added support for generic ``TypedDict``\ s.