I believe "a" below should be an optional key, not a required one.

Python 3.9.0 (default, Oct  7 2020, 23:09:01) 
[GCC 10.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import typing
>>> TD = typing.TypedDict("TD", {"a": str}, total=False)
>>> TD.__total__
False
>>> TD.__required_keys__
frozenset({'a'})
>>> TD.__optional_keys__
frozenset()
>>>

It looks like the issue is that _TypedDictMeta only respects "total" as a keyword argument to __new__, but the TypedDict function passes it along by setting __total__ in the generated namespace instead.

This fixes it:

diff --git a/Lib/typing.py b/Lib/typing.py
index 46c54c4..bb0696b 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -2050,7 +2050,7 @@ class body be required.
     except (AttributeError, ValueError):
         pass
 
-    return _TypedDictMeta(typename, (), ns)
+    return _TypedDictMeta(typename, (), ns, total=total)
 
 _TypedDict = type.__new__(_TypedDictMeta, 'TypedDict', (), {})
 TypedDict.__mro_entries__ = lambda bases: (_TypedDict,)

I can fix this, Paul, unless you want to take it. Probably deserves a regression test or two as well.

Your patch LGTM, Brandt.

Some notes on needed TypedDict doc fixes.

https://docs.python.org/3/library/typing.html#typing.TypedDict

"class typing.TypedDict(dict)"

The actual signature from inspect.signature is "(typename, fields=None, /, *, total=True, **kwargs)".  I presume fields not None and kwargs != {} are mutually exclusive.  AFAIK, the kwargs version of the call alternative is not in PEP 589.

"The type info for introspection can be accessed via Point2D.__annotations__ and Point2D.__total__."

'__total__' is not indexed.  __required_keys__ and __optional_keys__ are neither documented (including not in the PEP, which does not get revised) nor indexed.

It looks like this is a duplicate of issue 42059. We should just use their existing PR instead (PR 22736).