On Tue, Mar 2, 2021 at 3:06 PM David Foster <davidfstr@gmail.com> wrote:
>>> Q3. How will get_type_hints(...), get_options(...) and get_args(...)
>>> behave with TypedDicts (and their __annotations__ values) where keys are
>>> explicitly marked Required[...] or NotRequired[...]?
>> Good question. Presumably they would became similarly to how they treat
>> other type qualifiers like Final[] and Annotated[] (whatever that
>> behavior is), but I'll do some further research/thinking here.
> Suggestions:
>>>> TD = TypedDict("TD", {"a": Required[int]}, total=False)
>>>> get_type_hints(TD)
> {'a': typing.Required[int]}
>>>> a = get_type_hints(TD)["a"]
>>>> get_origin(a)
> typing.Required
>>>> get_args(a)
> (<class 'int'>,)

Yes, that's the *preserve* approach.

I could also see an argument that the hints be *erased*, leaving only
the requireness information in the `__required_keys__` and
`__optional_keys__` collections. Erased types are likely to be easier
for user code to work with at runtime.

Again, I'll do some more research RE the behavior of similar Final[] and
Annotated[] here when I have some bandwidth.

While Final is not allowed in a TypedDict, in contexts where it is allowed it is preserved. I recommend the same for [Not]Required.

--Guido van Rossum (python.org/~guido)