Added type annotation for tests/client/test_async_client.py

[hramezani]

Refs https://github.com/encode/httpx/issues/650

We have still 3 issues in this file:

tests/client/test_async_client.py:29: error: Argument 1 to "update" of "Headers" has incompatible type "Dict[str, str]"; expected "Union[Headers, Dict[Union[str, bytes], Union[str, bytes]], Sequence[Tuple[Union[str, bytes], Union[str, bytes]]], None]"
tests/client/test_async_client.py:148: error: Argument "headers" to "post" of "AsyncClient" has incompatible type "Dict[str, str]"; expected "Union[Headers, Dict[Union[str, bytes], Union[str, bytes]], Sequence[Tuple[Union[str, bytes], Union[str, bytes]]], None]"

In above two test we defined headers like:
headers = {"Custom-header": "value"}
headers = {"Expect": "100-continue"}
which have type Dict[str, str] and I think they are valid type based on HeaderTypes definition. we can fix them by replacing them by List of Tuples like headers = [("Expect", "100-continue")]. TBH, can not figure out why they are incompatible.

tests/client/test_async_client.py:100: error: "raise_for_status" of "Response" does not return a value

What should we do with this error 🤔? Shall we ignore checking for this line?

I don't have much experience in type annotation, that's why I am asking this questions.

[florimondmanca]

Hey, thanks for this! Definitely useful to expand our type coverage in tests to discover oddities like this.

TBH, can not figure out why they are incompatible.

I think it’s yet another case of « Dict is invariant in values », so the Union’s in the values make mypy say « I see those are str, but I am really expecting Union[str, bytes], so those don’t match, nope ».

TL;DR I think we’d need to update the HeaderTypes to use Mapping (or most likely MutableMapping) instead of Dict.

[florimondmanca]

As for…

What should we do with this error 🤔? Shall we ignore checking for this line?

Yes I think it makes sense to # type: ignore that particular assertion. :)

[hramezani]

Thanks @florimondmanca, I changed the HeaderTypes and used MutableMapping instead of Dict in a separate commit.

[florimondmanca]

Thanks! A few more thoughts from me. Might take a look at the preliminary work I'm mentioning below. :-)

[hramezani]

@florimondmanca I will wait for #991 and #993 to be merged and then I can rebase this PR.

[hramezani]

@florimondmanca, I rebased it. we just have one error in tests/client/test_async_client.py and one in tests/client/test_client.py 👍

[florimondmanca]

Nice yup! Thanks