Adding the `--strict` option to mypy

[DiddiLeija]

Overview

This is the second part of the discussion from #10065 (review).

Description

I have been working on converting the type hint commentaries into proper annotations (#10004, #10018, #10065, #10074). But I had a simple mistake on #10065 by annotating this:

        download_dir: str = None

when it must be annotated like this:

        download_dir: Optional[str] = None

We expected that Mypy was going to fail, but it just passed by. Then, we saw that Mypy accepts implicit optional annotations, until we use --no-implicit-optional.

What we want

We want Mypy to use --no-implicit-optional on its checks, to make a better diagnosis. View the PR review where the original discussion is for more information.

Code of Conduct

• I agree to follow the PSF Code of Conduct.

[DiddiLeija]

I opened the issue here because it is not exactly a Mypy problem. It is related to the way we use it on pypa/pip checks.

[pradyunsg]

Yea, we have to enable a bunch of mypy's strictness flags (this is probably the highest impact among those).

The ideal goal would be to get to a point where we can run mypy --strict . and have everything pass.

[DiddiLeija]

The ideal goal would be to get to a point where we can run mypy --strict . and have everything pass.

How can we make that for the CI checks?

[DiddiLeija]

How can we make that for the CI checks?

Sorry, I found it. We are already using options for Mypy checks (--pretty). I will submit a PR to add a --strict option to Mypy.

[DiddiLeija]

Can I self-assign this, as I created the related pull request?

[uranusjr]

Assigned

[DiddiLeija]

Hi, do we still wanna get this done? You know, we couldn't apply #10091, but maybe we can try again :)

Thoughts @pypa/pip-committers?

[pradyunsg]

I think so -- ideally, we'd be passing --strict to mypy.