Use --no-implicit-optional for type checking

[hauntsaninja]

Change Summary

This makes type checking PEP 484 compliant (as of 2018).
mypy will change its defaults soon.

See:
python/mypy#9091
python/mypy#13401

Checklist

• Unit tests for the changes exist
• Tests pass on CI and coverage remains at 100%
• Documentation reflects the changes where applicable
• changes/<pull request or issue id>-<github username>.md file added describing change
  (see changes/README.md for details)
• My PR is ready to review, please add a comment including the phrase "please review" to assign reviewers

[hauntsaninja]

please review :-)

[samuelcolvin]

Otherwise looks good, thank you.

Please update.

[samuelcolvin]

This is markdown, not rst.

[hauntsaninja]

I fixed the markdown, but it looks like tests on Python 3.8 are failing with a weird Literal[None] issue. I see the code to work around this — was that issue flaky or has something about my change reactivated it?

[samuelcolvin]

That's very weird, but I haven't seen that test being flakey before. I think it much be caused by your change, or be new.

[samuelcolvin]

I don't see it on other newer builds, so it must be caused by your changes.

[hauntsaninja]

I'll take a detailed look at it, but if I can't figure it out, how would you feel about potentially using the 3.7 code for 3.8 as well? If it can be activated by this seemingly no-op change, there may be a real issue here.

https://github.com/hauntsaninja/pydantic/blob/dab478aa81a59e0a5c69a0fe57bfe34f233994ff/pydantic/typing.py#L319

[samuelcolvin]

It looks like we have a custom implementation for a reason, but if it's really not necessary, we could remove it.

[samuelcolvin]

Notice

See twitter 🐦, I've you'd like this to be included in V1.10, please fix it and request a review TODAY.

Or if you need this in V1.10 but don't have time to complete it (or aren't the author), please comment here and on #4324

[samuelcolvin]

Let's wait and adopt this in the V2 codebase.

[Fokko]

Great to see this happening! 👍🏻 Don't forget to add py.typed: https://peps.python.org/pep-0561/#packaging-type-information

[samuelcolvin]

We've had a py.typed file since 2017?

[Fokko]

@samuelcolvin ah missed that one. I expected it to be on the root level. 👍🏻

[samuelcolvin]

The code base will change too much for V2 to keep this pr, but I'm tracking the issue in #4424