Upgrade mypy to version 0.931

[squahtx]

and fix all the new complaints.

Closes #11712.

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file. The entry should:
  • Be a short description of your change which makes sense to users. "Fixed a bug that prevented receiving messages from other servers." instead of "Moved X method from EventStore to EventWorkerStore.".
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• Code style is correct
  (run the linters)

[squahtx]

Due to https://github.com/python/typeshed/pull/6678/files?

[squahtx]

Due to https://github.com/python/typeshed/pull/5622/files?

[squahtx]

The previous version of mypy didn't think .__attrs_attrs__ was a real attribute.
mypy 0.931 thinks it is, and thinks that attribute is an object, which doesn't have a .name.

[DMRobertson]

Would mypy be happier with attrs.fields_dict here? Requires attrs 18.1.

(Probably fine as-is though.)

[squahtx]

That's a little cleaner, thanks! We already require attrs>=19.2.0 so it's fine to use.

[DMRobertson]

It still looks a bit odd to have the getattr call. Maybe get_sources could boil down to yield from attrs.asdict(self).items()? Actually, I think not: looks like one is supposed to inherit from _EventSourcesInner?

I'm happy with this as it stands.

[DMRobertson]

LGTM (and curious to see what we can do with mypy's initial(?) support for ParamSpec).

Just a couple of questions:

[DMRobertson]

Would mypy be happier with attrs.fields_dict here? Requires attrs 18.1.

(Probably fine as-is though.)

[DMRobertson]

Is e.value always guaranteed to be present? I.e. was the fallback of None redundant?

[squahtx]

Both of the exception types we catch here have a value attribute:

class StopIteration(Exception):
    value: Any

class _DefGen_Return(BaseException):
    def __init__(self, value: object) -> None:
        self.value = value

Since the exception comes from the generator gen, which is supposedly a Generator[..., ..., T], the StopIteration ought to contain a T.
I can't say the same for _DefGen_Return because I have no idea what its purpose is. I'm guessing it works the same way.

[DMRobertson]

Both of the exception types we catch here have a value attribute:

class StopIteration(Exception):
    value: Any

class _DefGen_Return(BaseException):
    def __init__(self, value: object) -> None:
        self.value = value

Since the exception comes from the generator gen, which is supposedly a Generator[..., ..., T], the StopIteration ought to contain a T. I can't say the same for _DefGen_Return because I have no idea what its purpose is. I'm guessing it works the same way.

Seems plausible: https://github.com/twisted/twisted/blob/5c24e99e671c4082a1ddc8dbeb869402294bd0dc/src/twisted/internet/defer.py#L1508-L1521

[DMRobertson]

Many thanks!