Declare registry on MetricWrapperBase as Optional

[reivilibre]

Dear maintainer @csmarchbanks,

The release of 0.13.0 yesterday appears to have caused us some type checking errors with Mypy (presumably this is a recent effort to annotate this library with types — thanks!).

I think this particular annotation is incomplete though — our code relies on passing None here and the code beneath says the following:

            if registry:
                registry.register(self)

In other words, I think this was intended to be optional.

Thanks!

Signed-off-by: Olivier Wilkinson (reivilibre) [email protected]

[csmarchbanks]

Thanks and good catch! When I look at your linked PR you are also using a custom proxy registry instead of a CollectorRegistry. Perhaps for now we should just leave out type checking on the registry until a Protocol or abc is created?

Would you also be able to fix the same issue in Enum in this file as well?

Once merged I will cut 0.13.1

[csmarchbanks]

FYI I am also going to allow Any as labelvalue types as we cast them to str anyway: #755.

[reivilibre]

Perhaps for now we should just leave out type checking on the registry until a Protocol or abc is created?

I think it's fair enough to leave it as is (with the type annotations) — if people like us are so keen on doing dubious things then a cast is OK to work around the problem in the meantime (it's no worse than it being Any — but for people who are respecting the annotations, it provides a little bit more safety net).

FYI I am also going to allow Any as labelvalue types as we cast them to str anyway

Thanks! I noticed they get cast to str internally but it's one of those things where you shouldn't second-guess the type annotations too much (though I suppose at this point, people are relying on the casts being there). It's good to have it stated explicitly, though — thanks for that (and for letting me know).

I've updated the PR to do the same for Enum :).

[csmarchbanks]

That sounds good, thanks!