Fix or suppress MyPy errors

[Codeglitches]

As discussed in #335 the code currently does not fair well when the types are analyzed by MyPy. This pull request makes some changes so that it does pass a MyPy analysis check without errors. This would be a good starting point to start working on adding Annotations throughout the code.

Not all errors are really solved. In a few places a dynamic code style is used or there is some type confusion. These errors that could not be solved without some more refactoring are suppressed using the # type: ignore comment.

Let me know what you think of the changes

[chrysn]

Thanks, that's a useful contribution; still looking through it.

Testing locally, mypy complains about cbor2 missing annotations (Skipping analyzing "cbor2": module is installed, but missing library stubs or py.typed marker). Were you using any particular branch thereof? (I tried with having the whl built from latest cbor2 master in my PYTHONPATH).

If I want to test this in CI, is there anything more than mypy aiocoap to test? (answered already in https://github.com/chrysn/aiocoap/issues/335#issuecomment-1892126945)

I've recently dropped support for Python 3.7, 3.8 and 3.9; did you apply any workarounds to support type checking in old versions, or is that something that rather happens on the boxes of developers anyway, where a recent Python is present (and at runtime on older Pythons, type information is discarded)?

[chrysn]

Apart from the experiments in #347, I've pushed some more changes:

• AIU Any is frowned upon; I think I found the right types to go there.
• I've merged in master, which also gives it a shot at CI

[chrysn]

To summarize the current state, there are two things I'd like to do differently still:

• Wherever lists of things are spelled out rather than done programmatically, there should be an if __debug__: guarded check that verifies them, and possibly offers code generation
• There are some large swaths of type: ignore that I'll go through, maybe I can provide better hints
• The enum situation could need enhancement, optionnumbers are becoming unsightly

Sorry for the delay in taking this up; are you still around and would you address those?

[chrysn]

The enum rework of #347 appears to work, allowing the enum definitions to themselves to stay easy -- one down.

[chrysn]

The one large copied list is now also verified, and I'm in the process of looking through the remaining ignores.

[chrysn]

... and the large swaths are fixed by overhauling typing in oscore (where this exercise actually helped find a bug).

Running a few last checks, but then I think this can go in together with #347.

[Codeglitches]

Thanks for merging this pull request. Sorry for not lending a hand on finishing it up properly; I was otherwise occupied.