Type hints for optional `None` values

[jrycw]

Currently, we employ three styles to describe parameters that might be assigned as None:

1. Union[str, None]
2. Optional[str]
3. str | None

I personally prefer style 3. However, since this style is only supported in Python 3.10 and later, I'd like to gather the team's opinions on the preferred style. I'm interested in submitting a PR to address this issue in our codebase once we reach a conclusion.

[machow]

Hey! I feel onboard with option 3! I think the only place we can't currently do it is in _tbl_data.py, since functools.singledispatch does some dynamic type annotation inspection, which breaks in that case (I think this is only an issue in python 3.9, but could be wrong).

In any event, a refactor that did (3) anywhere possible would be a huge contribution! Thanks for taking time to emphasize the value of consistency in the codebase :)

[jrycw]

@machow Thank you for your response. Another question arises: Do you think we could use native data structures for type hints now? For instance, replacing typing.List with list.

[machow]

Yeah, I think that now we are 3.9+, using list[...] should work. AFAICT the easiest way to check is to look up the python docs entry for the corresponding typing class, and see if there's a deprecation note:

https://docs.python.org/3/library/typing.html#typing.List

It looks like typing.Optional was deprecated in 3.10, but afaik as long as you have from __future__ import annotations, you should be able to use x | None. Or at the very least, use it wrapped in a string? "x | None"

[jrycw]

Thank you for pointing out the related docs. I'll start working on a PR to update our type hints using the new style.

[jrycw]

I'll go ahead and close this discussion since the resolution has been implemented in the merged PR #315.