TYP: Return annotations for io/{formats,json}

[twoertwein]

No description provided.

[datapythonista]

Looks good. It'd be good to have an issue about this for more context, and to somehow group the different issues in this effort. Also to add to the CI the validation you're using to find those. Does this make sense to you?

[twoertwein]

It'd be good to have an issue about this for more context

I will create an issue later today about it (many of these annotations could be easy first contributions). Inspired by @MarcoGorelli's #47497 I'm using pyright to find missing return annotations that it can infer. While this doesn't help pyright much (it infers them already), it helps mypy, and in some cases it also helps pyright (when pyright infers a Union (might be an overload) or infers Any/Unknown (might be able to find a narrower type).

Also to add to the CI the validation you're using to find those.

At the moment I'm just doing:

pyright --createstub pandas
grep -R "# -> " typings/pandas/

and then see which cases I feel comfortable annotating.

In terms of integrating something like that into the CI:

• [soon'ish?] @MarcoGorelli's (WIP) TYP: add some obvious -> None to pandas/core #47497 hook could be a way to catch some of the missing return values
• [in a few blue moons] If all functions have tight returns values, we have one fewer discrepancy between mypy and pyright: might be able to remove --skipunannotated run reportGeneralTypeIssues on all files (or the subset of files that currently pass). This would only catch missing return annotations that cause pyright to report errors.
• [in many blue moons] Using ENH: Using pyright to analyze missing type declarations #39813

[mroeschke]

Probably to be safe, this typing infraction should be address with an if width is not None or similar.

[twoertwein]

As far as I understand (not sure), width can only be None, when pandas is running in a non-interactive way (and I think it also requires that the user put None to set_options() for the default width). The function _repr_fits_horizontal_ exits early if console.in_interactive_session() is true which should ensure that the above line will never be reached with None. Probably makes sense to or this if condition with width is None:

pandas/pandas/core/frame.py

Line 1011 in a5ac19a

if ignore_width or not console.in_interactive_session():

[mroeschke]

Thanks, makes sense to me

[MarcoGorelli]

Inspired by @MarcoGorelli's #47497 I'm using pyright to find missing return annotations that it can infer.

Nice! Does this obliviate the need for #47497 and associated tool, or does pyright not find some obvious -> None statements?

[twoertwein]

Does this obliviate the need for #47497 and associated tool, or does pyright not find some obvious -> None statements?

Pyright is really good at inferring types :) but --createstubs does not care about private functions. Your hook is not only helpful to cover private functions but it is also helpful to enforce obvious -> None annotations. I believe that even #39813 (--verifytypes) does not enforce unannotated private functions.

[mroeschke]

Thanks @twoertwein As @datapythonista mentioned, would be good to have a general issue about this pyright specific check.

[twoertwein]

Opened #47521