TYP: make the type annotations of read_csv & read_table discoverable

[topper-123]

• closes ERR: read_csv exposes an internal function when bad argument is specified #25648
• tests added / passed
• passes black pandas
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

In master the type of read_csv and read_table is 'Any'. This PR makes the functions signatures discoverable by mypy. Also fixes the error message when wrong kwarg is passed.

[WillAyd]

I am on board with this. This probably also closes #25648

[WillAyd]

So maybe worth pulling the test case from #33023

[WillAyd]

@gfyoung

[gfyoung]

I'm a bit torn on this TBH

I see the benefits to this change (mypy + #25648, #33023), but on the other hand, it does mean we will need to maintain two copies of essentially the same signature. This function generator setup was meant to alleviate that.

If we're mostly okay with maintaining two copies of the signature, then go for it. @pandas-dev/pandas-core

[topper-123]

@WillAyd , good idea taking in that test from #33023. I'll do that in the next commit.

@gfyoung , that was the reason I added the test test_read_table_same_signature_as_read_csv, to ensure the signatures don't drift apart :-)

[gfyoung]

@topper-123 : Ah, that's a fair point. Okay...it still feels little hacky, but the test does make me feel better about this.

[simonjayhawkins]

Thanks @topper-123 lgtm.

[simonjayhawkins]

at some point, would be beneficial for consistency checking to not use the dictionary here as mypy doesn't check this.

[jreback]

any comments @TomAugspurger or @jorisvandenbossche

[TomAugspurger]

No comments.

…

On Thu, Jun 25, 2020 at 9:37 AM Jeff Reback ***@***.***> wrote: ***@***.**** approved this pull request. any comments @TomAugspurger <https://github.com/TomAugspurger> or @jorisvandenbossche <https://github.com/jorisvandenbossche> — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#34976 (review)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAKAOIVCUXXW5OVFSKHFMHTRYNOJDANCNFSM4OHB6EIQ> .

[WillAyd]

Thanks @topper-123