Re: [PATCH v5 19/36] qapi/events.py: add type hint annotations

[Markus Armbruster]

John Snow <jsnow@redhat.com> writes:

> On 10/7/20 7:49 AM, Markus Armbruster wrote:
>> Looks like commit message of PATCH 24 has an answer.
>> Copy to all the commits that omit -> None similarly?
>
> Probably not needed.
>
> It's covered by the class basics section in the mypy manual;
> https://mypy.readthedocs.io/en/stable/class_basics.html#annotating-init-methods
>
> and if you should happen to omit annotations for __init__ entirely as
> a novice, you will be treated to messages such as these:
>
> qapi/source.py:18: error: Function is missing a return type annotation
> qapi/source.py:18: note: Use "-> None" if function does not return a value
> Found 1 error in 1 file (checked 14 source files)
>
> Pretty good error!
>
> There's no error if you DO explicitly add a -> None from __init__, but
> at worst it's just extraneous (but correct) information.

Let me apply the zero-one-infinity rule:

* Zero: explain it in none of the commit messages, i.e. dumb down PATCH
  24.

* One: explain it in one.  Do it in the first one, please (here, I
  think).

* Infinity: explain it in every one.

Up to you!

> I could add a note to the style guide that I prefer omitting the
> return from __init__. I like omitting as much as I possibly can.
>
> (You'll notice I don't always type every local, either -- when local
> inference is accurate, I leave it alone.)

Type inference can save us from repeating the obvious over and over, and
that's lovely.