Re: [PATCH v4 3/6] qapi: Add minor typing workaround for 3.6

[Markus Armbruster]

John Snow <jsnow@redhat.com> writes:

> Pylint under 3.6 does not believe that Collection is subscriptable at
> runtime. It is, making this a Pylint
> bug. https://github.com/PyCQA/pylint/issues/2377
>
> They closed it as fixed, but that doesn't seem to be true as of Pylint
> 2.13.9, the latest version you can install under Python 3.6. 2.13.9 was
> released 2022-05-13, about seven months after the bug was closed.
>
> The least-annoying fix here is to just use the more specific type
> Sequence, only because it seems to work in 3.6.
>
> Signed-off-by: John Snow <jsnow@redhat.com>
> ---
>  scripts/qapi/expr.py | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/scripts/qapi/expr.py b/scripts/qapi/expr.py
> index 5a1782b57ea..8701351fdfc 100644
> --- a/scripts/qapi/expr.py
> +++ b/scripts/qapi/expr.py
> @@ -33,11 +33,11 @@
>  
>  import re
>  from typing import (
> -    Collection,
>      Dict,
>      Iterable,
>      List,
>      Optional,
> +    Sequence,
>      Union,
>      cast,
>  )
> @@ -195,8 +195,8 @@ def check_defn_name_str(name: str, info: QAPISourceInfo, 
> meta: str) -> None:
>  def check_keys(value: _JSONObject,
>                 info: QAPISourceInfo,
>                 source: str,
> -               required: Collection[str],
> -               optional: Collection[str]) -> None:
> +               required: Sequence[str],
> +               optional: Sequence[str]) -> None:
>      """
>      Ensure that a dict has a specific set of keys.

The actual arguments are always List[str].  You actually used that until
v3 of the patch, and switched to the maximally general Collection[str]
in v4, with rationale that ended up in commit 538cd41065a:

    qapi/expr.py: Modify check_keys to accept any Collection
    
    This is a minor adjustment that lets parameters @required and
    @optional take tuple arguments, in particular ().  Later patches will
    make use of that.

No later patch ever did.

I'd prefer maximally stupid List[str], but it's no big deal either way.