[issue33141] descriptor __set_name__ feature broken for dataclass descriptor fields

[Rick Teachey]

Rick Teachey <ricky at teachey.org> added the comment:

hmmm... if I check the C.d class attribute it seems to return the
descriptor instance object (not a field object) before any C instances have
been created. i guess this is just a part of how the dataclass
implementation works.

i didn't realize there's nothing "special" going on with descriptors here-
the descriptors "just work" by virtue of being set to the class attribute
at creation time. interesting.

maybe because of this descriptors should short-circuit the field creation
process entirely? that would be a shame though. having the option of
auto-including a descriptor in the class repr turns out to be very useful
and i'm already playing around with it in a project.

one idea: what if it there were a keyword argument to mark a field as a
descriptor, allowing tje descriptor to be set at type creation? this would
need to disallow init=True, i think. and setting a field default to a
descriptor class would then raise a type error.

---
Ricky.

"I've never met a Kentucky man who wasn't either thinking about going home
or actually going home." - Happy Chandler

On Mon, Mar 26, 2018 at 6:47 AM, Eric V. Smith <report at bugs.python.org>
wrote:

>
> Eric V. Smith <eric at trueblade.com> added the comment:
>
> I suppose I could, when overwriting the class member, check for
> inspect.ismethoddescriptor and call __set_name__ myself.
>
> ----------
> components: +Library (Lib)
> versions: +Python 3.8
>
> _______________________________________
> Python tracker <report at bugs.python.org>
> <https://bugs.python.org/issue33141>
> _______________________________________
>

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue33141>
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