[issue32428] dataclasses: make it an error to have initialized non-fields in a dataclass

[Guido van Rossum]

Guido van Rossum <guido at python.org> added the comment:

I liked the original design better, where things without annotations would
just be ignored. What changed?

On Dec 27, 2017 5:19 PM, "Ivan Levkivskyi" <report at bugs.python.org> wrote:

>
> Ivan Levkivskyi <levkivskyi at gmail.com> added the comment:
>
> > I'm not sure I understand the distinction.
>
> Initially I thought about only flagging code like this:
>
> @dataclass
> class C:
>     x = field()
>
> But not this:
>
> @dataclass
> class C:
>     x = 42
>
> Now I think we should probably flag both as errors.
>
> > How do we only pick out `y` and probably `prop`, and ignore the rest,
> without being overly fragile to new things being added? I guess ignoring
> dunders and things in `__annotations__`. Is that close enough?
>
> We had a similar problem while developing Protocol class (PEP 544).
> Currently we just a have a whitelist of names that are skipped:
>
> '__abstractmethods__', '__annotations__', '__weakref__', '__dict__',
> '__slots__', '__doc__', '__module__'
>
> (plus some internal typing API names)
>
> ----------
>
> _______________________________________
> Python tracker <report at bugs.python.org>
> <https://bugs.python.org/issue32428>
> _______________________________________
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