keyword-only attrs

[asvetlov]

It would be nice to support keyword-only constructor parameters, e.g.

@attr.s
class A:
    a = attr.ib()
    b = attr.ib(keyword=True)

A(1, 2)  # forbidden
A(1, b=2)  # passed

Should be allowed for Python 3 only.
Well, attrs should have no Python 3 specific code -- compilation of __init__ function with keyword-only arguments generates SyntaxError on Python 2, maybe enough.

I don't know what name is better: keyword, kw_only, keyword_only.

[hynek]

Theere is a half-finished PR for this #281 but nobody came around to fix it into a mergeable shape.

[asvetlov]

Looks like we are in opposite situation.
I have no time to work on the issue, the feature doesn't kick my ass yet.
You have no time for working on aiohttp and family problems for the same reason I guess.

[hynek]

Heh exactly. 😂 I didn’t mean it accusingly, just wanted to point out there’s some work.

[asvetlov]

Anyway thank you for raising issues. We have client tracing support by aiohttp client finally for example.