Allow arguments in Factory

[hynek]

useful e.g. with structlog

x = attr.ib(default=Factory(logger.new, foo="bar"))

[Zac-HD]

Based on my experience with Hypothesis (especially the builds() strategy), I'd suggest that attrs should instead leave users with

x = attr.ib(factory=lambda: logger.new(foo="bar"))

(though you might want to add some documentation suggesting this, or functools.partial)

Passing through arbitrary args and kwargs can cause a variety of problems. The main two for this case are that attr.Factory already has named arguments - so users cannot provide arguments with those names to a callable factory - and takes_self is in some ways worse (impossible to provide star-args without explicitly passing a value for takes_self positionally). Using named args=(), kw_args=None arguments and dealing with the None-to-dict() issue would work, but IMO it's screamingly ugly and the lambda-or-partial solution works just fine.

TLDR please don't add this feature.

[hynek]

Funny you brought it up because I was tending to the same conclusion but I wasn’t quite over the jump to close the issue. :)

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