[ruby-core:53383] [CommonRuby - Feature #7701] Non-optional (required) keyword args

Issue #7701 has been updated by headius (Charles Nutter).


trans (Thomas Sawyer) wrote:
> Wait. You are the one who brought it up in #16. I was just responding to that.

mame brought it up in #9.

> I agree for the opposite reason! Why the rush to add required keyword arguments when Ruby took, jeez, how many years, to get keyword arguments? Wouldn't it be prudent to give it some time first?

Because they should have been there to begin with?

> Really? That's what you got from what I wrote? Well, try reading what I wrote again. If you want a summary, I suppose the closest common description is YAGNI. 

I think the +1s on this bug indicate people do want it. Whether they need it remains to be seen.

> > def foo(a:, b:) .... end
> > foo(1) => ArgumentError("Method `foo' requires arguments `a', `b'")
> > Bad thing?
> 
> Yes.

Arguing against a feature solely based on YAGNI doesn't seem very effective. Your other arguments were better because they actually discuss concerns about the feature, rather than just saying "I don't think this will be useful, so let's not do it." Do you have other substantive concerns about the feature itself?

I think having required and optional kwargs goes nicely with required and optional positional args, and I personally think it will see good use in DSLs and more readable APIs. For the same reason optional kwargs are useful to have in Ruby 2.0, required kwargs provide the same benefits *plus* guarantees that you'll receive certain keywords. It's the naming+positional flexibility of kwargs with the strictness of required positional args.

In short, I'll summarize my rebuttal this way: Do you agree that keyword args are useful? Do you agree that being able to force certain args to be given is useful? Then why wouldn't required keyword args be a natural feature to have in place?
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Feature #7701: Non-optional (required) keyword args
https://bugs.ruby-lang.org/issues/7701#change-37580

Author: headius (Charles Nutter)
Status: Assigned
Priority: Normal
Assignee: nobu (Nobuyoshi Nakada)
Category: 
Target version: 


=begin
I would like to see keyword args expanded to include a non-optional form, to force callers to pass in keyword arguments.

Currently, we have required, optional, and rest positional args but only optional and rest keyword args. Consistency is one small reason to add required keyword args.

They would likely take the form of keyword with no default value:

  def foo(a:, b:)
    ...
  end

  foo(a: 1, b: 2) # ok
  foo(a: 1) # ArgumentError

Justifications:

* Consistency with positional args. A weak justification, I know.
* Avoiding a lot of boilerplate code by users wishing to enforce keywords being passed in. Example from tenderlove:

    def foo(a: raise('pass a'), b: raise('pass b'))

* Building a rich API atop keyword args would be easier (i.e. require fewer manual checks) if you could force some keywords to be passed in. Having to check everywhere when you require a keyword argument is unpleasant.
* Keyword args already enforces that no *additional* keyword args can be passed (without **), and it seems lopsided to have no way to enforce a minimum set of keyword args.
=end



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