Feature #16379
closed
Backporting ... to Ruby 2.4 - 2.6 and pass_keywords
Description
I've heard quite a few people saying that backporting ... to Ruby 2.4-2.6 would be a good way to do migration for keyword arguments.
In fact, if we have ... in Ruby 2.4+, I think ... could be the way to do 90%+ of delegation in a backward-compatible way, and would be vastly more elegant than a hidden Hash flag (ruby2_keywords).
What does the Ruby core team think about that?
I think ... works nicely for lexical delegation:
def delegate(...)
target(...)
end
It can also work for delegating in a separate method by using ... inside a block inside the method accepting ...:
https://eregon.me/blog/2019/11/10/the-delegation-challenge-of-ruby27.html#pass_keywords
def initialize(...)
@call_later = -> { target(...) }
end
def call
@call_later.call
end
If we don't want to backport ..., there is also the option to use pass_keywords like so:
pass_keywords def delegate(*args, &block)
target(*args, &block)
end
pass_keywords def initialize(*args, &block)
@call_later = -> { target(*args, &block) }
end
def call
@call_later.call
end
Which can easily work by making pass_keywords a no-op on Ruby <= 2.6 and make *args behave like ... on Ruby 2.7+.
I think both of these are easier to understand than ruby2_keywords, and both don't need to have any performance trade-off on unrelated code (#16188).
I'd like to have the opinion of the core team on this.
It has been suggested multiple times (notably in my blog post on 10 November), but I have not seen any opinion on this tracker about it.
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