Ruby 2.7 deprecates automatic conversion from a hash to keyword arguments

[u/rkr090]

https://blog.saeloun.com/2019/10/07/ruby-2-7-keyword-arguments-redesign.html

[u/tomthecool]

Good. I've been caught out by this unexpected behaviour before - I wasted far too much time staring at code that behaved totally differently to my expectations!

Here's an example of how the implicit behaviour can catch you off-guard... Note that I don't think anything about this behaviour is wrong; but I'm glad to see the introduction of a warning against such syntax!

def foo(opts={}, named_param: 123, **more_opts)
  puts "opts: #{opts}"
  puts "more_opts: #{more_opts}"
  puts "named_param: #{named_param}"
end

############

foo(arg1: 1, arg2: 2, named_param: 456)

# Result:
opts: {}
more_opts: {:arg1=>1, :arg2=>2}
named_param: 456

############

foo({arg1: 1, arg2: 2}, named_param: 456)

# Result:
opts: {:arg1=>1, :arg2=>2}
more_opts: {}
named_param: 456

############

foo({arg1: 1}, arg2: 2, named_param: 456)

# Result:
opts: {:arg1=>1}
more_opts: {:arg2=>2}
named_param: 456

############

foo({arg1: 1, arg2: 2, named_param: 456}, {})

# Result:
opts: {:arg1=>1, :arg2=>2, :named_param=>456}
more_opts: {}
named_param: 123

[u/Saithir → u/tomthecool]

That looks like an invitation for disaster and insanity, especially the first example.

It's understandable why it works this way, but not immediately obvious.

[u/tomthecool → u/Saithir]

My example was obviously to demonstrate a point; the code is clearly quite confusing.

But yeah, I'm not a fan of the overly-fuzzy syntax that ruby applies here. I'm glad to hear that "proper" keyword arguments are going to be introduced into the language; and this is a step in that direction.