Issue #14183 has been updated by Dan0042 (Daniel DeLorme).


@koic, would this not be good enough for you?

```ruby
str = 'Hello, %<foo>s, %<bar>s'
ary = [foo: 'foo', bar: 'bar']

ary.each do |h|
  format(str, **h)
end
```

But I have to say this would not even have been an issue if using class-based keyword arguments like I had suggested. Then ary[0] would have been a KwHash and the keyword semantics would naturally have flowed through to the block. I'm sorry to beat on a dead horse but it's so frustrating that I can't help myself :-(

> I think everyone agrees that keyword argument separation is disruptive, but it is no more disruptive to blocks than it is to method calls in general.

Yeah, it's pretty disruptive. To the extent that imho the cost is 10x the benefit. But oh well, dead horses, ships that sailed...

But more to the point, I think this example shows keyword separation is actually more disruptive to blocks than to method calls in general. Because the method that yields to the block is often/usually out of our control. I find this is quite similar to the situation with delegation, in the sense that there's an intermediary that used to just pass through the data to the intended destination, but now this doesn't work anymore. With delegation it was sender->delegator->target, with blocks it's object->method->block. With delegation it's easy enough to fix by adding `**kw` or `ruby2_keywords`, but with blocks it looks like the only choice is to **restructure the code**. That's a fair amount more disruptive than the simple find-and-replace operations we were seeing previously.

----------------------------------------
Feature #14183: "Real" keyword argument
https://bugs.ruby-lang.org/issues/14183#change-83018

* Author: mame (Yusuke Endoh)
* Status: Closed
* Priority: Normal
* Assignee: 
* Target version: Next Major
----------------------------------------
In RubyWorld Conference 2017 and RubyConf 2017, Matz officially said that Ruby 3.0 will have "real" keyword arguments.  AFAIK there is no ticket about it, so I'm creating this (based on my understanding).

In Ruby 2, the keyword argument is a normal argument that is a Hash object (whose keys are all symbols) and is passed as the last argument.  This design is chosen because of compatibility, but it is fairly complex, and has been a source of many corner cases where the behavior is not intuitive.  (Some related tickets: #8040, #8316, #9898, #10856, #11236, #11967, #12104, #12717, #12821, #13336, #13647, #14130)

In Ruby 3, a keyword argument will be completely separated from normal arguments.  (Like a block parameter that is also completely separated from normal arguments.)
This change will break compatibility; if you want to pass or accept keyword argument, you always need to use bare `sym: val` or double-splat `**` syntax:

```
# The following calls pass keyword arguments
foo(..., key: val)
foo(..., **hsh)
foo(..., key: val, **hsh)

# The following calls pass **normal** arguments
foo(..., {key: val})
foo(..., hsh)
foo(..., {key: val, **hsh})

# The following method definitions accept keyword argument
def foo(..., key: val)
end
def foo(..., **hsh)
end

# The following method definitions accept **normal** argument
def foo(..., hsh)
end
```

In other words, the following programs WILL NOT work:

```
# This will cause an ArgumentError because the method foo does not accept keyword argument
def foo(a, b, c, hsh)
  p hsh[:key]
end
foo(1, 2, 3, key: 42)

# The following will work; you need to use keyword rest operator explicitly
def foo(a, b, c, **hsh)
  p hsh[:key]
end
foo(1, 2, 3, key: 42)

# This will cause an ArgumentError because the method call does not pass keyword argument
def foo(a, b, c, key: 1)
end
h = {key: 42}
foo(1, 2, 3, h)

# The following will work; you need to use keyword rest operator explicitly
def foo(a, b, c, key: 1)
end
h = {key: 42}
foo(1, 2, 3, **h)
```

I think here is a transition path:

* Ruby 2.6 (or 2.7?) will output a warning when a normal argument is interpreted as keyword argument, or vice versa.
* Ruby 3.0 will use the new semantics.

---Files--------------------------------
vm_args.diff (4.19 KB)
vm_args_v2.diff (4.18 KB)


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