From: "zverok (Victor Shepelev) via ruby-core" <ruby-core@...>
Date: 2024-05-30T12:51:18+00:00
Subject: [ruby-core:118093] [Ruby master Bug#20513] the feature of kwargs in index methods has been removed without due consideration of utility and compatibility

Issue #20513 has been updated by zverok (Victor Shepelev).


To add: just a ���point-of-view��� thing: I imagine teaching Ruby to somebody, and helping them to become proficient in it, and to find how everything is consistent and convenient (I did that a lot). And I imagine the following dialog:

```
��� So, for your custom object to have `[]`, you just `def []`, like it is a common method!
��� Oh, nice! I like how there are ground rules and everything is conforming to them!
... 
��� Oh, I expermented with it a bit, and for some reason, `colored_hash[:key, color: :red]` doesn���t work?.. 
  What am I doing wrong?.. Is it a bug?..
��� You see, young padawan... Many versions ago, there was that thing about Keyword Argument Separation.
  And when it was being done, we forgot to handle the `[]` situation... And then, in a few years, when
  it was handled, in order to not break some code slightly, we just removed the feature.
��� Ugh.
```

I mean, looking at the language with a fresh eye, ���something semantically clear and conforming to the existing intuitions doesn���t work because it was prohibited arbitrarily during one historical transition��� might be really harmful for the language���s image.

----------------------------------------
Bug #20513: the feature of kwargs in index methods has been removed without due consideration of utility and compatibility 
https://bugs.ruby-lang.org/issues/20513#change-108523

* Author: bughit (bug hit)
* Status: Open
* Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
See #20218

The ability to pass kwargs to index methods has been in ruby for a long time, probably from the inception of kwargs, so there's code that makes use of it. Other than the multiple assignment edge-case it's been working fine and is not conceptually unsound. kwargs allow for more variability in store/lookup operations via index methods, letting you control where/how something is stored/looked up. 

this is from 2.6
```ruby
module IndexTest
  @store = {}

  def self.store
    @store
  end

  def self.key(name, namespace: nil)
    name = "#{namespace}:#{name}" if namespace
    name
  end

  def self.[](name, namespace: nil)
    p [name, namespace]
    @store[key(name, namespace: namespace)]
  end

  def self.[]=(name, opts = {}, val)
    p [name, opts, val]
    @store[key(name, namespace: opts[:namespace])] = val
  end


end

IndexTest['foo'] = 1
p IndexTest['foo']
IndexTest['foo', namespace: 'bar'] = 2
p IndexTest['foo', namespace: 'bar']
p IndexTest.store
```

A reasonable breaking change would be for `[]=` to have real kwargs, rather than the middle positional kwarg collector hash in the above example. 

I am not arguing that breaking changes can't be introduced, but that a removal of a long-standing feature deserves more consideration and deliberation than the following:

> I found that use of keyword arguments in multiple assignment is broken
> Can we also prohibit keyword arguments ... ?
> OK, prohibit keyword arguments





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