[ruby-core:118114] [Ruby master Bug#20513] the feature of kwargs in index methods has been removed without due consideration of utility and compatibility

30 May 2024

      Issue #20513 has been updated by jeremyevans0 (Jeremy Evans).

jeremyevans0 (Jeremy Evans) wrote in #note-14:
...
bughit (bug hit) wrote in #note-13:
...
...
Yes. The change is only for []=. Some methods like Dir[] do take keyword arguments, and it's unchanged.
Someone should correct the release notes.
Agreed.  I'll take care of that.
I submitted a pull request that updates NEWS and also fixes the error messages to be clear this is related to index assignment and not plain index: https://github.com/ruby/ruby/pull/10877

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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-108548

* Author: bughit (bug hit)
* Status: Closed
* 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
-- 
https://bugs.ruby-lang.org/