[ruby-core:85027] [Ruby trunk Feature#14371] New option "recursive: true" for Hash#transform_keys!

Issue #14371 has been updated by matz (Yukihiro Matsumoto).


I don't think this proposal is a good idea for following reasons:

* `transform_keys` method to modify value part of `Hash`
* `recursive` option to change the behavior this much
* it is much harder to implement `transform_keys(recursive:true)` (without bang)

I understand the intention behind the proposal. Probably you want to process JSON-like Array-Hash structures. I feel the recent demand to handle those data structures in Ruby. So we might need to add some utility methods in Ruby. I am not sure how yet. Maybe by adding methods to JSON module, or adding them both Array and Hash (like `dig`).

Matz.


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Feature #14371: New option "recursive: true" for Hash#transform_keys!
https://bugs.ruby-lang.org/issues/14371#change-69736

* Author: tagomoris (Satoshi TAGOMORI)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
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`Hash#transform_keys!` is available when we want to symbolize hash keys.
But in some/many cases (for example, receiver hash object is nested configuration tree loaded from any files), hash object are
nested object, which has hashes or arrays of hashes as values.
It's super useful if we can transform keys of such nested values.

My proposal is `Hash#transform_keys!(recursive: true, &:to_sym)`. Pseudo code is:

```ruby
def transform_keys!(recursive: false, &block)
  # do original transform_keys! here
  values.each do |v|
    if v.respond_to?(:each)
      v.each{|i| i.transform_keys!(recursive: true, &block) if i.respond_to?(:transform_keys!) }
    else v.respond_to?(:transform_keys!)
      v.transform_keys!(recursive: true, &block)
    end
  end if recursive
end
```

The most major usage example is: `config = MyAwesomeFormat.load(file); config.transform_keys!(recursive: true, &:to_sym)`.




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