[ruby-core:101877] [Ruby master Feature#17472] HashWithIndifferentAccess like Hash extension

[nobu@ruby-lang.org]

Issue #17472 has been updated by nobu (Nobuyoshi Nakada).


I had a vague original idea for this proposal, which extends the Hash class generically.
First I though about case-insensitive string hashes, it had been able by using `$=` in old days.
The special variable was removed, still there are that use cases, e.g., HTTP headers, command completions, etc.

As I glanced st.c again this time, confirmed that customizing key conversion per instances isn't possible as far as keeping the backward compatibility.
I think case-insensitive (only for String) Hash, like hashes compared by identity, would be possible, though.

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Feature #17472: HashWithIndifferentAccess like Hash extension
https://bugs.ruby-lang.org/issues/17472#change-89718

* Author: naruse (Yui NARUSE)
* Status: Open
* Priority: Normal
* Target version: 3.1
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Rails has [ActiveSupport::HashWithIndifferentAccess](https://api.rubyonrails.org/classes/ActiveSupport/HashWithIndifferentAccess.html), which is widely used in Rails to handle Request, Session, ActionView's form construction, ActiveRecord's DB communication, and so on. It receives String or Symbol and normalize them to fetch the value. But it is implemented with Ruby. If we provide C implementation of that, Rails will gain the performance improvement.

summary of previous discussion: https://github.com/rails/rails/pull/40182#issuecomment-687607812



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