Add `Style/HashNewKeywordArguments` cop

[r7kamura]

I have heard that future versions of Ruby are likely to deprecate the ability to pass default values with keyword arguments to Hash.new.

• https://bugs.ruby-lang.org/issues/19236

So I thought it would be a good idea to prepare a Cop that detects such usage and autocorrects it while it is still available. Since the signature is originally Hash.new(default_value = nil), there should be no problem deprecating the keyword arguments.

• https://ruby-doc.org/3.1.2/Hash.html#method-c-new

---

Before submitting the PR make sure the following are checked:

• [x] The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• [x] Wrote good commit messages.
• [ ] Commit message starts with [Fix #issue-number] (if the related issue exists).
• [x] Feature branch is up-to-date with master (if not - rebase it).
• [x] Squashed related commits together.
• [x] Added tests.
• [x] Ran bundle exec rake default. It executes all tests and runs RuboCop on its own code.
• [x] Added an entry (file) to the changelog folder named {change_type}_{change_description}.md if the new code introduces user-observable changes. See changelog entry format for details.

[r7kamura]

I am a little concerned about whether Style is the correct department. Semantically, Lint seems to be more correct, but I chose Style for now because I think Lint department is the place to put the most urgent Cop.

[koic]

Interesting. However, it is too early to judge the direction of this cop force yet. So, it should be decided after https://bugs.ruby-lang.org/issues/19236 is settled. Let's come back to this PR once https://bugs.ruby-lang.org/issues/19236 is closed.

[bbatsov]

Let's mark this PR as WIP in the mean time.

[Zopolis4]

https://bugs.ruby-lang.org/issues/19236 has been closed by ruby/ruby#7828, which has been shipped in Ruby 3.3.

[bbatsov]

@r7kamura can you rebase this on top of master, so we can finally merge it?

[r7kamura]

Thanks for the reminder 👍

I've resolved the conflict and rebased onto the latest master. It looks like there was a conflict due to the addition of a similarly named Style/HashSlice cop.

• https://github.com/rubocop/rubocop/pull/13507

[Earlopain]

There's significant overlap with the cop added in https://github.com/rubocop/rubocop/pull/13439. Is this PR needed anymore?

[bbatsov]

Oh, I had forgotten about this one.

[r7kamura]

Nice catch. I was completely unaware of its existence as well 😆

The purpose is the same, but in terms of the thoroughness of the explanation and the consideration for edge cases like capacity, Lint/HashNewWithKeywordArgumentsAsDefault is definitely superior.

I'll go ahead and close this pull request — thanks again!