Use frozen string literal in Active Storage

[koic]

Summary

Extends Style/FrozenStringLiteralComment RuboCop rule to activestorage/.

I also fixed that the "can not modify frozen String" error does not occur in rails/activestorage tests.

Related PR #29897.

/Cc @kirs

Other Information

There is the following Performance/UnfreezeString cop recently merged into RuboCop.

rubocop/rubocop#4586

It seems that String#+@ is superior to String#dup, but this PR does not using it because support target can not be limited to Ruby 2.3 or higher.

[rails-bot]

r? @eileencodes

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[kirs]

LGTM. Thanks for adding the rule for ActiveStorage!

I'm thinking that maybe now in .rubocop.yml we should use Exclude components that are not frozen string ready yet, instead of listing them under Include.

[rafaelfranca]

👍 to @kirs idea of flipping the whitelist to a blacklist. Could you do that?

[koic]

Thanks for your review and advise! I fixed it at 1822e04.

[matthewd]

That's not quite what @kirs meant.. we should end up with something more like:

Style/FrozenStringLiteralComment:
  Enabled: true
  EnforcedStyle: always
  Exclude:
    - 'railties/**/*'
    - 'actionview/test/**/*.builder'
    - 'actionview/test/**/*.ruby'
    - 'actionpack/test/**/*.builder'
    - 'actionpack/test/**/*.ruby'

(because AFAICS, railties is the only component not currently listed in the Include section)

[koic]

Oops! I was misunderstanding. Thanks @matthewd.

I reverted 1822e04.

Besides railties, top level components such as guides, tools, tasks, and Gemfile... also require string literal freezing. I'd like to do it by another PR because the target becomes wider. What do you think?

[kirs]

Let's do it in the separate PR as you suggest.

[koic]

Thank you, all!