Add Rails/UnprocessableContentStatus cop

[tuxagon]

About

In Rack 3.1.0, the status naming for HTTP status 422 was changed from :unprocessable_entity to :unprocessable_content to reflect the status. Both are supported, but there is a warning message that will display if using :unprocessable_entity.

This new cop provides a way to have Rubocop register the old status name usages as offenses and auto-correct them as well.

• PR that made the change in Rack: Update HTTP status codes and associated symbols rack/rack#2137

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Before submitting the PR make sure the following are checked:

• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Ran bundle exec rake default. It executes all tests and runs RuboCop on its own code.
• 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.
• If this is a new cop, consider making a corresponding update to the Rails Style Guide.
  • I'm not sure this is necessary due to Rack already providing a warning.

[Earlopain]

I believe you can use requires_gem for this: https://docs.rubocop.org/rubocop/development.html#requiring-a-gem

You may have to also do let(:gem_versions) { { 'rack' => '3.1.0' } } in tests to have them actually run, not 100% sure about that though

[tuxagon]

TIL I learned about requires_gem! Thanks for letting me know. It's much nicer.

[koic]

I think it would be better to name it Rails/DeprecatedHttpStatusNames instead of specializing it to a specific name. This way, it can be extended in the future when new deprecated status names appear.

Additionally, this cop could also check for payload_too_large.
https://github.com/rack/rack/blob/v3.2.0/lib/rack/utils.rb#L576-L579

[tuxagon]

Good suggestion! I've updated the cop to be more generally useful. I noticed the HttpStatus cop too and took some inspiration for the updated matcher. I also considered whether it made sense to have that cop handle the deprecations, but thought the deprecation may be helpful to have separately, and to not change the isolated focus of that.

[Earlopain]

This is only for head :unprocessable_entity, right? redirect_to is already handled by on_pair, same with render.

In that case it seems better to use on_send with RESTRICT_ON_SEND and simply look at the first positional argument.

[tuxagon]

That is what is was for. I looked at Rails/HttpStatus and used the same approach there, which I think probably makes the most sense.

[Earlopain]

Rails actually considers both symbols to part of their public api, regardless of what rack does with them: rails/rails#53383. So the next rails releases will no longer show the warning from rack.

This could still be nice for consistency + the other status code koic mentioned.