AO3-6691 Custom cops for house rules

[brianjaustin]

Issue

https://otwarchive.atlassian.net/browse/AO3-6691

Purpose

Adds custom Rubocop rules to automatically flag some things we have to do manually in PR review. For example, using departure for large tables.

[Bilka2]

I didn't look at the code itself much, my focus was more on the resulting messages and docs of the cops.

[Bilka2]

Is it possible to check the arguments of the method call? In that case it would be nice to have a cop that checks for calls to t that include the default option. For example, t('.email_address', :default => "Email address") should have the translation in the .yml file and be just t(".email_address").

[Bilka2]

This means that the cop will have false failures in those cases, leading to false positive failing tests on PRs. That's not great. Perhaps that would be helped if the offense could be considered a low severity. Though I don't know if that will keep the test from failing while still showing up on GitHub, I'd have to investigate how reviewdog handles it.

But did find that add_offense indeed supports a severity level.

[brianjaustin]

Here's what it looks like with severity: :convention https://github.com/brianjaustin/ao3-sandbox/pull/9/files

The action is still marked as failed, but at least the annotation looks a little bit less angry (the higher severities are either yellow or red with an ❌)

[Bilka2]

As tested here that unfortunately doesn't apply for commits from forks where reviewdog degrades to annotations. Oh well, was worth the try.

[Bilka2]

All the cops look good and I had a quick look over the code and tests as well, which looks fine (though I didn't look too deep).