.rubocop.yml: selectively enable Rails cops

[Bo98]

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Some Rails cops use ActiveRecordHelper which contains a cache checksum that involves checksuming a Rails database schema. This involves an amount of file traversal as it tries to find this schema, which can be slow.

For cached brew style runs on Homebrew/core, disabling these cops speeds up execution time by over 50%.

[BrewTestBot]

Review period ended.

[MikeMcQuaid]

Makes sense to me, thanks @Bo98. I wonder if we can just unconditionally disable these Rails cops and only enable those we find specifically useful?

[Rylan12]

Looks good to me!

After a quick glance at the Rails cops, I agree that it looks like most can be removed completely. Off the top of my head, I know we definitely want to keep Rails/Blank, Rails/Presence, and Rails/Present. There might be others, but if I had to guess those three are the main reason we use any Rails cops (unless they come by default which might be the case)

[MikeMcQuaid]

Looks good to me!

After a quick glance at the Rails cops, I agree that it looks like most can be removed completely. Off the top of my head, I know we definitely want to keep Rails/Blank, Rails/Presence, and Rails/Present. There might be others, but if I had to guess those three are the main reason we use any Rails cops (unless they come by default which might be the case)

Rails/ActiveSupportAliases, maybe Rails/Date, Rails/Delegate, Rails/DelegateAllowBlank, maybe Rails/EnvironmentVariableAccess (one day, currently disabled), maybe Rails/Exit, Rails/ExpandedDateRange, Rails/NegateInclude, Rails/SafeNavigation, Rails/SafeNavigationWithBlank look useful, too.

[Bo98]

We should monitor the changelog in rubocops-rails Dependabot PRs to see what new cops should be added.

[MikeMcQuaid]

Thanks @Bo98!