Show warning if `// periphery:ignore` unneeded

[subdan]

I want to see a warning if // periphery:ignore command is unneeded.

// periphery:ignore
func sayHello() {
    print("sayHello")
}
sayHello()

I want to see the following warning: Superfluous Ignore Command Violation: function sayHello is used and shouldn't marked as ignored. Please remove the ignore command.

---

SwiftLint shows a warning if a disable command doesn't needed.

// swiftlint:disable:next function_body_length
func sayHello() {
    print("Hello")
}

Warning: Superfluous Disable Command Violation: SwiftLint rule 'function_body_length' did not trigger a violation in the disabled region. Please remove the disable command. (superfluous_disable_command)

[maxwellE]

@subdan Are you working on this? I would be interested in adding this capability

[ileitch]

@maxwellE @geraldWilliam took a stab at this recently: https://github.com/peripheryapp/periphery/pull/551. It wasn't quite the right solution though. I've been wanting to take another look but haven't had time yet. I'll be focusing more on integrating Periphery into Reddit's build system soon, so hopefully I can allocate some time for this too.

[subdan]

@subdan Are you working on this? I would be interested in adding this capability

No

[maxwellE]

@ileitch was there any progress on this yet?

[tinder-maxwellelliott]

@ileitch Id like to take this up if you have any pointers on how to best tackle this

[ileitch]

Hey @maxwellE, sorry for the slow reply. I haven't had time to think about the right solution for this. I think a naive approach is possibly quite simple, but finding one that doesn't significantly impact performance might be a bit harder. Please have a go!

[maxwellE]

Would it make sense to have even a less performant version of this implemented behind a flag? I could dive into how SwiftLint accomplishes this same logic