Option for displaying elapsed time without using --debug.

[joshuapinter]

Is your feature request related to a problem? Please describe.

When you run rubocop it doesn't show the elapsed time. However, when you run rubocop --debug it outputs Finished in 3.1285830000415444 seconds at the end, but it also shows you the path of every file it is scanning.

I'd like to get the elapsed time without getting all the debug information. We use this in our CI to routinely monitor the performance to see if there are bottlenecks, etc.

We have tried using time rubocop and it works, but not as cleanly and varies from system to system (e.g. macOS to Ubuntu to CodeShip servers).

Describe the solution you'd like

If you are against outputting this by default, perhaps a simple option like --time or something that will output the elapsed time.

Describe alternatives you've considered

As mentioned above,

We have tried using time rubocop and it works, but not as cleanly and varies from system to system (e.g. macOS to Ubuntu to CodeShip servers).

Additional context

I'm happy to PR this if it's something you think is valuable and we decide on the details.

Thanks! I love this library!

[fatkodima]

I'm also seeing this as useful outside of --debug.
@bbatsov wdyt on this?

[dvandersluis]

I think it'd also be useful to be able to get a backtrace from a erroring cop without all the other noise from --debug.

[bbatsov]

I'd like to get the elapsed time without getting all the debug information. We use this in our CI to routinely monitor the performance to see if there are bottlenecks, etc.

Don't you have RuboCop checks as separate tasks which would be timed by your CI anyways? I'm not arguing with the proposal, but I do find the use-case a bit odd, as that information should be available anyways.

[joshuapinter]

It's a good question. We definitely could keep Rubocop as a separate task but we use a default rake task to essentially handle all prep, tests and linting, including Rubocop. This is all done in a multi-threaded fashion where possible. Similar to how rubocop does it.

This feature is certainly not mission critical but helpful in diagnosing where a bottleneck is in that rake command. Plus, it's helpful in benchmarking between different CIs, systems, etc.