What are forces?

[dvandersluis]

There isn't really any documentation about forces. What do forces do and why should a cop join one?

[bbatsov]

That's the best answer I can give is the commit that introduced them 4b144e1

It seemed like an useful concept back then (and the name was a pun on "police force"), but we never fledged it out fully.

[marcandre]

It seemed like an useful concept back then (and the name was a pun on "police force"), but we never fledged it out fully.

Indeed. And there's only one force today, to provide info about variable scope IIRC: VariableForce.

One limitation of forces in current implementation is that forces run separately from cops with a single callback. So a cop will get all the calls from the forces, then the callbacks from on_send etc. It's not possible to write a force currently that will trigger its callbacks among the normal callbacks. Because of this I believe all cops relying on VariableForce respond only to some of the force's callbacks and to no standard node callback.

[dvandersluis]

Thanks for the added info @marcandre!

[dvandersluis]

The puns are good 😁

So I guess the idea was to run all the cops in a single force at once?

[bbatsov]

Yep, they were meant to be a performance optimization. The initial versions of RuboCop were pretty slow due to some very dumb things I had done originally (e.g. having each cop parse every file) and for a while we've had a lot of initiatives focused on improved performance.