Last year at RubyKaigi I spoke about the past and the future of RuboCop. This talk marked the birth of the RuboCop HQ organization and the first time I spoke about RuboCop 1.0. There were 3 primary areas of work I outlined for RuboCop 1.0 back then:

Safe auto-correct (that doesn’t break your code)

Safe upgrades (that don’t introduce new offenses)

Modular design

We’ve already made a lot of progress on the first point and I wrote about that a while ago. Safe upgrades are currently in the works and I expect we’ll wrap them up fairly soon.

Today I’m going to focus on modular design. What do I mean by modular design? Historically RuboCop has bundled Ruby style checks, Rails style checks and performance checks. This worked out well for a while, but as the project grew bigger and more popular the number of the checks in each department skyrocketed and it became harder and harder to keep track of everything. There’s also the fact that the Ruby style checks are fairly stable, but the Rails and performance ones are constantly in flux, as many of them are relevant only to specific versions of Rails and the Ruby runtime. Naturally, there’s also the problem of not being able to release updates to Rails or performance checks independently of RuboCop itself. For me it had become clear that we were way past the point of the “majestic monolith” and we had to take some measure to prevent things from escalating any further.

So, what are we doing about all of this? The solution is pretty simple - we’ve decided to break the original RuboCop into 3 gems:

RuboCop Performance went live recently, and in RuboCop 0.68 we’ve removed all performance cops from RuboCop. Today I’m happy to announce the inaugural release of RuboCop Rails! RuboCop 0.71 will issue a warning about the pending removal of Rails-related cops from the core project and they will be deleted in RuboCop 0.72. Note that the initial version of the rubocop-rails gem is 2.0. It might seem a bit odd, but there’s a good story behind this. You are advised to switch to the new gem right away - it will take precedence over the Rails cops bundled with RuboCop itself. The core project will stop updating the Rails cops that are part of it effective immediately.

This announcement is the culmination of an entire year of hard work by the amazing Koichi Ito, who spearheaded the extraction of both the performance and the Rails cop departments. Going forward Koichi will be the primary steward of the new gems, while I’ll keep my attention mostly on the core project. I’ve long wanted to focus more on improving RuboCop’s internal, performance and default configuration, and I hope my reduced responsibilities will allow me to spend more time ruminating on how to build a better RuboCop core experience.

The extraction process had one nice side effect - it helped us improve RuboCop’s internals and provide a better extension API in general. There’s a lot of work left on the extension API front, but things are certainly moving in the right direction. The RuboCop ecosystem has been steadily growing for the past several years and I hope that soon we’re going to see more great additions to it (e.g. rubocop-minitest , rubocop-hanami , etc). Fingers crossed!

I know this transition means another (somewhat) painful upgrade for some of you, but I promise you that the pain is going to be worth it. We’re now at a striking distance from RuboCop 1.0 and the era of stability it should bring. I’ll write a bit more on that subject in the weeks to come. That’s all I have for you today! Keep hacking!