RuboCop 1.91: The Journey to 2.0 Begins

RuboCop 1.91 is out! It has the usual mix of new cops, new options and a small mountain of bug fixes, but the feature I want to talk about today is a single flag - --preview. It’s the first real step on our (long) journey to RuboCop 2.0. Since the beginning of time… …certain people have been unhappy with RuboCop’s defaults. I wrote almost exactly that sentence six years ago, right before RuboCop 1.0, when I ran a survey to work out which of our defaults were wrong. Some good came out of it - that’s how Layout/LineLength ended up at 120 - but a survey has an obvious weakness. It asks people what they prefer, and people are terrible at reporting what they actually do. So this time I went looking for evidence instead of opinions. I built a small tool that grabs the 500 most-starred Ruby repos on GitHub, resolves whatever .rubocop.yml they ship (following inherit_from chains and popular inherit_gem bases like standard and rubocop-rails-omakase), and tallies what they change about our…