Comment by chao-

That's a fair point. That's why I'm interested to know what is at the core of AlphaSite's complaint.

One challenge, as I see it, is that there are three kinds of Ruby projects that need to take different approaches to the matter, in increasing level of complexity:

(1) Developing a longer-lived, deployed or distributed project. Here you should definitely use both the Gemfile Ruby version and a .ruby-version file. You're normally only targeting one version at a time, but contributors and/or users are very unlikely to somehow accidentally end up using the wrong Ruby version without getting a very obvious notification that they are using the wrong Ruby version. That's annoying to encounter, but not difficult to solve once you know that the concept of a "version manager" exists.

(2) Hacking on your own small project or just banging out a script. You just want to run some Ruby version and get to it. You probably should default to the latest, unless there's some dependency requiring a lower version, and you might not know that until after you've gotten started. The inverse issue might also occur, e.g. you installed Ruby 3.1 a few years ago, you start hacking, and now you want to pull in a gem version that requires Ruby 3.4. You can manage this by putting the Ruby version in your Gemfile, or using a .ruby-version file, or both, but if you're relatively green and just diving in, this might not be on your radar.

(3) Developing a gem. You probably want to test/validate your gem across multiple Ruby versions, and possibly even different versions of your dependencies. You obviously don't want to lock yourself into a single Ruby version, and use of a .ruby-version file is inappropriate. There is tooling to do this, but it takes some learning to be able to utilize.

My belief is that it is worth it for install documentation for category (1) to be a little more explicit about how to get up and running. For category (2), I don't know what the right answer is, but I understand the potential pain points.

What I was most curious about is whether AlphaSite's complaint was with a specific version manager, or the fact that multiple options for version managers exist, or even the need for version managers at all?