16 May 2020

Tab completion for chruby and ruby-install on zsh

I switched to zsh as part of upgrading to macOS 10.15 Catalina. I’m not using oh-my-zsh, but I was incredibly helped by the Scripting OSX series, and my new best friend is Powerlevel10k.

Anyway, now that you’re caught up, my problem of the day is wanting tab-completion for my other best friends: chruby and ruby-install. There’s a bunch of tab-completion options for chruby rattling around in GitHub issues and pull requests, but none of them were easy enough to find. I eventually wound up extracting one from oh-my-zsh’s chruby plugin, which does way more than I wanted. Here’s the whole thing, which I keep in ~/.zsh/completion/_chruby:

#compdef chruby

compadd $(chruby | tr -d '* ')
local default_path='/usr/local/bin:/usr/bin'
if PATH=${default_path} type ruby &> /dev/null; then
  compadd system

Once I had chruby working, I wanted tab-completion for ruby-install. I figured I could also extract that from oh-my-zsh, but… it’s listed as a TODO. :/ So I wrote my own! As far as I can tell from my scatterbrained googling, this is literally the first zsh completion for ruby-install to ever be posted on the internet. Yay me? I keep this in (predictably) ~/.zsh/completion/_ruby-install.

#compdef ruby-install

compadd $(ruby-install | tail -n+2 | ruby -e '
ARGF.read.lines.each do |l|
  next @name = l.tr(":", "").strip if l.include?(":")
  puts "#{@name}-#{l.strip}"

(I know, I know, macOS won’t ship with a built-in Ruby starting with 10.16 or 10.17, and this will break then. I just don’t have the patience to rewrite it as a zsh script today.)

To include and activate these, you need something like this in your ~/.zshrc:

autoload -Uz compinit && compinit

And that’s it! Tab complete your way to happiness:

$ chruby ⇤
ruby-2.6.6  ruby-2.7.1  system

$ ruby-install ⇤
jruby-  rbx-4.15  ruby-2.5.8  ruby-2.7.1  mruby-2.1.0  ruby-2.4.10  ruby-2.6.6  truffleruby-20.0.0