Tmuxinator for Exercism

Vim and tmux are the backbone of all my development environments. tmuxinator is a Ruby gem that enables me to configure sets of terminal windows and panes for tmux sessions in YAML files, resulting in being able to use a single command, mux [project_name], to bring up a terminal-based development environment personalised exactly to me.

I’m currently infatuated with Exercism (see this post about my Exercism setup for Ruby exercises), and I wanted to use tmux with it so that for any exercise I do, I could always open up a project that would provide me windows for:

• a text editor
• a window for the exercise tests, preferably with a process runner that would run the tests automatically whenever I modified a file
• a console

Creating a YAML template that provides this kind of setup is something I do with tmuxinator for every project that I work on, but I did not want to have to create and maintain a new template for every Exercism exercise I pull down: I just wanted a single template that would work for any exercise in any language that I would potentially use on Exercism.

Dynamic tmuxinator templates

tmuxinator supports using ERB and handling command-line arguments in project files, which is something that I initially thought was interesting when I first started using it, but did not have a valid reason to use…until now. The support of command-line arguments would mean that I could use a single template for Exercism that takes a programming language and an exercise name as parameters, and results in being able to use a command like:

mux exercism <programming_language> <exercise_name>

I am currently doing exercises in Ruby, Elixir, and Elm, so the template below reflects that, but you should be able to adapt it to whatever language you may be using (and I’m sure I will adapt it to use others in the future):

~/.tmuxinator/exercism

<% lang = @args[0] %>
<% exercise = @args[1] %>

name: exercism
# Eg: mux exercism ruby hello-world => exercism/ruby/hello-world
root: ~/exercism/<%= lang %>/<%= exercise %>

on_project_first_start:
  <% if lang == "elm" %>
  - npm install
  <% end %>

pre_window:
  <% if lang == "ruby" %>
  - asdf local ruby 2.5.0
  <% elsif lang == "elixir" %>
  - asdf local elixir 1.5.3
  - asdf local erlang 20.2
  <% elsif lang == "elm" %>
  - asdf local elm 0.18.0
  <% end %>

startup_window: editor

windows:
  - editor: vim
  <% if lang == "ruby" %>
  - tests: guard --guardfile ~/exercism/ruby/Guardfile
  - console: irb
  <% elsif lang == "elixir" %>
  - tests: # placeholder window to run tests
  - console: iex
  <% elsif lang == "elm" %>
  - tests: npm run watch
  - console: elm repl
  <% end %>

A couple of notes on this setup:

• @args is the array available in the template where passed-in command line arguments get stored. Arguments can also be taken in as key-value pairs (eg mux exercism lang=ruby exercise=hello-world), which would then be available via a @settings variable (eg @settings["lang"]), but I think the basic array works best for this template.
• I use asdf for managing the versions of all languages, but you could use whatever version manager you would like in the pre_window config.

I keep all my tmuxinator templates in my dotfiles repo, so feel free to use them as examples to build on for your own templates, and good luck with your future Exercism-ing!