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Programming in Ruby

A literate programming file for configuring Emacs to support the Ruby programming language.

Getting Started

Ruby is probably already installed on the system, and if not, we certainly can download it from ruby-lang.org, but since I need to juggle different versions for each project, I use direnv and ruby-install:

brew install ruby-install

And then install one or more versions:

ruby-install -U
ruby-install ruby 3

New Project

While we could use a large project templating system, I keep it simple. For each project, create the following directory structure:

├── Gemfile
├── Rakefile
├── lib
│   └── hello_world.rb
└── test
    └── hello_world_test.rb

For instance:

mkdir -p ~/src/ruby-xp    # Change me
cd ~/src/ruby-xp
mkdir -p lib test

Now, do the following steps.

  1. Create a .envrc file with the Ruby you want to use: 
    use ruby 2.6.10
  2. Next, get Bundler: 
    gem install bundle
  3. Create a minimal Gemfile: 
    source 'https://rubygems.org'

gem 'rake', group: :development
gem 'rubocop', group: :development
gem 'solargraph', group: :development
  4. Grab all the dependencies: 
    bundle install
  5. Create a minimal Rakefile: 
    task default: %w[test]

task :run do
  ruby 'lib/hello_world.rb'
end

task :test do
  ruby 'test/hello_world_test.rb'
end
  6. Create the first program: 
    # frozen_string_literal: true

# The basic greeting class
class HelloWorld
  attr_reader :name

  def initialize(name = nil)
    @name = name
  end

  def greeting
    if @name
      "Hello there, #{@name}"
    else
      'Hello World!'
    end
  end
end

puts HelloWorld.new(ARGV.first).greeting
  7. Create the first test: 
    require 'test/unit'
require_relative '../lib/hello_world'

class TestHelloWorld < Test::Unit::TestCase
  def test_default
    assert_equal 'Hello World!', HelloWorld.new.greeting
  end

  def test_name
    assert_equal 'Hello there, Bob', HelloWorld.new('Bob').greeting
  end
end

Or something like that.

Existing Projects

For projects from work, I have found we need to isolate the Ruby environment. Once we use rbenv or rvm, but now, I just use direnv. Approach one is to use a local directory structure. Assuming I have a use_ruby function in ~/.config/direnv/direnvrc:

# From Apple: /usr/bin/ruby
use ruby 2.6.10
# Could use 3.2.1 from /opt/homebrew/bin/ruby

A better solution is to create a container to hold the Ruby environment. Begin with a Dockerfile:

## -*- dockerfile-image-name: "ruby-xp" -*-
FROM alpine:3.13

ENV NOKOGIRI_USE_SYSTEM_LIBRARIES=1

ADD Gemfile /

RUN apk update \
&& apk add ruby \
           ruby-etc \
           ruby-bigdecimal \
           ruby-io-console \
           ruby-irb \
           ca-certificates \
           libressl \
           bash \
&& apk add --virtual .build-dependencies \
           build-base \
           ruby-dev \
           libressl-dev \
&& gem install bundler || apk add ruby-bundler \
&& bundle config build.nokogiri --use-system-libraries \
&& bundle config git.allow_insecure true \
&& gem install json \
&& bundle install \
&& gem cleanup \
&& apk del .build-dependencies \
&& rm -rf /usr/lib/ruby/gems/*/cache/* \
          /var/cache/apk/* \
          /tmp/* \
          /var/tmp/*

Next, create a .envrc in the project’s directory:

CONTAINER_NAME=ruby-xp:latest
CONTAINER_WRAPPERS=(bash ruby irb gem bundle rake solargraph rubocop)

container_layout

While that approach works fairly well with my direnv configuration, Flycheck seems to want the checkers to be installed globally.

Configuration

While Emacs supplies a Ruby editing environment, we’ll still use use-package to grab the latest:

(use-package ruby-mode
  :mode (rx "." (optional "e") "rb" eos)
  :mode (rx "Rakefile" eos)
  :mode (rx "Gemfile" eos)
  :mode (rx "Berksfile" eos)
  :mode (rx "Vagrantfile" eos)
  :interpreter "ruby"

  :init
  (setq ruby-indent-level 2
        ruby-indent-tabs-mode nil)

  :hook (ruby-mode . superword-mode))

Ruby REPL

I am not sure I can learn a new language without a REPL connected to my editor, and for Ruby, this is inf-ruby:

(use-package inf-ruby
  :config
  (ha-local-leader 'ruby-mode-map
    "R" '("REPL" . inf-ruby)))

Electric Ruby

The ruby-electric project is a minor mode that aims to add the extra syntax when typing Ruby code.

(use-package ruby-electric
  :hook (ruby-mode . ruby-electric-mode))

Testing

The ruby-test-mode project aims a running Ruby test from Emacs seemless:

(use-package ruby-test-mode
  :hook (ruby-mode . ruby-test-mode)

  :config
  (ha-local-leader 'ruby-mode-map
    "t"  '(:ignore t :which-key "test")
    "t t" '("test one" . ruby-test-run-at-point)
    "t g" '("toggle code/test" . ruby-test-toggle-implementation-and-specification)
    "t A" '("test all" . ruby-test-run)
    "t a" '("retest" . ruby-test-rerun)))

Bundler

The Bundler project integrates bundler to install a projects Gems.

(use-package bundler
  :config
  (ha-local-leader 'ruby-mode-map
    "g"  '(:ignore t :which-key "bundler")
    "g o" '("open" . bundle-open)
    "g g" '("console" . bundle-console)
    "g c" '("check" . bundle-check)
    "g i" '("install" . bundle-install)
    "g u" '("update" . bundle-update)))

Rubocop?

The lint-like style checker of choice for Ruby is Rubocop. The rubocop.el mode should work with Flycheck. First install it with:

gem install rubocop

And then we may or may not need to enable the rubocop-mode:

(use-package rubocop
  :hook (ruby-mode . rubocop-mode))

Auxiliary Support

Cucumber

Seems that to understand and edit Cucumber feature definitions, you need cucumber.el:

(use-package feature-mode)

RSpec

https://github.com/pezra/rspec-mode

LSP

The built-in Eglot package natively supports Solargraph via eglot-server-programs (no extra package needed):

(use-package eglot
  :straight nil
  :after ruby-mode
  :defer t
  :hook (ruby-mode . eglot-ensure))

Keybindings for the eglot-based LSP sub-menu, wired into the ruby-mode local leader:

(use-package eglot
  :straight nil
  :after ruby-mode
  :config
  (ha-local-leader 'ruby-mode-map
    "w"  '(:ignore t :which-key "eglot")
    "wD" '("disconnect" . eglot-shutdown)
    "wR" '("reconnect" . eglot-reconnect)
    "w?" '("describe" . eglot-show-workspace-configuration)
    "wa" '("code actions" . eglot-code-actions)
    "wo" '("organize imports" . eglot-code-action-organize-imports)
    "wr" '("rename" . eglot-rename)
    "w=" '("format buffer" . eglot-format-buffer)))

Need to install Solargraph for the LSP server experience:

gem install solargraph

Or add it to your Gemfile:

gem 'solargraph', group: :development

Once installed, eglot finds and talks to solargraph automatically; no further Emacs configuration is needed.

Technical Artifacts

Let’s provide a name so we can require this file: