HotReloader

A dead simple ruby code hot reloader wrap around zeitwerk and listen.

See README for those gems for usage.

Install via Rubygems

$ gem install hot_reloader

OR ...

Add to your Gemfile

gem 'hot_reloader'

Following is a example for use hot_reloader with Roda:

For simple use case, you just need pass paths to HotReloader.eager_load or HotReloader.will_listen.

# config/environment.rb

require 'bundler'
Bundler.require(:default, ENV.fetch('RACK_ENV', "development"))
require_relative 'application'

paths = ["#{__dir__}/../app", "#{__dir__}/../app/models"]

if ENV['RACK_ENV'] == 'development'
  HotReloader.will_listen(*paths)
else
  HotReloader.eager_load(*paths)
end

For more advanced case(e.g. you need setup zeitwerk loader instance yourself), you can pass this instance to HotReloader methods too.

# config/environment.rb

require 'bundler'
Bundler.require(:default, ENV.fetch('RACK_ENV', "development"))
require_relative 'application'

loader = Zeitwerk::Loader.new
loader.push_dir("#{__dir__}/../app")
loader.push_dir("#{__dir__}/../app/models")

if ENV['RACK_ENV'] == 'development'
  HotReloader.will_listen(loader)
else
  HotReloader.eager_load(loader)
end

When you change root directories files(app/.rb or app/models/.rb for above case), all monitored files will be reload.

it is possible to trigger reload from any .rb files, even this file not follow constant lookup name convention, and this file folder not add to root directories use push_dir method.

Following is a example.

# app/app.rb

class App < Roda
  plugin :hash_routes
  
  Dir["routes/**/*.rb"].each do |route_file|
    load route_file
  end
end

# routes/blog.rb

class App
  hash_routes.on "blog" do |r|
    "blog"
  end
end

routes/blog.rb is not follow constant lookup name convention, so, routes/ folder can't be add to root directories use push_dir method, but you can always trigger with loader.reload if routes/blog.rb was changed, then when app/app.rb reloaded, it will load the newest code in routes/blog.rb from the Dir each loop.

For achieve this, you only need pass listened folders to will_listen method as secondary arg.

loader = Zeitwerk::Loader.new
loader.push_dir("#{__dir__}/../app")

listened_folders = ["#{__dir__}/../routes"]

if ENV['RACK_ENV'] == 'development'
  HotReloader.will_listen(loader, listened_folders)
else
  HotReloader.eager_load(loader)
end

config.ru which used to start rack based web server with command rackup -o 0.0.0.0 -p 9393

# config.ru

require_relative './config/environment'

if ENV['RACK_ENV'] == 'development'
  run ->(env) { App.call(env) }
else
  run App.freeze.app
end

Write whatever application needed initialize code into config/application.rb

# config/application.rb

DB = Sequel.connect(ENV.fetch("#{ENV.fetch('RACK_ENV', "development").upcase}_DATABASE_URL"), timeout: 10000)
Sequel::Model.plugin :timestamps
Sequel.extension :symbol_aref

Add roda code into app/app.rb

# app/app.rb

class App < Roda
  articles = ['programming ruby', 'programming rust']
  route do |r|
    r.post "articles" do
      articles << r.params["content"]
      "Count: #{articles.count}"
    end
	
	r.get "articles" do
      articles.join(', ')
    end
  end
end

Directory structure is like this:

├── app/app.rb
├── config/environment.rb
├── config/application.rb
├── config.ru
├── Gemfile
└── Gemfile.lock

After change code in app.rb, all constant get removed from memory, and app.rb evaluated again!

For a more rich WIP sample project, please check my another project marketbet_crawler.

• MRI 2.5+
• JRuby

zeitwerk https://github.com/fxn/zeitwerk

listen https://github.com/guard/listen

• Bug reports
• Source
• Patches:
  • Fork on Github.
  • Run gem install --dev hot_reloader or bundle install.
  • Create your feature branch: git checkout -b my-new-feature.
  • Commit your changes: git commit -am 'Add some feature'.
  • Push to the branch: git push origin my-new-feature.
  • Send a pull request :D.

Released under the MIT license, See LICENSE for details.