webpack-dev-server

#!/usr/bin/env ruby

RAILS_ENV = ENV['RAILS_ENV'] || 'development'
NODE_ENV  = ENV['NODE_ENV'] || RAILS_ENV

APP_PATH = File.expand_path('../', __dir__)

SET_NODE_PATH  = "NODE_PATH=#{APP_PATH}/node_modules"
WEBPACKER_BIN  = "./node_modules/.bin/webpack-dev-server"
WEBPACK_CONFIG = "#{APP_PATH}/config/webpack/#{NODE_ENV}.js"

# Warn the user if the configuration is not set
RAILS_ENV_CONFIG = File.join("config", "environments", "#{RAILS_ENV}.rb")

# Look into the environment file for a non-commented variable declaration
unless File.foreach(File.join(APP_PATH, RAILS_ENV_CONFIG)).detect { |line| line.match(/^\s*[^#]*config\.x\.webpacker\[\:dev_server_host\].*=/) }
  puts "Warning: if you want to use webpack-dev-server, you need to tell Webpacker to serve asset packs from it. Please set config.x.webpacker[:dev_server_host] in #{RAILS_ENV_CONFIG}.\n\n"
end

Dir.chdir(APP_PATH) do
  exec "#{SET_NODE_PATH} #{WEBPACKER_BIN} --config #{WEBPACK_CONFIG} --content-base #{APP_PATH}/public/packs #{ARGV.join(" ")}"
end