Check node and yarn (#222)

* Check node and yarn before installing webpacker

Verify node and yarn before running installer

Take 2

Fix case

Use a new puts

Remove .

* Change to Node.js

README.md

@@ -1,6 +1,6 @@
 # Webpacker
 ![travis-ci status](https://api.travis-ci.org/rails/webpacker.svg?branch=master)
-[![node](https://img.shields.io/badge/node-%3E%3D%206.4.0-brightgreen.svg)](https://nodejs.org/en/)
+[![node.js](https://img.shields.io/badge/node-%3E%3D%206.4.0-brightgreen.svg)](https://nodejs.org/en/)
 [![Gem](https://img.shields.io/gem/v/webpacker.svg)](https://github.com/rails/webpacker)
 
 Webpacker makes it easy to use the JavaScript preprocessor and bundler [Webpack](https://webpack.github.io)
@@ -15,7 +15,7 @@ that's been made default from that version forward.
 
 * Ruby 2.2+
 * Rails 4.2+
-* Node 6.4.0+
+* Node.js 6.4.0+
 * Yarn
 
 ## Installation

lib/tasks/webpacker.rake

@@ -1,6 +1,8 @@
 tasks = {
   "webpacker:install"         => "Installs and setup webpack with yarn",
   "webpacker:compile"         => "Compiles webpack bundles based on environment",
+  "webpacker:check_node"      => "Verifies if Node.js is installed",
+  "webpacker:check_yarn"      => "Verifies if yarn is installed",
   "webpacker:verify_install"  => "Verifies if webpacker is installed",
   "webpacker:yarn_install"    => "Support for older Rails versions. Install all JavaScript dependencies as specified via Yarn",
   "webpacker:install:react"   => "Installs and setup example react component",

lib/tasks/webpacker/check_node.rake

@@ -0,0 +1,16 @@
+namespace :webpacker do
+  desc "Verifies if Node.js is installed"
+  task :check_node do
+    begin
+      node_version = `node -v`
+      if node_version.tr("v", "").to_f < 6.4
+        puts "Webpacker requires Node.js >= 6.4 and you are using #{node_version}"
+        puts "Please upgrade Node.js https://nodejs.org/en/download/"
+        puts "Exiting!" && exit!
+      end
+    rescue Errno::ENOENT
+      puts "Node.js not installed. Please download and install Node.js https://nodejs.org/en/download/"
+      puts "Exiting!" && exit!
+    end
+  end
+end

lib/tasks/webpacker/check_yarn.rake

@@ -0,0 +1,11 @@
+namespace :webpacker do
+  desc "Verifies if yarn is installed"
+  task :check_yarn do
+    begin
+      `yarn --version`
+    rescue Errno::ENOENT
+      puts "Webpacker requires yarn. Please download and install Yarn https://yarnpkg.com/lang/en/docs/install/"
+      puts "Exiting!" && exit!
+    end
+  end
+end

lib/tasks/webpacker/install.rake

@@ -2,7 +2,7 @@ WEBPACKER_APP_TEMPLATE_PATH = File.expand_path("../../install/template.rb", __di
 
 namespace :webpacker do
   desc "Install webpacker in this application"
-  task :install do
+  task install: [:check_node, :check_yarn] do
     if Rails::VERSION::MAJOR >= 5
       exec "./bin/rails app:template LOCATION=#{WEBPACKER_APP_TEMPLATE_PATH}"
     else

lib/tasks/webpacker/verify_install.rake

@@ -2,7 +2,7 @@ require "webpacker/configuration"
 
 namespace :webpacker do
   desc "Verifies if webpacker is installed"
-  task :verify_install do
+  task verify_install: [:check_node, :check_yarn] do
     if File.exist?(Webpacker::Configuration.file_path)
       puts "Webpacker is installed 🎉 🍰"
       puts "Using #{Webpacker::Configuration.file_path} file for setting up webpack paths"