Merge pull request alphagov#135 from alphagov/add-node-version-checking

Add node version checking

.nvmrc

@@ -0,0 +1 @@
+8.9.4

.travis.yml

@@ -1,8 +1,5 @@
 language: node_js
 
-node_js:
-- 8
-
 script:
   - npm run lint
   - npm run build

README.md

@@ -11,14 +11,29 @@ designing government services.**
 
 ## Run locally
 
-Make sure you have [Node.js](https://nodejs.org/en/) installed.
+You'll need [Git](https://help.github.com/articles/set-up-git/) and [Node.js](https://nodejs.org/en/) installed to get this project running.
+
+Note: You will need the [active LTS (Long-term support)](https://github.com/nodejs/Release#release-schedule) Node.js version for this project (as specified in [.nvmrc](./.nvmrc))
+
+### Fork repository (optional)
+If you're an external contributor make sure to [fork this project first](https://help.github.com/articles/fork-a-repo/)
 
 ### Clone repository
 ```
 git clone git@github.com:alphagov/govuk-design-system.git # or clone your own fork
+
+cd govuk-design-system
 ```
 
-### Install dependencies
+### Using nvm (optional)
+If you work across multiple Node.js projects there's a good chance they require different Node.js and npm versions.
+
+To enable this we use [nvm (Node Version Manager)](https://github.com/creationix/nvm) to switch between versions easily.
+
+1. [install nvm](https://github.com/creationix/nvm#installation)
+2. Run `nvm install` in the project directory (this will use [.nvmrc](./.nvmrc))
+
+### Install npm dependencies
 ```
 npm install
 ```

bin/check-nvmrc.js

@@ -0,0 +1,33 @@
+#! /usr/bin/env node
+
+'use strict'
+
+var fs = require('fs')
+var path = require('path')
+
+fs.readFile(path.join(__dirname, '../.nvmrc'), 'utf8', function (error, data) {
+  if (error) throw error
+  var expectedVersion = data.trim()
+  var currentVersion = process.version.replace('v', '')
+
+  var versionMatchesExactly = expectedVersion === currentVersion
+  var versionMatchesMajor = expectedVersion.split('.')[0] === currentVersion.split('.')[0]
+
+  if (versionMatchesExactly) {
+    process.exit()
+  }
+
+  if (versionMatchesMajor) {
+    console.log('' +
+      'Warning: You are using Node.js version ' + currentVersion + ' which we do not use. ' +
+      'You may encounter issues, consider installing Node.js version ' + expectedVersion + '.' +
+    '')
+    process.exit()
+  }
+
+  console.log('' +
+    'You are using Node.js version ' + currentVersion + ' which we do not support. ' +
+    'Please install Node.js version ' + expectedVersion + ' and try again.' +
+  '')
+  process.exit(1) // exit with a failure mode
+})

package.json

@@ -13,6 +13,8 @@
   },
   "homepage": "https://github.com/alphagov/govuk-design-system#readme",
   "scripts": {
+    "preinstall": "node bin/check-nvmrc.js",
+    "prestart": "node bin/check-nvmrc.js",
     "build": "node tasks/build.js",
     "start": "node tasks/serve.js",
     "lint": "gulp scss:lint"
@@ -40,5 +42,8 @@
     "metalsmith-sass": "^1.5.0",
     "metalsmith-tagcleaner": "0.0.2",
     "nunjucks": "^3.0.1"
+  },
+  "engines": {
+    "node": "8.9.4"
   }
 }