Implement server-side code hot-swapping on file change

api/index.coffee

@@ -47,4 +47,4 @@ app.use notFound
 app.use errorHandler
 
 # Start the test server if run directly
-app.listen(5000, -> debug "Listening on 5000") if module is require.main
+app.listen(5000, -> debug "Listening on 5000") if module is require.main

boot.js

@@ -4,8 +4,10 @@
 
 import artsyXapp from 'artsy-xapp'
 import express from 'express'
-import { IpFilter } from 'express-ipfilter'
 import newrelic from 'artsy-newrelic'
+import path from 'path'
+import { IpFilter } from 'express-ipfilter'
+import { createReloadable, isDevelopment } from 'lib/reloadable'
 
 const debug = require('debug')('app')
 const app = module.exports = express()
@@ -16,23 +18,32 @@ app.use(
 )
 
 // Get an xapp token
-artsyXapp.init({
+const xappConfig = {
   url: process.env.ARTSY_URL,
   id: process.env.ARTSY_ID,
   secret: process.env.ARTSY_SECRET
-}, () => {
+}
+
+artsyXapp.init(xappConfig, () => {
   app.use(newrelic)
 
-  // Put client/api together
-  app.use('/api', require('./api'))
+  if (isDevelopment) {
+    const reloadAndMount = createReloadable(app)
 
-  // TODO: Possibly a terrible hack to not share `req.user` between both.
-  app.use((req, rest, next) => {
-    req.user = null
-    next()
-  })
+    // Enable server-side code hot-swapping on change
+    app.use('/api', reloadAndMount(path.resolve(__dirname, 'api'), {
+      mountPoint: '/api'
+    }))
 
-  app.use(require('./client'))
+    invalidateUserMiddleware(app)
+    reloadAndMount(path.resolve(__dirname, 'client'))
+
+    // Staging, Prod
+  } else {
+    app.use('/api', require('./api'))
+    invalidateUserMiddleware(app)
+    app.use(require('./client'))
+  }
 
   // Start the server and send a message to IPC for the integration test
   // helper to hook into.
@@ -50,3 +61,10 @@ artsyXapp.on('error', (error) => {
   console.warn(error)
   process.exit(1)
 })
+
+const invalidateUserMiddleware = (app) => {
+  app.use((req, rest, next) => {
+    req.user = null
+    next()
+  })
+}

client/apps/articles_list/routes.coffee

@@ -34,4 +34,4 @@ renderArticles = (res, req, result, published) ->
   res.locals.sd.HAS_PUBLISHED = published
   res.render 'index',
     articles: result.articles || []
-    current_channel: req.user?.get('current_channel')
+    current_channel: req.user?.get('current_channel')

client/apps/edit/routes.coffee

@@ -38,4 +38,4 @@ render = (req, res, article) ->
 setChannelIndexable = (channel, article) ->
   noIndex = sd.NO_INDEX_CHANNELS.split '|'
   if noIndex.includes channel.get('id')
-    article.set 'indexable', false
+    article.set 'indexable', false

client/index.coffee

@@ -6,4 +6,4 @@ setup = require "./lib/setup"
 express = require "express"
 
 app = module.exports = express()
-setup app
+setup app

lib/reloadable.js

@@ -0,0 +1,80 @@
+/**
+ * Dev utility for server-side code reloading without the restart. In development,
+ * watch for file-system changes and clear cached modules when a change occurs,
+ * thus effectively reloading the entire app on request.
+ */
+
+export const isDevelopment = process.env.NODE_ENV === 'development'
+
+export function createReloadable (app) {
+  return (folderPath, options = {}) => {
+    if (isDevelopment) {
+      const {
+        mountPoint = '/'
+      } = options
+
+      const onReload = (req, res, next) => require(folderPath)(req, res, next)
+
+      if (typeof onReload !== 'function') {
+        throw new Error(
+          '(lib/reloadable.js) Error initializing reloadable: `onReload` is ' +
+          'undefined. Did you forget to pass a callback function?'
+        )
+      }
+
+      const watcher = require('chokidar').watch(folderPath)
+
+      watcher.on('ready', () => {
+        watcher.on('all', () => {
+          Object.keys(require.cache).forEach(id => {
+            if (id.startsWith(folderPath)) {
+              delete require.cache[id]
+            }
+          })
+        })
+      })
+
+      let currentResponse = null
+      let currentNext = null
+
+      app.use((req, res, next) => {
+        currentResponse = res
+        currentNext = next
+
+        res.on('finish', () => {
+          currentResponse = null
+          currentNext = null
+        })
+
+        next()
+      })
+
+      /**
+       * In case of an uncaught exception show it to the user and proceed, rather
+       * than exiting the process.
+       */
+      process.on('uncaughtException', (error) => {
+        if (currentResponse) {
+          currentNext(error)
+          currentResponse = null
+          currentNext = null
+        } else {
+          process.abort()
+        }
+      })
+
+      app.use(mountPoint, (req, res, next) => {
+        onReload(req, res, next)
+      })
+
+      return onReload
+
+      // Node env not 'development', exit
+    } else {
+      throw new Error(
+        '(lib/reloadable.js) NODE_ENV must be set to "development" to use ' +
+        'reloadable.js'
+      )
+    }
+  }
+}

package.json

@@ -32,6 +32,7 @@
     "babel-preset-react": "^6.24.1",
     "babel-preset-stage-3": "^6.24.1",
     "babelify": "^7.3.0",
+    "babel-runtime": "^6.25.0",
     "backbone": "^1.2.3",
     "backbone-super-sync": "^1.1.1",
     "bcryptjs": "^2.4.3",
@@ -101,6 +102,7 @@
     "browserify": "^14.1.0",
     "browserify-dev-middleware": "^1.5.0",
     "caching-coffeeify": "^0.5.1",
+    "chokidar": "^1.7.0",
     "cssify": "^0.7.0",
     "eslint": "^3.19.0",
     "eslint-config-standard": "^10.2.1",

test-reload/index.js

@@ -0,0 +1,7 @@
+import express from 'express'
+
+const app = module.exports = express()
+
+app.get('/bar', (req, res, next) => {
+  res.send('working! 41')
+})

yarn.lock

@@ -1956,9 +1956,9 @@ cheerio@^0.19.0:
     htmlparser2 "~3.8.1"
     lodash "^3.2.0"
 
-chokidar@^1.0.0, chokidar@^1.0.1, chokidar@^1.4.3, chokidar@^1.6.1:
-  version "1.6.1"
-  resolved "https://registry.yarnpkg.com/chokidar/-/chokidar-1.6.1.tgz#2f4447ab5e96e50fb3d789fd90d4c72e0e4c70c2"
+chokidar@^1.0.0, chokidar@^1.0.1, chokidar@^1.4.3, chokidar@^1.6.1, chokidar@^1.7.0:
+  version "1.7.0"
+  resolved "https://registry.yarnpkg.com/chokidar/-/chokidar-1.7.0.tgz#798e689778151c8076b4b360e5edd28cda2bb468"
   dependencies:
     anymatch "^1.3.0"
     async-each "^1.0.0"