From 3b3a4e5dcd5f7a9438c2bb81afa0a27f97438a75 Mon Sep 17 00:00:00 2001
From: Arunoda Susiripala <arunoda.susiripala@gmail.com>
Date: Fri, 3 Mar 2017 11:51:52 +0530
Subject: [PATCH 01/11] Use file hashes instead of BUILD_ID. Now JSON pages
 also not prefixed with a hash and doesn't support immutable caching. Instead
 it supports Etag bases caching.

---
 lib/router/index.js   | 10 +---------
 lib/router/router.js  | 12 +-----------
 server/build/index.js | 19 ++++++++++++++++--
 server/document.js    |  6 +++---
 server/index.js       | 45 ++++++++++++++++++-------------------------
 server/render.js      |  4 ++--
 6 files changed, 43 insertions(+), 53 deletions(-)

diff --git a/lib/router/index.js b/lib/router/index.js
index 550ef110d3e2a..de3ac9ba6935f 100644
--- a/lib/router/index.js
+++ b/lib/router/index.js
@@ -1,4 +1,4 @@
-/* global window, location */
+/* global window */
 import _Router from './router'
 
 const SingletonRouter = {
@@ -76,11 +76,3 @@ export const createRouter = function (...args) {
 
 // Export the actual Router class, which is usually used inside the server
 export const Router = _Router
-
-export function _notifyBuildIdMismatch (nextRoute) {
-  if (SingletonRouter.onAppUpdated) {
-    SingletonRouter.onAppUpdated(nextRoute)
-  } else {
-    location.href = nextRoute
-  }
-}
diff --git a/lib/router/router.js b/lib/router/router.js
index 518d1faff7746..ebbf9fb5b7420 100644
--- a/lib/router/router.js
+++ b/lib/router/router.js
@@ -4,7 +4,6 @@ import evalScript from '../eval-script'
 import shallowEquals from '../shallow-equals'
 import PQueue from '../p-queue'
 import { loadGetInitialProps, getURL } from '../utils'
-import { _notifyBuildIdMismatch } from './'
 import fetch from 'unfetch'
 
 if (typeof window !== 'undefined' && typeof navigator.serviceWorker !== 'undefined') {
@@ -260,14 +259,6 @@ export default class Router extends EventEmitter {
     const jsonPageRes = await this.fetchRoute(route)
     const jsonData = await jsonPageRes.json()
 
-    if (jsonData.buildIdMismatch) {
-      _notifyBuildIdMismatch(as)
-
-      const error = Error('Abort due to BUILD_ID mismatch')
-      error.cancelled = true
-      throw error
-    }
-
     const newData = {
       ...loadComponent(jsonData),
       jsonPageRes
@@ -320,8 +311,7 @@ export default class Router extends EventEmitter {
   }
 
   doFetchRoute (route) {
-    const { buildId } = window.__NEXT_DATA__
-    const url = `/_next/${encodeURIComponent(buildId)}/pages${route}`
+    const url = `/_next/pages${route}`
     return fetch(url, {
       method: 'GET',
       headers: { 'Accept': 'application/json' }
diff --git a/server/build/index.js b/server/build/index.js
index 65dcf31da8f44..0fcff294423b3 100644
--- a/server/build/index.js
+++ b/server/build/index.js
@@ -11,7 +11,8 @@ export default async function build (dir) {
   const compiler = await webpack(dir, { buildDir })
 
   try {
-    await runCompiler(compiler)
+    const webpackStats = await runCompiler(compiler)
+    await writeBuildStats(buildDir, webpackStats)
     await writeBuildId(buildDir)
   } catch (err) {
     console.error(`> Failed to build on ${buildDir}`)
@@ -30,6 +31,7 @@ function runCompiler (compiler) {
       if (err) return reject(err)
 
       const jsonStats = stats.toJson()
+
       if (jsonStats.errors.length > 0) {
         const error = new Error(jsonStats.errors[0])
         error.errors = jsonStats.errors
@@ -37,11 +39,24 @@ function runCompiler (compiler) {
         return reject(error)
       }
 
-      resolve()
+      resolve(jsonStats)
     })
   })
 }
 
+async function writeBuildStats (dir, webpackStats) {
+  const chunkHashMap = {}
+  webpackStats.chunks
+    // We are not interested about pages
+    .filter(({ files }) => !/^bundles/.test(files[0]))
+    .forEach(({ hash, files }) => {
+      chunkHashMap[files[0]] = { hash }
+    })
+
+  const buildStatsPath = join(dir, '.next', 'build-stats.json')
+  await fs.writeFile(buildStatsPath, JSON.stringify(chunkHashMap), 'utf8')
+}
+
 async function writeBuildId (dir) {
   const buildIdPath = join(dir, '.next', 'BUILD_ID')
   const buildId = uuid.v4()
diff --git a/server/document.js b/server/document.js
index 588da328f7b8d..bef4cd71218de 100644
--- a/server/document.js
+++ b/server/document.js
@@ -61,14 +61,14 @@ export class NextScript extends Component {
 
   render () {
     const { staticMarkup, __NEXT_DATA__ } = this.context._documentProps
-    let { buildId } = __NEXT_DATA__
+    let { buildStats } = __NEXT_DATA__
 
     return <div>
       {staticMarkup ? null : <script dangerouslySetInnerHTML={{
         __html: `__NEXT_DATA__ = ${htmlescape(__NEXT_DATA__)}; module={};`
       }} />}
-      { staticMarkup ? null : <script type='text/javascript' src={`/_next/${buildId}/commons.js`} /> }
-      { staticMarkup ? null : <script type='text/javascript' src={`/_next/${buildId}/main.js`} /> }
+      { staticMarkup ? null : <script type='text/javascript' src={`/_next/${buildStats['commons.js'].hash}/commons.js`} /> }
+      { staticMarkup ? null : <script type='text/javascript' src={`/_next/${buildStats['main.js'].hash}/main.js`} /> }
     </div>
   }
 }
diff --git a/server/index.js b/server/index.js
index 27978aa6e6d02..74750e84dc766 100644
--- a/server/index.js
+++ b/server/index.js
@@ -25,9 +25,16 @@ export default class Server {
     this.quiet = quiet
     this.router = new Router()
     this.hotReloader = dev ? new HotReloader(this.dir, { quiet }) : null
-    this.renderOpts = { dir: this.dir, dev, staticMarkup, hotReloader: this.hotReloader }
     this.http = null
     this.config = getConfig(this.dir)
+    this.buildStats = !dev ? require(join(this.dir, '.next', 'build-stats.json')) : null
+    this.renderOpts = {
+      dev,
+      staticMarkup,
+      dir: this.dir,
+      hotReloader: this.hotReloader,
+      buildStats: this.buildStats
+    }
 
     this.defineRoutes()
   }
@@ -83,31 +90,27 @@ export default class Server {
         await this.serveStatic(req, res, p)
       },
 
-      '/_next/:buildId/main.js': async (req, res, params) => {
-        if (!this.handleBuildId(params.buildId, res)) {
-          throwBuildIdMismatchError()
+      '/_next/:hash/main.js': async (req, res, params) => {
+        if (params.hash !== this.buildStats['main.js'].hash) {
+          throwNoHashError()
         }
 
+        res.setHeader('Cache-Control', 'max-age=365000000, immutable')
         const p = join(this.dir, '.next/main.js')
         await this.serveStatic(req, res, p)
       },
 
-      '/_next/:buildId/commons.js': async (req, res, params) => {
-        if (!this.handleBuildId(params.buildId, res)) {
-          throwBuildIdMismatchError()
+      '/_next/:hash/commons.js': async (req, res, params) => {
+        if (params.hash !== this.buildStats['commons.js'].hash) {
+          throwNoHashError()
         }
 
+        res.setHeader('Cache-Control', 'max-age=365000000, immutable')
         const p = join(this.dir, '.next/commons.js')
         await this.serveStatic(req, res, p)
       },
 
-      '/_next/:buildId/pages/:path*': async (req, res, params) => {
-        if (!this.handleBuildId(params.buildId, res)) {
-          res.setHeader('Content-Type', 'application/json')
-          res.end(JSON.stringify({ buildIdMismatch: true }))
-          return
-        }
-
+      '/_next/pages/:path*': async (req, res, params) => {
         const paths = params.path || ['index']
         const pathname = `/${paths.join('/')}`
 
@@ -291,16 +294,6 @@ export default class Server {
     }
   }
 
-  handleBuildId (buildId, res) {
-    if (this.dev) return true
-    if (buildId !== this.renderOpts.buildId) {
-      return false
-    }
-
-    res.setHeader('Cache-Control', 'max-age=365000000, immutable')
-    return true
-  }
-
   getCompilationError (page) {
     if (!this.hotReloader) return
 
@@ -313,6 +306,6 @@ export default class Server {
   }
 }
 
-function throwBuildIdMismatchError () {
-  throw new Error('BUILD_ID Mismatched!')
+function throwNoHashError () {
+  throw new Error('Invalid Build File Hash')
 }
diff --git a/server/render.js b/server/render.js
index e4551197465ec..163f6b386c7be 100644
--- a/server/render.js
+++ b/server/render.js
@@ -31,7 +31,7 @@ export function renderErrorToHTML (err, req, res, pathname, query, opts = {}) {
 async function doRender (req, res, pathname, query, {
   err,
   page,
-  buildId,
+  buildStats,
   hotReloader,
   dir = process.cwd(),
   dev = false,
@@ -93,7 +93,7 @@ async function doRender (req, res, pathname, query, {
       props,
       pathname,
       query,
-      buildId,
+      buildStats,
       err: (err && dev) ? errorToJSON(err) : null
     },
     dev,

From e1d2ad0dbe479efadaeae783bb6f88078bcb0d10 Mon Sep 17 00:00:00 2001
From: Arunoda Susiripala <arunoda.susiripala@gmail.com>
Date: Fri, 3 Mar 2017 11:54:01 +0530
Subject: [PATCH 02/11] Remove appUpdated Router Events hook. Becuase now we
 don't need it because there's no buildId validation.

---
 readme.md | 1 -
 1 file changed, 1 deletion(-)

diff --git a/readme.md b/readme.md
index 4d4037bc43b65..a05b1c697133d 100644
--- a/readme.md
+++ b/readme.md
@@ -310,7 +310,6 @@ Here's a list of supported events:
 - `routeChangeStart(url)` - Fires when a route starts to change
 - `routeChangeComplete(url)` - Fires when a route changed completely
 - `routeChangeError(err, url)` - Fires when there's an error when changing routes
-- `appUpdated(nextRoute)` - Fires when switching pages and there's a new version of the app
 
 > Here `url` is the URL shown in the browser. If you call `Router.push(url, as)` (or similar), then the value of `url` will be `as`.
 

From fdd36a5a0a307becdbd1d85ae3881b3a15b03d26 Mon Sep 17 00:00:00 2001
From: Arunoda Susiripala <arunoda.susiripala@gmail.com>
Date: Fri, 3 Mar 2017 11:59:05 +0530
Subject: [PATCH 03/11] Remove buildId generation.

---
 bin/next-start        | 2 +-
 server/build/index.js | 7 -------
 2 files changed, 1 insertion(+), 8 deletions(-)

diff --git a/bin/next-start b/bin/next-start
index 854a11e9b2671..793f8bce822e3 100755
--- a/bin/next-start
+++ b/bin/next-start
@@ -48,7 +48,7 @@ const dir = resolve(argv._[0] || '.')
 
 const srv = new Server({ dir })
 
-if (!existsSync(resolve(dir, '.next', 'BUILD_ID'))) {
+if (!existsSync(resolve(dir, '.next', 'build-stats.json'))) {
   console.error(`> Could not find a valid build in the '.next' directory! Try building your app with 'next build' before starting the server.`)
   process.exit(1)
 }
diff --git a/server/build/index.js b/server/build/index.js
index 0fcff294423b3..4f2f46a33b61b 100644
--- a/server/build/index.js
+++ b/server/build/index.js
@@ -13,7 +13,6 @@ export default async function build (dir) {
   try {
     const webpackStats = await runCompiler(compiler)
     await writeBuildStats(buildDir, webpackStats)
-    await writeBuildId(buildDir)
   } catch (err) {
     console.error(`> Failed to build on ${buildDir}`)
     throw err
@@ -56,9 +55,3 @@ async function writeBuildStats (dir, webpackStats) {
   const buildStatsPath = join(dir, '.next', 'build-stats.json')
   await fs.writeFile(buildStatsPath, JSON.stringify(chunkHashMap), 'utf8')
 }
-
-async function writeBuildId (dir) {
-  const buildIdPath = join(dir, '.next', 'BUILD_ID')
-  const buildId = uuid.v4()
-  await fs.writeFile(buildIdPath, buildId, 'utf8')
-}

From 3fcfc86ab9c037ba5f88d89ebf73f02a1c074feb Mon Sep 17 00:00:00 2001
From: Arunoda Susiripala <arunoda.susiripala@gmail.com>
Date: Fri, 3 Mar 2017 12:13:45 +0530
Subject: [PATCH 04/11] Turn off hash checks in the dev mode.

---
 server/document.js | 15 ++++++++++++---
 server/index.js    | 22 ++++++++++------------
 2 files changed, 22 insertions(+), 15 deletions(-)

diff --git a/server/document.js b/server/document.js
index bef4cd71218de..a2682aa1b0f50 100644
--- a/server/document.js
+++ b/server/document.js
@@ -59,16 +59,25 @@ export class NextScript extends Component {
     _documentProps: PropTypes.any
   }
 
+  getChunkScript (filename) {
+    const { __NEXT_DATA__ } = this.context._documentProps
+    let { buildStats } = __NEXT_DATA__
+    const hash = buildStats ? buildStats[filename].hash : '-'
+
+    return (
+      <script type='text/javascript' src={`/_next/${hash}/${filename}`} />
+    )
+  }
+
   render () {
     const { staticMarkup, __NEXT_DATA__ } = this.context._documentProps
-    let { buildStats } = __NEXT_DATA__
 
     return <div>
       {staticMarkup ? null : <script dangerouslySetInnerHTML={{
         __html: `__NEXT_DATA__ = ${htmlescape(__NEXT_DATA__)}; module={};`
       }} />}
-      { staticMarkup ? null : <script type='text/javascript' src={`/_next/${buildStats['commons.js'].hash}/commons.js`} /> }
-      { staticMarkup ? null : <script type='text/javascript' src={`/_next/${buildStats['main.js'].hash}/main.js`} /> }
+      { staticMarkup ? null : this.getChunkScript('commons.js') }
+      { staticMarkup ? null : this.getChunkScript('main.js') }
     </div>
   }
 }
diff --git a/server/index.js b/server/index.js
index 74750e84dc766..57508c92aa7bb 100644
--- a/server/index.js
+++ b/server/index.js
@@ -91,20 +91,13 @@ export default class Server {
       },
 
       '/_next/:hash/main.js': async (req, res, params) => {
-        if (params.hash !== this.buildStats['main.js'].hash) {
-          throwNoHashError()
-        }
-
-        res.setHeader('Cache-Control', 'max-age=365000000, immutable')
+        this.handleBuildHash('main.js', params.hash, res)
         const p = join(this.dir, '.next/main.js')
         await this.serveStatic(req, res, p)
       },
 
       '/_next/:hash/commons.js': async (req, res, params) => {
-        if (params.hash !== this.buildStats['commons.js'].hash) {
-          throwNoHashError()
-        }
-
+        this.handleBuildHash('commons.js', params.hash, res)
         res.setHeader('Cache-Control', 'max-age=365000000, immutable')
         const p = join(this.dir, '.next/commons.js')
         await this.serveStatic(req, res, p)
@@ -304,8 +297,13 @@ export default class Server {
     const p = resolveFromList(id, errors.keys())
     if (p) return errors.get(p)[0]
   }
-}
 
-function throwNoHashError () {
-  throw new Error('Invalid Build File Hash')
+  handleBuildHash (filename, hash, res) {
+    if (this.dev) return
+    if (hash !== this.buildStats[filename].hash) {
+      throw new Error(`Invalid Build File Hash(${hash}) for chunk: ${filename}`)
+    }
+
+    res.setHeader('Cache-Control', 'max-age=365000000, immutable')
+  }
 }

From 6d0511b96ab4d32b09879ecff53fa46e18f93fb1 Mon Sep 17 00:00:00 2001
From: Arunoda Susiripala <arunoda.susiripala@gmail.com>
Date: Fri, 3 Mar 2017 12:23:40 +0530
Subject: [PATCH 05/11] Update tests.

---
 test/integration/ondemand/test/index.test.js   | 4 ++--
 test/integration/production/test/index.test.js | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/test/integration/ondemand/test/index.test.js b/test/integration/ondemand/test/index.test.js
index 0726a8d446937..cf53fa83a16b7 100644
--- a/test/integration/ondemand/test/index.test.js
+++ b/test/integration/ondemand/test/index.test.js
@@ -31,12 +31,12 @@ describe('On Demand Entries', () => {
   })
 
   it('should compile pages for JSON page requests', async () => {
-    const pageContent = await renderViaHTTP(context.appPort, '/_next/-/pages/about')
+    const pageContent = await renderViaHTTP(context.appPort, '/_next/pages/about')
     expect(pageContent.includes('About Page')).toBeTruthy()
   })
 
   it('should dispose inactive pages', async () => {
-    await renderViaHTTP(context.appPort, '/_next/-/pages/about')
+    await renderViaHTTP(context.appPort, '/_next/pages/about')
     const aboutPagePath = resolve(__dirname, '../.next/bundles/pages/about.json')
     expect(existsSync(aboutPagePath)).toBeTruthy()
 
diff --git a/test/integration/production/test/index.test.js b/test/integration/production/test/index.test.js
index 2cd043c22807b..5e378ddee9f7d 100644
--- a/test/integration/production/test/index.test.js
+++ b/test/integration/production/test/index.test.js
@@ -40,7 +40,7 @@ describe('Production Usage', () => {
   describe('JSON pages', () => {
     describe('when asked for a normal page', () => {
       it('should serve the normal page', async () => {
-        const url = `http://localhost:${appPort}/_next/${app.renderOpts.buildId}/pages`
+        const url = `http://localhost:${appPort}/_next/pages`
         const res = await fetch(url, { compress: false })
         expect(res.headers.get('Content-Encoding')).toBeNull()
 
@@ -51,7 +51,7 @@ describe('Production Usage', () => {
 
     describe('when asked for a page with an unknown encoding', () => {
       it('should serve the normal page', async () => {
-        const url = `http://localhost:${appPort}/_next/${app.renderOpts.buildId}/pages`
+        const url = `http://localhost:${appPort}/_next/pages`
         const res = await fetch(url, {
           compress: false,
           headers: {

From 6cfd8eccbe387f122962c875b624602cb4dd3625 Mon Sep 17 00:00:00 2001
From: Arunoda Susiripala <arunoda.susiripala@gmail.com>
Date: Fri, 3 Mar 2017 23:32:29 +0530
Subject: [PATCH 06/11] Revert "Remove buildId generation."

This reverts commit fdd36a5a0a307becdbd1d85ae3881b3a15b03d26.
---
 bin/next-start        | 2 +-
 server/build/index.js | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/bin/next-start b/bin/next-start
index 793f8bce822e3..854a11e9b2671 100755
--- a/bin/next-start
+++ b/bin/next-start
@@ -48,7 +48,7 @@ const dir = resolve(argv._[0] || '.')
 
 const srv = new Server({ dir })
 
-if (!existsSync(resolve(dir, '.next', 'build-stats.json'))) {
+if (!existsSync(resolve(dir, '.next', 'BUILD_ID'))) {
   console.error(`> Could not find a valid build in the '.next' directory! Try building your app with 'next build' before starting the server.`)
   process.exit(1)
 }
diff --git a/server/build/index.js b/server/build/index.js
index 4f2f46a33b61b..0fcff294423b3 100644
--- a/server/build/index.js
+++ b/server/build/index.js
@@ -13,6 +13,7 @@ export default async function build (dir) {
   try {
     const webpackStats = await runCompiler(compiler)
     await writeBuildStats(buildDir, webpackStats)
+    await writeBuildId(buildDir)
   } catch (err) {
     console.error(`> Failed to build on ${buildDir}`)
     throw err
@@ -55,3 +56,9 @@ async function writeBuildStats (dir, webpackStats) {
   const buildStatsPath = join(dir, '.next', 'build-stats.json')
   await fs.writeFile(buildStatsPath, JSON.stringify(chunkHashMap), 'utf8')
 }
+
+async function writeBuildId (dir) {
+  const buildIdPath = join(dir, '.next', 'BUILD_ID')
+  const buildId = uuid.v4()
+  await fs.writeFile(buildIdPath, buildId, 'utf8')
+}

From b326a836adb90d4ae507c676d75599372edd200b Mon Sep 17 00:00:00 2001
From: Arunoda Susiripala <arunoda.susiripala@gmail.com>
Date: Fri, 3 Mar 2017 23:57:08 +0530
Subject: [PATCH 07/11] Bring back the buildId validation.

---
 lib/router/index.js  |  9 +++++++++
 lib/router/router.js | 13 ++++++++++++-
 server/index.js      | 23 ++++++++---------------
 server/render.js     |  2 ++
 4 files changed, 31 insertions(+), 16 deletions(-)

diff --git a/lib/router/index.js b/lib/router/index.js
index de3ac9ba6935f..aa9d4439b872c 100644
--- a/lib/router/index.js
+++ b/lib/router/index.js
@@ -76,3 +76,12 @@ export const createRouter = function (...args) {
 
 // Export the actual Router class, which is usually used inside the server
 export const Router = _Router
+
+export function _notifyBuildIdMismatch (nextRoute) {
+  if (SingletonRouter.onAppUpdated) {
+    SingletonRouter.onAppUpdated(nextRoute)
+  } else {
+    console.warn(`An app update detected. Loading the SSR version of "${nextRoute}"`)
+    window.location.href = nextRoute
+  }
+}
diff --git a/lib/router/router.js b/lib/router/router.js
index ebbf9fb5b7420..9fc0946874fde 100644
--- a/lib/router/router.js
+++ b/lib/router/router.js
@@ -1,10 +1,11 @@
 import { parse, format } from 'url'
 import { EventEmitter } from 'events'
+import fetch from 'unfetch'
 import evalScript from '../eval-script'
 import shallowEquals from '../shallow-equals'
 import PQueue from '../p-queue'
 import { loadGetInitialProps, getURL } from '../utils'
-import fetch from 'unfetch'
+import { _notifyBuildIdMismatch } from './'
 
 if (typeof window !== 'undefined' && typeof navigator.serviceWorker !== 'undefined') {
   navigator.serviceWorker.getRegistrations()
@@ -259,6 +260,16 @@ export default class Router extends EventEmitter {
     const jsonPageRes = await this.fetchRoute(route)
     const jsonData = await jsonPageRes.json()
 
+    const { buildId } = window.__NEXT_DATA__
+
+    if (buildId !== jsonPageRes.headers.get('Next-Build-Id')) {
+      _notifyBuildIdMismatch(as)
+
+      const error = Error('Abort due to BUILD_ID mismatch')
+      error.cancelled = true
+      throw error
+    }
+
     const newData = {
       ...loadComponent(jsonData),
       jsonPageRes
diff --git a/server/index.js b/server/index.js
index 57508c92aa7bb..3c59c13fb2d89 100644
--- a/server/index.js
+++ b/server/index.js
@@ -1,7 +1,7 @@
 import { resolve, join } from 'path'
 import { parse as parseUrl } from 'url'
 import { parse as parseQs } from 'querystring'
-import fs from 'mz/fs'
+import fs from 'fs'
 import http, { STATUS_CODES } from 'http'
 import {
   renderToHTML,
@@ -28,12 +28,14 @@ export default class Server {
     this.http = null
     this.config = getConfig(this.dir)
     this.buildStats = !dev ? require(join(this.dir, '.next', 'build-stats.json')) : null
+    this.buildId = !dev ? this.readBuildId() : null
     this.renderOpts = {
       dev,
       staticMarkup,
       dir: this.dir,
       hotReloader: this.hotReloader,
-      buildStats: this.buildStats
+      buildStats: this.buildStats,
+      buildId: this.buildId
     }
 
     this.defineRoutes()
@@ -64,8 +66,6 @@ export default class Server {
     if (this.hotReloader) {
       await this.hotReloader.start()
     }
-
-    this.renderOpts.buildId = await this.readBuildId()
   }
 
   async close () {
@@ -107,6 +107,7 @@ export default class Server {
         const paths = params.path || ['index']
         const pathname = `/${paths.join('/')}`
 
+        res.setHeader('Next-Build-Id', this.buildId)
         await this.renderJSON(req, res, pathname)
       },
 
@@ -273,18 +274,10 @@ export default class Server {
     }
   }
 
-  async readBuildId () {
+  readBuildId () {
     const buildIdPath = join(this.dir, '.next', 'BUILD_ID')
-    try {
-      const buildId = await fs.readFile(buildIdPath, 'utf8')
-      return buildId.trim()
-    } catch (err) {
-      if (err.code === 'ENOENT') {
-        return '-'
-      } else {
-        throw err
-      }
-    }
+    const buildId = fs.readFileSync(buildIdPath, 'utf8')
+    return buildId.trim()
   }
 
   getCompilationError (page) {
diff --git a/server/render.js b/server/render.js
index 163f6b386c7be..fac5dffb61bc7 100644
--- a/server/render.js
+++ b/server/render.js
@@ -31,6 +31,7 @@ export function renderErrorToHTML (err, req, res, pathname, query, opts = {}) {
 async function doRender (req, res, pathname, query, {
   err,
   page,
+  buildId,
   buildStats,
   hotReloader,
   dir = process.cwd(),
@@ -93,6 +94,7 @@ async function doRender (req, res, pathname, query, {
       props,
       pathname,
       query,
+      buildId,
       buildStats,
       err: (err && dev) ? errorToJSON(err) : null
     },

From 530febf4492f2e9df7d2ab39af881b4ff615da00 Mon Sep 17 00:00:00 2001
From: Arunoda Susiripala <arunoda.susiripala@gmail.com>
Date: Sat, 4 Mar 2017 00:01:58 +0530
Subject: [PATCH 08/11] Handle buildId validation only in production.

---
 lib/router/router.js | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/router/router.js b/lib/router/router.js
index 9fc0946874fde..bff9514a782b6 100644
--- a/lib/router/router.js
+++ b/lib/router/router.js
@@ -262,7 +262,10 @@ export default class Router extends EventEmitter {
 
     const { buildId } = window.__NEXT_DATA__
 
-    if (buildId !== jsonPageRes.headers.get('Next-Build-Id')) {
+    if (
+      process.env.NODE_ENV === 'production' &&
+      buildId !== jsonPageRes.headers.get('Next-Build-Id')
+    ) {
       _notifyBuildIdMismatch(as)
 
       const error = Error('Abort due to BUILD_ID mismatch')

From 6b9ba615d879269f76a902dfd836732f3fbe8331 Mon Sep 17 00:00:00 2001
From: Arunoda Susiripala <arunoda.susiripala@gmail.com>
Date: Tue, 7 Mar 2017 23:29:06 +0530
Subject: [PATCH 09/11] Add BUILD_ID to path again.

---
 lib/router/router.js                          | 11 ++++------
 readme.md                                     |  1 +
 server/index.js                               | 21 ++++++++++++++++---
 .../integration/production/test/index.test.js |  4 ++--
 4 files changed, 25 insertions(+), 12 deletions(-)

diff --git a/lib/router/router.js b/lib/router/router.js
index bff9514a782b6..ed6f1e82b5299 100644
--- a/lib/router/router.js
+++ b/lib/router/router.js
@@ -260,12 +260,7 @@ export default class Router extends EventEmitter {
     const jsonPageRes = await this.fetchRoute(route)
     const jsonData = await jsonPageRes.json()
 
-    const { buildId } = window.__NEXT_DATA__
-
-    if (
-      process.env.NODE_ENV === 'production' &&
-      buildId !== jsonPageRes.headers.get('Next-Build-Id')
-    ) {
+    if (jsonData.buildIdMismatch) {
       _notifyBuildIdMismatch(as)
 
       const error = Error('Abort due to BUILD_ID mismatch')
@@ -325,7 +320,9 @@ export default class Router extends EventEmitter {
   }
 
   doFetchRoute (route) {
-    const url = `/_next/pages${route}`
+    const { buildId } = window.__NEXT_DATA__
+    const url = `/_next/${encodeURIComponent(buildId)}/pages${route}`
+
     return fetch(url, {
       method: 'GET',
       headers: { 'Accept': 'application/json' }
diff --git a/readme.md b/readme.md
index a05b1c697133d..4d4037bc43b65 100644
--- a/readme.md
+++ b/readme.md
@@ -310,6 +310,7 @@ Here's a list of supported events:
 - `routeChangeStart(url)` - Fires when a route starts to change
 - `routeChangeComplete(url)` - Fires when a route changed completely
 - `routeChangeError(err, url)` - Fires when there's an error when changing routes
+- `appUpdated(nextRoute)` - Fires when switching pages and there's a new version of the app
 
 > Here `url` is the URL shown in the browser. If you call `Router.push(url, as)` (or similar), then the value of `url` will be `as`.
 
diff --git a/server/index.js b/server/index.js
index 3c59c13fb2d89..d8d992c2f2841 100644
--- a/server/index.js
+++ b/server/index.js
@@ -28,7 +28,7 @@ export default class Server {
     this.http = null
     this.config = getConfig(this.dir)
     this.buildStats = !dev ? require(join(this.dir, '.next', 'build-stats.json')) : null
-    this.buildId = !dev ? this.readBuildId() : null
+    this.buildId = !dev ? this.readBuildId() : '-'
     this.renderOpts = {
       dev,
       staticMarkup,
@@ -103,11 +103,16 @@ export default class Server {
         await this.serveStatic(req, res, p)
       },
 
-      '/_next/pages/:path*': async (req, res, params) => {
+      '/_next/:buildId/pages/:path*': async (req, res, params) => {
+        if (!this.handleBuildId(params.buildId, res)) {
+          res.setHeader('Content-Type', 'application/json')
+          res.end(JSON.stringify({ buildIdMismatch: true }))
+          return
+        }
+
         const paths = params.path || ['index']
         const pathname = `/${paths.join('/')}`
 
-        res.setHeader('Next-Build-Id', this.buildId)
         await this.renderJSON(req, res, pathname)
       },
 
@@ -280,6 +285,16 @@ export default class Server {
     return buildId.trim()
   }
 
+  handleBuildId (buildId, res) {
+    if (this.dev) return true
+    if (buildId !== this.renderOpts.buildId) {
+      return false
+    }
+
+    res.setHeader('Cache-Control', 'max-age=365000000, immutable')
+    return true
+  }
+
   getCompilationError (page) {
     if (!this.hotReloader) return
 
diff --git a/test/integration/production/test/index.test.js b/test/integration/production/test/index.test.js
index 5e378ddee9f7d..2cd043c22807b 100644
--- a/test/integration/production/test/index.test.js
+++ b/test/integration/production/test/index.test.js
@@ -40,7 +40,7 @@ describe('Production Usage', () => {
   describe('JSON pages', () => {
     describe('when asked for a normal page', () => {
       it('should serve the normal page', async () => {
-        const url = `http://localhost:${appPort}/_next/pages`
+        const url = `http://localhost:${appPort}/_next/${app.renderOpts.buildId}/pages`
         const res = await fetch(url, { compress: false })
         expect(res.headers.get('Content-Encoding')).toBeNull()
 
@@ -51,7 +51,7 @@ describe('Production Usage', () => {
 
     describe('when asked for a page with an unknown encoding', () => {
       it('should serve the normal page', async () => {
-        const url = `http://localhost:${appPort}/_next/pages`
+        const url = `http://localhost:${appPort}/_next/${app.renderOpts.buildId}/pages`
         const res = await fetch(url, {
           compress: false,
           headers: {

From 6ec03949ca9101a4314d5a0dd04141305ffbf2d5 Mon Sep 17 00:00:00 2001
From: Arunoda Susiripala <arunoda.susiripala@gmail.com>
Date: Tue, 7 Mar 2017 23:35:28 +0530
Subject: [PATCH 10/11] Remove duplicate immutable header.

---
 server/index.js | 1 -
 1 file changed, 1 deletion(-)

diff --git a/server/index.js b/server/index.js
index d8d992c2f2841..f08a9fec8ed95 100644
--- a/server/index.js
+++ b/server/index.js
@@ -98,7 +98,6 @@ export default class Server {
 
       '/_next/:hash/commons.js': async (req, res, params) => {
         this.handleBuildHash('commons.js', params.hash, res)
-        res.setHeader('Cache-Control', 'max-age=365000000, immutable')
         const p = join(this.dir, '.next/commons.js')
         await this.serveStatic(req, res, p)
       },

From 0bd1f2c4bc8cf4d4bfe1343f504bd71cd8c8e771 Mon Sep 17 00:00:00 2001
From: Arunoda Susiripala <arunoda.susiripala@gmail.com>
Date: Tue, 7 Mar 2017 23:49:03 +0530
Subject: [PATCH 11/11] Fix tests.

---
 test/integration/ondemand/test/index.test.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/test/integration/ondemand/test/index.test.js b/test/integration/ondemand/test/index.test.js
index cf53fa83a16b7..0726a8d446937 100644
--- a/test/integration/ondemand/test/index.test.js
+++ b/test/integration/ondemand/test/index.test.js
@@ -31,12 +31,12 @@ describe('On Demand Entries', () => {
   })
 
   it('should compile pages for JSON page requests', async () => {
-    const pageContent = await renderViaHTTP(context.appPort, '/_next/pages/about')
+    const pageContent = await renderViaHTTP(context.appPort, '/_next/-/pages/about')
     expect(pageContent.includes('About Page')).toBeTruthy()
   })
 
   it('should dispose inactive pages', async () => {
-    await renderViaHTTP(context.appPort, '/_next/pages/about')
+    await renderViaHTTP(context.appPort, '/_next/-/pages/about')
     const aboutPagePath = resolve(__dirname, '../.next/bundles/pages/about.json')
     expect(existsSync(aboutPagePath)).toBeTruthy()