[Experimental] Add basePath support

packages/next/build/entries.ts

@@ -77,6 +77,7 @@ export function createEntrypoints(
     generateEtags: config.generateEtags,
     ampBindInitData: config.experimental.ampBindInitData,
     canonicalBase: config.canonicalBase,
+    basePath: config.experimental.basePath,
   }
 
   Object.keys(pages).forEach(page => {

packages/next/build/webpack-config.ts

@@ -724,6 +724,9 @@ export default async function getBaseWebpackConfig(
         'process.env.__NEXT_REACT_MODE': JSON.stringify(
           config.experimental.reactMode
         ),
+        'process.env.__NEXT_ROUTER_BASEPATH': JSON.stringify(
+          config.experimental.basePath
+        ),
         ...(isServer
           ? {
               // Fix bad-actors in the npm ecosystem (e.g. `node-formidable`)

packages/next/build/webpack/loaders/next-serverless-loader.ts

@@ -21,6 +21,7 @@ export type ServerlessLoaderQuery = {
   ampBindInitData: boolean | string
   generateEtags: string
   canonicalBase: string
+  basePath: string
 }
 
 const nextServerlessLoader: loader.Loader = function() {
@@ -36,8 +37,10 @@ const nextServerlessLoader: loader.Loader = function() {
     absoluteDocumentPath,
     absoluteErrorPath,
     generateEtags,
+    basePath,
   }: ServerlessLoaderQuery =
     typeof this.query === 'string' ? parse(this.query.substr(1)) : this.query
+
   const buildManifest = join(distDir, BUILD_MANIFEST).replace(/\\/g, '/')
   const reactLoadableManifest = join(distDir, REACT_LOADABLE_MANIFEST).replace(
     /\\/g,
@@ -128,6 +131,16 @@ const nextServerlessLoader: loader.Loader = function() {
       export default async (req, res) => {
         try {
           await initServer()
+
+          ${
+            basePath
+              ? `
+          if(req.url.startsWith('${basePath}')) {
+            req.url = req.url.replace('${basePath}', '')
+          }
+          `
+              : ''
+          }
           const parsedUrl = parse(req.url, true)
 
           const params = ${
@@ -181,6 +194,15 @@ const nextServerlessLoader: loader.Loader = function() {
     export const config = ComponentInfo['confi' + 'g'] || {}
     export const _app = App
     export async function renderReqToHTML(req, res, fromExport, _renderOpts, _params) {
+      ${
+        basePath
+          ? `
+      if(req.url.startsWith('${basePath}')) {
+        req.url = req.url.replace('${basePath}', '')
+      }
+      `
+          : ''
+      }
       const options = {
         App,
         Document,

packages/next/next-server/lib/router/router.ts

@@ -18,6 +18,12 @@ import { isDynamicRoute } from './utils/is-dynamic'
 import { getRouteMatcher } from './utils/route-matcher'
 import { getRouteRegex } from './utils/route-regex'
 
+function addBasePath(path: string): string {
+  // @ts-ignore variable is always a string
+  const p: string = process.env.__NEXT_ROUTER_BASEPATH
+  return path.indexOf(p) !== 0 ? p + path : path
+}
+
 function toRoute(path: string): string {
   return path.replace(/\/$/, '') || '/'
 }
@@ -284,7 +290,7 @@ export default class Router implements BaseRouter {
       if (!options._h && this.onlyAHashChange(as)) {
         this.asPath = as
         Router.events.emit('hashChangeStart', as)
-        this.changeState(method, url, as)
+        this.changeState(method, url, addBasePath(as))
         this.scrollToHash(as)
         Router.events.emit('hashChangeComplete', as)
         return resolve(true)
@@ -346,7 +352,7 @@ export default class Router implements BaseRouter {
         }
 
         Router.events.emit('beforeHistoryChange', as)
-        this.changeState(method, url, as, options)
+        this.changeState(method, url, addBasePath(as), options)
         const hash = window.location.hash.substring(1)
 
         if (process.env.NODE_ENV !== 'production') {

packages/next/next-server/server/config.ts

@@ -53,6 +53,7 @@ const defaultConfig: { [key: string]: any } = {
     deferScripts: false,
     reactMode: 'legacy',
     workerThreads: false,
+    basePath: '',
   },
   future: {
     excludeDefaultMomentLocales: false,
@@ -106,9 +107,44 @@ function assignDefaults(userConfig: { [key: string]: any }) {
       `Specified assetPrefix is not a string, found type "${typeof result.assetPrefix}" https://err.sh/zeit/next.js/invalid-assetprefix`
     )
   }
-  if (result.experimental && result.experimental.css) {
-    // The new CSS support requires granular chunks be enabled.
-    result.experimental.granularChunks = true
+  if (result.experimental) {
+    if (result.experimental.css) {
+      // The new CSS support requires granular chunks be enabled.
+      result.experimental.granularChunks = true
+    }
+
+    if (typeof result.experimental.basePath !== 'string') {
+      throw new Error(
+        `Specified basePath is not a string, found type "${typeof result
+          .experimental.basePath}"`
+      )
+    }
+
+    if (result.experimental.basePath !== '') {
+      if (result.experimental.basePath === '/') {
+        throw new Error(
+          `Specified basePath /. basePath has to be either an empty string or a path prefix"`
+        )
+      }
+
+      if (!result.experimental.basePath.startsWith('/')) {
+        throw new Error(
+          `Specified basePath has to start with a /, found "${result.experimental.basePath}"`
+        )
+      }
+
+      if (result.experimental.basePath !== '/') {
+        if (result.experimental.basePath.endsWith('/')) {
+          throw new Error(
+            `Specified basePath should not end with /, found "${result.experimental.basePath}"`
+          )
+        }
+
+        if (result.assetPrefix === '') {
+          result.assetPrefix = result.experimental.basePath
+        }
+      }
+    }
   }
   return result
 }

packages/next/next-server/server/next-server.ts

@@ -232,6 +232,16 @@ export default class Server {
       parsedUrl.query = parseQs(parsedUrl.query)
     }
 
+    if (parsedUrl.pathname!.startsWith(this.nextConfig.experimental.basePath)) {
+      // If replace ends up replacing the full url it'll be `undefined`, meaning we have to default it to `/`
+      parsedUrl.pathname =
+        parsedUrl.pathname!.replace(
+          this.nextConfig.experimental.basePath,
+          ''
+        ) || '/'
+      req.url = req.url!.replace(this.nextConfig.experimental.basePath, '')
+    }
+
     res.statusCode = 200
     return this.run(req, res, parsedUrl).catch(err => {
       this.logError(err)

test/integration/basepath/components/hello-chunkfilename.js

@@ -0,0 +1 @@
+export default () => <div>test chunkfilename</div>

test/integration/basepath/components/hello-context.js

@@ -0,0 +1,13 @@
+import React from 'react'
+import PropTypes from 'prop-types'
+
+export default class extends React.Component {
+  static contextTypes = {
+    data: PropTypes.object,
+  }
+
+  render() {
+    const { data } = this.context
+    return <div>{data.title}</div>
+  }
+}

test/integration/basepath/components/hello1.js

@@ -0,0 +1 @@
+export default () => <p>Hello World 1</p>

test/integration/basepath/components/hello2.js

@@ -0,0 +1 @@
+export default () => <p>Hello World 2</p>

test/integration/basepath/components/hello3.js

@@ -0,0 +1 @@
+export default () => <p>Hello World 1</p>

test/integration/basepath/components/hello4.js

@@ -0,0 +1 @@
+export default () => <p>Hello World 2</p>

test/integration/basepath/components/hmr/dynamic.js

@@ -0,0 +1,12 @@
+export default () => {
+  return (
+    <div id="dynamic-component">
+      Dynamic Component
+      <style jsx>{`
+        div {
+          font-size: 100px;
+        }
+      `}</style>
+    </div>
+  )
+}

test/integration/basepath/components/nested1.js

@@ -0,0 +1,10 @@
+import dynamic from 'next/dynamic'
+
+const Nested2 = dynamic(() => import('./nested2'))
+
+export default () => (
+  <div>
+    Nested 1
+    <Nested2 />
+  </div>
+)

test/integration/basepath/components/nested2.js

@@ -0,0 +1,12 @@
+import dynamic from 'next/dynamic'
+
+const BrowserLoaded = dynamic(async () => () => <div>Browser hydrated</div>, {
+  ssr: false,
+})
+
+export default () => (
+  <div>
+    <div>Nested 2</div>
+    <BrowserLoaded />
+  </div>
+)

test/integration/basepath/components/welcome.js

@@ -0,0 +1,17 @@
+import React from 'react'
+
+export default class Welcome extends React.Component {
+  state = { name: null }
+
+  componentDidMount() {
+    const { name } = this.props
+    this.setState({ name })
+  }
+
+  render() {
+    const { name } = this.state
+    if (!name) return null
+
+    return <p>Welcome, {name}</p>
+  }
+}

test/integration/basepath/next.config.js

@@ -0,0 +1,9 @@
+module.exports = {
+  onDemandEntries: {
+    // Make sure entries are not getting disposed.
+    maxInactiveAge: 1000 * 60 * 60,
+  },
+  experimental: {
+    basePath: '/docs',
+  },
+}

test/integration/basepath/pages/hello.js

@@ -0,0 +1,9 @@
+import Link from 'next/link'
+
+export default () => (
+  <Link href="/other-page">
+    <a id="other-page-link">
+      <h1>Hello World</h1>
+    </a>
+  </Link>
+)

test/integration/basepath/pages/hmr/about.js

@@ -0,0 +1,7 @@
+export default () => {
+  return (
+    <div className="hmr-about-page">
+      <p>This is the about page.</p>
+    </div>
+  )
+}

test/integration/basepath/pages/hmr/about1.js

@@ -0,0 +1,7 @@
+export default () => {
+  return (
+    <div className="hmr-about-page">
+      <p>This is the about page.</p>
+    </div>
+  )
+}

test/integration/basepath/pages/hmr/about2.js

@@ -0,0 +1,7 @@
+export default () => {
+  return (
+    <div className="hmr-about-page">
+      <p>This is the about page.</p>
+    </div>
+  )
+}

test/integration/basepath/pages/hmr/about3.js

@@ -0,0 +1,7 @@
+export default () => {
+  return (
+    <div className="hmr-about-page">
+      <p>This is the about page.</p>
+    </div>
+  )
+}

test/integration/basepath/pages/hmr/about4.js

@@ -0,0 +1,7 @@
+export default () => {
+  return (
+    <div className="hmr-about-page">
+      <p>This is the about page.</p>
+    </div>
+  )
+}

test/integration/basepath/pages/hmr/about5.js

@@ -0,0 +1,7 @@
+export default () => {
+  return (
+    <div className="hmr-about-page">
+      <p>This is the about page.</p>
+    </div>
+  )
+}

test/integration/basepath/pages/hmr/about6.js

@@ -0,0 +1,7 @@
+export default () => {
+  return (
+    <div className="hmr-about-page">
+      <p>This is the about page.</p>
+    </div>
+  )
+}

test/integration/basepath/pages/hmr/about7.js

@@ -0,0 +1,7 @@
+export default () => {
+  return (
+    <div className="hmr-about-page">
+      <p>This is the about page.</p>
+    </div>
+  )
+}

test/integration/basepath/pages/hmr/contact.js

@@ -0,0 +1,5 @@
+export default () => (
+  <div className="hmr-contact-page">
+    <p>This is the contact page.</p>
+  </div>
+)

test/integration/basepath/pages/hmr/counter.js

@@ -0,0 +1,19 @@
+import React from 'react'
+
+export default class Counter extends React.Component {
+  state = { count: 0 }
+
+  incr() {
+    const { count } = this.state
+    this.setState({ count: count + 1 })
+  }
+
+  render() {
+    return (
+      <div>
+        <p>COUNT: {this.state.count}</p>
+        <button onClick={() => this.incr()}>Increment</button>
+      </div>
+    )
+  }
+}

test/integration/basepath/pages/hmr/error-in-gip.js

@@ -0,0 +1,11 @@
+import React from 'react'
+export default class extends React.Component {
+  static getInitialProps() {
+    const error = new Error('an-expected-error-in-gip')
+    throw error
+  }
+
+  render() {
+    return <div>Hello</div>
+  }
+}

test/integration/basepath/pages/hmr/index.js

@@ -0,0 +1,9 @@
+import Link from 'next/link'
+
+export default () => (
+  <div>
+    <Link href="/hmr/error-in-gip">
+      <a id="error-in-gip-link">Bad Page</a>
+    </Link>
+  </div>
+)

test/integration/basepath/pages/hmr/style-dynamic-component.js

@@ -0,0 +1,8 @@
+import React from 'react'
+import dynamic from 'next/dynamic'
+
+const HmrDynamic = dynamic(import('../../components/hmr/dynamic'))
+
+export default () => {
+  return <HmrDynamic />
+}