From a4c61b39fd44960dc17a57c8bdb6eb0113b7dacb Mon Sep 17 00:00:00 2001
From: Jan Potoms <2109932+Janpot@users.noreply.github.com>
Date: Tue, 14 Jul 2020 23:10:29 +0200
Subject: [PATCH 01/14] Start on repeated slash redirect

---
 .../next/client/normalize-trailing-slash.ts   | 20 +++--
 packages/next/lib/load-custom-routes.ts       | 37 --------
 .../next/next-server/server/next-server.ts    | 50 ++++++++++-
 .../repeated-slash-redirect/next.config.js    |  3 +
 .../pages/[[...slug]].js                      |  7 ++
 .../test/index.test.js                        | 85 +++++++++++++++++++
 .../trailing-slashes/test/index.test.js       | 39 ---------
 7 files changed, 155 insertions(+), 86 deletions(-)
 create mode 100644 test/integration/repeated-slash-redirect/next.config.js
 create mode 100644 test/integration/repeated-slash-redirect/pages/[[...slug]].js
 create mode 100644 test/integration/repeated-slash-redirect/test/index.test.js

diff --git a/packages/next/client/normalize-trailing-slash.ts b/packages/next/client/normalize-trailing-slash.ts
index fdb22d9fad44..52282a0a74b4 100644
--- a/packages/next/client/normalize-trailing-slash.ts
+++ b/packages/next/client/normalize-trailing-slash.ts
@@ -7,20 +7,22 @@ export function removePathTrailingSlash(path: string): string {
   return path.endsWith('/') && path !== '/' ? path.slice(0, -1) : path
 }
 
+export function ensurePathTrailingSlash(path: string): string {
+  if (/\.[^/]+\/?$/.test(path)) {
+    return removePathTrailingSlash(path)
+  } else if (path.endsWith('/')) {
+    return path
+  } else {
+    return path + '/'
+  }
+}
+
 /**
  * Normalizes the trailing slash of a path according to the `trailingSlash` option
  * in `next.config.js`.
  */
 const normalizePathTrailingSlash = process.env.__NEXT_TRAILING_SLASH
-  ? (path: string): string => {
-      if (/\.[^/]+\/?$/.test(path)) {
-        return removePathTrailingSlash(path)
-      } else if (path.endsWith('/')) {
-        return path
-      } else {
-        return path + '/'
-      }
-    }
+  ? ensurePathTrailingSlash
   : removePathTrailingSlash
 
 /**
diff --git a/packages/next/lib/load-custom-routes.ts b/packages/next/lib/load-custom-routes.ts
index 324863c1d060..d6c04b000b19 100644
--- a/packages/next/lib/load-custom-routes.ts
+++ b/packages/next/lib/load-custom-routes.ts
@@ -357,43 +357,6 @@ export default async function loadCustomRoutes(
     loadRedirects(config),
   ])
 
-  if (config.experimental.trailingSlash) {
-    redirects.unshift(
-      {
-        source: '/:path*/:file.:ext/',
-        destination: '/:path*/:file.:ext',
-        permanent: true,
-      },
-      {
-        source: '/:path*/:notfile([^/.]+)',
-        destination: '/:path*/:notfile/',
-        permanent: true,
-      }
-    )
-    if (config.basePath) {
-      redirects.unshift({
-        source: config.basePath,
-        destination: config.basePath + '/',
-        permanent: true,
-        basePath: false,
-      })
-    }
-  } else {
-    redirects.unshift({
-      source: '/:path+/',
-      destination: '/:path+',
-      permanent: true,
-    })
-    if (config.basePath) {
-      redirects.unshift({
-        source: config.basePath + '/',
-        destination: config.basePath,
-        permanent: true,
-        basePath: false,
-      })
-    }
-  }
-
   return {
     headers,
     rewrites,
diff --git a/packages/next/next-server/server/next-server.ts b/packages/next/next-server/server/next-server.ts
index ff0a17ed57e7..f2c6ab61d411 100644
--- a/packages/next/next-server/server/next-server.ts
+++ b/packages/next/next-server/server/next-server.ts
@@ -62,7 +62,10 @@ import { compile as compilePathToRegex } from 'next/dist/compiled/path-to-regexp
 import { loadEnvConfig } from '../../lib/load-env-config'
 import './node-polyfill-fetch'
 import { PagesManifest } from '../../build/webpack/plugins/pages-manifest-plugin'
-import { removePathTrailingSlash } from '../../client/normalize-trailing-slash'
+import {
+  removePathTrailingSlash,
+  ensurePathTrailingSlash,
+} from '../../client/normalize-trailing-slash'
 import getRouteFromAssetPath from '../lib/router/utils/get-route-from-asset-path'
 
 const getCustomRouteMatcher = pathMatch(true)
@@ -444,6 +447,11 @@ export default class Server {
       ...staticFilesRoute,
     ]
 
+    const normalizePathTrailingSlash = this.nextConfig.experimental
+      .trailingSlash
+      ? ensurePathTrailingSlash
+      : removePathTrailingSlash
+
     const getCustomRouteBasePath = (r: { basePath?: false }) => {
       return r.basePath !== false && this.renderOpts.dev
         ? this.nextConfig.basePath
@@ -541,6 +549,46 @@ export default class Server {
       } as Route
     })
 
+    redirects.unshift({
+      type: 'redirect',
+      match: (url) => url.startsWith(this.nextConfig.basePath),
+      statusCode: 308,
+      name: `Redirect slashes`,
+      fn: async (_req, res, params, parsedUrl) => {
+        const { pathname } = parsedUrl
+        const slashesNormalized = normalizePathTrailingSlash(
+          pathname?.replace(/\/\/+/g, '/') || '/'
+        )
+
+        if (slashesNormalized === pathname) {
+          return { finished: false }
+        }
+
+        const { parsedDestination } = prepareDestination(
+          slashesNormalized,
+          params,
+          parsedUrl.query,
+          false,
+          ''
+        )
+        const updatedDestination = formatUrl(parsedDestination)
+
+        res.setHeader('Location', updatedDestination)
+        res.statusCode = 308
+
+        // Since IE11 doesn't support the 308 header add backwards
+        // compatibility using refresh header
+        if (res.statusCode === 308) {
+          res.setHeader('Refresh', `0;url=${updatedDestination}`)
+        }
+
+        res.end()
+        return {
+          finished: true,
+        }
+      },
+    } as Route)
+
     const rewrites = this.customRoutes.rewrites.map((rewrite) => {
       const rewriteRoute = getCustomRoute(rewrite, 'rewrite')
       return {
diff --git a/test/integration/repeated-slash-redirect/next.config.js b/test/integration/repeated-slash-redirect/next.config.js
new file mode 100644
index 000000000000..ed8e3d3f74af
--- /dev/null
+++ b/test/integration/repeated-slash-redirect/next.config.js
@@ -0,0 +1,3 @@
+module.exports = {
+  // target: 'serverless',
+}
diff --git a/test/integration/repeated-slash-redirect/pages/[[...slug]].js b/test/integration/repeated-slash-redirect/pages/[[...slug]].js
new file mode 100644
index 000000000000..443e21fb7cb8
--- /dev/null
+++ b/test/integration/repeated-slash-redirect/pages/[[...slug]].js
@@ -0,0 +1,7 @@
+export async function getServerSideProps({ query: { slug } }) {
+  return { props: { slug: slug || [] } }
+}
+
+export default function Page({ slug }) {
+  return <div>{slug.join('/')}</div>
+}
diff --git a/test/integration/repeated-slash-redirect/test/index.test.js b/test/integration/repeated-slash-redirect/test/index.test.js
new file mode 100644
index 000000000000..a66bccf20212
--- /dev/null
+++ b/test/integration/repeated-slash-redirect/test/index.test.js
@@ -0,0 +1,85 @@
+/* eslint-env jest */
+
+import fs from 'fs-extra'
+import { join } from 'path'
+import {
+  launchApp,
+  killApp,
+  findPort,
+  nextBuild,
+  nextStart,
+  fetchViaHTTP,
+} from 'next-test-utils'
+
+jest.setTimeout(1000 * 60 * 2)
+
+let appDir = join(__dirname, '..')
+const nextConfigPath = join(appDir, 'next.config.js')
+let nextConfigContent
+let appPort
+let app
+
+const runTests = (isDev = false) => {
+  it.each([
+    ['/hello//world', '/hello/world'],
+    ['//hello/world', '/hello/world'],
+    ['/hello/world//', '/hello/world'],
+    ['//', '/'],
+    ['/hello///world', '/hello/world'],
+    ['/hello///world////foo', '/hello/world/foo'],
+    ['/hello//world?foo=bar//baz', '/hello/world?foo=bar%2F%2Fbaz'],
+  ])('it should redirect %s to %s', async (from, to) => {
+    const res = await fetchViaHTTP(appPort, from, undefined, {
+      redirect: 'manual',
+    })
+    expect(res.status).toBe(308)
+    const location = new URL(res.headers.get('location'), 'http://n')
+    const locPathname = location.href.slice(location.origin.length)
+    expect(locPathname).toBe(to)
+  })
+}
+
+describe('Repeated trailing slashes', () => {
+  describe('dev mode', () => {
+    beforeAll(async () => {
+      appPort = await findPort()
+      app = await launchApp(appDir, appPort)
+    })
+    afterAll(() => killApp(app))
+    runTests(true)
+  })
+
+  describe('server mode', () => {
+    beforeAll(async () => {
+      await nextBuild(appDir, [], {
+        stdout: true,
+      })
+      appPort = await findPort()
+      app = await nextStart(appDir, appPort)
+    })
+    afterAll(() => killApp(app))
+    runTests()
+  })
+
+  describe('serverless mode', () => {
+    beforeAll(async () => {
+      nextConfigContent = await fs.readFile(nextConfigPath, 'utf8')
+      await fs.writeFile(
+        nextConfigPath,
+        nextConfigContent.replace(/\/\/ target/, 'target'),
+        'utf8'
+      )
+      await nextBuild(appDir, [], {
+        stdout: true,
+      })
+      appPort = await findPort()
+      app = await nextStart(appDir, appPort)
+    })
+    afterAll(async () => {
+      await fs.writeFile(nextConfigPath, nextConfigContent, 'utf8')
+      await killApp(app)
+    })
+
+    runTests()
+  })
+})
diff --git a/test/integration/trailing-slashes/test/index.test.js b/test/integration/trailing-slashes/test/index.test.js
index 97682630deca..e9565f78c6b4 100644
--- a/test/integration/trailing-slashes/test/index.test.js
+++ b/test/integration/trailing-slashes/test/index.test.js
@@ -232,23 +232,6 @@ describe('Trailing slashes', () => {
     })
 
     testWithoutTrailingSlash()
-
-    it('should have a redirect in the routesmanifest', async () => {
-      const manifest = await fs.readJSON(
-        join(appDir, '.next', 'routes-manifest.json')
-      )
-      expect(manifest).toEqual(
-        expect.objectContaining({
-          redirects: expect.arrayContaining([
-            expect.objectContaining({
-              source: '/:path+/',
-              destination: '/:path+',
-              statusCode: 308,
-            }),
-          ]),
-        })
-      )
-    })
   })
 
   describe('production mode, trailingSlash: true', () => {
@@ -270,28 +253,6 @@ describe('Trailing slashes', () => {
     })
 
     testWithTrailingSlash()
-
-    it('should have a redirect in the routesmanifest', async () => {
-      const manifest = await fs.readJSON(
-        join(appDir, '.next', 'routes-manifest.json')
-      )
-      expect(manifest).toEqual(
-        expect.objectContaining({
-          redirects: expect.arrayContaining([
-            expect.objectContaining({
-              source: '/:path*/:file.:ext/',
-              destination: '/:path*/:file.:ext',
-              statusCode: 308,
-            }),
-            expect.objectContaining({
-              source: '/:path*/:notfile([^/.]+)',
-              destination: '/:path*/:notfile/',
-              statusCode: 308,
-            }),
-          ]),
-        })
-      )
-    })
   })
 
   describe('dev mode, with basepath, trailingSlash: true', () => {

From c6019c2fbb92507533490af5ceb543427d5cf446 Mon Sep 17 00:00:00 2001
From: Jan Potoms <2109932+Janpot@users.noreply.github.com>
Date: Tue, 14 Jul 2020 23:11:10 +0200
Subject: [PATCH 02/14] Update next-server.ts

---
 packages/next/next-server/server/next-server.ts | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/packages/next/next-server/server/next-server.ts b/packages/next/next-server/server/next-server.ts
index f2c6ab61d411..f67e9dbfbd8b 100644
--- a/packages/next/next-server/server/next-server.ts
+++ b/packages/next/next-server/server/next-server.ts
@@ -551,10 +551,10 @@ export default class Server {
 
     redirects.unshift({
       type: 'redirect',
-      match: (url) => url.startsWith(this.nextConfig.basePath),
+      match: (url) => url!.startsWith(this.nextConfig.basePath),
       statusCode: 308,
       name: `Redirect slashes`,
-      fn: async (_req, res, params, parsedUrl) => {
+      fn: async (_req, res, _params, parsedUrl) => {
         const { pathname } = parsedUrl
         const slashesNormalized = normalizePathTrailingSlash(
           pathname?.replace(/\/\/+/g, '/') || '/'
@@ -566,7 +566,7 @@ export default class Server {
 
         const { parsedDestination } = prepareDestination(
           slashesNormalized,
-          params,
+          {},
           parsedUrl.query,
           false,
           ''

From 68077a922ef2803155e9f00fcdc38a2814f0fbc0 Mon Sep 17 00:00:00 2001
From: Jan Potoms <2109932+Janpot@users.noreply.github.com>
Date: Tue, 14 Jul 2020 23:43:06 +0200
Subject: [PATCH 03/14] Fix custom-routes test

---
 test/integration/custom-routes/test/index.test.js | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/test/integration/custom-routes/test/index.test.js b/test/integration/custom-routes/test/index.test.js
index c7a0026f3b67..641c996671c6 100644
--- a/test/integration/custom-routes/test/index.test.js
+++ b/test/integration/custom-routes/test/index.test.js
@@ -495,14 +495,6 @@ const runTests = (isDev = false) => {
         pages404: true,
         basePath: '',
         redirects: [
-          {
-            destination: '/:path+',
-            regex: normalizeRegEx(
-              '^(?:\\/((?:[^\\/]+?)(?:\\/(?:[^\\/]+?))*))\\/$'
-            ),
-            source: '/:path+/',
-            statusCode: 308,
-          },
           {
             destination: '/:lang/about',
             regex: normalizeRegEx(

From ef47453e99a43b2210e567bf888784bc985aeadf Mon Sep 17 00:00:00 2001
From: Jan Potoms <2109932+Janpot@users.noreply.github.com>
Date: Wed, 15 Jul 2020 00:04:46 +0200
Subject: [PATCH 04/14] fix matcher

---
 packages/next/next-server/server/next-server.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/next/next-server/server/next-server.ts b/packages/next/next-server/server/next-server.ts
index f67e9dbfbd8b..c27acfc93cbe 100644
--- a/packages/next/next-server/server/next-server.ts
+++ b/packages/next/next-server/server/next-server.ts
@@ -551,7 +551,7 @@ export default class Server {
 
     redirects.unshift({
       type: 'redirect',
-      match: (url) => url!.startsWith(this.nextConfig.basePath),
+      match: getCustomRouteMatcher('/(.*)'),
       statusCode: 308,
       name: `Redirect slashes`,
       fn: async (_req, res, _params, parsedUrl) => {

From 124fcc11e35a3df0ae696d8312472e4375804d46 Mon Sep 17 00:00:00 2001
From: Jan Potoms <2109932+Janpot@users.noreply.github.com>
Date: Sat, 18 Jul 2020 18:56:09 +0200
Subject: [PATCH 05/14] revert

---
 .../next/client/normalize-trailing-slash.ts   | 20 ++++----
 packages/next/lib/load-custom-routes.ts       | 44 ++++++++++++++++
 .../next/next-server/server/next-server.ts    | 50 +------------------
 .../custom-routes/test/index.test.js          | 16 ++++++
 .../test/index.test.js                        |  7 +--
 .../trailing-slashes/test/index.test.js       | 40 +++++++++++++++
 6 files changed, 112 insertions(+), 65 deletions(-)

diff --git a/packages/next/client/normalize-trailing-slash.ts b/packages/next/client/normalize-trailing-slash.ts
index 53451dd98d7e..6cbd6f72e0dd 100644
--- a/packages/next/client/normalize-trailing-slash.ts
+++ b/packages/next/client/normalize-trailing-slash.ts
@@ -5,20 +5,18 @@ export function removePathTrailingSlash(path: string): string {
   return path.endsWith('/') && path !== '/' ? path.slice(0, -1) : path
 }
 
-export function ensurePathTrailingSlash(path: string): string {
-  if (/\.[^/]+\/?$/.test(path)) {
-    return removePathTrailingSlash(path)
-  } else if (path.endsWith('/')) {
-    return path
-  } else {
-    return path + '/'
-  }
-}
-
 /**
  * Normalizes the trailing slash of a path according to the `trailingSlash` option
  * in `next.config.js`.
  */
 export const normalizePathTrailingSlash = process.env.__NEXT_TRAILING_SLASH
-  ? ensurePathTrailingSlash
+  ? (path: string): string => {
+      if (/\.[^/]+\/?$/.test(path)) {
+        return removePathTrailingSlash(path)
+      } else if (path.endsWith('/')) {
+        return path
+      } else {
+        return path + '/'
+      }
+    }
   : removePathTrailingSlash
diff --git a/packages/next/lib/load-custom-routes.ts b/packages/next/lib/load-custom-routes.ts
index d6c04b000b19..d4fe3a4613bb 100644
--- a/packages/next/lib/load-custom-routes.ts
+++ b/packages/next/lib/load-custom-routes.ts
@@ -357,6 +357,50 @@ export default async function loadCustomRoutes(
     loadRedirects(config),
   ])
 
+  if (config.experimental.trailingSlash) {
+    redirects.unshift(
+      {
+        source: '/:path*/:file.:ext/',
+        destination: '/:path*/:file.:ext',
+        permanent: true,
+      },
+      {
+        source: '/:path*/:notfile([^/.]+)',
+        destination: '/:path*/:notfile/',
+        permanent: true,
+      }
+    )
+    if (config.basePath) {
+      redirects.unshift({
+        source: config.basePath,
+        destination: config.basePath + '/',
+        permanent: true,
+        basePath: false,
+      })
+    }
+  } else {
+    redirects.unshift({
+      source: '/:path+/',
+      destination: '/:path+',
+      permanent: true,
+    })
+    if (config.basePath) {
+      redirects.unshift({
+        source: config.basePath + '/',
+        destination: config.basePath,
+        permanent: true,
+        basePath: false,
+      })
+    }
+  }
+
+  // multiple slashes redirect
+  redirects.unshift({
+    source: '/:before*/{(/+)}:after(.*)',
+    destination: '/:before*/:after',
+    permanent: true,
+  })
+
   return {
     headers,
     rewrites,
diff --git a/packages/next/next-server/server/next-server.ts b/packages/next/next-server/server/next-server.ts
index c27acfc93cbe..ff0a17ed57e7 100644
--- a/packages/next/next-server/server/next-server.ts
+++ b/packages/next/next-server/server/next-server.ts
@@ -62,10 +62,7 @@ import { compile as compilePathToRegex } from 'next/dist/compiled/path-to-regexp
 import { loadEnvConfig } from '../../lib/load-env-config'
 import './node-polyfill-fetch'
 import { PagesManifest } from '../../build/webpack/plugins/pages-manifest-plugin'
-import {
-  removePathTrailingSlash,
-  ensurePathTrailingSlash,
-} from '../../client/normalize-trailing-slash'
+import { removePathTrailingSlash } from '../../client/normalize-trailing-slash'
 import getRouteFromAssetPath from '../lib/router/utils/get-route-from-asset-path'
 
 const getCustomRouteMatcher = pathMatch(true)
@@ -447,11 +444,6 @@ export default class Server {
       ...staticFilesRoute,
     ]
 
-    const normalizePathTrailingSlash = this.nextConfig.experimental
-      .trailingSlash
-      ? ensurePathTrailingSlash
-      : removePathTrailingSlash
-
     const getCustomRouteBasePath = (r: { basePath?: false }) => {
       return r.basePath !== false && this.renderOpts.dev
         ? this.nextConfig.basePath
@@ -549,46 +541,6 @@ export default class Server {
       } as Route
     })
 
-    redirects.unshift({
-      type: 'redirect',
-      match: getCustomRouteMatcher('/(.*)'),
-      statusCode: 308,
-      name: `Redirect slashes`,
-      fn: async (_req, res, _params, parsedUrl) => {
-        const { pathname } = parsedUrl
-        const slashesNormalized = normalizePathTrailingSlash(
-          pathname?.replace(/\/\/+/g, '/') || '/'
-        )
-
-        if (slashesNormalized === pathname) {
-          return { finished: false }
-        }
-
-        const { parsedDestination } = prepareDestination(
-          slashesNormalized,
-          {},
-          parsedUrl.query,
-          false,
-          ''
-        )
-        const updatedDestination = formatUrl(parsedDestination)
-
-        res.setHeader('Location', updatedDestination)
-        res.statusCode = 308
-
-        // Since IE11 doesn't support the 308 header add backwards
-        // compatibility using refresh header
-        if (res.statusCode === 308) {
-          res.setHeader('Refresh', `0;url=${updatedDestination}`)
-        }
-
-        res.end()
-        return {
-          finished: true,
-        }
-      },
-    } as Route)
-
     const rewrites = this.customRoutes.rewrites.map((rewrite) => {
       const rewriteRoute = getCustomRoute(rewrite, 'rewrite')
       return {
diff --git a/test/integration/custom-routes/test/index.test.js b/test/integration/custom-routes/test/index.test.js
index 641c996671c6..c90ccadd545b 100644
--- a/test/integration/custom-routes/test/index.test.js
+++ b/test/integration/custom-routes/test/index.test.js
@@ -495,6 +495,22 @@ const runTests = (isDev = false) => {
         pages404: true,
         basePath: '',
         redirects: [
+          {
+            destination: '/:before*/:after',
+            regex: normalizeRegEx(
+              '^(?:\\/((?:[^\\/]+?)(?:\\/(?:[^\\/]+?))*))?\\/(\\/+)(.*)$'
+            ),
+            source: '/:before*/{(/+)}:after(.*)',
+            statusCode: 308,
+          },
+          {
+            destination: '/:path+',
+            regex: normalizeRegEx(
+              '^(?:\\/((?:[^\\/]+?)(?:\\/(?:[^\\/]+?))*))\\/$'
+            ),
+            source: '/:path+/',
+            statusCode: 308,
+          },
           {
             destination: '/:lang/about',
             regex: normalizeRegEx(
diff --git a/test/integration/repeated-slash-redirect/test/index.test.js b/test/integration/repeated-slash-redirect/test/index.test.js
index a66bccf20212..98c25124d1a1 100644
--- a/test/integration/repeated-slash-redirect/test/index.test.js
+++ b/test/integration/repeated-slash-redirect/test/index.test.js
@@ -29,11 +29,8 @@ const runTests = (isDev = false) => {
     ['/hello///world////foo', '/hello/world/foo'],
     ['/hello//world?foo=bar//baz', '/hello/world?foo=bar%2F%2Fbaz'],
   ])('it should redirect %s to %s', async (from, to) => {
-    const res = await fetchViaHTTP(appPort, from, undefined, {
-      redirect: 'manual',
-    })
-    expect(res.status).toBe(308)
-    const location = new URL(res.headers.get('location'), 'http://n')
+    const res = await fetchViaHTTP(appPort, from)
+    const location = new URL(res.url)
     const locPathname = location.href.slice(location.origin.length)
     expect(locPathname).toBe(to)
   })
diff --git a/test/integration/trailing-slashes/test/index.test.js b/test/integration/trailing-slashes/test/index.test.js
index 5cb4c3e6c02d..44bc308c71db 100644
--- a/test/integration/trailing-slashes/test/index.test.js
+++ b/test/integration/trailing-slashes/test/index.test.js
@@ -3,6 +3,7 @@
 import webdriver from 'next-webdriver'
 
 import cheerio from 'cheerio'
+import fs from 'fs-extra'
 import {
   fetchViaHTTP,
   renderViaHTTP,
@@ -216,6 +217,23 @@ describe('Trailing slashes', () => {
     })
 
     testWithoutTrailingSlash()
+
+    it('should have a redirect in the routesmanifest', async () => {
+      const manifest = await fs.readJSON(
+        join(appDir, '.next', 'routes-manifest.json')
+      )
+      expect(manifest).toEqual(
+        expect.objectContaining({
+          redirects: expect.arrayContaining([
+            expect.objectContaining({
+              source: '/:path+/',
+              destination: '/:path+',
+              statusCode: 308,
+            }),
+          ]),
+        })
+      )
+    })
   })
 
   describe('production mode, trailingSlash: true', () => {
@@ -231,6 +249,28 @@ describe('Trailing slashes', () => {
     })
 
     testWithTrailingSlash()
+
+    it('should have a redirect in the routesmanifest', async () => {
+      const manifest = await fs.readJSON(
+        join(appDir, '.next', 'routes-manifest.json')
+      )
+      expect(manifest).toEqual(
+        expect.objectContaining({
+          redirects: expect.arrayContaining([
+            expect.objectContaining({
+              source: '/:path*/:file.:ext/',
+              destination: '/:path*/:file.:ext',
+              statusCode: 308,
+            }),
+            expect.objectContaining({
+              source: '/:path*/:notfile([^/.]+)',
+              destination: '/:path*/:notfile/',
+              statusCode: 308,
+            }),
+          ]),
+        })
+      )
+    })
   })
 
   describe('dev mode, with basepath, trailingSlash: true', () => {

From 23b0aed27091bbd297f24471ca2f025390a6e424 Mon Sep 17 00:00:00 2001
From: Jan Potoms <2109932+Janpot@users.noreply.github.com>
Date: Sat, 18 Jul 2020 19:38:51 +0200
Subject: [PATCH 06/14] ignore files

---
 packages/next/lib/load-custom-routes.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/next/lib/load-custom-routes.ts b/packages/next/lib/load-custom-routes.ts
index d4fe3a4613bb..40899d414c6d 100644
--- a/packages/next/lib/load-custom-routes.ts
+++ b/packages/next/lib/load-custom-routes.ts
@@ -396,7 +396,7 @@ export default async function loadCustomRoutes(
 
   // multiple slashes redirect
   redirects.unshift({
-    source: '/:before*/{(/+)}:after(.*)',
+    source: '/:before*/{(/+)}:after(|.*/[^/.]+|[^/.]+)',
     destination: '/:before*/:after',
     permanent: true,
   })

From a18cbb09c836195007fd021165132560e2239221 Mon Sep 17 00:00:00 2001
From: Jan Potoms <2109932+Janpot@users.noreply.github.com>
Date: Sat, 18 Jul 2020 20:06:57 +0200
Subject: [PATCH 07/14] fix custom-routes

---
 test/integration/custom-routes/test/index.test.js | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/test/integration/custom-routes/test/index.test.js b/test/integration/custom-routes/test/index.test.js
index c90ccadd545b..ed3550c0d2c5 100644
--- a/test/integration/custom-routes/test/index.test.js
+++ b/test/integration/custom-routes/test/index.test.js
@@ -496,11 +496,11 @@ const runTests = (isDev = false) => {
         basePath: '',
         redirects: [
           {
-            destination: '/:before*/:after',
             regex: normalizeRegEx(
-              '^(?:\\/((?:[^\\/]+?)(?:\\/(?:[^\\/]+?))*))?\\/(\\/+)(.*)$'
+              '^(?:\\/((?:[^\\/]+?)(?:\\/(?:[^\\/]+?))*))?\\/(\\/+)(|.*\\/[^\\/.]+|[^\\/.]+)$'
             ),
-            source: '/:before*/{(/+)}:after(.*)',
+            source: '/:before*/{(/+)}:after(|.*/[^/.]+|[^/.]+)',
+            destination: '/:before*/:after',
             statusCode: 308,
           },
           {

From 332995302d10855d25fcf52dc6825135e178328a Mon Sep 17 00:00:00 2001
From: Jan Potoms <2109932+Janpot@users.noreply.github.com>
Date: Mon, 20 Jul 2020 10:47:02 +0200
Subject: [PATCH 08/14] WIP

---
 .../next/client/normalize-trailing-slash.ts   |  4 +++
 .../next/next-server/lib/router/router.ts     |  6 ++---
 .../repeated-slash-redirect/pages/linker.js   | 25 +++++++++++++++++++
 .../test/index.test.js                        | 16 +++++++++---
 4 files changed, 45 insertions(+), 6 deletions(-)
 create mode 100644 test/integration/repeated-slash-redirect/pages/linker.js

diff --git a/packages/next/client/normalize-trailing-slash.ts b/packages/next/client/normalize-trailing-slash.ts
index 6cbd6f72e0dd..5c258fef667f 100644
--- a/packages/next/client/normalize-trailing-slash.ts
+++ b/packages/next/client/normalize-trailing-slash.ts
@@ -20,3 +20,7 @@ export const normalizePathTrailingSlash = process.env.__NEXT_TRAILING_SLASH
       }
     }
   : removePathTrailingSlash
+
+export function normalizePathSlashes(path: string): string {
+  return normalizePathTrailingSlash(path.replace(/\/\/+/g, '/'))
+}
diff --git a/packages/next/next-server/lib/router/router.ts b/packages/next/next-server/lib/router/router.ts
index 9b10e5db6d70..bd5d2c83bb99 100644
--- a/packages/next/next-server/lib/router/router.ts
+++ b/packages/next/next-server/lib/router/router.ts
@@ -19,7 +19,7 @@ import { searchParamsToUrlQuery } from './utils/search-params-to-url-query'
 import { parseRelativeUrl } from './utils/parse-relative-url'
 import {
   removePathTrailingSlash,
-  normalizePathTrailingSlash,
+  normalizePathSlashes,
 } from '../../../client/normalize-trailing-slash'
 
 const basePath = (process.env.__NEXT_ROUTER_BASEPATH as string) || ''
@@ -27,7 +27,7 @@ const basePath = (process.env.__NEXT_ROUTER_BASEPATH as string) || ''
 export function addBasePath(path: string): string {
   return basePath
     ? path === '/'
-      ? normalizePathTrailingSlash(basePath)
+      ? normalizePathSlashes(basePath)
       : basePath + path
     : path
 }
@@ -48,7 +48,7 @@ export function resolveHref(currentPath: string, href: Url): string {
   const urlAsString =
     typeof href === 'string' ? href : formatWithValidation(href)
   const finalUrl = new URL(urlAsString, base)
-  finalUrl.pathname = normalizePathTrailingSlash(finalUrl.pathname)
+  finalUrl.pathname = normalizePathSlashes(finalUrl.pathname)
   // if the origin didn't change, it means we received a relative href
   return finalUrl.origin === base.origin
     ? finalUrl.href.slice(finalUrl.origin.length)
diff --git a/test/integration/repeated-slash-redirect/pages/linker.js b/test/integration/repeated-slash-redirect/pages/linker.js
new file mode 100644
index 000000000000..e70939a79867
--- /dev/null
+++ b/test/integration/repeated-slash-redirect/pages/linker.js
@@ -0,0 +1,25 @@
+import Link from 'next/link'
+import { useRouter } from 'next/router'
+
+export async function getServerSideProps({ query }) {
+  return {
+    props: { href: query.href || '/' },
+  }
+}
+
+export default function Linker({ href }) {
+  const router = useRouter()
+  const pushRoute = () => {
+    router.push(href)
+  }
+  return (
+    <div>
+      <Link href={href}>
+        <a id="link">link to {href}</a>
+      </Link>
+      <button id="route-pusher" onClick={pushRoute}>
+        push route {href}
+      </button>
+    </div>
+  )
+}
diff --git a/test/integration/repeated-slash-redirect/test/index.test.js b/test/integration/repeated-slash-redirect/test/index.test.js
index 98c25124d1a1..e7758cafd4eb 100644
--- a/test/integration/repeated-slash-redirect/test/index.test.js
+++ b/test/integration/repeated-slash-redirect/test/index.test.js
@@ -1,5 +1,6 @@
 /* eslint-env jest */
 
+import cheerio from 'cheerio'
 import fs from 'fs-extra'
 import { join } from 'path'
 import {
@@ -9,6 +10,7 @@ import {
   nextBuild,
   nextStart,
   fetchViaHTTP,
+  renderViaHTTP,
 } from 'next-test-utils'
 
 jest.setTimeout(1000 * 60 * 2)
@@ -20,20 +22,28 @@ let appPort
 let app
 
 const runTests = (isDev = false) => {
-  it.each([
+  const cases = [
     ['/hello//world', '/hello/world'],
     ['//hello/world', '/hello/world'],
     ['/hello/world//', '/hello/world'],
     ['//', '/'],
     ['/hello///world', '/hello/world'],
     ['/hello///world////foo', '/hello/world/foo'],
-    ['/hello//world?foo=bar//baz', '/hello/world?foo=bar%2F%2Fbaz'],
-  ])('it should redirect %s to %s', async (from, to) => {
+    ['/hello//world?foo=bar//baz', '/hello/world?foo=bar//baz'],
+  ]
+
+  it.each(cases)('it should redirect %s to %s', async (from, to) => {
     const res = await fetchViaHTTP(appPort, from)
     const location = new URL(res.url)
     const locPathname = location.href.slice(location.origin.length)
     expect(locPathname).toBe(to)
   })
+
+  it.each(cases)('it should rewrite href %s to %s', async (from, to) => {
+    const content = await renderViaHTTP(appPort, `/linker?href=${from}`)
+    const $ = cheerio.load(content)
+    expect($('#link').attr('href')).toBe(to)
+  })
 }
 
 describe('Repeated trailing slashes', () => {

From 16681d5d13caf5e7cd1b4cb797c51782fedd9d7c Mon Sep 17 00:00:00 2001
From: Jan Potoms <2109932+Janpot@users.noreply.github.com>
Date: Thu, 23 Jul 2020 00:16:51 +0200
Subject: [PATCH 09/14] Add more tests

---
 .../pages/[[...slug]].js                      |  2 +-
 .../repeated-slash-redirect/pages/linker.js   |  2 +-
 .../test/index.test.js                        | 27 +++++++++++++++----
 3 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/test/integration/repeated-slash-redirect/pages/[[...slug]].js b/test/integration/repeated-slash-redirect/pages/[[...slug]].js
index 443e21fb7cb8..c9648d10e7a8 100644
--- a/test/integration/repeated-slash-redirect/pages/[[...slug]].js
+++ b/test/integration/repeated-slash-redirect/pages/[[...slug]].js
@@ -3,5 +3,5 @@ export async function getServerSideProps({ query: { slug } }) {
 }
 
 export default function Page({ slug }) {
-  return <div>{slug.join('/')}</div>
+  return <div id="page">{slug.join('/')}</div>
 }
diff --git a/test/integration/repeated-slash-redirect/pages/linker.js b/test/integration/repeated-slash-redirect/pages/linker.js
index e70939a79867..abec3a4cc08b 100644
--- a/test/integration/repeated-slash-redirect/pages/linker.js
+++ b/test/integration/repeated-slash-redirect/pages/linker.js
@@ -14,7 +14,7 @@ export default function Linker({ href }) {
   }
   return (
     <div>
-      <Link href={href}>
+      <Link href="/[[...slug]]" as={href}>
         <a id="link">link to {href}</a>
       </Link>
       <button id="route-pusher" onClick={pushRoute}>
diff --git a/test/integration/repeated-slash-redirect/test/index.test.js b/test/integration/repeated-slash-redirect/test/index.test.js
index e7758cafd4eb..8e0cc78a018e 100644
--- a/test/integration/repeated-slash-redirect/test/index.test.js
+++ b/test/integration/repeated-slash-redirect/test/index.test.js
@@ -12,6 +12,7 @@ import {
   fetchViaHTTP,
   renderViaHTTP,
 } from 'next-test-utils'
+import webdriver from 'next-webdriver'
 
 jest.setTimeout(1000 * 60 * 2)
 
@@ -21,12 +22,18 @@ let nextConfigContent
 let appPort
 let app
 
+function getPathWithNormalizedQuery(url) {
+  const parsed = new URL(url, 'http://n')
+  if (parsed.search) {
+    parsed.search = `?${parsed.searchParams}`
+  }
+  return parsed.pathname + parsed.search
+}
+
 const runTests = (isDev = false) => {
   const cases = [
     ['/hello//world', '/hello/world'],
-    ['//hello/world', '/hello/world'],
     ['/hello/world//', '/hello/world'],
-    ['//', '/'],
     ['/hello///world', '/hello/world'],
     ['/hello///world////foo', '/hello/world/foo'],
     ['/hello//world?foo=bar//baz', '/hello/world?foo=bar//baz'],
@@ -34,9 +41,9 @@ const runTests = (isDev = false) => {
 
   it.each(cases)('it should redirect %s to %s', async (from, to) => {
     const res = await fetchViaHTTP(appPort, from)
-    const location = new URL(res.url)
-    const locPathname = location.href.slice(location.origin.length)
-    expect(locPathname).toBe(to)
+    expect(getPathWithNormalizedQuery(res.url)).toBe(
+      getPathWithNormalizedQuery(to)
+    )
   })
 
   it.each(cases)('it should rewrite href %s to %s', async (from, to) => {
@@ -44,6 +51,16 @@ const runTests = (isDev = false) => {
     const $ = cheerio.load(content)
     expect($('#link').attr('href')).toBe(to)
   })
+
+  it.each(cases)('it should navigate a href %s to %s', async (from, to) => {
+    const browser = await webdriver(appPort, `/linker?href=${from}`)
+    await browser.elementByCss('#link').click()
+    await browser.waitForElementByCss('#page')
+    const href = await browser.eval('window.location.href')
+    expect(getPathWithNormalizedQuery(href)).toBe(
+      getPathWithNormalizedQuery(to)
+    )
+  })
 }
 
 describe('Repeated trailing slashes', () => {

From c0968679af41363123a042f0ecb4e2f415b34a8b Mon Sep 17 00:00:00 2001
From: Jan Potoms <2109932+Janpot@users.noreply.github.com>
Date: Sat, 23 Jan 2021 19:28:23 +0100
Subject: [PATCH 10/14] typescript

---
 packages/next/lib/load-custom-routes.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/next/lib/load-custom-routes.ts b/packages/next/lib/load-custom-routes.ts
index 1cf65bd194eb..1892e21381b7 100644
--- a/packages/next/lib/load-custom-routes.ts
+++ b/packages/next/lib/load-custom-routes.ts
@@ -515,7 +515,7 @@ export default async function loadCustomRoutes(
     source: '/:before*/{(/+)}:after(|.*/[^/.]+|[^/.]+)',
     destination: '/:before*/:after',
     permanent: true,
-  })
+  } as Redirect)
 
   return {
     headers,

From 11dcb59bea89697ba7493f052986ad1fe19f01af Mon Sep 17 00:00:00 2001
From: Jan Potoms <2109932+Janpot@users.noreply.github.com>
Date: Sat, 23 Jan 2021 19:50:53 +0100
Subject: [PATCH 11/14] fix test

---
 test/integration/build-output/test/index.test.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/integration/build-output/test/index.test.js b/test/integration/build-output/test/index.test.js
index cf8eca1c83ff..468cc1fc6bb0 100644
--- a/test/integration/build-output/test/index.test.js
+++ b/test/integration/build-output/test/index.test.js
@@ -104,7 +104,7 @@ describe('Build Output', () => {
       expect(parseFloat(err404FirstLoad)).toBeCloseTo(67, 1)
       expect(err404FirstLoad.endsWith('kB')).toBe(true)
 
-      expect(parseFloat(sharedByAll)).toBeCloseTo(63.5, 1)
+      expect(parseFloat(sharedByAll)).toBeCloseTo(63.6, 1)
       expect(sharedByAll.endsWith('kB')).toBe(true)
 
       if (_appSize.endsWith('kB')) {

From 2c235d86620434ff7f6f7cc484306f750dc8c342 Mon Sep 17 00:00:00 2001
From: Jan Potoms <2109932+Janpot@users.noreply.github.com>
Date: Sat, 23 Jan 2021 21:42:14 +0100
Subject: [PATCH 12/14] fix telemetry redirects count

---
 packages/next/build/index.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/next/build/index.ts b/packages/next/build/index.ts
index eef4d1e54d93..015bf2e8c341 100644
--- a/packages/next/build/index.ts
+++ b/packages/next/build/index.ts
@@ -1263,7 +1263,7 @@ export default async function build(
         hasReportWebVitals: namedExports?.includes('reportWebVitals') ?? false,
         rewritesCount: rewrites.length,
         headersCount: headers.length,
-        redirectsCount: redirects.length - 1, // reduce one for trailing slash
+        redirectsCount: redirects.length - 2, // subtract two for internal redirects
       })
     )
 

From d6c6abbe0cb7245a1342030f48a8f5098e0b4e61 Mon Sep 17 00:00:00 2001
From: Jan Potoms <2109932+Janpot@users.noreply.github.com>
Date: Sun, 24 Jan 2021 18:53:08 +0100
Subject: [PATCH 13/14] Update packages/next/lib/load-custom-routes.ts

Co-authored-by: JJ Kasper <jj@jjsweb.site>
---
 packages/next/lib/load-custom-routes.ts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/packages/next/lib/load-custom-routes.ts b/packages/next/lib/load-custom-routes.ts
index 1892e21381b7..e6654f11e5c8 100644
--- a/packages/next/lib/load-custom-routes.ts
+++ b/packages/next/lib/load-custom-routes.ts
@@ -515,6 +515,7 @@ export default async function loadCustomRoutes(
     source: '/:before*/{(/+)}:after(|.*/[^/.]+|[^/.]+)',
     destination: '/:before*/:after',
     permanent: true,
+    locale: config.i18n ? false : undefined,
   } as Redirect)
 
   return {

From 84a24475dbb1b301c0ed9579cf436836efe82286 Mon Sep 17 00:00:00 2001
From: Jan Potoms <2109932+Janpot@users.noreply.github.com>
Date: Mon, 25 Jan 2021 23:24:23 +0100
Subject: [PATCH 14/14] Dedupe leading slashes

---
 packages/next/next-server/lib/router/router.ts              | 2 +-
 test/integration/repeated-slash-redirect/test/index.test.js | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/packages/next/next-server/lib/router/router.ts b/packages/next/next-server/lib/router/router.ts
index fee41a7274f3..847285079e19 100644
--- a/packages/next/next-server/lib/router/router.ts
+++ b/packages/next/next-server/lib/router/router.ts
@@ -270,7 +270,7 @@ export function resolveHref(
     return (resolveAs ? [urlAsString] : urlAsString) as string
   }
   try {
-    const finalUrl = new URL(urlAsString, base)
+    const finalUrl = new URL(urlAsString.replace(/^\/+/, '/'), base)
     finalUrl.pathname = normalizePathSlashes(finalUrl.pathname)
     let interpolatedAs = ''
 
diff --git a/test/integration/repeated-slash-redirect/test/index.test.js b/test/integration/repeated-slash-redirect/test/index.test.js
index 8e0cc78a018e..31c0c4656d91 100644
--- a/test/integration/repeated-slash-redirect/test/index.test.js
+++ b/test/integration/repeated-slash-redirect/test/index.test.js
@@ -32,6 +32,7 @@ function getPathWithNormalizedQuery(url) {
 
 const runTests = (isDev = false) => {
   const cases = [
+    ['//hello/world', '/hello/world'],
     ['/hello//world', '/hello/world'],
     ['/hello/world//', '/hello/world'],
     ['/hello///world', '/hello/world'],