From 03365886f1b8a87cc14c825ac8cf3829a05e472d Mon Sep 17 00:00:00 2001
From: Seth Falco <seth@falco.fun>
Date: Tue, 29 Mar 2022 18:06:39 +0100
Subject: [PATCH] bug: allow scheme-relative url in links

---
 packages/next/shared/lib/router/router.ts     | 16 +++++----
 .../repeated-slashes/app/pages/invalid.js     | 36 ++++++++++---------
 .../repeated-slashes/test/index.test.js       | 28 +++++++--------
 3 files changed, 44 insertions(+), 36 deletions(-)

diff --git a/packages/next/shared/lib/router/router.ts b/packages/next/shared/lib/router/router.ts
index 2816ab180e804a..7c78d209082177 100644
--- a/packages/next/shared/lib/router/router.ts
+++ b/packages/next/shared/lib/router/router.ts
@@ -214,10 +214,14 @@ export function delBasePath(path: string): string {
  */
 export function isLocalURL(url: string): boolean {
   // prevent a hydration mismatch on href for url with anchor refs
-  if (url.startsWith('/') || url.startsWith('#') || url.startsWith('?'))
+  if (
+    url.match(/^\/(?!\/)/) !== null ||
+    url.startsWith('#') ||
+    url.startsWith('?')
+  )
     return true
   try {
-    // absolute urls can be local if they are on the same origin
+    // absolute and scheme-relative urls can be local if they are on the same origin
     const locationOrigin = getLocationOrigin()
     const resolved = new URL(url, locationOrigin)
     return resolved.origin === locationOrigin && hasBasePath(resolved.pathname)
@@ -318,9 +322,9 @@ export function resolveHref(
 
   // repeated slashes and backslashes in the URL are considered
   // invalid and will never match a Next.js page/file
-  const urlProtoMatch = urlAsString.match(/^[a-zA-Z]{1,}:\/\//)
-  const urlAsStringNoProto = urlProtoMatch
-    ? urlAsString.slice(urlProtoMatch[0].length)
+  const urlSchemeMatch = urlAsString.match(/^(?:[a-zA-Z]+:)?\/\//)
+  const urlAsStringNoProto = urlSchemeMatch
+    ? urlAsString.slice(urlSchemeMatch[0].length)
     : urlAsString
 
   const urlParts = urlAsStringNoProto.split('?')
@@ -330,7 +334,7 @@ export function resolveHref(
       `Invalid href passed to next/router: ${urlAsString}, repeated forward-slashes (//) or backslashes \\ are not valid in the href`
     )
     const normalizedUrl = normalizeRepeatedSlashes(urlAsStringNoProto)
-    urlAsString = (urlProtoMatch ? urlProtoMatch[0] : '') + normalizedUrl
+    urlAsString = (urlSchemeMatch ? urlSchemeMatch[0] : '') + normalizedUrl
   }
 
   // Return because it cannot be routed by the Next.js router
diff --git a/test/integration/repeated-slashes/app/pages/invalid.js b/test/integration/repeated-slashes/app/pages/invalid.js
index 907fd59f457a43..8586781ca2f791 100644
--- a/test/integration/repeated-slashes/app/pages/invalid.js
+++ b/test/integration/repeated-slashes/app/pages/invalid.js
@@ -14,43 +14,47 @@ export default function Invalid() {
   return (
     <>
       <p id="invalid">invalid page</p>
-      <Link href="/another" as="//google.com">
-        <a id="page-with-as-slashes">to /another as //google.com</a>
+      <Link href="/another" as="/google.com//maps">
+        <a id="page-with-as-slashes">to /another as /google.com//maps</a>
       </Link>
       <br />
 
-      <Link href="//google.com">
-        <a id="href-with-slashes">to //google.com</a>
+      <Link href="/google.com//maps">
+        <a id="href-with-slashes">to /google.com//maps</a>
       </Link>
       <br />
 
-      <Link href="//google.com?hello=1">
-        <a id="href-with-slashes-query">to //google.com?hello=1</a>
+      <Link href="/google.com//maps?hello=1">
+        <a id="href-with-slashes-query">to /google.com//maps?hello=1</a>
       </Link>
       <br />
 
-      <Link href="//google.com#hello">
-        <a id="href-with-slashes-hash">to //google.com#hello</a>
+      <Link href="/google.com//maps#hello">
+        <a id="href-with-slashes-hash">to /google.com//maps#hello</a>
       </Link>
       <br />
 
-      <Link href="/another" as="\/\/google.com">
-        <a id="page-with-as-backslashes">to /another as \\/\\/google.com</a>
+      <Link href="/another" as="\/google.com\/\/maps">
+        <a id="page-with-as-backslashes">
+          to /another as \\/google.com\\/\\/maps
+        </a>
       </Link>
       <br />
 
-      <Link href="\/\/google.com">
-        <a id="href-with-backslashes">to \\/\\/google.com</a>
+      <Link href="\/google.com\/\/maps">
+        <a id="href-with-backslashes">to \\/google.com\\/\\/maps</a>
       </Link>
       <br />
 
-      <Link href="\/\/google.com?hello=1">
-        <a id="href-with-backslashes-query">to \\/\\/google.com?hello=1</a>
+      <Link href="\/google.com\/\/maps?hello=1">
+        <a id="href-with-backslashes-query">
+          to \\/google.com\\/\\/maps?hello=1
+        </a>
       </Link>
       <br />
 
-      <Link href="\/\/google.com#hello">
-        <a id="href-with-backslashes-hash">to \\/\\/google.com#hello</a>
+      <Link href="\/google.com\/\/maps#hello">
+        <a id="href-with-backslashes-hash">to \\/google.com\\/\\/maps#hello</a>
       </Link>
       <br />
     </>
diff --git a/test/integration/repeated-slashes/test/index.test.js b/test/integration/repeated-slashes/test/index.test.js
index 347550441580a6..8d68e326e4898b 100644
--- a/test/integration/repeated-slashes/test/index.test.js
+++ b/test/integration/repeated-slashes/test/index.test.js
@@ -289,12 +289,12 @@ function runTests({ isDev = false, isExport = false, isPages404 = false }) {
       `/invalid${isExport ? '.html' : ''}`
     )
     const invalidHrefs = [
-      '//google.com',
-      '//google.com?hello=1',
-      '//google.com#hello',
-      '\\/\\/google.com',
-      '\\/\\/google.com?hello=1',
-      '\\/\\/google.com#hello',
+      '/google.com//maps',
+      '/google.com//maps?hello=1',
+      '/google.com//maps#hello',
+      '\\/google.com\\/\\/maps',
+      '\\/google.com\\/\\/maps?hello=1',
+      '\\/google.com\\/\\/maps#hello',
     ]
 
     for (const href of invalidHrefs) {
@@ -313,24 +313,24 @@ function runTests({ isDev = false, isExport = false, isPages404 = false }) {
       {
         page: '/another',
         href: '/another',
-        as: '//google.com',
-        pathname: '/google.com',
+        as: '/google.com//maps',
+        pathname: '/google.com/maps',
       },
       {
         page: isPages404 ? '/404' : '/_error',
-        href: '//google.com',
-        pathname: '/google.com',
+        href: '/google.com//maps',
+        pathname: '/google.com/maps',
       },
       {
         page: isPages404 ? '/404' : '/_error',
-        href: '//google.com?hello=1',
-        pathname: '/google.com',
+        href: '/google.com//maps?hello=1',
+        pathname: '/google.com/maps',
         search: '?hello=1',
       },
       {
         page: isPages404 ? '/404' : '/_error',
-        href: '//google.com#hello',
-        pathname: '/google.com',
+        href: '/google.com//maps#hello',
+        pathname: '/google.com/maps',
         hash: '#hello',
       },
     ]) {