From 9d3eedabc076371b0b5e646a7f681ffecc9d5fdc Mon Sep 17 00:00:00 2001
From: JJ Kasper <jj@jjsweb.site>
Date: Mon, 21 Nov 2022 12:44:53 -0800
Subject: [PATCH] Update experimental skipTrailingSlashRedirect handling

---
 packages/next/build/webpack-config.ts         |  3 ++
 .../next/client/normalize-trailing-slash.ts   |  2 +-
 .../app/pages/index.js                        |  4 ++
 .../index.test.ts                             | 48 +++++++++++++++++++
 4 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/packages/next/build/webpack-config.ts b/packages/next/build/webpack-config.ts
index 2e7bebaaf90d..aaa3821d304a 100644
--- a/packages/next/build/webpack-config.ts
+++ b/packages/next/build/webpack-config.ts
@@ -299,6 +299,9 @@ export function getDefineEnv({
     'process.env.__NEXT_NO_MIDDLEWARE_URL_NORMALIZE': JSON.stringify(
       config.experimental.skipMiddlewareUrlNormalize
     ),
+    'process.env.__NEXT_MANUAL_TRAILING_SLASH': JSON.stringify(
+      config.experimental?.skipTrailingSlashRedirect
+    ),
     'process.env.__NEXT_HAS_WEB_VITALS_ATTRIBUTION': JSON.stringify(
       config.experimental.webVitalsAttribution &&
         config.experimental.webVitalsAttribution.length > 0
diff --git a/packages/next/client/normalize-trailing-slash.ts b/packages/next/client/normalize-trailing-slash.ts
index d2405675a1de..11547936af6b 100644
--- a/packages/next/client/normalize-trailing-slash.ts
+++ b/packages/next/client/normalize-trailing-slash.ts
@@ -6,7 +6,7 @@ import { parsePath } from '../shared/lib/router/utils/parse-path'
  * in `next.config.js`.
  */
 export const normalizePathTrailingSlash = (path: string) => {
-  if (!path.startsWith('/')) {
+  if (!path.startsWith('/') || process.env.__NEXT_MANUAL_TRAILING_SLASH) {
     return path
   }
 
diff --git a/test/e2e/skip-trailing-slash-redirect/app/pages/index.js b/test/e2e/skip-trailing-slash-redirect/app/pages/index.js
index 04fbd07fee5b..8cf5943c3cd9 100644
--- a/test/e2e/skip-trailing-slash-redirect/app/pages/index.js
+++ b/test/e2e/skip-trailing-slash-redirect/app/pages/index.js
@@ -8,6 +8,10 @@ export default function Page(props) {
         to another
       </Link>
       <br />
+      <Link href="/another/" id="to-another-with-slash">
+        to another
+      </Link>
+      <br />
       <Link href="/blog/first" id="to-blog-first">
         to /blog/first
       </Link>
diff --git a/test/e2e/skip-trailing-slash-redirect/index.test.ts b/test/e2e/skip-trailing-slash-redirect/index.test.ts
index e31d7a6909fc..cb3e14c15f54 100644
--- a/test/e2e/skip-trailing-slash-redirect/index.test.ts
+++ b/test/e2e/skip-trailing-slash-redirect/index.test.ts
@@ -174,6 +174,54 @@ describe('skip-trailing-slash-redirect', () => {
     expect(await res.text()).toContain('another page')
   })
 
+  it('should not apply trailing slash to links on client', async () => {
+    const browser = await webdriver(next.url, '/')
+    await browser.eval('window.beforeNav = 1')
+
+    expect(
+      new URL(
+        await browser.elementByCss('#to-another').getAttribute('href'),
+        'http://n'
+      ).pathname
+    ).toBe('/another')
+
+    await browser.elementByCss('#to-another').click()
+    await browser.waitForElementByCss('#another')
+
+    expect(await browser.eval('window.location.pathname')).toBe('/another')
+
+    await browser.back().waitForElementByCss('#to-another')
+
+    expect(
+      new URL(
+        await browser
+          .elementByCss('#to-another-with-slash')
+          .getAttribute('href'),
+        'http://n'
+      ).pathname
+    ).toBe('/another/')
+
+    await browser.elementByCss('#to-another-with-slash').click()
+    await browser.waitForElementByCss('#another')
+
+    expect(await browser.eval('window.location.pathname')).toBe('/another/')
+
+    await browser.back().waitForElementByCss('#to-another')
+    expect(await browser.eval('window.beforeNav')).toBe(1)
+  })
+
+  it('should not apply trailing slash on load on client', async () => {
+    let browser = await webdriver(next.url, '/another')
+    await check(() => browser.eval('next.router.isReady ? "yes": "no"'), 'yes')
+
+    expect(await browser.eval('location.pathname')).toBe('/another')
+
+    browser = await webdriver(next.url, '/another/')
+    await check(() => browser.eval('next.router.isReady ? "yes": "no"'), 'yes')
+
+    expect(await browser.eval('location.pathname')).toBe('/another/')
+  })
+
   it('should respond to index correctly', async () => {
     const res = await fetchViaHTTP(next.url, '/', undefined, {
       redirect: 'manual',