From f0b1d6d46c554f9bf6b80bfd3031b06fe0b07e21 Mon Sep 17 00:00:00 2001
From: JJ Kasper <jj@jjsweb.site>
Date: Thu, 19 Nov 2020 18:54:40 -0600
Subject: [PATCH] Update default locale handling with locale: false

---
 .../next/next-server/lib/router/router.ts     |  9 +++--
 .../pages/locale-false.js                     |  8 ++++
 .../i18n-support/pages/locale-false.js        |  8 ++++
 test/integration/i18n-support/test/shared.js  | 39 +++++++++++++++++++
 4 files changed, 60 insertions(+), 4 deletions(-)

diff --git a/packages/next/next-server/lib/router/router.ts b/packages/next/next-server/lib/router/router.ts
index 43c16506f26f7..fac214e74ffe0 100644
--- a/packages/next/next-server/lib/router/router.ts
+++ b/packages/next/next-server/lib/router/router.ts
@@ -616,7 +616,10 @@ export default class Router implements BaseRouter {
     let localeChange = options.locale !== this.locale
 
     if (process.env.__NEXT_I18N_SUPPORT) {
-      this.locale = options.locale || this.locale
+      this.locale =
+        options.locale === false
+          ? this.defaultLocale
+          : options.locale || this.locale
 
       if (typeof options.locale === 'undefined') {
         options.locale = this.locale
@@ -627,12 +630,10 @@ export default class Router implements BaseRouter {
       } = require('../i18n/normalize-locale-path') as typeof import('../i18n/normalize-locale-path')
 
       const parsedAs = parseRelativeUrl(hasBasePath(as) ? delBasePath(as) : as)
-
       const localePathResult = normalizeLocalePath(
         parsedAs.pathname,
         this.locales
       )
-
       if (localePathResult.detectedLocale) {
         this.locale = localePathResult.detectedLocale
         url = addBasePath(localePathResult.pathname)
@@ -1228,7 +1229,7 @@ export default class Router implements BaseRouter {
           this.locales
         )
         parsedAs.pathname = localePathResult.pathname
-        options.locale = localePathResult.detectedLocale || options.locale
+        options.locale = localePathResult.detectedLocale || this.defaultLocale
         asPath = formatWithValidation(parsedAs)
       }
     }
diff --git a/test/integration/i18n-support-base-path/pages/locale-false.js b/test/integration/i18n-support-base-path/pages/locale-false.js
index 8c1f6186861b7..e0de4c056aeea 100644
--- a/test/integration/i18n-support-base-path/pages/locale-false.js
+++ b/test/integration/i18n-support-base-path/pages/locale-false.js
@@ -42,6 +42,14 @@ export default function Page(props) {
         <a id="to-gssp-slug">to /gssp/first</a>
       </Link>
       <br />
+      <Link href={`/gssp/first`} locale={false}>
+        <a id="to-gssp-slug-default">to /gssp/first (default locale)</a>
+      </Link>
+      <br />
+      <Link href={`/gsp`} locale={false}>
+        <a id="to-gsp-default">to /gsp (default locale)</a>
+      </Link>
+      <br />
     </>
   )
 }
diff --git a/test/integration/i18n-support/pages/locale-false.js b/test/integration/i18n-support/pages/locale-false.js
index 8c1f6186861b7..e0de4c056aeea 100644
--- a/test/integration/i18n-support/pages/locale-false.js
+++ b/test/integration/i18n-support/pages/locale-false.js
@@ -42,6 +42,14 @@ export default function Page(props) {
         <a id="to-gssp-slug">to /gssp/first</a>
       </Link>
       <br />
+      <Link href={`/gssp/first`} locale={false}>
+        <a id="to-gssp-slug-default">to /gssp/first (default locale)</a>
+      </Link>
+      <br />
+      <Link href={`/gsp`} locale={false}>
+        <a id="to-gsp-default">to /gsp (default locale)</a>
+      </Link>
+      <br />
     </>
   )
 }
diff --git a/test/integration/i18n-support/test/shared.js b/test/integration/i18n-support/test/shared.js
index 0133bf52863eb..96d4982a43afd 100644
--- a/test/integration/i18n-support/test/shared.js
+++ b/test/integration/i18n-support/test/shared.js
@@ -27,6 +27,44 @@ async function addDefaultLocaleCookie(browser) {
 }
 
 export function runTests(ctx) {
+  it('should use default locale when no locale is in href with locale false', async () => {
+    const browser = await webdriver(
+      ctx.appPort,
+      `${ctx.basePath}/nl/locale-false?nextLocale=fr`
+    )
+
+    await browser.eval('window.beforeNav = 1')
+
+    if (!ctx.isDev) {
+      await browser.eval(`(function() {
+        document.querySelector('#to-gssp-slug-default').scrollIntoView()
+        document.querySelector('#to-gsp-default').scrollIntoView()
+      })()`)
+
+      await check(async () => {
+        const hrefs = await browser.eval(`Object.keys(window.next.router.sdc)`)
+        hrefs.sort()
+
+        assert.deepEqual(
+          hrefs.map((href) =>
+            new URL(href).pathname
+              .replace(ctx.basePath, '')
+              .replace(/^\/_next\/data\/[^/]+/, '')
+          ),
+          [
+            '/en-US/gsp.json',
+            '/fr/gsp.json',
+            '/fr/gsp/fallback/first.json',
+            '/fr/gsp/fallback/hello.json',
+          ]
+        )
+        return 'yes'
+      }, 'yes')
+    }
+
+    expect(await browser.eval('window.beforeNav')).toBe(1)
+  })
+
   if (ctx.isDev) {
     it('should show error for redirect and notFound returned at same time', async () => {
       const html = await renderViaHTTP(
@@ -715,6 +753,7 @@ export function runTests(ctx) {
               .replace(/^\/_next\/data\/[^/]+/, '')
           ),
           [
+            '/en-US/gsp.json',
             '/fr/gsp.json',
             '/fr/gsp/fallback/first.json',
             '/fr/gsp/fallback/hello.json',