Fix trailing slash with locale domain

packages/next/src/client/get-domain-locale.ts

@@ -1,6 +1,7 @@
 import type { DomainLocale } from '../server/config'
 import type { normalizeLocalePath as NormalizeFn } from './normalize-locale-path'
 import type { detectDomainLocale as DetectFn } from './detect-domain-locale'
+import { normalizePathTrailingSlash } from './normalize-trailing-slash'
 
 const basePath = (process.env.__NEXT_ROUTER_BASEPATH as string) || ''
 
@@ -21,7 +22,9 @@ export function getDomainLocale(
     if (domain) {
       const proto = `http${domain.http ? '' : 's'}://`
       const finalLocale = target === domain.defaultLocale ? '' : `/${target}`
-      return `${proto}${domain.domain}${basePath}${finalLocale}${path}`
+      return `${proto}${domain.domain}${normalizePathTrailingSlash(
+        `${basePath}${finalLocale}${path}`
+      )}`
     }
     return false
   } else {

test/integration/i18n-support/test/index.test.js

@@ -240,6 +240,28 @@ describe('i18n Support', () => {
             return 'yes'
           }, 'yes')
         })
+
+        it('should have correct locale domain hrefs', async () => {
+          const res = await fetchViaHTTP(
+            curCtx.appPort,
+            '/do-BE/frank/',
+            undefined,
+            {
+              redirect: 'manual',
+            }
+          )
+          expect(res.status).toBe(200)
+
+          const html = await res.text()
+          const $ = cheerio.load(html)
+
+          expect($('#to-fallback-hello')[0].attribs.href).toBe(
+            'http://example.do/do-BE/gsp/fallback/hello/'
+          )
+          expect($('#to-no-fallback-first')[0].attribs.href).toBe(
+            'http://example.do/do-BE/gsp/no-fallback/first/'
+          )
+        })
       }
 
       it('should redirect correctly', async () => {