Validate i18n locale domain (#50220)

The `domain` value is meant to be a hostname and not include `http` or
port so this ensures we validate it doesn't contain `:` unexpectedly
causing invalid behavior.

Closes: #49656
x-ref:
#24991 (comment)

---------

Co-authored-by: Jiachi Liu <inbox@huozhi.im>

packages/next/src/server/config.ts

@@ -537,6 +537,13 @@ function assignDefaults(
         if (!item.defaultLocale) return true
         if (!item.domain || typeof item.domain !== 'string') return true
 
+        if (item.domain.includes(':')) {
+          console.warn(
+            `i18n domain: "${item.domain}" is invalid it should be a valid domain without protocol (https://) or port (:3000) e.g. example.vercel.sh`
+          )
+          return true
+        }
+
         const defaultLocaleDuplicate = i18n.domains?.find(
           (altItem) =>
             altItem.defaultLocale === item.defaultLocale &&

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

@@ -550,4 +550,30 @@ describe('i18n Support', () => {
     )
     expect(stderr).toContain(`eN, fr`)
   })
+
+  it('should show proper error for invalid locale domain', async () => {
+    nextConfig.write(`
+      module.exports = {
+        i18n: {
+          locales: ['en', 'fr', 'nl', 'eN', 'fr'],
+          domains: [
+            {
+              domain: 'hello:3000',
+              defaultLocale: 'en',
+            }
+          ],
+          defaultLocale: 'en',
+        }
+      }
+    `)
+
+    const { code, stderr } = await nextBuild(appDir, undefined, {
+      stderr: true,
+    })
+    nextConfig.restore()
+    expect(code).toBe(1)
+    expect(stderr).toContain(
+      `i18n domain: "hello:3000" is invalid it should be a valid domain without protocol (https://) or port (:3000) e.g. example.vercel.sh`
+    )
+  })
 })