fix: setLocale throws error updating locale cookie from plugin

specs/basic_usage.spec.ts

@@ -355,7 +355,3 @@ test('dynamic parameters', async () => {
   const product2dom = getDom(product2Html)
   expect(product2dom.querySelector('#i18n-alt-en').href).toEqual('/products/red-mug')
 })
-
-test('(#2554) using `setLocale` in plugin should not throw an error', async () => {
-  await expect($fetch('/?pluginSetLocale')).resolves.to.not.toThrowError()
-})

specs/fixtures/issues/2554/app.vue

@@ -0,0 +1,3 @@
+<template>
+  <NuxtPage />
+</template>

specs/fixtures/issues/2554/nuxt.config.ts

@@ -0,0 +1,7 @@
+export default defineNuxtConfig({
+  modules: ['@nuxtjs/i18n'],
+  i18n: {
+    locales: ['en', 'fr'],
+    strategy: 'no_prefix'
+  }
+})

specs/fixtures/issues/2554/package.json

@@ -0,0 +1,14 @@
+{
+  "name": "nuxt3-test-issues-2473",
+  "private": true,
+  "scripts": {
+    "build": "nuxt build",
+    "dev": "nuxt dev",
+    "generate": "nuxt generate",
+    "preview": "nuxt preview"
+  },
+  "devDependencies": {
+    "@nuxtjs/i18n": "latest",
+    "nuxt": "latest"
+  }
+}

specs/fixtures/issues/2554/pages/index.vue

@@ -0,0 +1,3 @@
+<template>
+  <div>Hello</div>
+</template>

specs/fixtures/issues/2554/plugins/set-locale-plugin.ts

@@ -0,0 +1,8 @@
+import { defineNuxtPlugin } from '#imports'
+
+export default defineNuxtPlugin(async nuxtApp => {
+  if ('pluginSetLocale' in nuxtApp._route.query && typeof nuxtApp._route.query.pluginSetLocale === 'string') {
+    const app = useNuxtApp()
+    await app.$i18n.setLocale(nuxtApp._route.query.pluginSetLocale)
+  }
+})

specs/issues/2554.spec.ts

@@ -0,0 +1,22 @@
+import { test, expect, describe } from 'vitest'
+import { fileURLToPath } from 'node:url'
+import { URL } from 'node:url'
+import { setup, url } from '../utils'
+import { renderPage } from '../helper'
+
+describe('#2554', async () => {
+  await setup({
+    rootDir: fileURLToPath(new URL(`../fixtures/issues/2554`, import.meta.url)),
+    browser: true
+  })
+
+  test('should not throw an error when using `setLocale` from plugin', async () => {
+    const { page } = await renderPage('/')
+
+    const res1 = await page.goto(url('/?pluginSetLocale=fr'))
+    expect(res1?.ok()).toBeTruthy()
+
+    const res2 = await page.goto(url('/?pluginSetLocale=en'))
+    expect(res2?.ok()).toBeTruthy()
+  })
+})

src/runtime/internal.ts

@@ -25,6 +25,7 @@ import { initCommonComposableOptions, type CommonComposableOptions } from './uti
 import type { Locale } from 'vue-i18n'
 import type { DetectBrowserLanguageOptions, LocaleObject } from '#build/i18n.options.mjs'
 import type { RouteLocationNormalized, RouteLocationNormalizedLoaded } from 'vue-router'
+import type { CookieRef } from 'nuxt/app'
 
 export function formatMessage(message: string) {
   return NUXT_I18N_MODULE_ID + ' ' + message
@@ -93,7 +94,25 @@ export function getBrowserLocale(): string | undefined {
   return ret
 }
 
-export function getLocaleCookie(): string | undefined {
+export function getI18nCookie() {
+  const detect = nuxtI18nOptions.detectBrowserLanguage
+  const cookieKey = (detect && detect.cookieKey) || nuxtI18nOptionsDefault.detectBrowserLanguage.cookieKey
+  const date = new Date()
+  const cookieOptions: Record<string, any> = {
+    expires: new Date(date.setDate(date.getDate() + 365)),
+    path: '/',
+    sameSite: detect && detect.cookieCrossOrigin ? 'none' : 'lax',
+    secure: (detect && detect.cookieCrossOrigin) || (detect && detect.cookieSecure)
+  }
+
+  if (detect && detect.cookieDomain) {
+    cookieOptions.domain = detect.cookieDomain
+  }
+
+  return useNuxtCookie<string | undefined>(cookieKey, cookieOptions)
+}
+
+export function getLocaleCookie(cookieRef: CookieRef<string | undefined>): string | undefined {
   const detect = nuxtI18nOptions.detectBrowserLanguage
 
   __DEBUG__ &&
@@ -107,37 +126,22 @@ export function getLocaleCookie(): string | undefined {
     return
   }
 
-  const localeCookie = useNuxtCookie(detect.cookieKey)
-  const localeCode: string | undefined = localeCookie.value ?? undefined
+  const localeCode: string | undefined = cookieRef.value ?? undefined
   __DEBUG__ && console.log(`getLocaleCookie cookie (${process.client ? 'client' : 'server'}) -`, localeCode)
 
   if (localeCode && localeCodes.includes(localeCode)) {
     return localeCode
   }
 }
 
-export function setLocaleCookie(locale: string) {
-  const { useCookie, cookieKey, cookieDomain, cookieSecure, cookieCrossOrigin } =
-    nuxtI18nOptions.detectBrowserLanguage || nuxtI18nOptionsDefault.detectBrowserLanguage
+export function setLocaleCookie(cookieRef: CookieRef<string | undefined>, locale: string) {
+  const { useCookie } = nuxtI18nOptions.detectBrowserLanguage || nuxtI18nOptionsDefault.detectBrowserLanguage
 
   if (!useCookie) {
     return
   }
 
-  const date = new Date()
-  const cookieOptions: Record<string, any> = {
-    expires: new Date(date.setDate(date.getDate() + 365)),
-    path: '/',
-    sameSite: cookieCrossOrigin ? 'none' : 'lax',
-    secure: cookieCrossOrigin || cookieSecure
-  }
-
-  if (cookieDomain) {
-    cookieOptions.domain = cookieDomain
-  }
-
-  const localeCookie = useNuxtCookie(cookieKey, cookieOptions)
-  localeCookie.value = locale
+  cookieRef.value = locale
 }
 
 export type DetectBrowserLanguageNotDetectReason =
@@ -160,6 +164,7 @@ export type DetectLocaleContext = {
   ssg: DetectLocaleForSSGStatus
   callType: DetectLocaleCallType
   firstAccess: boolean
+  localeCookie: CookieRef<string | undefined>
 }
 
 export const DefaultDetectBrowserLanguageFromResult: DetectBrowserLanguageFromResult = {
@@ -176,7 +181,7 @@ export function detectBrowserLanguage(
   locale: Locale = ''
 ): DetectBrowserLanguageFromResult {
   const { strategy } = nuxtI18nOptions
-  const { ssg, callType, firstAccess } = detectLocaleContext
+  const { ssg, callType, firstAccess, localeCookie } = detectLocaleContext
   __DEBUG__ && console.log('detectBrowserLanguage: (ssg, callType, firstAccess) - ', ssg, callType, firstAccess)
 
   // browser detection is ignored if it's a nuxt generate.
@@ -223,7 +228,7 @@ export function detectBrowserLanguage(
 
   // get preferred language from cookie if present and enabled
   if (useCookie) {
-    matchedLocale = cookieLocale = getLocaleCookie()
+    matchedLocale = cookieLocale = localeCookie.value
     localeFrom = 'cookie'
     __DEBUG__ && console.log('detectBrowserLanguage: cookieLocale', cookieLocale)
   }

src/runtime/plugins/i18n.ts

@@ -25,7 +25,8 @@ import {
   getLocaleCookie as _getLocaleCookie,
   setLocaleCookie as _setLocaleCookie,
   detectBrowserLanguage,
-  DefaultDetectBrowserLanguageFromResult
+  DefaultDetectBrowserLanguageFromResult,
+  getI18nCookie
 } from '../internal'
 import { getComposer, getLocale, setLocale } from '../routing/utils'
 import { extendI18n, createLocaleFromRouteGetter } from '../routing/extends'
@@ -68,6 +69,7 @@ export default defineNuxtPlugin({
     const getLocaleFromRoute = createLocaleFromRouteGetter()
     const getDefaultLocale = (defaultLocale: string) => defaultLocale || vueI18nOptions.locale || 'en-US'
 
+    const localeCookie = getI18nCookie()
     // detect initial locale
     let initialLocale = detectLocale(
       route,
@@ -77,7 +79,8 @@ export default defineNuxtPlugin({
       {
         ssg: isSSG && nuxtI18nOptions.strategy === 'no_prefix' ? 'ssg_ignore' : 'normal',
         callType: 'setup',
-        firstAccess: true
+        firstAccess: true,
+        localeCookie
       }
     )
     __DEBUG__ && console.log('first detect initial locale', initialLocale)
@@ -124,7 +127,7 @@ export default defineNuxtPlugin({
           ? detectBrowserLanguage(
               route,
               vueI18nOptions.locale,
-              { ssg: 'ssg_setup', callType: 'setup', firstAccess: true },
+              { ssg: 'ssg_setup', callType: 'setup', firstAccess: true, localeCookie },
               initialLocale
             )
           : DefaultDetectBrowserLanguageFromResult
@@ -187,8 +190,8 @@ export default defineNuxtPlugin({
           composer.differentDomains = nuxtI18nOptions.differentDomains
           composer.defaultLocale = nuxtI18nOptions.defaultLocale
           composer.getBrowserLocale = () => _getBrowserLocale()
-          composer.getLocaleCookie = () => _getLocaleCookie()
-          composer.setLocaleCookie = (locale: string) => _setLocaleCookie(locale)
+          composer.getLocaleCookie = () => _getLocaleCookie(localeCookie)
+          composer.setLocaleCookie = (locale: string) => _setLocaleCookie(localeCookie, locale)
 
           composer.onBeforeLanguageSwitch = (oldLocale, newLocale, initialSetup, context) =>
             nuxt.callHook('i18n:beforeLocaleSwitch', { oldLocale, newLocale, initialSetup, context })
@@ -394,7 +397,8 @@ export default defineNuxtPlugin({
           {
             ssg: isSSGModeInitialSetup() && nuxtI18nOptions.strategy === 'no_prefix' ? 'ssg_ignore' : 'normal',
             callType: 'routing',
-            firstAccess: routeChangeCount === 0
+            firstAccess: routeChangeCount === 0,
+            localeCookie
           }
         )
         __DEBUG__ && console.log('detect locale', locale)

src/runtime/utils.ts

@@ -18,7 +18,6 @@ import {
 import {
   wrapComposable,
   detectBrowserLanguage,
-  getLocaleCookie,
   callVueI18nInterfaces,
   getVueI18nPropertyValue,
   defineGetter,
@@ -179,7 +178,7 @@ export function detectLocale(
   const initialLocale = isFunction(initialLocaleLoader) ? initialLocaleLoader() : initialLocaleLoader
   __DEBUG__ && console.log('detectLocale: initialLocale -', initialLocale)
 
-  const { ssg, callType, firstAccess } = detectLocaleContext
+  const { ssg, callType, firstAccess, localeCookie } = detectLocaleContext
   __DEBUG__ && console.log('detectLocale: (ssg, callType, firstAccess) - ', ssg, callType, firstAccess)
 
   const {
@@ -232,7 +231,7 @@ export function detectLocale(
       _detectBrowserLanguage
     )
   if (!finalLocale && _detectBrowserLanguage && _detectBrowserLanguage.useCookie) {
-    finalLocale = getLocaleCookie() || ''
+    finalLocale = localeCookie.value || ''
   }
 
   __DEBUG__ && console.log('detectLocale: finalLocale last (finalLocale, defaultLocale) -', finalLocale, defaultLocale)