feat: align with upstream 1.5.9.9

app/plugins/locale.ts

@@ -0,0 +1,59 @@
+import {
+  LOCALE_COOKIE_KEY,
+  LOCALE_PREFERENCE_KEY,
+  isSupportedLocale,
+  loadLocaleMessages,
+  resolveClientInitialLocale,
+  resolveLocaleFromAcceptLanguage,
+  setLocale,
+  useLocale,
+  type Locale,
+  type LocalePreference
+} from '~/utils/locale'
+
+// 语言初始化插件（服务端 + 客户端通用）。
+// - 仅当用户手动选择过语言（偏好为 manual）时信任 cookie 中保存的语言；
+//   否则每次进入都按 Accept-Language / 浏览器语言跟随系统语言，系统语言变化后自动切换。
+// - 客户端沿用服务端解析结果（cookie）以保证水合一致，cookie 缺失时才按浏览器语言解析。
+// 在渲染前 await 目标语言词典，避免懒加载导致的水合不匹配。
+export default defineNuxtPlugin(async () => {
+  const { currentLocale } = useLocale()
+  const localeCookie = useCookie<Locale | undefined>(LOCALE_COOKIE_KEY, {
+    maxAge: 60 * 60 * 24 * 365,
+    sameSite: 'lax',
+    path: '/'
+  })
+  const preferenceCookie = useCookie<LocalePreference | undefined>(LOCALE_PREFERENCE_KEY, {
+    maxAge: 60 * 60 * 24 * 365,
+    sameSite: 'lax',
+    path: '/'
+  })
+
+  let resolved: Locale
+  let isManualPreference = false
+  if (preferenceCookie.value === 'manual' && isSupportedLocale(localeCookie.value)) {
+    isManualPreference = true
+    resolved = localeCookie.value
+  } else if (import.meta.server) {
+    const headers = useRequestHeaders(['accept-language'])
+    resolved = resolveLocaleFromAcceptLanguage(headers['accept-language'])
+  } else if (isSupportedLocale(localeCookie.value)) {
+    // 沿用服务端解析结果（本次会话跟随系统得到），避免水合不一致
+    resolved = localeCookie.value
+  } else {
+    resolved = resolveClientInitialLocale()
+  }
+
+  // 渲染前确保词典就绪：中文为静态内置；非兜底语言在此 await 其动态 chunk。
+  await loadLocaleMessages(resolved)
+  setLocale(resolved, isManualPreference)
+
+  // 由当前语言驱动 <html lang>，服务端渲染即写入，客户端切换语言时响应式更新。
+  useHead({ htmlAttrs: { lang: currentLocale } })
+
+  if (import.meta.client) {
+    watch(currentLocale, (value) => {
+      localeCookie.value = value
+    })
+  }
+})