fix(web): ensure language switcher sets cookie to persist user choice

packages/web/src/components/Footer.astro

@@ -1,6 +1,6 @@
 ---
 import config from "virtual:starlight/user-config"
-import LanguageSelect from "@astrojs/starlight/components/LanguageSelect.astro"
+import LanguageSelect from "./LanguageSelect.astro"
 import { Icon } from "@astrojs/starlight/components"
 
 const { lang, editUrl, lastUpdated, entry } = Astro.locals.starlightRoute

packages/web/src/components/LanguageSelect.astro

@@ -0,0 +1,17 @@
+---
+import Default from "@astrojs/starlight/components/LanguageSelect.astro"
+---
+
+<Default />
+
+<script>
+  const select = document.querySelector("starlight-lang-select select") as HTMLSelectElement | null
+  if (select) {
+    select.addEventListener("change", (e) => {
+      const target = e.currentTarget as HTMLSelectElement
+      const path = target.value
+      const locale = path === "/docs/" ? "en" : path.match(/\/docs\/([^/]+)/)?.[1] || "en"
+      document.cookie = `oc_locale=${encodeURIComponent(locale)}; Path=/; Max-Age=31536000; SameSite=Lax`
+    })
+  }
+</script>

packages/web/src/middleware.ts

@@ -85,10 +85,14 @@ export const onRequest = defineMiddleware((ctx, next) => {
 
   if (ctx.url.pathname !== "/docs" && ctx.url.pathname !== "/docs/") return next()
 
-  const locale =
-    localeFromCookie(ctx.request.headers.get("cookie")) ??
-    localeFromAcceptLanguage(ctx.request.headers.get("accept-language"))
-  if (!locale || locale === "root") return next()
+  const cookieLocale = localeFromCookie(ctx.request.headers.get("cookie"))
+  if (cookieLocale !== null) {
+    if (cookieLocale === "root") return next()
+    return redirect(ctx.url, `/docs/${cookieLocale}/`)
+  }
+
+  const acceptLanguageLocale = localeFromAcceptLanguage(ctx.request.headers.get("accept-language"))
+  if (!acceptLanguageLocale || acceptLanguageLocale === "root") return next()
 
-  return redirect(ctx.url, `/docs/${locale}/`)
+  return redirect(ctx.url, `/docs/${acceptLanguageLocale}/`)
 })