From 53a957dc493bdf9fa72a9fd29e8e29ff8522ede3 Mon Sep 17 00:00:00 2001
From: Luke Vella <me@lukevella.com>
Date: Wed, 28 May 2025 09:44:41 +0100
Subject: [PATCH] =?UTF-8?q?=F0=9F=90=9B=20Fix=20locale=20fallback=20mechan?=
 =?UTF-8?q?ism=20(#1734)?=
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---
 apps/web/src/middleware.ts                     | 16 +++++-----------
 packages/languages/src/get-preferred-locale.ts | 13 ++++++++-----
 2 files changed, 13 insertions(+), 16 deletions(-)

diff --git a/apps/web/src/middleware.ts b/apps/web/src/middleware.ts
index 70b2b5590..71a048d83 100644
--- a/apps/web/src/middleware.ts
+++ b/apps/web/src/middleware.ts
@@ -1,12 +1,9 @@
-import languages from "@rallly/languages";
 import { getPreferredLocale } from "@rallly/languages/get-preferred-locale";
 import { getPosthogBootstrapCookie } from "@rallly/posthog/utils";
 import { NextResponse } from "next/server";
 
 import { withAuth } from "@/auth/edge";
 
-const supportedLocales = Object.keys(languages);
-
 export const middleware = withAuth(async (req) => {
   const { nextUrl } = req;
   const newUrl = nextUrl.clone();
@@ -19,15 +16,12 @@ export const middleware = withAuth(async (req) => {
     return NextResponse.redirect(newUrl);
   }
 
-  const locale =
-    req.auth?.user?.locale ||
-    getPreferredLocale({
-      acceptLanguageHeader: req.headers.get("accept-language") ?? undefined,
-    });
+  const locale = getPreferredLocale({
+    userLocale: req.auth?.user?.locale ?? undefined,
+    acceptLanguageHeader: req.headers.get("accept-language") ?? undefined,
+  });
 
-  if (supportedLocales.includes(locale)) {
-    newUrl.pathname = `/${locale}${pathname}`;
-  }
+  newUrl.pathname = `/${locale}${pathname}`;
 
   const res = NextResponse.rewrite(newUrl);
   res.headers.set("x-locale", locale);
diff --git a/packages/languages/src/get-preferred-locale.ts b/packages/languages/src/get-preferred-locale.ts
index cb306abe3..4f5812a59 100644
--- a/packages/languages/src/get-preferred-locale.ts
+++ b/packages/languages/src/get-preferred-locale.ts
@@ -1,14 +1,18 @@
 import { match } from "@formatjs/intl-localematcher";
 import Negotiator from "negotiator";
-import languages, { defaultLocale } from "./index";
-
-const locales = Object.keys(languages);
+import { defaultLocale, supportedLngs } from "./index";
 
 export function getPreferredLocale({
+  userLocale,
   acceptLanguageHeader,
 }: {
+  userLocale?: string;
   acceptLanguageHeader?: string;
 }) {
+  if (userLocale && supportedLngs.includes(userLocale)) {
+    return userLocale;
+  }
+
   if (!acceptLanguageHeader) {
     return defaultLocale;
   }
@@ -22,9 +26,8 @@ export function getPreferredLocale({
     .filter((lang) => lang !== "*");
 
   try {
-    return match(preferredLanguages, locales, defaultLocale);
+    return match(preferredLanguages, supportedLngs, defaultLocale);
   } catch (e) {
-    console.warn("Failed to match locale", e);
     return defaultLocale;
   }
 }