feat: add query string for locale rewrites in middleware. add tests

packages/next/src/middlewares/__tests__/appMiddleware.ts

@@ -388,6 +388,16 @@ describe('appMiddleware', () => {
 
 		res = await AppMiddleware(req, { appRouter: true });
 		expect(res.headers.get('x-middleware-rewrite')).toBe('http://test.com/en/post-name');
+
+		// add default locale with a query string, expecting this to fail
+		req = new NextRequest('http://test.com/post-name?s=query', {
+			method: 'GET',
+		});
+
+		res = await AppMiddleware(req, { appRouter: true });
+		expect(res.headers.get('x-middleware-rewrite')).toBe(
+			'http://test.com/en/post-name?s=query',
+		);
 	});
 
 	it('[polylang no locale detection] supports locales with app router', async () => {

packages/next/src/middlewares/appMidleware.ts

@@ -120,6 +120,9 @@ export async function AppMiddleware(
 	const site = getSiteByHost(hostname, !hasPolylangIntegration ? locale : undefined);
 	const isMultisiteRequest = site !== null && typeof site.sourceUrl !== 'undefined';
 
+	// ensure we re-add the query string when rewriting/redirecing
+	const queryString = Array.from(searchParams.keys()).length ? `?${searchParams.toString()}` : '';
+
 	const {
 		redirectStrategy,
 		sourceUrl,
@@ -161,7 +164,7 @@ export async function AppMiddleware(
 			shouldRedirect = true;
 			const pathNameWithoutLocale = pathname.replace(`/${locale}`, '');
 			response = NextResponse.redirect(
-				new URL(pathNameWithoutLocale, req.url.replace(`/${locale}`, '')),
+				new URL(pathNameWithoutLocale + queryString, req.url.replace(`/${locale}`, '')),
 			);
 		}
 		// if we detected a non-default locale, there isn't a supported locale in the URL already
@@ -175,14 +178,17 @@ export async function AppMiddleware(
 		) {
 			shouldRedirect = true;
 			response = NextResponse.redirect(
-				new URL(`/${locale}${pathname.startsWith('/') ? '' : '/'}${pathname}`, req.url),
+				new URL(
+					`/${locale}${pathname.startsWith('/') ? '' : '/'}${pathname}${queryString}`,
+					req.url,
+				),
 			);
 		}
 		// nothing else and there's not a locale in path then rewrite to add default locale
 		else if (pathnameIsMissingLocale && !isValidLocale(firstPathSlice)) {
 			response = NextResponse.rewrite(
 				new URL(
-					`/${defaultAppRouterLocale}${pathname.startsWith('/') ? '' : '/'}${pathname}`,
+					`/${defaultAppRouterLocale}${pathname.startsWith('/') ? '' : '/'}${pathname}${queryString}`,
 					req.url,
 				),
 			);
@@ -191,9 +197,6 @@ export async function AppMiddleware(
 
 	if (isMultisiteRequest && !shouldRedirect) {
 		const hostNameOrSlug = site.slug || hostname;
-		const queryString = Array.from(searchParams.keys()).length
-			? `?${searchParams.toString()}`
-			: '';
 		const pagesRouterRewrite = `/_sites/${hostNameOrSlug}${pathname}${queryString}`;
 		const appRouterRewrite = locale
 			? `/${locale}/${hostNameOrSlug}${pathname.replace(`/${locale}`, '')}${queryString}`