fix: preserve query parameters during i18n redirects to a localized path (#1118)

* fix: preserve query parameters during i18n redirects to a localized path

* handle trailingSlash

* add changeset

Author: tsurumeso

.changeset/i18n_redirects_with_query_parameters.md

@@ -0,0 +1,5 @@
+---
+"@opennextjs/aws": patch
+---
+
+Preserve query parameters during i18n redirects to a localized path

packages/open-next/src/core/routing/i18n/index.ts

@@ -4,7 +4,7 @@ import type { InternalEvent, InternalResult } from "types/open-next";
 
 import { emptyReadableStream } from "utils/stream.js";
 import { debug } from "../../../adapters/logger.js";
-import { constructNextUrl } from "../util.js";
+import { constructNextUrl, convertToQueryString } from "../util.js";
 import { acceptLanguage } from "./accept-header";
 
 function isLocalizedPath(path: string): boolean {
@@ -164,11 +164,16 @@ export function handleLocaleRedirect(
   const defaultLocale = domainLocale?.defaultLocale ?? i18n.defaultLocale;
 
   if (detectedLocale.toLowerCase() !== defaultLocale.toLowerCase()) {
+    const nextUrl = constructNextUrl(
+      internalEvent.url,
+      `/${detectedLocale}${NextConfig.trailingSlash ? "/" : ""}`,
+    );
+    const queryString = convertToQueryString(internalEvent.query);
     return {
       type: "core",
       statusCode: 307,
       headers: {
-        Location: constructNextUrl(internalEvent.url, `/${detectedLocale}`),
+        Location: `${nextUrl}${queryString}`,
       },
       body: emptyReadableStream(),
       isBase64Encoded: false,

packages/tests-unit/tests/core/routing/i18n.test.ts

@@ -14,6 +14,7 @@ vi.mock("@opennextjs/aws/adapters/config/index.js", () => {
         defaultLocale: "en",
         locales: ["en", "fr"],
       },
+      trailingSlash: undefined,
     },
   };
 });
@@ -232,6 +233,48 @@ describe("handleLocaleRedirect", () => {
     expect(result).toBe(false);
   });
 
+  it("should redirect to the localized path with a query parameter", () => {
+    const event = createEvent({
+      url: "http://localhost?foo=bar",
+      headers: {
+        "accept-language": "fr",
+      },
+    });
+
+    const result = handleLocaleRedirect(event);
+
+    expect(result).toMatchObject({
+      statusCode: 307,
+      headers: {
+        Location: "http://localhost/fr?foo=bar",
+      },
+    });
+  });
+
+  it("should redirect to the localized path with a query parameter when trailingSlash is true", () => {
+    const trailingSlashSpy = vi
+      .spyOn(NextConfig, "trailingSlash", "get")
+      .mockReturnValue(true);
+
+    const event = createEvent({
+      url: "http://localhost?foo=bar",
+      headers: {
+        "accept-language": "fr",
+      },
+    });
+
+    const result = handleLocaleRedirect(event);
+
+    expect(result).toMatchObject({
+      statusCode: 307,
+      headers: {
+        Location: "http://localhost/fr/?foo=bar",
+      },
+    });
+
+    trailingSlashSpy.mockRestore();
+  });
+
   describe("using domain", () => {
     it("should redirect to the preferred domain if the domain is different", () => {
       vi.spyOn(NextConfig, "i18n", "get").mockReturnValue({