From 8d45f68bbbefd4dbff0365a69564b29ef1c1d0b5 Mon Sep 17 00:00:00 2001
From: Oleg Isonen <oleg008@gmail.com>
Date: Wed, 1 Jul 2026 15:52:28 +0000
Subject: [PATCH] fix: handle redirects for unmatched routes

---
 packages/cli/src/prebuild.test.ts | 32 +++++++++++++++++++++++++++++++
 packages/cli/src/prebuild.ts      | 31 ++++++++++++++++++++++++++++++
 2 files changed, 63 insertions(+)

diff --git a/packages/cli/src/prebuild.test.ts b/packages/cli/src/prebuild.test.ts
index 672d6cee464c..0c2ef3b2000b 100644
--- a/packages/cli/src/prebuild.test.ts
+++ b/packages/cli/src/prebuild.test.ts
@@ -5,9 +5,11 @@ import {
   readdir,
   readFile,
   rm,
+  symlink,
   writeFile,
 } from "node:fs/promises";
 import { join } from "node:path";
+import { pathToFileURL } from "node:url";
 import { tmpdir } from "node:os";
 import { bundleVersion } from "@webstudio-is/protocol";
 import { generateRedirectsModule, prebuild } from "./prebuild";
@@ -20,6 +22,35 @@ const rootFolderId = "root";
 const elementComponent = "ws:element";
 const slowPrebuildTestTimeout = 15_000;
 type Redirects = Array<{ old: string; new: string; status?: "301" | "302" }>;
+type GeneratedRouteModule = {
+  loader: (args: { request: Request }) => Response | Promise<Response>;
+};
+
+const importGeneratedRoute = async (path: string) => {
+  await symlink(join(originalCwd, "node_modules"), "node_modules", "dir");
+  return (await import(
+    `${pathToFileURL(join(tempDir, path)).href}?test=${crypto.randomUUID()}`
+  )) as GeneratedRouteModule;
+};
+
+const expectGeneratedRedirectFallback = async (path: string) => {
+  const routeModule = await importGeneratedRoute(path);
+  const redirectResponse = await routeModule.loader({
+    request: new Request("https://example.com/dl.php?filename=file.pdf"),
+  });
+  expect(redirectResponse.status).toBe(301);
+  expect(redirectResponse.headers.get("Location")).toBe("/downloads/file.pdf");
+
+  try {
+    await routeModule.loader({
+      request: new Request("https://example.com/not-a-redirect"),
+    });
+    throw new Error("Expected unmatched request to throw a 404 response.");
+  } catch (error) {
+    expect(error).toBeInstanceOf(Response);
+    expect((error as Response).status).toBe(404);
+  }
+};
 
 const getFilePaths = async (dir: string): Promise<string[]> => {
   const entries = await readdir(dir, { withFileTypes: true });
@@ -302,6 +333,7 @@ describe("prebuild", () => {
     expect(routeTemplate).toContain("../__generated__/_index.server");
     expect(routeTemplate).not.toContain("__CLIENT__");
     expect(routeTemplate).not.toContain("__SERVER__");
+    await expectGeneratedRedirectFallback("app/routes/$.tsx");
 
     await expect(
       readFile("app/__generated__/stale.ts", "utf8")
diff --git a/packages/cli/src/prebuild.ts b/packages/cli/src/prebuild.ts
index 92d087880fb8..5baac98e8528 100644
--- a/packages/cli/src/prebuild.ts
+++ b/packages/cli/src/prebuild.ts
@@ -196,6 +196,28 @@ export const generateRedirectsModule = (pageRedirects: Pages["redirects"]) => {
     `;
 };
 
+const generateRedirectFallbackRoute = (runtime: "remix" | "react-router") => {
+  const loaderFunctionArgs =
+    runtime === "react-router" ? "react-router" : "@remix-run/server-runtime";
+
+  return `
+    import { type LoaderFunctionArgs } from ${JSON.stringify(loaderFunctionArgs)};
+    import { redirectRequest } from "../redirect-url";
+    // @todo think about how to make __generated__ typeable
+    // @ts-ignore
+    import { redirects } from "../__generated__/$resources.redirects";
+
+    export const loader = ({ request }: LoaderFunctionArgs) => {
+      const redirectResponse = redirectRequest(request, redirects);
+      if (redirectResponse !== undefined) {
+        return redirectResponse;
+      }
+
+      throw new Response("Not Found", { status: 404 });
+    };
+    `;
+};
+
 export const prebuild = async (options: {
   /**
    * Do we need download assets
@@ -732,6 +754,15 @@ export const prebuild = async (options: {
     generateRedirectsModule(pages.redirects)
   );
 
+  if (pages.redirects !== undefined && pages.redirects.length > 0) {
+    await createFileIfNotExists(
+      join(routesDir, "$.tsx"),
+      generateRedirectFallbackRoute(
+        options.template.includes("react-router") ? "react-router" : "remix"
+      )
+    );
+  }
+
   if (options.assets === true && siteData.assets.length > 0) {
     const downloading = spinner();
     downloading.start("Downloading fonts and images");