fix(cacheInterceptor): handle index route cache key

.changeset/fix-cache-interceptor-index-route.md

@@ -0,0 +1,5 @@
+---
+"@opennextjs/aws": patch
+---
+
+Fix cache interception for index routes by normalizing the route path to `/` while reading the generated cache asset from `/index`.

packages/open-next/src/core/routing/cacheInterceptor.ts

@@ -265,23 +265,23 @@ export async function cacheInterceptor(
   localizedPath = localizedPath.replace(/\/$/, "");
 
   // Then we decode the path params
-  localizedPath = decodePathParams(localizedPath);
+  localizedPath = decodePathParams(localizedPath) || "/";
+
+  // The route is keyed as `/` in the prerender manifest, but the generated
+  // cache asset for the app index route is uploaded as `/index`.
+  const cacheKey = localizedPath === "/" ? "/index" : localizedPath;
 
   debug("Checking cache for", localizedPath, PrerenderManifest);
 
   const isISR =
-    Object.keys(PrerenderManifest?.routes ?? {}).includes(
-      localizedPath ?? "/",
-    ) ||
+    Object.keys(PrerenderManifest?.routes ?? {}).includes(localizedPath) ||
     Object.values(PrerenderManifest?.dynamicRoutes ?? {}).some((dr) =>
       new RegExp(dr.routeRegex).test(localizedPath),
     );
   debug("isISR", isISR);
   if (isISR) {
     try {
-      const cachedData = await globalThis.incrementalCache.get(
-        localizedPath ?? "/index",
-      );
+      const cachedData = await globalThis.incrementalCache.get(cacheKey);
       debug("cached data in interceptor", cachedData);
 
       if (!cachedData?.value) {
@@ -295,7 +295,7 @@ export async function cacheInterceptor(
       ) {
         const _hasBeenRevalidated = cachedData.shouldBypassTagCache
           ? false
-          : await hasBeenRevalidated(localizedPath, tags, cachedData);
+          : await hasBeenRevalidated(cacheKey, tags, cachedData);
 
         if (_hasBeenRevalidated) {
           return event;
@@ -305,11 +305,7 @@ export async function cacheInterceptor(
       // Check if the cache entry is stale (valid but needs background revalidation)
       const _isStale = cachedData.shouldBypassTagCache
         ? false
-        : await isStale(
-            localizedPath,
-            tags,
-            cachedData.lastModified ?? Date.now(),
-          );
+        : await isStale(cacheKey, tags, cachedData.lastModified ?? Date.now());
 
       const host = event.headers.host;
       switch (cachedData?.value?.type) {

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

@@ -11,6 +11,11 @@ vi.mock("@opennextjs/aws/adapters/config/index.js", () => ({
   NextConfig: {},
   PrerenderManifest: {
     routes: {
+      "/": {
+        initialRevalidateSeconds: 120,
+        srcRoute: "/",
+        dataRoute: "/index.rsc",
+      },
       "/albums": {
         initialRevalidateSeconds: false,
         srcRoute: "/albums",
@@ -144,6 +149,15 @@ describe("cacheInterceptor", () => {
 
     const body = await fromReadableStream(result.body);
     expect(body).toEqual("Hello, world!");
+    expect(incrementalCache.get).toHaveBeenCalledWith("/albums");
+    expect(tagCache.getLastModified).toHaveBeenCalledWith(
+      "/albums",
+      expect.any(Number),
+    );
+    expect(tagCache.isStale).toHaveBeenCalledWith(
+      "/albums",
+      expect.any(Number),
+    );
     expect(result).toEqual(
       expect.objectContaining({
         type: "core",
@@ -159,6 +173,70 @@ describe("cacheInterceptor", () => {
     );
   });
 
+  it("should retrieve index app router content from the index cache key", async () => {
+    const event = createEvent({
+      url: "/",
+    });
+    incrementalCache.get.mockResolvedValueOnce({
+      value: {
+        type: "app",
+        html: "Index page",
+      },
+      lastModified: new Date("2024-01-01T23:59:30Z").getTime(),
+    });
+
+    const result = await cacheInterceptor(event);
+
+    const body = await fromReadableStream(result.body);
+    expect(body).toEqual("Index page");
+    expect(incrementalCache.get).toHaveBeenCalledWith("/index");
+    expect(tagCache.getLastModified).toHaveBeenCalledWith(
+      "/index",
+      expect.any(Number),
+    );
+    expect(tagCache.isStale).toHaveBeenCalledWith("/index", expect.any(Number));
+    expect(result).toEqual(
+      expect.objectContaining({
+        headers: expect.objectContaining({
+          "cache-control": "s-maxage=90, stale-while-revalidate=2592000",
+          "x-opennext-cache": "HIT",
+        }),
+      }),
+    );
+  });
+
+  it("should revalidate stale index content using the route path", async () => {
+    const event = createEvent({
+      url: "/",
+    });
+    incrementalCache.get.mockResolvedValueOnce({
+      value: {
+        type: "app",
+        html: "Index page",
+      },
+      lastModified: new Date("2024-01-01T23:57:00Z").getTime(),
+    });
+
+    const result = await cacheInterceptor(event);
+
+    expect(incrementalCache.get).toHaveBeenCalledWith("/index");
+    expect(queue.send).toHaveBeenCalledWith(
+      expect.objectContaining({
+        MessageBody: expect.objectContaining({
+          url: "/",
+        }),
+      }),
+    );
+    expect(result).toEqual(
+      expect.objectContaining({
+        headers: expect.objectContaining({
+          "cache-control": "s-maxage=1, stale-while-revalidate=2592000",
+          "x-opennext-cache": "STALE",
+        }),
+      }),
+    );
+  });
+
   it("should take no action when tagCache lasModified is -1 for app type", async () => {
     const event = createEvent({
       url: "/albums",