fix revalidation issue with route handlers (#63213)

### What
When a route handler uses an API that opts it into dynamic rendering
(such as `no-store` on a fetch), and also specifies a `revalidate` time,
the `revalidate` time is ignored and route is treated as fully static.

### Why
`revalidate: 0` and `revalidate: false` have different semantic
meanings: `false` essentially means cache forever, whereas `0` means
it's dynamic. Since `0` is also falsey, the code we have to fallback
with a default `revalidate` value for route handlers is incorrectly not
marking the route as dynamic, and as a result, caching the route without
an expiration time.

### How
This updates the fallback handling for app routes respect a revalidation
value of `0`, so that the page can properly be marked dynamic.

### Test Explanation
This adds 2 new routes handlers: both have a revalidation time specified
& use `no-store` on a fetch, but only one of them specifies `export
const dynamic = 'force-static'`. The one that doesn't specify
`force-static` is correctly omitted from the prerender manifest. The one
that is `force-static` is correctly in the prerender manifest with the
right expiration time. An additional test case was added to verify that
this data refreshes after the specified interval.

Closes NEXT-2764

packages/next/src/export/routes/app-route.ts

@@ -91,7 +91,10 @@ export async function exportAppRoute(
     }
 
     const blob = await response.blob()
-    const revalidate = context.renderOpts.store?.revalidate || false
+    const revalidate =
+      typeof context.renderOpts.store?.revalidate === 'undefined'
+        ? false
+        : context.renderOpts.store.revalidate
 
     const headers = toNodeOutgoingHttpHeaders(response.headers)
     const cacheTags = (context.renderOpts as any).fetchTags

test/e2e/app-dir/app-static/app-static.test.ts

@@ -210,6 +210,33 @@ createNextDescribe(
       }
     })
 
+    if (!isDev && !process.env.CUSTOM_CACHE_HANDLER) {
+      it('should properly revalidate a route handler that triggers dynamic usage with force-static', async () => {
+        // wait for the revalidation period
+        let res = await next.fetch('/route-handler/no-store-force-static')
+
+        let data = await res.json()
+        // grab the initial timestamp
+        const initialTimestamp = data.now
+
+        // confirm its cached still
+        res = await next.fetch('/route-handler/no-store-force-static')
+
+        data = await res.json()
+
+        expect(data.now).toBe(initialTimestamp)
+
+        // wait for the revalidation time
+        await waitFor(3000)
+
+        // verify fresh data
+        res = await next.fetch('/route-handler/no-store-force-static')
+        data = await res.json()
+
+        expect(data.now).not.toBe(initialTimestamp)
+      })
+    }
+
     if (!process.env.CUSTOM_CACHE_HANDLER) {
       it.each([
         {
@@ -637,6 +664,8 @@ createNextDescribe(
             "response-url/page.js",
             "response-url/page_client-reference-manifest.js",
             "route-handler-edge/revalidate-360/route.js",
+            "route-handler/no-store-force-static/route.js",
+            "route-handler/no-store/route.js",
             "route-handler/post/route.js",
             "route-handler/revalidate-360-isr/route.js",
             "route-handler/revalidate-360/route.js",
@@ -1269,6 +1298,26 @@ createNextDescribe(
               "initialRevalidateSeconds": false,
               "srcRoute": "/partial-gen-params-no-additional-slug/[lang]/[slug]",
             },
+            "/route-handler/no-store-force-static": {
+              "dataRoute": null,
+              "experimentalBypassFor": [
+                {
+                  "key": "Next-Action",
+                  "type": "header",
+                },
+                {
+                  "key": "content-type",
+                  "type": "header",
+                  "value": "multipart/form-data",
+                },
+              ],
+              "initialHeaders": {
+                "content-type": "application/json",
+                "x-next-cache-tags": "_N_T_/layout,_N_T_/route-handler/layout,_N_T_/route-handler/no-store-force-static/layout,_N_T_/route-handler/no-store-force-static/route,_N_T_/route-handler/no-store-force-static",
+              },
+              "initialRevalidateSeconds": 3,
+              "srcRoute": "/route-handler/no-store-force-static",
+            },
             "/route-handler/revalidate-360-isr": {
               "dataRoute": null,
               "experimentalBypassFor": [

test/e2e/app-dir/app-static/app/route-handler/no-store-force-static/route.ts

@@ -0,0 +1,11 @@
+export const dynamic = 'force-static'
+export const revalidate = 3
+
+export async function GET() {
+  const data = await fetch(
+    'https://next-data-api-endpoint.vercel.app/api/random',
+    { cache: 'no-store' }
+  ).then((res) => res.text())
+
+  return Response.json({ now: Date.now(), data })
+}

test/e2e/app-dir/app-static/app/route-handler/no-store/route.ts

@@ -0,0 +1,10 @@
+export const revalidate = 5
+
+export async function GET() {
+  const data = await fetch(
+    'https://next-data-api-endpoint.vercel.app/api/random',
+    { cache: 'no-store' }
+  ).then((res) => res.text())
+
+  return Response.json({ now: Date.now(), data })
+}