Add Header Indicating Suspense Cache HIT

packages/next-on-pages/templates/_worker.js/utils/cache.ts

@@ -8,6 +8,8 @@ const NEXT_CACHE_SOFT_TAGS_HEADER = 'x-next-cache-soft-tags';
 
 const REQUEST_CONTEXT_KEY = Symbol.for('__cloudflare-request-context__');
 
+const CF_NEXT_SUSPENSE_CACHE_HEADER = 'cf-next-suspense-cache';
+
 /**
  * Handles an internal request to the suspense cache.
  *
@@ -50,14 +52,17 @@ export async function handleSuspenseCacheRequest(request: Request) {
 				const data = await cache.get(cacheKey, { softTags });
 				if (!data) return new Response(null, { status: 404 });
 
-				return new Response(JSON.stringify(data.value), {
-					status: 200,
-					headers: {
-						'Content-Type': 'application/json',
-						'x-vercel-cache-state': 'fresh',
-						age: `${(Date.now() - (data.lastModified ?? Date.now())) / 1000}`,
+				return new Response(
+					JSON.stringify(adjustCacheValueForResponse(data.value)),
+					{
+						status: 200,
+						headers: {
+							'Content-Type': 'application/json',
+							'x-vercel-cache-state': 'fresh',
+							age: `${(Date.now() - (data.lastModified ?? Date.now())) / 1000}`,
+						},
 					},
-				});
+				);
 			}
 			case 'POST': {
 				// Retrieve request context.
@@ -124,3 +129,21 @@ async function getInternalCacheAdaptor(
 function getTagsFromHeader(req: Request, key: string): string[] | undefined {
 	return req.headers.get(key)?.split(',')?.filter(Boolean);
 }
+
+function adjustCacheValueForResponse(value: IncrementalCacheValue | null) {
+	switch (value?.kind) {
+		case 'FETCH':
+			return {
+				...value,
+				data: {
+					...value.data,
+					headers: {
+						...value.data.headers,
+						[CF_NEXT_SUSPENSE_CACHE_HEADER]: 'HIT',
+					},
+				},
+			};
+		default:
+			return value;
+	}
+}

pages-e2e/features/appFetchCache/assets/app/api/cache/route.js

@@ -0,0 +1,13 @@
+export const runtime = 'edge';
+
+export async function GET(request) {
+	const url = new URL('/api/hello', request.url);
+	const data = await fetch(url.href, { next: { tags: ['cache'] } });
+
+	return new Response(
+		JSON.stringify({
+			body: await data.text(),
+			headers: Object.fromEntries([...data.headers.entries()]),
+		}),
+	);
+}

pages-e2e/features/appFetchCache/fetch-cache.test.ts

@@ -0,0 +1,26 @@
+import { describe, it } from 'vitest';
+
+describe('Simple App server API route with fetch caching', () => {
+	it('should return a cached fetch response from the suspense cache', async ({
+		expect,
+	}) => {
+		const initialResp = await fetch(`${DEPLOYMENT_URL}/api/cache`);
+		const initialRespJson = await initialResp.json();
+
+		expect(initialRespJson.body).toEqual(expect.stringMatching('Hello world'));
+		expect(initialRespJson.headers).toEqual(
+			expect.not.objectContaining({ 'cf-next-suspense-cache': 'HIT' }),
+		);
+
+		// artificial delay to ensure cache entry updates
+		await new Promise(res => setTimeout(res, 3000));
+
+		const cachedResp = await fetch(`${DEPLOYMENT_URL}/api/cache`);
+		const cachedRespJson = await cachedResp.json();
+
+		expect(cachedRespJson.body).toEqual(expect.stringMatching('Hello world'));
+		expect(cachedRespJson.headers).toEqual(
+			expect.objectContaining({ 'cf-next-suspense-cache': 'HIT' }),
+		);
+	});
+});

pages-e2e/features/appFetchCache/main.feature

@@ -0,0 +1,3 @@
+{
+	"setup": "node --loader tsm setup.ts"
+}

pages-e2e/features/appFetchCache/setup.ts

@@ -0,0 +1,2 @@
+import { copyWorkspaceAssets } from '../_utils/copyWorkspaceAssets';
+await copyWorkspaceAssets();

pages-e2e/fixtures/app14.0.0/main.fixture

@@ -16,8 +16,8 @@
 		"compatibilityFlags": ["nodejs_compat"],
 		"kvNamespaces": {
 			"MY_KV": {
-				"production": {"id": "00000000000000000000000000000000"},
-				"staging": {"id": "00000000000000000000000000000000"}
+				"production": { "id": "00000000000000000000000000000000" },
+				"staging": { "id": "00000000000000000000000000000000" }
 			}
 		}
 	}

pages-e2e/fixtures/appLatest/main.fixture

@@ -10,7 +10,8 @@
 		"appConfigsRewritesRedirectsHeaders",
 		"appWasm",
 		"appServerActions",
-		"appGetRequestContext"
+		"appGetRequestContext",
+		"appFetchCache"
 	],
 	"localSetup": "./setup.sh",
 	"buildConfig": {
@@ -21,8 +22,8 @@
 		"compatibilityFlags": ["nodejs_compat"],
 		"kvNamespaces": {
 			"MY_KV": {
-				"production": {"id": "00000000000000000000000000000000"},
-				"staging": {"id": "00000000000000000000000000000000"}
+				"production": { "id": "00000000000000000000000000000000" },
+				"staging": { "id": "00000000000000000000000000000000" }
 			}
 		}
 	}