correct wrong logic

Author: dario-piotrowicz

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

@@ -10,6 +10,9 @@ const CACHE_TAGS_HEADER = 'x-vercel-cache-tags';
 // https://github.com/vercel/next.js/blob/ba23d986/packages/next/src/lib/constants.ts#L18
 const NEXT_CACHE_SOFT_TAGS_HEADER = 'x-next-cache-soft-tags';
 
+// https://github.com/vercel/next.js/blob/fc25fcef/packages/next/src/server/lib/incremental-cache/fetch-cache.ts#L21
+const CACHE_STATE_HEADER = 'x-vercel-cache-state';
+
 /**
  * Handles an internal request to the suspense cache.
  *
@@ -52,20 +55,15 @@ export async function handleSuspenseCacheRequest(
 					NEXT_CACHE_SOFT_TAGS_HEADER,
 				);
 
-				// Retrieve the value from the cache.
 				const data = await incrementalCache.get(cacheKey, { softTags });
 				if (!data) return new Response(null, { status: 404 });
 
-				const lastModified =
-					typeof data.curRevalidate === 'number'
-						? data.curRevalidate
-						: Date.now();
 				return new Response(JSON.stringify(data.value), {
 					status: 200,
 					headers: {
 						'Content-Type': 'application/json',
-						'x-vercel-cache-state': 'fresh',
-						age: `${(Date.now() - lastModified) / 1000}`,
+						[CACHE_STATE_HEADER]: 'fresh',
+						age: `${data.age}`,
 					},
 				});
 			}

packages/next-on-pages/templates/cache/incrementalCache.ts

@@ -39,7 +39,7 @@ export class CacheHandler {
 /* eslint-enable */
 
 /**
- * Simplified version of the IncrementalCache from Next.js
+ * Simplified (and tweaked) version of the IncrementalCache from Next.js
  * source: https://github.com/vercel/next.js/blob/c4adae89b/packages/next/src/server/lib/incremental-cache/index.ts#L65
  */
 export class IncrementalCache {
@@ -89,12 +89,16 @@ export class IncrementalCache {
 			tags?: string[];
 			softTags?: string[];
 		} = {},
-	): Promise<IncrementalCacheEntry | null> {
-		let entry: IncrementalCacheEntry | null = null;
+	): Promise<(IncrementalCacheEntry & { age?: number }) | null> {
+		let entry: (IncrementalCacheEntry & { age?: number }) | null = null;
 		let revalidate = ctx.revalidate;
 
 		const cacheData = await this.cacheHandler?.get(cacheKey, ctx);
 
+		const age = cacheData
+			? (Date.now() - (cacheData.lastModified || 0)) / 1000
+			: undefined;
+
 		if (cacheData?.value?.kind === 'FETCH') {
 			const combinedTags = [...(ctx.tags || []), ...(ctx.softTags || [])];
 			// if a tag was revalidated we don't return stale data
@@ -107,9 +111,10 @@ export class IncrementalCache {
 			}
 
 			revalidate = revalidate || cacheData.value.revalidate;
-			const age = (Date.now() - (cacheData.lastModified || 0)) / 1000;
-
-			const isStale = typeof revalidate === 'number' && age > revalidate;
+			const isStale =
+				typeof revalidate === 'number' &&
+				typeof age === 'number' &&
+				age > revalidate;
 			const data = cacheData.value.data;
 
 			return {
@@ -119,6 +124,7 @@ export class IncrementalCache {
 					data,
 					revalidate: revalidate,
 				},
+				age,
 				revalidateAfter:
 					typeof revalidate === 'number' && Date.now() + revalidate * 1000,
 			};
@@ -128,31 +134,30 @@ export class IncrementalCache {
 		let revalidateAfter: false | number;
 
 		if (cacheData?.lastModified === -1) {
-			isStale = -1;
 			revalidateAfter = -1 * CACHE_ONE_YEAR;
+			isStale = -1;
 		} else {
 			revalidateAfter = 1 * 1000 + (cacheData?.lastModified || Date.now());
-
 			isStale = revalidateAfter < Date.now() ? true : undefined;
 		}
 
-		if (cacheData) {
-			entry = {
-				isStale,
-				revalidateAfter,
-				value: cacheData.value,
-			};
-		}
+		entry = {
+			isStale,
+			revalidateAfter,
+			value: null,
+		};
 
-		if (!cacheData) {
-			entry = {
-				isStale,
-				value: null,
-				revalidateAfter,
-			};
+		if (cacheData) {
+			entry.value = cacheData.value;
+			entry.age = age;
+		} else {
 			await this.set(cacheKey, entry.value, ctx);
 		}
-		return entry;
+
+		return {
+			...entry,
+			age,
+		};
 	}
 
 	async set(