server-adapter: prevent to replace correct swr header (#162)

* prevent to replace correct swr header

Author: Tietew

README.md

@@ -509,15 +509,15 @@ public, max-age=0, s-maxage=31536000, must-revalidate
 `NextServer` does not seem to set an appropriate value for the `stale-while-revalidate` cache header. For example, the header might look like this:
 
 ```
-s-maxage=600 stale-while-revalidate
+s-maxage=600, stale-while-revalidate
 ```
 
 This prevents CloudFront from caching the stale data.
 
 To work around the issue, the server function checks if the response includes the `stale-while-revalidate` header. If found, it sets the value to 30 days:
 
 ```
-s-maxage=600 stale-while-revalidate=2592000
+s-maxage=600, stale-while-revalidate=2592000
 ```
 
 #### WORKAROUND: Set `NextServer` working directory (AWS specific)

packages/open-next/package.json

@@ -39,6 +39,7 @@
     "@aws-sdk/client-sqs": "^3.398.0",
     "@node-minify/core": "^8.0.6",
     "@node-minify/terser": "^8.0.6",
+    "@open-next/utils": "workspace:*",
     "@tsconfig/node18": "^1.0.1",
     "esbuild": "^0.18.18",
     "@esbuild-plugins/node-resolve": "0.2.2",

packages/open-next/src/adapters/plugins/routing/default.ts

@@ -12,6 +12,7 @@ import {
   revalidateIfRequired,
 } from "./util";
 import { convertRes } from "../../routing/util";
+
 //#endOverride
 
 //#override processInternalEvent
@@ -21,7 +22,7 @@ export async function processInternalEvent(
   const reqProps = {
     method: internalEvent.method,
     url: internalEvent.url,
-    //WORKAROUND: We pass this header to the serverless function to mimic a prefetch request which will not trigger revalidation since we handle revalidation differently
+    // WORKAROUND: We pass this header to the serverless function to mimic a prefetch request which will not trigger revalidation since we handle revalidation differently
     // There is 3 way we can handle revalidation:
     // 1. We could just let the revalidation go as normal, but due to race condtions the revalidation will be unreliable
     // 2. We could alter the lastModified time of our cache to make next believe that the cache is fresh, but this could cause issues with stale data since the cdn will cache the stale data as if it was fresh

packages/open-next/src/adapters/plugins/routing/util.ts

@@ -54,16 +54,6 @@ export function fixCacheHeaderForHtmlPages(
   }
 }
 
-export function fixSWRCacheHeader(headers: Record<string, string | undefined>) {
-  // WORKAROUND: `NextServer` does not set correct SWR cache headers — https://github.com/serverless-stack/open-next#workaround-nextserver-does-not-set-correct-swr-cache-headers
-  if (headers["cache-control"]?.includes("stale-while-revalidate")) {
-    headers["cache-control"] = headers["cache-control"].replace(
-      "stale-while-revalidate",
-      "stale-while-revalidate=2592000", // 30 days
-    );
-  }
-}
-
 export function addOpenNextHeader(headers: Record<string, string | undefined>) {
   headers["X-OpenNext"] = process.env.OPEN_NEXT_VERSION;
 }
@@ -121,3 +111,13 @@ export async function revalidateIfRequired(
     debug(e);
   }
 }
+
+export function fixSWRCacheHeader(headers: Record<string, string | undefined>) {
+  // WORKAROUND: `NextServer` does not set correct SWR cache headers — https://github.com/serverless-stack/open-next#workaround-nextserver-does-not-set-correct-swr-cache-headers
+  if (headers["cache-control"]) {
+    headers["cache-control"] = headers["cache-control"].replace(
+      /\bstale-while-revalidate(?!=)/,
+      "stale-while-revalidate=2592000", // 30 days
+    );
+  }
+}

packages/tests-unit/.gitignore

@@ -0,0 +1 @@
+coverage

packages/tests-unit/tests/utils.test.ts

@@ -0,0 +1,38 @@
+import { fixSWRCacheHeader } from "@open-next/utils";
+
+describe("Utils", () => {
+  describe("fixSWRCacheHeader", () => {
+    it("Does not update swr if already set", () => {
+      const headers = {
+        "cache-control": "maxage=69,stale-while-revalidate=11",
+      };
+      fixSWRCacheHeader(headers);
+
+      expect(headers).toEqual({
+        "cache-control": "maxage=69,stale-while-revalidate=11",
+      });
+    });
+
+    it("Does not add swr if not exists", () => {
+      const headers = {
+        "cache-control": "maxage=69",
+      };
+      fixSWRCacheHeader(headers);
+
+      expect(headers).toEqual({
+        "cache-control": "maxage=69",
+      });
+    });
+
+    it("Sets time on swf if not defined", () => {
+      const headers = {
+        "cache-control": "maxage=69,stale-while-revalidate",
+      };
+      fixSWRCacheHeader(headers);
+
+      expect(headers).toEqual({
+        "cache-control": "maxage=69,stale-while-revalidate=2592000",
+      });
+    });
+  });
+});

packages/utils/src/index.ts

@@ -14,3 +14,13 @@ export async function wait(n: number = 1000) {
     setTimeout(res, n);
   });
 }
+
+export function fixSWRCacheHeader(headers: Record<string, string | undefined>) {
+  // WORKAROUND: `NextServer` does not set correct SWR cache headers — https://github.com/serverless-stack/open-next#workaround-nextserver-does-not-set-correct-swr-cache-headers
+  if (headers["cache-control"]) {
+    headers["cache-control"] = headers["cache-control"].replace(
+      /\bstale-while-revalidate(?!=)/,
+      "stale-while-revalidate=2592000", // 30 days
+    );
+  }
+}