only add x-fah-middleware routes to routes that have middleware enabled

Author: mathu97

packages/@apphosting/adapter-nextjs/src/overrides.ts

@@ -146,9 +146,12 @@ export async function validateNextConfigOverride(
  * Modifies the app's route manifest (routes-manifest.json) to add Firebase App Hosting
  * specific overrides (i.e headers).
  *
- * This function adds the following headers to all routes:
+ * It adds the following headers to all routes:
  * - x-fah-adapter: The Firebase App Hosting adapter version used to build the app.
+ *
+ * It also adds the following headers to all routes for which middleware is enabled:
  * - x-fah-middleware: When middleware is enabled.
+ *
  * @param appPath The path to the app directory.
  * @param distDir The path to the dist directory.
  * @param adapterMetadata The adapter metadata.
@@ -158,38 +161,48 @@ export async function addRouteOverrides(
   distDir: string,
   adapterMetadata: AdapterMetadata,
 ) {
-  const middlewareManifest = loadMiddlewareManifest(appPath, distDir);
   const routeManifest = loadRouteManifest(appPath, distDir);
+
+  // Add the adapter version to all routes
   routeManifest.headers.push({
     source: "/:path*",
     headers: [
       {
         key: "x-fah-adapter",
         value: `nextjs-${adapterMetadata.adapterVersion}`,
       },
-      ...(middlewareExists(middlewareManifest)
-        ? [
-            {
-              key: "x-fah-middleware",
-              value: "true",
-            },
-          ]
-        : []),
     ],
     /*
-      NextJs converts the source string to a regex using path-to-regexp (https://github.com/pillarjs/path-to-regexp) at
-      build time: https://github.com/vercel/next.js/blob/canary/packages/next/src/build/index.ts#L1273.
-      This regex is then used to match the route against the request path.
+    NextJs converts the source string to a regex using path-to-regexp (https://github.com/pillarjs/path-to-regexp) at
+    build time: https://github.com/vercel/next.js/blob/canary/packages/next/src/build/index.ts#L1273.
+    This regex is then used to match the route against the request path.
 
-      This regex was generated by building a sample NextJs app with the source string `/:path*` and then inspecting the
-      routes-manifest.json file.
-    */
+    This regex was generated by building a sample NextJs app with the source string `/:path*` and then inspecting the
+    routes-manifest.json file.
+  */
     regex: "^(?:/((?:[^/]+?)(?:/(?:[^/]+?))*))?(?:/)?$",
   });
 
-  await writeRouteManifest(appPath, distDir, routeManifest);
-}
+  // Add the middleware header to all routes for which middleware is enabled
+  const middlewareManifest = loadMiddlewareManifest(appPath, distDir);
+  const rootMiddleware = middlewareManifest.middleware["/"];
+  if (!rootMiddleware?.matchers) {
+    console.log("No middleware found for root path, skipping route overrides");
+    return;
+  }
 
-function middlewareExists(middlewareManifest: MiddlewareManifest) {
-  return Object.keys(middlewareManifest.middleware).length > 0;
+  rootMiddleware.matchers.forEach((matcher) => {
+    routeManifest.headers.push({
+      source: matcher.regexp,
+      headers: [
+        {
+          key: "x-fah-middleware",
+          value: "true",
+        },
+      ],
+      regex: matcher.regexp,
+    });
+  });
+
+  await writeRouteManifest(appPath, distDir, routeManifest);
 }