On NextJS deploy check if not-found is static (#6558)

CHANGELOG.md

@@ -1,3 +1,4 @@
 - Added the ability to deploy Angular apps using [the new application-builder](https://angular.dev/tools/cli/esbuild). (#6480)
 - Fixed an issue where `--non-interactive` flag is not respected in Firestore indexes deploys. (#6539)
 - Fixed an issue where `login:use` would not work outside of a Firebase project directory. (#6526)
+- Prevent app router static `not-found` requiring a Cloud Function in Next.js deployments. (#6558)

src/frameworks/next/index.ts

@@ -47,6 +47,7 @@ import {
   getHeadersFromMetaFiles,
   cleanI18n,
   getNextVersion,
+  hasStaticAppNotFoundComponent,
 } from "./utils";
 import { NODE_VERSION, NPM_COMMAND_TIMEOUT_MILLIES, SHARP_VERSION, I18N_ROOT } from "../constants";
 import type {
@@ -215,6 +216,13 @@ export async function build(dir: string): Promise<BuildResult> {
         dynamicRoutes
       );
 
+      if (
+        unrenderedServerComponents.has("/_not-found") &&
+        (await hasStaticAppNotFoundComponent(dir, distDir))
+      ) {
+        unrenderedServerComponents.delete("/_not-found");
+      }
+
       for (const key of unrenderedServerComponents) {
         reasonsForBackend.add(`non-static component ${key}`);
       }

src/frameworks/next/utils.ts

@@ -338,7 +338,7 @@ export function getNonStaticServerComponents(
   appPathRoutesManifest: AppPathRoutesManifest,
   prerenderedRoutes: string[],
   dynamicRoutes: string[]
-): string[] {
+): Set<string> {
   const nonStaticServerComponents = Object.entries(appPathsManifest)
     .filter(([it, src]) => {
       if (extname(src) !== ".js") return;
@@ -347,7 +347,7 @@ export function getNonStaticServerComponents(
     })
     .map(([it]) => it);
 
-  return nonStaticServerComponents;
+  return new Set(nonStaticServerComponents);
 }
 
 /**
@@ -407,3 +407,17 @@ export function getNextVersion(cwd: string): string | undefined {
 
   return nextVersionSemver.toString();
 }
+
+/**
+ * Whether the Next.js project has a static `not-found` page in the app directory.
+ *
+ * The Next.js build manifests are misleading regarding the existence of a static
+ * `not-found` component. Therefore, we check if a `_not-found.html` file exists
+ * in the generated app directory files to know whether `not-found` is static.
+ */
+export async function hasStaticAppNotFoundComponent(
+  sourceDir: string,
+  distDir: string
+): Promise<boolean> {
+  return pathExists(join(sourceDir, distDir, "server", "app", "_not-found.html"));
+}

src/test/frameworks/next/utils.spec.ts

@@ -461,7 +461,7 @@ describe("Next.js utils", () => {
           Object.keys(prerenderManifest.routes),
           Object.keys(prerenderManifest.dynamicRoutes)
         )
-      ).to.deep.equal(["/api/test/route"]);
+      ).to.deep.equal(new Set(["/api/test/route"]));
     });
   });