fix: routes with null data routes can be filtered now

packages/runtime/src/templates/edge-shared/rsc-data.ts

@@ -1,14 +1,18 @@
 import type { EdgeFunction } from 'https://edge.netlify.com'
 
+// These are copied from next/dist/build. This file gets copied as part of the next
+// runtime build and can't reference the next package directly.
+//
+// Latest types at https://github.com/vercel/next.js/blob/4a2df3c3752aeddc50fd5ab053440eccf71ae50b/packages/next/src/build/index.ts#L140
 export declare type SsgRoute = {
   initialRevalidateSeconds: number | false
   srcRoute: string | null
-  dataRoute: string
+  dataRoute: string | null
 }
 export declare type DynamicSsgRoute = {
   routeRegex: string
   fallback: string | null | false
-  dataRoute: string
+  dataRoute: string | null
   dataRouteRegex: string
 }
 export declare type PrerenderManifest = {
@@ -35,7 +39,7 @@ const rscifyPath = (route: string) => {
 export const getRscDataRouter = ({ routes: staticRoutes, dynamicRoutes }: PrerenderManifest): EdgeFunction => {
   const staticRouteSet = new Set(
     Object.entries(staticRoutes)
-      .filter(([, { dataRoute }]) => dataRoute.endsWith('.rsc'))
+      .filter(([, { dataRoute }]) => dataRoute?.endsWith('.rsc'))
       .map(([route]) => route),
   )
 

test/rsc-data.spec.ts

@@ -0,0 +1,40 @@
+import { getRscDataRouter, PrerenderManifest } from '../packages/runtime/src/templates/edge-shared/rsc-data'
+
+const basePrerenderManifest: PrerenderManifest = {
+  version: 3,
+  routes: {},
+  dynamicRoutes: {},
+  notFoundRoutes: [],
+}
+
+describe('getRscDataRouter', () => {
+  it('should create a RSC data router when data routes are not present for routes', () => {
+    const manifest: PrerenderManifest = {
+      ...basePrerenderManifest,
+      routes: {
+        '/': {
+          initialRevalidateSeconds: 1,
+          srcRoute: null,
+          dataRoute: '/index.json.rsc',
+        },
+        '/api/hello': {
+          initialRevalidateSeconds: false,
+          srcRoute: '/api/hello',
+          dataRoute: null,
+        },
+      },
+    }
+
+    let rscDataRouter
+
+    // Normally type checking would pick this up, but because this file is copied when generating
+    // edge functions for the build, we need to make sure it's valid for builds.
+    //
+    // See https://github.com/netlify/next-runtime/issues/1940
+    expect(() => {
+      rscDataRouter = getRscDataRouter(manifest)
+    }).not.toThrow()
+
+    expect(typeof rscDataRouter).toBe('function')
+  })
+})