fix: use static 404 for non-prerendered dynamic routes without fallback

cypress/integration/default/dynamic-routes.spec.ts

@@ -49,7 +49,7 @@ describe('Dynamic Routing', () => {
     cy.request({ url: '/getStaticProps/3/', headers: { 'x-nf-debug-logging': '1' }, failOnStatusCode: false }).then(
       (res) => {
         expect(res.status).to.eq(404)
-        expect(res.headers).to.have.property('x-nf-render-mode', 'odb')
+        expect(res.headers).to.not.have.property('x-nf-render-mode')
         expect(res.body).to.contain('Custom 404')
       },
     )
@@ -102,7 +102,7 @@ describe('Dynamic Routing', () => {
       failOnStatusCode: false,
     }).then((res) => {
       expect(res.status).to.eq(404)
-      expect(res.headers).to.have.property('x-nf-render-mode', 'odb')
+      expect(res.headers).to.not.have.property('x-nf-render-mode')
       expect(res.body).to.contain('Custom 404')
     })
   })

packages/runtime/src/helpers/redirects.ts

@@ -19,6 +19,7 @@ import {
   isApiRoute,
   redirectsForNextRoute,
   redirectsForNextRouteWithData,
+  redirectsForNext404Route,
   routeToDataRoute,
 } from './utils'
 
@@ -187,13 +188,15 @@ const generateDynamicRewrites = ({
   basePath,
   buildId,
   i18n,
+  is404Isr,
 }: {
   dynamicRoutes: RoutesManifest['dynamicRoutes']
   prerenderedDynamicRoutes: PrerenderManifest['dynamicRoutes']
   basePath: string
   i18n: NextConfig['i18n']
   buildId: string
   middleware: Array<string>
+  is404Isr: boolean
 }): {
   dynamicRoutesThatMatchMiddleware: Array<string>
   dynamicRewrites: NetlifyConfig['redirects']
@@ -207,9 +210,11 @@ const generateDynamicRewrites = ({
     if (route.page in prerenderedDynamicRoutes) {
       if (matchesMiddleware(middleware, route.page)) {
         dynamicRoutesThatMatchMiddleware.push(route.page)
+      } else if (prerenderedDynamicRoutes[route.page].fallback === false && !is404Isr) {
+        dynamicRewrites.push(...redirectsForNext404Route({ route: route.page, buildId, basePath, i18n }))
       } else {
         dynamicRewrites.push(
-          ...redirectsForNextRoute({ buildId, route: route.page, basePath, to: ODB_FUNCTION_PATH, status: 200, i18n }),
+          ...redirectsForNextRoute({ route: route.page, buildId, basePath, to: ODB_FUNCTION_PATH, i18n }),
         )
       }
     } else {
@@ -263,6 +268,10 @@ export const generateRedirects = async ({
 
   const staticRouteEntries = Object.entries(prerenderedStaticRoutes)
 
+  const is404Isr = staticRouteEntries.some(
+    ([route, { initialRevalidateSeconds }]) => is404Route(route, i18n) && initialRevalidateSeconds !== false,
+  )
+
   const routesThatMatchMiddleware: Array<string> = []
 
   const { staticRoutePaths, staticIsrRewrites, staticIsrRoutesThatMatchMiddleware } = generateStaticIsrRewrites({
@@ -295,6 +304,7 @@ export const generateRedirects = async ({
     basePath,
     buildId,
     i18n,
+    is404Isr,
   })
   netlifyConfig.redirects.push(...dynamicRewrites)
   routesThatMatchMiddleware.push(...dynamicRoutesThatMatchMiddleware)

packages/runtime/src/helpers/utils.ts

@@ -72,9 +72,18 @@ export const netlifyRoutesForNextRouteWithData = ({ route, dataRoute }: { route:
 export const routeToDataRoute = (route: string, buildId: string, locale?: string) =>
   `/_next/data/${buildId}${locale ? `/${locale}` : ''}${route === '/' ? '/index' : route}.json`
 
-const netlifyRoutesForNextRoute = (route: string, buildId: string, i18n?: I18n): Array<string> => {
+const netlifyRoutesForNextRoute = (
+  route: string,
+  buildId: string,
+  i18n?: I18n,
+): Array<{ redirect: string; locale: string | false }> => {
   if (!i18n?.locales?.length) {
-    return netlifyRoutesForNextRouteWithData({ route, dataRoute: routeToDataRoute(route, buildId) })
+    return netlifyRoutesForNextRouteWithData({ route, dataRoute: routeToDataRoute(route, buildId) }).map(
+      (redirect) => ({
+        redirect,
+        locale: false,
+      }),
+    )
   }
   const { locales, defaultLocale } = i18n
   const routes = []
@@ -87,7 +96,10 @@ const netlifyRoutesForNextRoute = (route: string, buildId: string, i18n?: I18n):
       ...netlifyRoutesForNextRouteWithData({
         route: locale === defaultLocale ? route : `/${locale}${route}`,
         dataRoute,
-      }),
+      }).map((redirect) => ({
+        redirect,
+        locale,
+      })),
     )
   })
   return routes
@@ -115,13 +127,33 @@ export const redirectsForNextRoute = ({
   status?: number
   force?: boolean
 }): NetlifyConfig['redirects'] =>
-  netlifyRoutesForNextRoute(route, buildId, i18n).map((redirect) => ({
+  netlifyRoutesForNextRoute(route, buildId, i18n).map(({ redirect }) => ({
     from: `${basePath}${redirect}`,
     to,
     status,
     force,
   }))
 
+export const redirectsForNext404Route = ({
+  route,
+  buildId,
+  basePath,
+  i18n,
+  force = false,
+}: {
+  route: string
+  buildId: string
+  basePath: string
+  i18n: I18n
+  force?: boolean
+}): NetlifyConfig['redirects'] =>
+  netlifyRoutesForNextRoute(route, buildId, i18n).map(({ redirect, locale }) => ({
+    from: `${basePath}${redirect}`,
+    to: locale ? `${basePath}/server/pages/${locale}/404.html` : `${basePath}/server/pages/404.html`,
+    status: 404,
+    force,
+  }))
+
 export const redirectsForNextRouteWithData = ({
   route,
   dataRoute,