action: support not found

packages/next/src/server/app-render/action-handler.ts

@@ -193,6 +193,7 @@ export async function handleAction({
   generateFlight: (options: {
     actionResult: ActionResult
     skipFlight: boolean
+    asNotFound?: boolean
   }) => Promise<RenderResult>
   staticGenerationStore: StaticGenerationStore
 }): Promise<undefined | RenderResult | 'not-found'> {
@@ -363,28 +364,33 @@ export async function handleAction({
         res.statusCode = 303
         return new RenderResult('')
       } else if (isNotFoundError(err)) {
+        res.statusCode = 404
+
+        await Promise.all(staticGenerationStore.pendingRevalidates || [])
         if (isFetchAction) {
-          throw new Error('Invariant: not implemented.')
+          const promise = Promise.reject(err)
+          try {
+            await promise
+          } catch (_) {}
+          return generateFlight({
+            skipFlight: false,
+            actionResult: promise,
+            asNotFound: true,
+          })
         }
-        await Promise.all(staticGenerationStore.pendingRevalidates || [])
-        res.statusCode = 404
         return 'not-found'
       }
 
       if (isFetchAction) {
         res.statusCode = 500
-        const rejectedPromise = Promise.reject(err)
+        await Promise.all(staticGenerationStore.pendingRevalidates || [])
+        const promise = Promise.reject(err)
         try {
-          // we need to await the promise to trigger the rejection early
-          // so that it's already handled by the time we call
-          // the RSC runtime. Otherwise, it will throw an unhandled
-          // promise rejection error in the renderer.
-          await rejectedPromise
-        } catch (_) {
-          // swallow error, it's gonna be handled on the client
-        }
+          await promise
+        } catch (_) {}
+
         return generateFlight({
-          actionResult: rejectedPromise,
+          actionResult: promise,
           // if the page was not revalidated, we can skip the rendering the flight tree
           skipFlight: !staticGenerationStore.pathWasRevalidated,
         })

packages/next/src/server/app-render/app-render.tsx

@@ -939,6 +939,7 @@ export async function renderToHTMLOrFlight(
     const generateFlight = async (options?: {
       actionResult: ActionResult
       skipFlight: boolean
+      asNotFound?: boolean
     }): Promise<RenderResult> => {
       /**
        * Use router state to decide at what common layout to render the page.
@@ -1176,7 +1177,7 @@ export async function renderToHTMLOrFlight(
               injectedCSS: new Set(),
               injectedFontPreloadTags: new Set(),
               rootLayoutIncluded: false,
-              asNotFound: pathname === '/404',
+              asNotFound: pathname === '/404' || options?.asNotFound,
             })
           ).map((path) => path.slice(1)) // remove the '' (root) segment
 

test/e2e/app-dir/actions/app-action.test.ts

@@ -78,7 +78,7 @@ createNextDescribe(
       }, '/header?name=test&constructor=FormData')
     })
 
-    it('should support notFound', async () => {
+    it('should support notFound (javascript disabled)', async () => {
       const browser = await next.browser('/server', {
         // TODO we should also test this with javascript on but not-found is not implemented yet.
         disableJavaScript: true,
@@ -91,6 +91,16 @@ createNextDescribe(
       }, 'my-not-found')
     })
 
+    it('should support notFound', async () => {
+      const browser = await next.browser('/server')
+
+      await browser.elementByCss('#nowhere').click()
+
+      await check(() => {
+        return browser.elementByCss('h1').text()
+      }, 'my-not-found')
+    })
+
     it('should support uploading files', async () => {
       const logs: string[] = []
       next.on('stdout', (log) => {