From 2f10a12cefd18035e18896aa05171af48c1c62e2 Mon Sep 17 00:00:00 2001
From: Josh Story <story@hey.com>
Date: Tue, 10 Dec 2024 08:44:53 -0800
Subject: [PATCH] [dynamicIO] use new heuristic to track whether server render
 is dynamic

Instead of relying on onError just use the timing of the prerender resolution to determine whether the server render completed before aborting.
---
 .../next/src/server/app-render/app-render.tsx | 25 ++++++++++++++++---
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/packages/next/src/server/app-render/app-render.tsx b/packages/next/src/server/app-render/app-render.tsx
index 5cb7087f768e9..3036d801d4440 100644
--- a/packages/next/src/server/app-render/app-render.tsx
+++ b/packages/next/src/server/app-render/app-render.tsx
@@ -2716,11 +2716,12 @@ async function prerenderToStream(
           ctx,
           res.statusCode === 404
         )
+        let prerenderIsPending = true
         const reactServerResult = (reactServerPrerenderResult =
           await createReactServerPrerenderResult(
             prerenderAndAbortInSequentialTasks(
-              () =>
-                workUnitAsyncStorage.run(
+              async () => {
+                const prerenderResult = await workUnitAsyncStorage.run(
                   // The store to scope
                   finalRenderPrerenderStore,
                   // The function to run
@@ -2730,8 +2731,9 @@ async function prerenderToStream(
                   clientReferenceManifest.clientModules,
                   {
                     onError: (err: unknown) => {
+                      // TODO we can remove this once https://github.com/facebook/react/pull/31715 lands
+                      // because we won't have onError calls when halting the prerender
                       if (finalServerController.signal.aborted) {
-                        serverIsDynamic = true
                         return
                       }
 
@@ -2739,8 +2741,23 @@ async function prerenderToStream(
                     },
                     signal: finalServerController.signal,
                   }
-                ),
+                )
+                prerenderIsPending = false
+                return prerenderResult
+              },
               () => {
+                if (finalServerController.signal.aborted) {
+                  // If the server controller is already aborted we must have called something
+                  // that required aborting the prerender synchronously such as with new Date()
+                  serverIsDynamic = true
+                  return
+                }
+
+                if (prerenderIsPending) {
+                  // If prerenderIsPending then we have blocked for longer than a Task and we assume
+                  // there is something unfinished.
+                  serverIsDynamic = true
+                }
                 finalServerController.abort()
               }
             )