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• fix(rsc): handle router errors gracefully in flight response stream #88444 👈 (View in Graphite)
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Failing test suites

Commit: afee814 | About building and testing Next.js

pnpm test-start test/production/app-dir/parallel-routes-static/index.test.ts (job)

• app-dir parallel-routes-static > should static generate parallel routes (DD)

expect(received).toBe(expected) // Object.is equality

Expected: true
Received: false

   8 |   it('should static generate parallel routes', async () => {
   9 |     const rscExtension = '.rsc'
> 10 |     expect(await next.hasFile('.next/server/app/nested/foo.html')).toBe(true)
     |                                                                    ^
  11 |     expect(await next.hasFile('.next/server/app/nested/foo.meta')).toBe(true)
  12 |
  13 |     // we do not output '.rsc' statically with cache components

  at Object.toBe (production/app-dir/parallel-routes-static/index.test.ts:10:68)

pnpm test-start test/e2e/app-dir/use-cache/use-cache.test.ts (job)

• use-cache > should prerender fully cacheable pages as static HTML (DD)

expect(received).toEqual(expected) // deep equality

- Expected  - 1
+ Received  + 0

@@ -14,11 +14,10 @@
    "/form",
    "/imported-from-client",
    "/logs",
    "/method-props",
    "/nested-in-unstable-cache",
-   "/not-found",
    "/on-demand-revalidate",
    "/passed-to-client",
    "/react-cache",
    "/referential-equality",
    "/revalidate-and-redirect/redirect",

  469 |         .sort()
  470 |
> 471 |       expect(prerenderedRouteKeys).toEqual(
      |                                    ^
  472 |         [
  473 |           '/_not-found',
  474 |           // [id] route, first entry in generateStaticParams

  at Object.toEqual (e2e/app-dir/use-cache/use-cache.test.ts:471:36)

Hey @wyattjoh — following up here since you mentioned in #87041 that you were experimenting with this approach.

It looks like this has been in draft with a couple of test failures since mid-January. Is this still something you're planning to land, or has the approach hit a wall?

The underlying issue (#86251) has been open for ~4 months now and has 10 upvotes — notFound() is essentially broken when cacheComponents: true is enabled with Suspense boundaries, which is a pretty common pattern. A few people in the #87041 thread have flagged it as a production blocker.

Happy to help move this forward if there's anything I can pick up — whether that's rebasing, fixing the failing tests, or iterating on the approach. Just let me know.

I don't have any immediate plans to pick this back up, but the approach in this PR could serve as a reasonable starting point for a proper fix. The core idea of using controller.close() instead of controller.error() for router errors so the serialized error data reaches the client is sound, though the test failures around static prerendering need to be worked through.

The buffering approach suggested in #87041 would break streaming, so that's not a viable path forward. The fix needs to preserve streaming behavior while still allowing error boundaries to handle notFound()/forbidden()/unauthorized() correctly within Suspense boundaries.

I may revisit this when I have some time. If anyone else wants to pick it up in the meantime, the work here should give you a head start on the direction.