Turbopack: Implement TraceRawVcs and NonLocalValue correctly for Effects #89133

bgw · 2026-01-28T00:03:14Z

In subsequent PRs, I want to store a ResolvedVc (specifically, a FileSystemPath, which contains a Vc<Box<dyn FileSystem>>) inside of an Effect.

To do this in a way that wouldn't break a hypothetical future tracing garbage collector, we must implement TraceRawVcs on Effect.

The previous PR changed the Effect type from a closure to a trait in order to enable this.

bgw · 2026-01-28T00:03:35Z

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nextjs-bot · 2026-01-28T00:15:06Z

Failing test suites

Commit: fd04529 | About building and testing Next.js

pnpm test packages/next/src/server/app-render/action-handler.test.ts (job)

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Details:

C:\actions-runner\_work\next.js\next.js\packages\next\src\server\app-render\action-handler.ts:1
({"Object.<anonymous>":function(module,exports,require,__dirname,__filename,jest){import { RSC_HEADER, RSC_CONTENT_TYPE_HEADER, NEXT_ROUTER_STATE_TREE_HEADER, ACTION_HEADER, NEXT_ACTION_NOT_FOUND_HEADER, NEXT_ROUTER_PREFETCH_HEADER, NEXT_ROUTER_SEGMENT_PREFETCH_HEADER, NEXT_URL, NEXT_ACTION_REVALIDATED_HEADER } from '../../client/components/app-router-headers';
                                                                                  ^^^^^^

SyntaxError: Cannot use import statement outside a module

  3 | describe('parseHostHeader', () => {
  4 |   it('should return correct host', () => {
> 5 |     expect(parseHostHeader({})).toBe(undefined)
    |                        ^
  6 |
  7 |     expect(
  8 |       parseHostHeader({

  at Runtime.createScriptFromCode (../node_modules/.pnpm/jest-runtime@29.7.0/node_modules/jest-runtime/build/index.js:1505:14)
  at Object.<anonymous> (../packages/next/src/server/app-render/action-handler.test.ts:5:24)

codspeed-hq · 2026-01-28T00:15:18Z

Merging this PR will not alter performance

✅ 17 untouched benchmarks
⏩ 3 skipped benchmarks¹

_{Comparing bgw/effect-trace-raw-vcs (fd04529) with bgw/effect-trait (86cb33f)}

3 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

lukesandberg · 2026-01-28T00:28:30Z

turbopack/crates/turbo-tasks/src/effect.rs

                    EffectState::NotStarted(_) => {
-                        let EffectState::NotStarted(inner) = std::mem::replace(
-                            &mut *guard,
-                            EffectState::Started(Event::new(|| || "Effect".to_string())),
-                        ) else {
-                            unreachable!();
+                        let EffectState::NotStarted(effect) =
+                            std::mem::replace(&mut *guard, EffectState::Invalid)
+                        else {
+                            unreachable!()
                        };
-                        State::NotStarted(inner)
+                        let effect: Arc<dyn DynEffect> = Arc::from(effect);
+                        *guard = EffectState::Started(
+                            effect.clone(),
+                            Event::new(|| || "Effect".to_string()),
+                        );
+                        State::NotStarted(effect)


can't we just capture effect in the match condition and then assign back? i guess that requires an additional clone on the effect Arc?

I actually tried rewriting it that way, using a manual drop(guard) call. The appears to be some limitation of rustc's analysis here that cause it to think that the future is no longer Send because it thinks the mutex guard might get held across an await point (even though it isn't because of the drop(guard) call).

nextjs-bot · 2026-01-28T00:39:28Z

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Metric	Canary	PR	Change	Trend
Cold (Listen)	456ms	456ms	✓	▁█▁▁▁
Cold (Ready in log)	438ms	438ms	✓	▂█▁▂▂
Cold (First Request)	1.211s	1.166s	✓	▂█▁▅▄
Warm (Listen)	456ms	457ms	✓	▁█▁▁▁
Warm (Ready in log)	442ms	444ms	✓	▁█▁▁▁
Warm (First Request)	340ms	346ms	✓	▂█▁▂▁

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Metric	Canary	PR	Change	Trend
Cold (Listen)	456ms	456ms	✓	█▁█▁█
Cold (Ready in log)	441ms	439ms	✓	▆▆▇▅▆
Cold (First Request)	1.772s	1.768s	✓	▄▃▅▃▃
Warm (Listen)	456ms	456ms	✓	▁▅▅█▅
Warm (Ready in log)	440ms	441ms	✓	▅▄▅▄▄
Warm (First Request)	1.766s	1.779s	✓	▄▃▅▃▃

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Metric	Canary	PR	Change	Trend
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81 files with content-based hashes (individual files not comparable between builds)

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middleware-b..fest.js gzip	763 B	770 B	✓
Total	763 B	770 B	⚠️ +7 B

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_buildManifest.js gzip	451 B	450 B	✓
Total	451 B	450 B	✅ -1 B

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page.js gzip	248 kB	249 kB	✓
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middleware-b..fest.js gzip	616 B	614 B	✓
middleware-r..fest.js gzip	156 B	155 B	✓
middleware.js gzip	33.2 kB	33.1 kB	✓
edge-runtime..pack.js gzip	842 B	842 B	✓
Total	34.8 kB	34.8 kB	✅ -82 B

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_buildManifest.js gzip	732 B	736 B	✓
Total	732 B	736 B	⚠️ +4 B

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0.pack gzip	3.79 MB	3.8 MB	🔴 +10.9 kB (+0%)
index.pack gzip	102 kB	102 kB	✓
index.pack.old gzip	103 kB	102 kB	✓
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app-page-exp..prod.js gzip	166 kB	166 kB	✓
app-page-tur...dev.js gzip	311 kB	311 kB	✓
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app-page-tur..prod.js gzip	164 kB	164 kB	✓
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app-page.run..prod.js gzip	164 kB	164 kB	✓
app-route-ex...dev.js gzip	70.4 kB	70.4 kB	✓
app-route-ex..prod.js gzip	48.9 kB	48.9 kB	✓
app-route-tu...dev.js gzip	70.4 kB	70.4 kB	✓
app-route-tu..prod.js gzip	49 kB	49 kB	✓
app-route-tu...dev.js gzip	70 kB	70 kB	✓
app-route-tu..prod.js gzip	48.7 kB	48.7 kB	✓
app-route.ru...dev.js gzip	70 kB	70 kB	✓
app-route.ru..prod.js gzip	48.7 kB	48.7 kB	✓
dist_client_...dev.js gzip	324 B	324 B	✓
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dist_client_...dev.js gzip	318 B	318 B	✓
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server.runti..prod.js gzip	62.5 kB	62.5 kB	✓
Total	2.77 MB	2.77 MB	✓

…nctioning

nextjs-bot added created-by: Turbopack team PRs by the Turbopack team. Turbopack Related to Turbopack with Next.js. labels Jan 28, 2026

bgw mentioned this pull request Jan 28, 2026

Turbopack: Define Effect as a trait instead of a closure #89080

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bgw requested review from lukesandberg and sokra January 28, 2026 00:07

bgw marked this pull request as ready for review January 28, 2026 00:07

lukesandberg reviewed Jan 28, 2026

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lukesandberg approved these changes Jan 28, 2026

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bgw force-pushed the bgw/effect-trait branch from ad63b21 to a574d15 Compare January 29, 2026 00:28

bgw force-pushed the bgw/effect-trace-raw-vcs branch from 8249ad2 to c11b2a1 Compare January 29, 2026 00:28

bgw added 3 commits January 30, 2026 14:06

Turbopack: Implement TraceRawVcs and NonLocalValue correctly for Effects

ea8aee6

Fix type complexity clippy lint

28bbbd5

Add comment about the spawn intentionally preventing Vc reads from fu…

fd04529

…nctioning

bgw force-pushed the bgw/effect-trace-raw-vcs branch from c11b2a1 to fd04529 Compare January 31, 2026 05:20

bgw force-pushed the bgw/effect-trait branch from a574d15 to 86cb33f Compare January 31, 2026 05:20

bgw mentioned this pull request Jan 31, 2026

Turbopack: Add FsError type, return it from write/write_link effects #89326

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Turbopack: Implement TraceRawVcs and NonLocalValue correctly for Effects #89133

Turbopack: Implement TraceRawVcs and NonLocalValue correctly for Effects #89133

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Turbopack: Implement TraceRawVcs and NonLocalValue correctly for Effects #89133

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Merging this PR will not alter performance

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