Turbopack: remove ChunkableModuleReference trait #89745

mischnic · 2026-02-10T08:48:07Z

Previously, we checked "has to implement ChunkableModuleReference and .chunking_type() has to be Some"

Now, it's just ".chunking_type() has to be Some"

So not many logic changes were necessary.

99% of references are chunkable anyway, so the free try_downcast().is_some() to guard chunking_type() wasn't helping anyway.

mischnic · 2026-02-10T08:48:55Z

Turbopack: remove ChunkableModuleReference trait #89745 👈 (View in Graphite)
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codspeed-hq · 2026-02-10T08:53:58Z

Merging this PR will not alter performance

✅ 17 untouched benchmarks
⏩ 3 skipped benchmarks¹

_{Comparing mischnic/remove-ChunkableModuleReference (87d1a1c) with canary (c76b0fe)}

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. ↩

crates/next-core/src/hmr_entry.rs

turbopack/crates/turbopack-css/src/references/url.rs

nextjs-bot · 2026-02-10T09:33:50Z

Tests Passed

nextjs-bot · 2026-02-10T09:45:47Z

Stats from current PR

✅ No significant changes detected

📊 All Metrics

📖 Metrics Glossary

Dev Server Metrics:

Listen = TCP port starts accepting connections
First Request = HTTP server returns successful response
Cold = Fresh build (no cache)
Warm = With cached build artifacts

Build Metrics:

Fresh = Clean build (no .next directory)
Cached = With existing .next directory

Change Thresholds:

Time: Changes < 50ms AND < 10%, OR < 2% are insignificant
Size: Changes < 1KB AND < 1% are insignificant
All other changes are flagged to catch regressions

⚡ Dev Server

Metric	Canary	PR	Change	Trend
Cold (Listen)	454ms	455ms	✓	▅█▅▁█
Cold (Ready in log)	439ms	439ms	✓	▇▇▇▆▇
Cold (First Request)	1.136s	1.098s	✓	▇██▇▇
Warm (Listen)	456ms	456ms	✓	▁█▁▁▁
Warm (Ready in log)	443ms	442ms	✓	▃▇▄▁▆
Warm (First Request)	331ms	338ms	✓	▂▂█▁▂

📦 Dev Server (Webpack) (Legacy)

📦 Dev Server (Webpack)

Metric	Canary	PR	Change	Trend
Cold (Listen)	457ms	455ms	✓	▁▁▁█▁
Cold (Ready in log)	459ms	459ms	✓	▃▁▂█▂
Cold (First Request)	1.939s	1.964s	✓	▁▁▁█▁
Warm (Listen)	456ms	456ms	✓	▁▁▁█▁
Warm (Ready in log)	457ms	458ms	✓	▂▁▂█▁
Warm (First Request)	1.939s	1.952s	✓	▁▁▁█▁

⚡ Production Builds

Metric	Canary	PR	Change	Trend
Fresh Build	3.784s	3.748s	✓	▄▃▄▂▂
Cached Build	3.844s	3.772s	✓	▂▁▂▁▁

📦 Production Builds (Webpack) (Legacy)

📦 Production Builds (Webpack)

Metric	Canary	PR	Change	Trend
Fresh Build	14.568s	14.546s	✓	▁▁▁█▁
Cached Build	14.646s	14.616s	✓	▁▁▁█▁
node_modules Size	467 MB	467 MB	✓	▁▁▁▁▁

📦 Bundle Sizes

Bundle Sizes

⚡ Turbopack

Client

Main Bundles: **437 kB** → **437 kB** ⚠️ +11 B

81 files with content-based hashes (individual files not comparable between builds)

Server

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	756 B	759 B	✓
Total	756 B	759 B	⚠️ +3 B

Build Details

Build Manifests

	Canary	PR	Change
_buildManifest.js gzip	451 B	452 B	✓
Total	451 B	452 B	⚠️ +1 B

📦 Webpack

Client

Main Bundles

	Canary	PR	Change
5528-HASH.js gzip	5.47 kB	N/A	-
6280-HASH.js gzip	57 kB	N/A	-
6335.HASH.js gzip	169 B	N/A	-
912-HASH.js gzip	4.53 kB	N/A	-
e8aec2e4-HASH.js gzip	62.5 kB	N/A	-
framework-HASH.js gzip	59.7 kB	59.7 kB	✓
main-app-HASH.js gzip	255 B	254 B	✓
main-HASH.js gzip	39.1 kB	39.1 kB	✓
webpack-HASH.js gzip	1.68 kB	1.68 kB	✓
262-HASH.js gzip	N/A	4.53 kB	-
2889.HASH.js gzip	N/A	169 B	-
5602-HASH.js gzip	N/A	5.49 kB	-
6948ada0-HASH.js gzip	N/A	62.5 kB	-
9544-HASH.js gzip	N/A	57.6 kB	-
Total	230 kB	231 kB	⚠️ +613 B

Polyfills

	Canary	PR	Change
polyfills-HASH.js gzip	39.4 kB	39.4 kB	✓
Total	39.4 kB	39.4 kB	✓

Pages

	Canary	PR	Change
_app-HASH.js gzip	194 B	194 B	✓
_error-HASH.js gzip	183 B	180 B	🟢 3 B (-2%)
css-HASH.js gzip	331 B	330 B	✓
dynamic-HASH.js gzip	1.81 kB	1.81 kB	✓
edge-ssr-HASH.js gzip	256 B	256 B	✓
head-HASH.js gzip	351 B	352 B	✓
hooks-HASH.js gzip	384 B	383 B	✓
image-HASH.js gzip	580 B	581 B	✓
index-HASH.js gzip	260 B	260 B	✓
link-HASH.js gzip	2.49 kB	2.49 kB	✓
routerDirect..HASH.js gzip	320 B	319 B	✓
script-HASH.js gzip	386 B	386 B	✓
withRouter-HASH.js gzip	315 B	315 B	✓
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Total	7.97 kB	7.97 kB	✅ -1 B

Server

Edge SSR

	Canary	PR	Change
edge-ssr.js gzip	126 kB	126 kB	✓
page.js gzip	249 kB	249 kB	✓
Total	375 kB	376 kB	⚠️ +431 B

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	616 B	614 B	✓
middleware-r..fest.js gzip	156 B	155 B	✓
middleware.js gzip	33.3 kB	33.2 kB	✓
edge-runtime..pack.js gzip	842 B	842 B	✓
Total	34.9 kB	34.8 kB	✅ -137 B

Build Details

Build Manifests

	Canary	PR	Change
_buildManifest.js gzip	733 B	735 B	✓
Total	733 B	735 B	⚠️ +2 B

Build Cache

	Canary	PR	Change
0.pack gzip	3.84 MB	3.85 MB	🔴 +9.36 kB (+0%)
index.pack gzip	103 kB	103 kB	✓
index.pack.old gzip	103 kB	102 kB	🟢 1.08 kB (-1%)
Total	4.04 MB	4.05 MB	⚠️ +9.14 kB

🔄 Shared (bundler-independent)

Runtimes

	Canary	PR	Change
app-page-exp...dev.js gzip	315 kB	315 kB	✓
app-page-exp..prod.js gzip	167 kB	167 kB	✓
app-page-tur...dev.js gzip	315 kB	315 kB	✓
app-page-tur..prod.js gzip	167 kB	167 kB	✓
app-page-tur...dev.js gzip	312 kB	312 kB	✓
app-page-tur..prod.js gzip	166 kB	166 kB	✓
app-page.run...dev.js gzip	312 kB	312 kB	✓
app-page.run..prod.js gzip	166 kB	166 kB	✓
app-route-ex...dev.js gzip	70.5 kB	70.5 kB	✓
app-route-ex..prod.js gzip	49 kB	49 kB	✓
app-route-tu...dev.js gzip	70.5 kB	70.5 kB	✓
app-route-tu..prod.js gzip	49 kB	49 kB	✓
app-route-tu...dev.js gzip	70.1 kB	70.1 kB	✓
app-route-tu..prod.js gzip	48.8 kB	48.8 kB	✓
app-route.ru...dev.js gzip	70.1 kB	70.1 kB	✓
app-route.ru..prod.js gzip	48.7 kB	48.7 kB	✓
dist_client_...dev.js gzip	324 B	324 B	✓
dist_client_...dev.js gzip	326 B	326 B	✓
dist_client_...dev.js gzip	318 B	318 B	✓
dist_client_...dev.js gzip	317 B	317 B	✓
pages-api-tu...dev.js gzip	43.2 kB	43.2 kB	✓
pages-api-tu..prod.js gzip	32.9 kB	32.9 kB	✓
pages-api.ru...dev.js gzip	43.2 kB	43.2 kB	✓
pages-api.ru..prod.js gzip	32.8 kB	32.8 kB	✓
pages-turbo....dev.js gzip	52.5 kB	52.5 kB	✓
pages-turbo...prod.js gzip	39.4 kB	39.4 kB	✓
pages.runtim...dev.js gzip	52.5 kB	52.5 kB	✓
pages.runtim..prod.js gzip	39.4 kB	39.4 kB	✓
server.runti..prod.js gzip	62.7 kB	62.7 kB	✓
Total	2.8 MB	2.8 MB	⚠️ +3 B

lukesandberg · 2026-02-10T21:38:38Z

turbopack/crates/turbopack-core/src/reference/mod.rs

        .iter()
        .map(|reference| async {
-            if let Some(reference) =
-                ResolvedVc::try_downcast::<Box<dyn ChunkableModuleReference>>(*reference)


so this would be the most concerning try_downcast case, but since nearly everything is chunkable your theory is that this wasn't saving us very much

nextjs-bot · 2026-02-12T06:06:42Z

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approve CI run for commit: 87d1a1c

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nextjs-bot · 2026-02-12T06:06:42Z

Allow CI Workflow Run

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Note: this should only be enabled once the PR is ready to go and can only be enabled by a maintainer

nextjs-bot added created-by: Turbopack team PRs by the Turbopack team. Turbopack Related to Turbopack with Next.js. labels Feb 10, 2026

mischnic requested a review from a team February 10, 2026 08:49

mischnic marked this pull request as ready for review February 10, 2026 08:50

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crates/next-core/src/hmr_entry.rs Outdated Show resolved Hide resolved

turbopack/crates/turbopack-css/src/references/url.rs Outdated Show resolved Hide resolved

mischnic force-pushed the mischnic/remove-ChunkableModuleReference branch from 87cb976 to ae1112f Compare February 10, 2026 09:24

mischnic added 2 commits February 10, 2026 12:53

Turbopack: remove ChunkableModuleReference

f3ad7ce

fixup

87d1a1c

mischnic force-pushed the mischnic/remove-ChunkableModuleReference branch from ae1112f to 87d1a1c Compare February 10, 2026 11:53

lukesandberg reviewed Feb 10, 2026

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lukesandberg approved these changes Feb 10, 2026

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mischnic changed the title ~~Turbopack: remove ChunkableModuleReference~~ Turbopack: remove ChunkableModuleReference trait Feb 11, 2026

mischnic merged commit c28948e into canary Feb 11, 2026
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mischnic deleted the mischnic/remove-ChunkableModuleReference branch February 11, 2026 08:46

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Turbopack: remove ChunkableModuleReference trait #89745

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Turbopack: remove ChunkableModuleReference trait #89745

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