Add support for with type text under a new experimental flag, following what webpack did by lukesandberg · Pull Request #89560 · vercel/next.js

lukesandberg · 2026-02-05T23:24:14Z

Summary

Adds support for the TC39 import ... with { type: "text" } proposal to Turbopack, allowing files to be imported as strings.

This is gated behind a new experimental flag turbopackImportTypeText.

// next.config.js
export default {
  experimental: {
    turbopackImportTypeText: true,
  },
}

import text from './file.txt' with { type: 'text' }
// text is a string containing the file contents

Related TC39 Proposals

type: "text" - Stage 2 - Import file contents as a string
type: "bytes" - Stage 2.7 - Import file contents as a Uint8Array (already supported via turbopackImportTypeBytes)

Implementation Details

Created TextSourceTransform which transforms any file into an ES module exporting the file contents as a string
Added ResourceHasModifier rule condition to match on ident modifiers, enabling proper module type resolution after source transforms
Refactored BytesSourceTransform to use the same pattern for consistency
Both transforms add a modifier to the ident (text_module / bytes_module) for uniqueness, allowing the same file to be imported both normally and with a type attribute

Using a source transform is simpler and allows the modules to participate in other bundler optimizations more easily (scope hoisting in particular)

This also fixes a few bugs where with imports would conflict with other module type rules:

if you attempted to import a .js file with type:'bytes' didn't work since the file extension matching would trigger first.
if you set a module type rule in your next config it would override the with attribute

Test Plan

Expanded e2e tests at test/e2e/turbopack-import-with-type/

lukesandberg · 2026-02-05T23:24:36Z

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nextjs-bot · 2026-02-05T23:36:14Z

Tests Passed

codspeed-hq · 2026-02-05T23:47:17Z

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing import_with_type_text_turbopack (6194f5d) with canary (09851e2)}

Summary

✅ 17 untouched benchmarks
⏩ 3 skipped benchmarks¹

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. ↩

nextjs-bot · 2026-02-06T00:10:50Z

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)	455ms	455ms	✓	▁█▁▁▁
Cold (Ready in log)	439ms	439ms	✓	▂█▁▁▂
Cold (First Request)	1.187s	1.141s	✓	▃█▄▁▃
Warm (Listen)	457ms	456ms	✓	▁█▁▁▁
Warm (Ready in log)	444ms	443ms	✓	▁█▁▁▁
Warm (First Request)	340ms	343ms	✓	▂█▂▁▁

📦 Dev Server (Webpack) (Legacy)

📦 Dev Server (Webpack)

Metric	Canary	PR	Change	Trend
Cold (Listen)	455ms	456ms	✓	▁▅▁▁▁
Cold (Ready in log)	438ms	439ms	✓	▅▅▄▁▁
Cold (First Request)	1.830s	1.848s	✓	▃▄▃▁▁
Warm (Listen)	457ms	456ms	✓	▁▄▁▁▁
Warm (Ready in log)	439ms	437ms	✓	▃▄▅▁▁
Warm (First Request)	1.841s	1.850s	✓	▂▄▃▁▁

⚡ Production Builds

Metric	Canary	PR	Change	Trend
Fresh Build	3.875s	3.900s	✓	▁█▁▁▁
Cached Build	3.878s	3.908s	✓	▁█▁▁▁

📦 Production Builds (Webpack) (Legacy)

📦 Production Builds (Webpack)

Metric	Canary	PR	Change	Trend
Fresh Build	13.862s	13.882s	✓	▁▄▂▁▁
Cached Build	13.905s	13.939s	✓	▁▃▂▁▁
node_modules Size	467 MB	467 MB	✓	█████

📦 Bundle Sizes

Bundle Sizes

⚡ Turbopack

Client

Main Bundles: **437 kB** → **437 kB** ⚠️ +13 B

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

Server

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	766 B	762 B	✓
Total	766 B	762 B	✅ -4 B

Build Details

Build Manifests

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

📦 Webpack

Client

Main Bundles

	Canary	PR	Change
5528-HASH.js gzip	5.47 kB	N/A	-
6280-HASH.js gzip	56.9 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	256 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	4.52 kB	-
2889.HASH.js gzip	N/A	169 B	-
5602-HASH.js gzip	N/A	5.48 kB	-
6948ada0-HASH.js gzip	N/A	62.5 kB	-
9544-HASH.js gzip	N/A	57.5 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	375 kB	⚠️ +474 B

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	617 B	615 B	✓
middleware-r..fest.js gzip	156 B	155 B	✓
middleware.js gzip	33 kB	33.2 kB	✓
edge-runtime..pack.js gzip	842 B	842 B	✓
Total	34.6 kB	34.8 kB	⚠️ +253 B

Build Details

Build Manifests

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

Build Cache

	Canary	PR	Change
0.pack gzip	3.85 MB	3.85 MB	🔴 +5.58 kB (+0%)
index.pack gzip	102 kB	102 kB	✓
index.pack.old gzip	103 kB	102 kB	✓
Total	4.05 MB	4.06 MB	⚠️ +4.82 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	165 kB	165 kB	✓
app-page.run...dev.js gzip	312 kB	312 kB	✓
app-page.run..prod.js gzip	165 kB	165 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	43.1 kB	43.1 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	39.3 kB	39.3 kB	✓
server.runti..prod.js gzip	62.7 kB	62.7 kB	✓
Total	2.8 MB	2.8 MB	⚠️ +3 B

turbopack/crates/turbopack/src/lib.rs

…ng what webpack did

…`with` attribute and add a test

nextjs-bot added created-by: Turbopack team PRs by the Turbopack team. tests Turbopack Related to Turbopack with Next.js. type: next labels Feb 5, 2026

mischnic reviewed Feb 6, 2026

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turbopack/crates/turbopack/src/lib.rs Outdated Show resolved Hide resolved

lukesandberg force-pushed the import_with_type_text_turbopack branch from 5800c64 to 1b6c494 Compare February 7, 2026 00:33

lukesandberg marked this pull request as ready for review February 7, 2026 03:22

lukesandberg requested a review from mischnic February 7, 2026 03:22

lukesandberg mentioned this pull request Feb 7, 2026

Simplify how json imports workby turning it into a source transform #89631

Draft

lukesandberg added 8 commits February 7, 2026 00:02

Add support for with type text under a new experimental flag, followi…

1ecaebb

…ng what webpack did

tweak

baed40c

add 'import js as thing' tests

bd4233c

simplify our transforms

e780d16

simplify the bytes transform

5a0f24c

fix json

9130565

Fix a relative ordering issue where a configuration could override a …

15ab1e4

…`with` attribute and add a test

disable under webpack

4f31ce0

lukesandberg force-pushed the import_with_type_text_turbopack branch from f5b9826 to 4f31ce0 Compare February 7, 2026 08:02

fix indent and side effects comment

6194f5d

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Add support for with type text under a new experimental flag, following what webpack did#89560

Add support for with type text under a new experimental flag, following what webpack did#89560
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