chore: remove logic of parallelCodeSplitting #12424

JSerFeng · 2025-12-11T09:52:25Z

Summary

Remove deprecated parallelCodeSplitting.

Checklist

Tests updated (or not required).
Documentation updated (or not required).

Note

Removes the deprecated experiments.parallelCodeSplitting option and deletes the parallel code-splitting implementation, consolidating chunk graph building to a single path.

Core:
- Delete parallel code-splitting implementation (new_code_splitter.rs, related helpers) and unify build_chunk_graph to the legacy path.
- Remove parallel_code_splitting from Experiments/builders and simplify code-splitting cache logic.
API/Bindings:
- Drop parallelCodeSplitting from TypeScript bindings (napi-binding.d.ts) and public API (core.api.md).
Config:
- Remove handling of experiments.parallelCodeSplitting from defaults, normalization, and types.
Docs:
- Remove documentation for experiments.parallelCodeSplitting (EN/ZN).
Tests/Benchmarks:
- Update snapshots and configs to exclude the option; remove parallel code-splitting benchmark and test variants.

^{Written by Cursor Bugbot for commit ecc27b0. This will update automatically on new commits. Configure here.}

netlify · 2025-12-11T09:52:31Z

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Copilot

Pull request overview

This PR removes the deprecated experiments.parallelCodeSplitting feature from Rspack. The feature was deprecated in version 1.6.2 due to severe performance regressions in edge cases with large numbers of cyclic chunks. The removal includes all associated code, configuration options, documentation, and tests.

Key Changes

Removed the parallelCodeSplitting configuration option from all language bindings (TypeScript, Rust)
Deleted the entire alternative code splitting implementation (~1,856 lines in new_code_splitter.rs)
Deleted the associated available_modules.rs module (~205 lines)
Simplified the build chunk graph logic to always use the legacy code splitter

Reviewed changes

Copilot reviewed 18 out of 19 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
website/docs/en/config/experiments.mdx	Removed English documentation for the deprecated option
website/docs/zh/config/experiments.mdx	Removed Chinese documentation for the deprecated option
packages/rspack/src/config/types.ts	Removed TypeScript type definition for `parallelCodeSplitting`
packages/rspack/src/config/normalization.ts	Removed normalization and deprecation warning logic
packages/rspack/src/config/defaults.ts	Removed default value assignment
packages/rspack/etc/core.api.md	Removed from API documentation
crates/rspack_core/src/options/experiments/mod.rs	Removed field from Rust `Experiments` struct
crates/rspack_core/src/compilation/mod.rs	Removed conditional logic and unused imports
crates/rspack_core/src/compilation/build_chunk_graph/new_code_splitter.rs	Deleted entire alternative implementation file
crates/rspack_core/src/compilation/build_chunk_graph/available_modules.rs	Deleted supporting module file
crates/rspack_core/src/compilation/build_chunk_graph/mod.rs	Removed `build_chunk_graph_new` function and module declarations
crates/rspack_core/src/compilation/build_chunk_graph/artifact.rs	Removed `NewCodeSplitter` from cache, removed `can_skip_rebuilding_new` method
crates/rspack_binding_api/src/raw_options/raw_experiments/mod.rs	Removed from Node.js binding
crates/rspack/src/builder/mod.rs	Removed builder method for the option
crates/node_binding/napi-binding.d.ts	Removed from TypeScript type definitions
tests/rspack-test/watchCases/build-chunk-graph/runtime-chunk-recover-error/rspack.config.js	Updated test to no longer test both code splitting variants
tests/rspack-test/defaultsCases/default/base.js	Updated defaults test expectation
crates/rspack/tests/snapshots/defaults__default_options.snap	Updated snapshot
xtask/benchmark/benches/groups/build_chunk_graph.rs	Removed benchmark for parallel code splitting

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Copilot · 2025-12-11T09:56:15Z

tests/rspack-test/watchCases/build-chunk-graph/runtime-chunk-recover-error/rspack.config.js

-module.exports = [true, false].map((parallelCodeSplitting, index) =>
-	config(index, parallelCodeSplitting)
-);
+module.exports = [0, 1].map(index => config(index));


The test now exports two identical configurations since parallelCodeSplitting was removed. This appears redundant - consider exporting a single configuration instead of duplicating it, or removing this test if it was specifically designed to test the parallelCodeSplitting feature difference.

Suggested change

module.exports = [0, 1].map(index => config(index));

module.exports = config(0);

github-actions · 2025-12-11T10:00:46Z

Rsdoctor Bundle Diff Analysis

Found 5 project(s) in monorepo.

📁 react-10k

Path: ../build-tools-performance/cases/react-10k/dist/rsdoctor-data.json

📌 Baseline Commit: 127d0af7b7 | PR: #12405

Metric	Current	Baseline	Change
📊 Total Size	5.7 MB	5.7 MB	0 B (0.0%)
📄 JavaScript	5.7 MB	5.7 MB	0 B (0.0%)
🎨 CSS	21.0 B	21.0 B	0 B (0.0%)
🌐 HTML	0 B	0 B	N/A
📁 Other Assets	0 B	0 B	N/A

📦 Download Diff Report: react-10k Bundle Diff

📁 react-5k

Path: ../build-tools-performance/cases/react-5k/dist/rsdoctor-data.json

📌 Baseline Commit: 127d0af7b7 | PR: #12405

Metric	Current	Baseline	Change
📊 Total Size	2.7 MB	2.7 MB	0 B (0.0%)
📄 JavaScript	2.7 MB	2.7 MB	0 B (0.0%)
🎨 CSS	21.0 B	21.0 B	0 B (0.0%)
🌐 HTML	0 B	0 B	N/A
📁 Other Assets	0 B	0 B	N/A

📦 Download Diff Report: react-5k Bundle Diff

📁 react-1k

Path: ../build-tools-performance/cases/react-1k/dist/rsdoctor-data.json

📌 Baseline Commit: 127d0af7b7 | PR: #12405

Metric	Current	Baseline	Change
📊 Total Size	823.6 KB	823.6 KB	0 B (0.0%)
📄 JavaScript	823.6 KB	823.6 KB	0 B (0.0%)
🎨 CSS	0 B	0 B	N/A
🌐 HTML	0 B	0 B	N/A
📁 Other Assets	0 B	0 B	N/A

📦 Download Diff Report: react-1k Bundle Diff

📁 ui-components

Path: ../build-tools-performance/cases/ui-components/dist/rsdoctor-data.json

📌 Baseline Commit: 127d0af7b7 | PR: #12405

Metric	Current	Baseline	Change
📊 Total Size	2.1 MB	2.1 MB	0 B (0.0%)
📄 JavaScript	2.0 MB	2.0 MB	0 B (0.0%)
🎨 CSS	83.0 KB	83.0 KB	0 B (0.0%)
🌐 HTML	0 B	0 B	N/A
📁 Other Assets	0 B	0 B	N/A

📦 Download Diff Report: ui-components Bundle Diff

📁 rome

Path: ../build-tools-performance/cases/rome/dist/rsdoctor-data.json

📌 Baseline Commit: 127d0af7b7 | PR: #12405

Metric	Current	Baseline	Change
📊 Total Size	984.3 KB	984.3 KB	0 B (0.0%)
📄 JavaScript	984.3 KB	984.3 KB	0 B (0.0%)
🎨 CSS	0 B	0 B	N/A
🌐 HTML	0 B	0 B	N/A
📁 Other Assets	0 B	0 B	N/A

📦 Download Diff Report: rome Bundle Diff

Generated by Rsdoctor GitHub Action

github-actions · 2025-12-11T10:05:09Z

📦 Binary Size-limit

Comparing 05ab715 to chore(ci): fix artifact discovery logic in Rsdoctor action (#12405) by yifancong

🎉 Size decreased by 258.38KB from 48.21MB to 47.96MB (⬇️0.52%)

codspeed-hq · 2025-12-11T10:09:27Z

CodSpeed Performance Report

Merging #12424 will not alter performance

_{Comparing chore/remove-new-code-splitting (05ab715) with main (127d0af)}

Summary

✅ 16 untouched
⏩ 1 skipped¹

1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩

JSerFeng · 2025-12-11T11:51:03Z

@cursor remove the needless second config, just export one config as the parallelCodeSplitting is removed tests/rspack-test/watchCases/build-chunk-graph/runtime-chunk-recover-error/rspack.config.js

cursor · 2025-12-11T11:51:13Z

Changed the watch-case config to export a single build variant now that parallelCodeSplitting is gone; the redundant array mapping was removed so the test only runs once.

module.exports = config(0);

No other files touched; let me know if you’d like this scenario parameterized differently.

_{Learn more about Cursor Agents}

Co-authored-by: 1114550440 <1114550440@qq.com>

CLAassistant · 2025-12-11T11:52:13Z

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
1 out of 2 committers have signed the CLA.

✅ JSerFeng
❌ cursoragent
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

cursor · 2025-12-11T11:52:16Z

Cursor Agent can help with this pull request. Just @cursor in comments and I'll start working on changes in this branch.
_{Learn more about Cursor Agents}

JSerFeng · 2025-12-11T11:55:28Z

@cursor remove extra config definition as well, use module.export = config

cursor · 2025-12-11T11:55:35Z

Dropped the helper factory and now export the config object directly (module.exports = { ... }) per the review note.
Output filename no longer uses an index placeholder since only a single build variant remains.

module.exports = {
	entry: {
		entry1: "./entry1.js",
		entry2: "./entry2.js"
	},
	output: {
		filename: "[name].js"
	},
	optimization: {
		runtimeChunk: "single"
	},
	experiments: {
		incremental: {
			buildChunkGraph: true
		}
	}
};

Ready for another pass if more cleanup is desired.

_{Learn more about Cursor Agents}

Co-authored-by: 1114550440 <1114550440@qq.com>

JSerFeng · 2025-12-12T04:21:23Z

tests/rspack-test/watchCases/build-chunk-graph/runtime-chunk-recover-error/rspack.config.js

 	},
 	output: {
-		filename: `[name].${index}.js`
+		filename: "[name].js"


改成 name.0.js

JSerFeng · 2025-12-12T04:21:47Z

@cursor fix the review comment above

JSerFeng · 2025-12-12T05:47:49Z

@cursor fix the review comment above

cursor · 2025-12-12T05:47:57Z

Updated the watch-case config so the emitted files end with .0, per the review:

	output: {
		filename: "[name].0.js"
	},

Config is still exported directly with a single build variant. Let me know if you need further tweaks.

_{Learn more about Cursor Agents}

Co-authored-by: 1114550440 <1114550440@qq.com>

JSerFeng · 2025-12-12T06:47:25Z

@cursor remove 2 extra error in runtime-chunk-recover-error/1/error.js

cursor · 2025-12-12T06:47:32Z

Trimmed runtime-chunk-recover-error/1/errors.js down to the two expected patterns so the watch test only asserts the unique errors:

module.exports = [
  /Module parse failed/,
  /JavaScript parse error: Expression expected/,
];

Let me know if there are other fixtures that still reference the removed parallel splitter.

_{Learn more about Cursor Agents}

Co-authored-by: 1114550440 <1114550440@qq.com>

chore: remove logic of parallel code splitting

ecc27b0

Copilot AI review requested due to automatic review settings December 11, 2025 09:52

JSerFeng requested review from h-a-n-a and hardfist as code owners December 11, 2025 09:52

JSerFeng marked this pull request as draft December 11, 2025 09:52

github-actions bot added the team The issue/pr is created by the member of Rspack. label Dec 11, 2025

Copilot started reviewing on behalf of JSerFeng December 11, 2025 09:53 View session

Copilot AI reviewed Dec 11, 2025

View reviewed changes

Fix: Only run runtime-chunk-recover-error test for one entry

3bfde05

Co-authored-by: 1114550440 <1114550440@qq.com>

Refactor: Simplify rspack config for runtime chunk recovery

1260e3b

Co-authored-by: 1114550440 <1114550440@qq.com>

JSerFeng commented Dec 12, 2025

View reviewed changes

Fix: Change runtime chunk filename to [name].0.js

bb0177a

Co-authored-by: 1114550440 <1114550440@qq.com>

Fix: Remove duplicate errors in runtime chunk recover test

05ab715

Co-authored-by: 1114550440 <1114550440@qq.com>

	module.exports = [0, 1].map(index => config(index));
	module.exports = config(0);

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chore: remove logic of parallelCodeSplitting #12424

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