perf: require rspack to improve startup performance#5673
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chenjiahan merged 1 commit intomainfrom Jul 25, 2025
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Pull Request Overview
This PR improves startup performance by replacing direct ES module imports of @rspack/core with a CommonJS require approach. The change addresses a ~30ms startup delay caused by Node.js's cjs-module-lexer when importing from the CJS-only Rspack bundle.
Key changes:
- Created a new
rspack.tsmodule that usescreateRequireto load Rspack via CommonJS - Updated all files to import
rspackfrom the new module instead of directly from@rspack/core - Modified plugin files to receive
rspackfrom the bundler chain context instead of importing it
Reviewed Changes
Copilot reviewed 13 out of 13 changed files in this pull request and generated no comments.
Show a summary per file
| File | Description |
|---|---|
| packages/core/src/rspack.ts | New module providing CommonJS-based Rspack import for performance |
| packages/core/src/server/devMiddlewares.ts | Updated to use centralized rspack import |
| packages/core/src/provider/rspackConfig.ts | Updated to use centralized rspack import |
| packages/core/src/provider/createCompiler.ts | Updated to use centralized rspack import |
| packages/core/src/provider/build.ts | Updated to use centralized rspack import |
| packages/core/src/plugins/sri.ts | Updated to receive rspack from chain context |
| packages/core/src/plugins/rspackProfile.ts | Updated to use centralized rspack import |
| packages/core/src/plugins/progress.ts | Updated to receive rspack from chain context |
| packages/core/src/plugins/output.ts | Updated to receive rspack from chain context |
| packages/core/src/plugins/moduleFederation.ts | Updated to use centralized rspack import |
| packages/core/src/plugins/minimize.ts | Updated to receive rspack from chain context |
| packages/core/src/pluginHelper.ts | Updated to use centralized rspack import |
| packages/core/src/index.ts | Updated to use centralized rspack import |
Comments suppressed due to low confidence (1)
packages/core/src/rspack.ts:10
- The variable name
rspackon line 10 shadows the exportedrspackon line 13, which could be confusing. Consider renaming the internal variable torspackModuleorrspackCorefor clarity.
const rspack =
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Summary
Currently, Rspack only provides a CJS bundle, so we use require to load it for better startup performance. If we use
import { rspack } from '@rspack/core', Node.js will usecjs-module-lexerto parse it, which slows down startup by 25-30ms.We can remove this module once
@rspack/coreprovides an ESM bundle in the future.Before
After
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