feat: using rspack EsmLibraryPlugin for better esm output #1273
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Pull Request Overview
This PR introduces experimental support for better ESM output using Rspack's EsmLibraryPlugin and adds module type detection for TypeScript files. The changes enable a new experiments.advancedEsm configuration option that generates more static-analysis-friendly ESM output with code splitting support, while also implementing automatic detection of module types based on file extensions (.mts, .cts) and package.json type fields.
Key changes:
- Added
experiments.advancedEsmconfiguration option for enhanced ESM output format - Implemented module type detection for .mts (ESM) and .cts (CommonJS) file extensions
- Updated test snapshots to reflect the new ESM output format with runtime chunks
Reviewed Changes
Copilot reviewed 50 out of 52 changed files in this pull request and generated 3 comments.
Show a summary per file
| File | Description |
|---|---|
| website/docs/*/config/lib/experiments.mdx | Added documentation for the new experiments.advancedEsm configuration option |
| website/docs/*/config/lib/_meta.json | Added experiments to documentation navigation |
| tests/scripts/shared.ts | Updated generateBundleEsmConfig to enable advancedEsm by default |
| tests/package.json | Reverted dependency version changes |
| tests/integration/**/index.test.ts | Updated test snapshots to match new ESM output format |
| tests/integration/package-json/** | Added test fixtures for package.json type field detection |
| packages/core/src/types/config.ts | Added LibExperiments type definition with advancedEsm option |
| packages/core/src/config.ts | Implemented EsmLibraryPlugin integration and module type detection logic |
| examples/**/rslib.config.ts | Enabled advancedEsm in example configurations |
| packages/plugin-dts/package.json | Reverted version changes |
Files not reviewed (1)
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JSerFeng
commented
Oct 16, 2025
| expect(entries.esm).toMatchInlineSnapshot(` | ||
| "import node_path from "node:path"; | ||
| const { join } = node_path; | ||
| const { join: join } = node_path; |
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not sure why, I'm looking into it
JSerFeng
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should check
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chenjiahan
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Summary
Using EsmLibraryPlugin for better ESM output
Now you can use
experiments.advancedEsmto enable new esm format.Compared to the previous, this supports split chunk, and every single output chunk can easily statically analyzed if scope hoisted. Not use rspack runtime to load chunks anymore
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