refactor: migrate to tsdown

[sxzz]

Summary by CodeRabbit

• Chores
  • Updated build scripts and development dependencies to use a new build tool.
  • Adjusted configuration files to align with the new build process.

[coderabbitai]

Walkthrough

The build system was switched from tsup to tsdown. This involved updating build scripts and development dependencies in package.json, changing import sources in configuration files, and removing two configuration options specific to tsup.

Changes

Files	Change Summary
package.json	Replaced tsup with tsdown in build scripts and devDependencies.
tsdown-runtime.config.ts	Updated imports from tsup to tsdown and changed config import path accordingly.
tsdown.config.ts	Changed imports from tsup to tsdown; removed cjsInterop and splitting from options object.

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📜 Recent review details

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📥 Commits

Reviewing files that changed from the base of the PR and between a73a3eb and 2fe0da3.

⛔ Files ignored due to path filters (1)

• pnpm-lock.yaml is excluded by !**/pnpm-lock.yaml

📒 Files selected for processing (3)

• package.json (2 hunks)
• tsdown-runtime.config.ts (1 hunks)
• tsdown.config.ts (1 hunks)

🔇 Additional comments (5)

tsdown.config.ts (2)

1-1: Package import updated to tsdown.

Import source updated from 'tsup' to 'tsdown' as part of the migration.

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3-15: Properties removed from commonOptions.

The 'cjsInterop' and 'splitting' properties were removed from the configuration. These options are likely not supported or needed in tsdown.

tsdown-runtime.config.ts (1)

1-2: Import sources updated for tsdown migration.

Both imports have been updated:

1. 'defineConfig' now from 'tsdown' instead of 'tsup'
2. 'commonOptions' now from './tsdown.config' instead of './tsup.config'

package.json (2)

108-109: Build commands updated to use tsdown.

Build scripts correctly updated to use the new tool and configuration files.

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185-185:

✅ Verification successful

Dependency updated from tsup to tsdown.

Replaced tsup with tsdown version ^0.9.6.

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🌐 Web query:

Is tsdown a stable replacement for tsup? What are the differences?

💡 Result:

Is tsdown a stable replacement for tsup? Differences Explained

tsdown is positioned as a modern, fast, and library-focused alternative to tsup, and recent developments indicate that it is both compatible and a promising upgrade for most use cases—especially for library bundling in the TypeScript ecosystem.

Stability and Maturity

• Stability: As of April 2025, tsdown is actively maintained, recently released (v0.9.1), and reports 100% JSR score, suggesting a high degree of reliability and adoption for production usage[9][4].
• Migration Compatibility: tsdown is explicitly designed to be compatible with tsup’s main options and features. The migration process is streamlined: a dedicated command (npx tsdown migrate) is provided, ensuring a smooth transition from tsup with minimal changes required[1][3][6][9].
• Codebase Heritage: tsdown’s codebase incorporates and builds upon code from tsup, ensuring that common practices and configurations from tsup projects are well-supported[1][3][6][9].

Major Differences

Feature	tsup	tsdown
Underlying Bundler	esbuild	Rolldown (Rust-based, much faster)
Performance	Fast (esbuild-optimized)	Even faster (Rolldown-optimized, written in Rust)
Focus	General-purpose JS/TS bundling	Library bundling (TypeScript/JavaScript)
Default Experience	Simple, but may require more config for libraries	Out-of-the-box for libraries; minimal config
Plugin Ecosystem	esbuild and some Rollup plugins	Full Rollup, Rolldown, unplugin & some Vite plugins
Type Declarations (.d.ts)	Supported (can require config)	Automatic generation built-in
Multiple Output Formats	Supported	Built-in for esm, cjs, and iife
Migration Tool	N/A	Provided (tsdown migrate command)
Integration	Standalone	Part of Rolldown ecosystem, future-ready (Vite Library)

Technical Distinctions

• Performance: tsdown is notably faster thanks to Rolldown’s Rust core[2][3][6].
• Configuration: tsdown minimizes configuration, offering sensible defaults for most library needs[2].
• Ecosystem Extensibility: tsdown supports the entire Rolldown and most of the Rollup plugin ecosystems, offering more flexibility than tsup[2][3][6].
• Future-Proof: tsdown is described as the “official project of Rolldown” and is expected to be foundational for tools like Rolldown Vite’s Library Mode, indicating ongoing support and integration with modern tooling[2].

Migration Considerations

• A migration tool (npx tsdown migrate) is available to convert tsup-based projects, minimizing friction[1][3][6][9].
• The migration may modify configuration files, so committing or backing up before running is advised[1].

Conclusion

tsdown is a stable and, in many cases, superior replacement for tsup, especially for library bundling. It offers better performance, a richer ecosystem, and easier migration for existing tsup users. Projects focused on building libraries with TypeScript or JavaScript will likely benefit most from switching[1][2][3][6][9]. However, users deeply tied to the esbuild ecosystem or with highly custom build requirements not addressed by tsdown may want to test migration on a non-critical project first.

Citations:

• 1: https://tsdown.dev/guide/migrate-from-tsup
• 2: https://tsdown.dev/guide/
• 3: https://github.com/sxzz/tsdown
• 4: https://github.com/rolldown/tsdown/releases
• 5: https://www.npmjs.com/package/tinyglobby?activeTab=dependents
• 6: https://github.com/rolldown/tsdown
• 7: https://dspace.mit.edu/bitstream/handle/1721.1/149622/MIT-LCS-TR-354.pdf?sequence=1&isAllowed=y
• 8: https://scholarworks.uvm.edu/cgi/viewcontent.cgi?article=1050&context=calsfac
• 9: https://jsr.io/@sxzz/tsdown
• 10: https://boa.unimib.it/retrieve/af032b4d-614a-4ada-b657-48fd1e772c8f/Kang-2024-Nature%20Computational%20Science-Arxiv-PrePrint.pdf

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Approve tsdown replacement

tsdown ^0.9.6 is a production-ready, actively maintained alternative to tsup with faster Rust-powered bundling, built-in type declaration support, and a dedicated migration tool (npx tsdown migrate). This change can be merged as is.

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[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License

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[pkg-pr-new]

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npm i https://pkg.pr.new/unplugin-vue-router@629

commit: 2fe0da3

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 62.35%. Comparing base (a73a3eb) to head (2fe0da3).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #629   +/-   ##
=======================================
  Coverage   62.35%   62.35%           
=======================================
  Files          32       32           
  Lines        3140     3140           
  Branches      586      586           
=======================================
  Hits         1958     1958           
  Misses       1176     1176           
  Partials        6        6           

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