Build: Fix dts bundling external detection

[mrginglymus]

• Closes [Bug]: 10.0.0-beta.0 - some types not bundled #32365

What I did

The logic for determining if an import was external was flawed:-

storybook/scripts/build/utils/dts-process.ts

Line 26 in 069516a

(dep) => id.startsWith(dep) || id.includes(`${sep}node_modules${sep}${dep}${sep}`)

The id.startsWith(dep) was presumably used instead of id === dep in order to catch subpath imports. However, because no / was included, it also matches substrings. Given that react is fixed as an external dependency, all dependencies starting with react (e.g. react-router-dom) are also, incorrectly, marked as external.

The change adds a simple equality check, and updates the startsWith to include a trailing / to ensure only subpath imports are matched.

Checklist for Contributors

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  MIGRATION.MD

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  Available labels

  • bug: Internal changes that fixes incorrect behavior.
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  • dependencies: Upgrading (sometimes downgrading) dependencies.
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[nx-cloud]

View your CI Pipeline Execution ↗ for commit 1199f3d

Command	Status	Duration	Result
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☁️ Nx Cloud last updated this comment at 2025-09-01 21:15:24 UTC

[storybook-app-bot]

Package Benchmarks

^{Commit: 1199f3d, ran on 1 September 2025 at 21:48:57 UTC}

The following packages have significant changes to their size or dependencies:

@storybook/nextjs

	Before	After	Difference
Dependency count	529	529	0
Self size	928 KB	928 KB	🚨 +126 B 🚨
Dependency size	58.14 MB	58.27 MB	🚨 +130 KB 🚨
Bundle Size Analyzer	Link	Link

[JReinhold]

Thanks for spotting this!

[ndelangen]

Thanks a lot! Great catch!