fix(types): emit auto-import paths as files, not directories

[danielroe]

🔗 Linked issue

originally reported against Nuxt: nuxt/nuxt#35248, but it reproduces in pure Nitro
also related: #1528, #4297

❓ Type of change

• 📖 Documentation (updates to the documentation, readme, or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

writeTypes emits const foo: typeof import('<path>').foo per auto-imported binding

for some packages, the path ends up being the package directory rather than a file; this works fine for TypeScript with moduleResolution: bundler, but Deno's TS host doesn't apply Node directory resolution to relative specifiers and bails

this PR treats ./ the same as an empty subpath & falls back to resolvedPath, which ends up having its extension stripped

both typescript + deno should resolve this equally well.

note: packages with different exports.types vs exports.imports (eg #2384) won't work correctly, either before or after this fix (but the error slightly changes 😆)

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[vercel]

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[coderabbitai]

📝 Walkthrough

Walkthrough

The PR fixes node module path resolution in Nitro's writeTypes function. When generating type declarations, the import path logic now uses lookupNodeModuleSubpath to compute subpaths and conditionally joins directory components only when the subpath is meaningful (not "./"), otherwise falling back to the previously resolved path. A new test validates this behavior with packages defining exports only at ".".

Changes

Node module subpath resolution in type declarations

Layer / File(s)	Summary
Path resolution fix and test validation src/build/types.ts, test/unit/types-imports.test.ts	writeTypes now uses lookupNodeModuleSubpath to determine if a subpath should be joined to the directory path; a new test verifies that import specifiers reference file paths rather than package directories for exports-only packages.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'fix(types): emit auto-import paths as files, not directories' follows conventional commits format with a clear 'fix' type prefix and descriptive scope.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description check	✅ Passed	The pull request description clearly relates to the changeset, explaining the bug fix for emitted auto-import paths and the exact changes made to resolve type path handling in both TypeScript and Deno.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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commit: 1700580