Stop the module walk at the drive root on Windows (infinite loop)

[DylanPiercey]

Description

The node_modules and imports walks terminated only on dir !== ctx.root, with root defaulting to "/" — which a drive-rooted Windows path never equals, since dirname("D:/") returns "D:/" itself. Any resolution that failed to resolve (missing package, or unsatisfiable exports under silent) therefore looped forever on Windows. Both walks now also stop when a directory is its own parent, i.e. the file system root.

Reproduced before the fix with resolveSync("missing-pkg", { from: "C:\\project\\src\\index.js", silent: true, ... }) — hard hang, killed by timeout; after the fix it returns undefined. New tests cover the missing-module throw, the silent variant, and #import walks from Windows paths without the root option — the existing Windows tests all passed root: "C:\\", which is why the loop was never hit in CI.

Motivation and Context

This is what's hanging the Windows CI job in marko-js/vite (https://github.com/marko-js/vite/actions/runs/29170390485/job/86590525203) since @marko/vite switched its CJS detection to resolve-sync: isCJSModule probes bare ids with silent: true on every .js resolve, and the first unresolvable id on a Windows runner spins forever.

Checklist:

• I have updated/added documentation affected by my changes.
• I have added tests to cover my changes.

🤖 Generated with Claude Code

https://claude.ai/code/session_01KZUGLZL3YoBToFLSEv2Nys

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[changeset-bot]

🦋 Changeset detected

Latest commit: cf39f9a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
resolve-sync	Patch

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Review details

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Configuration used: Organization UI

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📥 Commits

Reviewing files that changed from the base of the PR and between 14c7018 and cf39f9a.

📒 Files selected for processing (3)

• .changeset/windows-root-walk.md
• src/__tests__/index.test.ts
• src/index.ts

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix-windows-root-walk

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.01%. Comparing base (14c7018) to head (cf39f9a).

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #12      +/-   ##
==========================================
+ Coverage   96.95%   97.01%   +0.06%     
==========================================
  Files           1        1              
  Lines         394      402       +8     
  Branches       83       87       +4     
==========================================
+ Hits          382      390       +8     
  Misses         11       11              
  Partials        1        1              

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