fix(vfsevents): fix fsnotify Windows drive-letter path round-trip

[funkyshu]

fsnotify: Windows drive-letter file:// URI round-trip produces an invalid path (#344)

The fsnotify watcher's Start() built the path passed to fsnotify.Add() by naively stripping the "file://" prefix off the location's URI (file:///C:/Temp/... -> /C:/Temp/...). For a Windows drive-letter path this leaves a stray leading slash, which Windows rejects:

failed to add watch path: failed to add watch path /C:/Temp/TestDebouncingEdgeCases3938112569/001: GetFileAttributes: The filename, directory name, or volume label syntax is incorrect.

convertEvent() had the mirror problem on the way back out: it built the event's URI by naively prepending "file://" to the native OS path fsnotify reports (C:\Temp\...), producing an invalid URI with backslashes and no leading slash before the drive letter.

Fix

Added vfsPathToNative/nativePathToURI helpers (each with a GOOS-parameterized ...OS variant so the Windows-specific behavior can be unit tested from any platform) that correctly convert between VFS-style paths (forward slashes, leading slash before a drive letter) and native OS paths in both directions. Start() now uses vfsPathToNative before calling fsnotify.Add(), and convertEvent() now uses nativePathToURI when building the event URI.

Tests

• Re-enabled the fsnotify watcher tests that were temporarily skipped on Windows for this issue in fix: sftp conn-timer data race + enable -race in CI (fixes #338) #343 (TestFSNotifyWatcherTestSuite, TestDebouncing, TestDebouncingEdgeCases, TestEventAnalysis), updating a couple of assertions that previously assumed a native path could be substring/equality-compared against a file:// URI.
• Added path_test.go with GOOS-parameterized unit tests for the new conversion helpers (drive-letter stripping/re-adding, separator conversion, round-trip) so the Windows code path is verified without needing a Windows runner.

Fixes #344

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[Copilot]

Pull request overview

This PR fixes Windows drive-letter file:// URI round-tripping in the contrib/vfsevents fsnotify watcher by introducing explicit conversions between VFS-style paths/URIs and native OS paths. This prevents invalid watch paths like /C:/... from reaching fsnotify.Add() on Windows and ensures emitted event URIs are valid file:///C:/... URLs.

Changes:

• Add vfsPathToNative / nativePathToURI helpers (plus GOOS-parameterized variants) and use them in Start() and convertEvent().
• Re-enable and update fsnotify watcher tests to compare against normalized file:// URIs across platforms.
• Add unit tests for the new path conversion helpers and record the fix in the contrib changelog.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
contrib/vfsevents/watchers/fsnotify/fsnotify.go	Fixes Windows path handling by converting VFS URI paths to native paths for fsnotify.Add(), and native event paths back to file:// URIs.
contrib/vfsevents/watchers/fsnotify/path_test.go	Adds unit tests for the new conversion helpers (including Windows drive-letter behavior via GOOS parameterization).
contrib/vfsevents/watchers/fsnotify/fsnotify_test.go	Re-enables Windows tests and updates assertions to compare event URIs using the new helper.
contrib/vfsevents/watchers/fsnotify/event_analysis_test.go	Un-skips Windows and updates URI/path substring checks to be slash-normalized.
contrib/vfsevents/watchers/fsnotify/debounce_test.go	Un-skips Windows tests now that drive-letter conversion is fixed.
contrib/vfsevents/CHANGELOG.md	Documents the Windows drive-letter file:// round-trip fix under Unreleased.

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[funkyshu]

Pushed a follow-up commit addressing self-review feedback:

• Drive-root paths: a location watching an entire Windows drive (e.g. C:\) was being reduced to a bare "C:", which Windows interprets as "current directory on drive C", not the drive root. vfsPathToNativeOS now re-adds the trailing separator when stripping leaves a bare drive letter.
• Authority-safety: Start() now derives the watch path via Location.Path() instead of hand-parsing Location.URI(), so a location with a non-empty authority (e.g. file://host/C:/Temp) can no longer have the authority swept into the path and mangled by the drive-letter conversion. Extracted into a small, directly testable resolveWatchPath/resolveWatchPathOS pair.
• Authority round-trip: convertEvent()'s URI conversion now preserves the location's authority instead of silently dropping it.
• Cross-referenced the near-duplicate drive-letter logic in backend/os/file.go's toNativeOSPath (can't import across module boundaries) so the two stay in sync going forward.
• Extended path_test.go with cases for the drive-root fix, authority preservation, and a new resolveWatchPathOS suite that builds real (virtual) vfs.Locations via vfssimple to exercise the full location -> native-path path, still without needing a Windows runner.

[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (1)

contrib/vfsevents/watchers/fsnotify/fsnotify.go:569

• The comment says this function “mirrors” backend/os.toNativeOSPath, but the implementations already diverge: this version also normalizes a bare drive letter ("C:") into an explicit drive root ("C:\") after trimming trailing slashes. Please clarify the note so future changes don’t incorrectly assume the logic is identical.

// NOTE: mirrors the unexported toNativeOSPath in
// github.com/c2fo/vfs/v7/backend/os/file.go; keep both in sync if the Windows
// drive-letter handling changes.