GeezerVison

Walkthrough

Changes to crates/vm/src/stdlib/os.rs optimize Windows directory iteration by pre-caching lstat metadata in DirEntry objects using OnceCell. The public lstat function signature changed from accepting OsPathOrFd<'_> to OsPath, with implementation forwarding to stat with FollowSymlinks(false). Platform-conditional cache initialization handles Windows and non-Windows paths separately.

Changes

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Areas requiring extra attention:

• Public API signature change for lstat(): verify all call sites are compatible with the new OsPath-only parameter
• Windows-specific pre-caching logic: ensure win32_xstat integration correctly populates OnceCell and handles edge cases (removed files, permission errors)
• Platform-conditional initialization: confirm non-Windows codepaths maintain original OnceCell behavior and performance characteristics
• DirEntry construction: validate that pre-cached vs. empty lstat assignments don't introduce cache inconsistencies or memory leaks

Possibly related PRs

• Fix os.remove #6352: Modifies the same DirEntry/ScandirIterator and Windows-specific scandir/lstat handling with DirEntry construction and Windows metadata logic changes.
• windows umask, win32_xstat_slow_impl, fake EXT_SUFFIX #6340: Implements the win32_xstat functionality that this PR integrates into lstat pre-caching for directory iteration.

Poem

🐰 Hops through Windows paths with glee,
Caching stat before it's free,
OnceCell guards the metadata's keep,
While scandir's cache runs swift and deep! ✨

Pre-merge checks and finishing touches

Learnt from: moreal
Repo: RustPython/RustPython PR: 5847
File: vm/src/stdlib/stat.rs:547-567
Timestamp: 2025-06-27T14:47:28.810Z
Learning: In RustPython's stat module implementation, platform-specific constants like SF_SUPPORTED and SF_SYNTHETIC should be conditionally declared only for the platforms where they're available (e.g., macOS), following CPython's approach of optional declaration using #ifdef checks rather than providing fallback values for other platforms.

Learnt from: moreal
Repo: RustPython/RustPython PR: 5847
File: vm/src/stdlib/stat.rs:547-567
Timestamp: 2025-06-27T14:47:28.810Z
Learning: In RustPython's stat module implementation, platform-specific constants like SF_SUPPORTED and SF_SYNTHETIC should be conditionally declared only for the platforms where they're available (e.g., macOS), following CPython's approach of optional declaration using #ifdef checks rather than providing fallback values for other platforms.

Learnt from: moreal
Repo: RustPython/RustPython PR: 5847
File: vm/src/stdlib/stat.rs:547-567
Timestamp: 2025-06-27T14:47:28.810Z
Learning: In RustPython's stat module implementation, platform-specific constants like SF_SUPPORTED and SF_SYNTHETIC should be conditionally declared only for the platforms where they're available (e.g., macOS), following CPython's approach of optional declaration rather than providing fallback values for other platforms.

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