Replace sync with async fs

[PolarBearEs]

No description provided.

[greptile-apps]

Greptile Summary

This PR replaces synchronous std::fs and Path::exists() calls with async equivalents — either tokio::fs directly or tokio::task::spawn_blocking wrappers — to avoid blocking the async executor during filesystem operations. A secondary improvement is the consistent elimination of TOCTOU-prone check-then-act patterns (e.g., if !path.exists() { return Ok(None) }) in favour of attempting the operation and handling ErrorKind::NotFound.

• AuthResolver::new is restricted to #[cfg(test)]; a new new_async constructor wraps load_docker_config in spawn_blocking and is used in all production call sites.
• Synchronous helpers in store/fs.rs (read_json_if_exists, reconcile_partial_file) and new async wrappers in store/mod.rs (atomic_write_bytes_blocking, ensure_store_layout_blocking, etc.) replace the direct blocking calls that previously ran on the async executor.
• Path::exists() is replaced by tokio::fs::try_exists throughout; unlike exists(), try_exists propagates I/O errors other than NotFound rather than silently returning false.

Confidence Score: 5/5

Safe to merge — all changed code paths are correct and the async migration is consistent throughout.

The change is a mechanical but thorough conversion: blocking filesystem calls are moved off the async executor via spawn_blocking wrappers, and TOCTOU check-then-act patterns are replaced with operation-first + NotFound matching. The unusual implicit-return pattern used in save_reference and load_reference is already established elsewhere in the module and is correct. No logic paths were altered beyond the async/error-handling improvements.

No files require special attention. src/store/mod.rs has the most churn but all changes are consistent with the pattern established earlier in the file.

Important Files Changed

Filename	Overview
src/store/mod.rs	Largest change: wraps all blocking I/O in spawn_blocking helpers; replaces Path::exists() with tokio_fs::try_exists; adds remove_file_if_exists helper. Logic is consistent and TOCTOU-safe.
src/store/fs.rs	read_json_if_exists and reconcile_partial_file updated to match on ErrorKind::NotFound instead of pre-checking existence, eliminating TOCTOU races.
src/auth.rs	new() restricted to #[cfg(test)]; new_async() added for production use via spawn_blocking. load_docker_config switches to ErrorKind::NotFound matching.
src/serve_registry/server.rs	Single change: path.exists() → tokio_fs::try_exists. Errors beyond NotFound now propagate instead of silently returning false.
src/export/oci_archive.rs	blob_path().exists() → tokio_fs::try_exists for missing-blob detection. Correct and minimal change.
src/pull/orchestrator.rs	AuthResolver::new() replaced with new_async().await. No logic changes.
src/runtime.rs	AuthResolver::new() replaced with new_async().await. No logic changes.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Caller: pull / serve] --> B[AuthResolver::new_async]
    B --> C[spawn_blocking: load_docker_config]
    C -->|NotFound| D[Ok: None]
    C -->|Ok| E[Ok: DockerConfig]
    C -->|Other error| F[Err propagated]

    A2[Store::open / open_active] --> G[ensure_directory_blocking]
    G --> H{shared_lock?}
    H -->|yes| I[acquire_shared_cache_lock]
    H -->|no| J[lock = None]
    I --> K[ensure_store_layout_blocking]
    J --> K
    K --> L[Store ready]

    L --> M[save_blob_bytes]
    M --> N[tokio_fs::try_exists]
    N -->|exists + complete| O[return Ok early]
    N -->|missing| P[atomic_write_bytes_blocking]

    L --> Q[save_reference]
    Q --> R[spawn_blocking: atomic_write_json]

    L --> S[load_reference]
    S --> T[spawn_blocking: read_json_if_exists]
    T -->|NotFound| U[Ok: None]
    T -->|Ok| V[Ok: Some record]

Loading

_{Reviews (1): Last reviewed commit: "Replace sync with async fs" | Re-trigger Greptile}