Make VFS locking APIs explicit by removing default lock/unlock implementations

[Copilot]

This change removes implicit locking behavior from the Vfs trait to reduce accidental misuse. lock, unlock, and check_reserved_lock are now required trait methods, marking an intentional breaking change for the next major/minor incompatible release (0.7.0).

• Trait API (breaking)

  • Removed default bodies for:
    • Vfs::lock
    • Vfs::unlock
    • Vfs::check_reserved_lock
  • Implementers must now define locking semantics explicitly.

• Internal/example implementers updated

  • Updated MockVfs test implementation to provide the required methods.
  • Updated examples/memvfs.rs to implement check_reserved_lock in addition to existing lock/unlock methods.

• Changelog

  • Added 0.7.0 (unreleased) entry documenting the incompatible API change and what downstream implementers must do.

pub trait Vfs: Send + Sync {
    // ...
    fn lock(&self, handle: &mut Self::Handle, level: LockLevel) -> VfsResult<()>;
    fn unlock(&self, handle: &mut Self::Handle, level: LockLevel) -> VfsResult<()>;
    fn check_reserved_lock(&self, handle: &mut Self::Handle) -> VfsResult<bool>;
    // ...
}

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Make locking VFS methods mandatory</issue_title>
<issue_description>This will result in an incompatible release, but will make it less of a footgun to use. If users want existing behavior, they can stub back in the default methods.</issue_description>

<agent_instructions>remove the default implementations of lock, unlock, and check locked methods on the vfs trait. fix the example vfs and tests if needed. add changelog entry for 0.7.0 (unreleased) with a clear message on the incompatible version bump</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Make locking VFS methods mandatory #69

---

🔒 GitHub Advanced Security automatically protects Copilot coding agent pull requests. You can protect all pull requests by enabling Advanced Security for your repositories. Learn more about Advanced Security.