kqueue always returns an "No such file or directory" on Watcher::unwatch

[squidfunk]

System details

• OS/Platform name and version: macOS 13.0 Ventura
• Rust version (if building from source): rustc --version: rustc 1.81.0 (eeb90cda1 2024-09-04)
• Notify version (or commit hash if building from git): 7.0.0 with macos_kqueue feature flag
• If you're running as a privileged user (root, System): -
• If you're running in a container, details on the runtime and overlay: -
• If you're running in a VM, details on the hypervisor: -

What you did (as detailed as you can)

I'm trying to use kqueue on macOS, but Watcher::unwatch always returns an error. Here is a minimal reproduction:

mkdir kqueue_repro && cd kqueue_repro
cargo init .
cargo add notify --features macos_kqueue

Source of the program:

use std::error::Error;
use std::path::PathBuf;
use notify::{recommended_watcher, RecursiveMode, Watcher};

fn main() -> Result<(), Box<dyn Error>> {
    let path = PathBuf::from("src");

    let mut watcher = recommended_watcher(|event| println!("{:?}", event))?;
    watcher.watch(&path, RecursiveMode::Recursive)?;
    watcher.unwatch(&path)?; // <- This always returns "No such file or directory"

    Ok(())
}

Stepping through the source of kqueue.rs, and subsequently the kqueue crate, the error seems to be triggered in Watcher::remove_filename, specifically when calling Watcher::delete_kevents. What's also very weird is that when I try to set a break point in this function CodeLLDB goes absolutely nuts and allocates more than 40 GB before my computer goes poof.

What you expected

Watcher::unwatch does not throw.

What happened

Error: Error { kind: Generic("No such file or directory (os error 2) about [\".../src\"]"), paths: [] }

[alexvoss]

Ran the reproduction and it shows the same error on my MacOS Sonoma 14.7 (23H124) machine.

rustc --version 
rustc 1.83.0 (90b35a623 2024-11-26) (Homebrew)