crash on macOS (fsevent) after watching same file twice, then unwatching

[cmyr]

The following snippet consistently crashes for me:

        let (tx, rx) = channel();
        let path = PathBuf::from("/usr/local/bin/git");
        let mut w = watcher(tx, Duration::from_secs(1)).unwrap();
        w.watch(&path, RecursiveMode::NonRecursive).unwrap();
        w.watch(&path, RecursiveMode::NonRecursive).unwrap();
        w.unwatch(&path).unwrap();
    }

I'm not sure what I should expect if attempting to explicitly watch the same file twice; it might be reasonable to either return an error from watch?

edit: I'm now wondering if this crash isn't due to modifying the underlying cfarray during iteration (here) , and ending up out of bounds.

I can put together a PR for this, but I wonder if we shouldn't also have some clearer expectations around how to behave with duplicate entries? Since this is going to be (likely) very implementation dependent, I suspect we should disallow it? I'll defer to @passcod on that.

[passcod]

My plan would be more to silently ignore duplicate paths. This is how it's shaping up to be in the next version. ("frontend" would never pass overlapping or duplicate paths to "backend")

[cmyr]

@passcod sounds good. I expect to be making quite extensive use of this crate in xi over the next little while, and I should have some downtime in december; if you're doing a rewrite and want a hand with anything feel free to ping me.

[passcod]

Thanks — If you subscribe to the discussion in #117... I might not follow that design precisely but I'll chime in there when I'm getting to it seriously.