No file system events observed when not using recursive mode

[cedrickring]

We tried to listen for events on a single file, without the need for watching recursively. However without specifying recursive=True, no events were observed.

Platform: macOS 12.6 & Ubuntu 18.04
Python: 3.9.14

Code to reproduce:

import sys
import time
import logging
from watchdog.observers import Observer
from watchdog.events import LoggingEventHandler

if __name__ == "__main__":
    logging.basicConfig(level=logging.INFO,
                        format='%(asctime)s - %(message)s',
                        datefmt='%Y-%m-%d %H:%M:%S')
    path = sys.argv[1] if len(sys.argv) > 1 else '.'
    event_handler = LoggingEventHandler()
    observer = Observer()
    observer.schedule(event_handler, path)
    observer.start()
    try:
        while True:
            time.sleep(1)
    finally:
        observer.stop()
        observer.join()

and launching with: python file.py <path to single file>.

Also using the FSEventsObserver on macOS didn't change the outcome. Only specifying recursive=True did.

[kurtmckee]

I don't think the underlying operating system calls support watching a single file -- the watchdog code and the underlying OS API's document that it's only supported to watch a directory.

While it may be possible to specify a file path without triggering an error, it's not supported.

[cedrickring]

I totally agree with your points. However, the docs should point out that you always need to watch recursively or just default to it on some machines...

[Rosuav]

Agreed. I got bitten by this today; a script that worked absolutely fine on my Linux box (Debian Bullseye, inotify) utterly failed to report anything on my client's Mac. Setting recursive=True made it work. Having this be the default when using FSEvents would solve that issue.

[BoboTiG]

I agree that recursive could be true by default for FSEvents. Anyone willing to chime in? I will be happy to review a PR :)

[Rosuav]

I'll have a whack at it, but I don't have a Mac to test on, so all I can say is, the tests haven't started failing on Linux.

#1013