stop_event weird behavior

[CNSeniorious000]

Description

If watchfiles is imported inside a separated thread and stop_event is deleted after being set, it will be weirdly reset to False.

I can't clearly explain this, so I upload a minimal reproduction repo here:

https://github.com/CNSeniorious000/watchfiles-repro

Example Code

class Reloader:
    def start(self):
        from threading import Thread

        self.thread = Thread(target=self.run)
        self.thread.start()

    def stop(self):
        self._event.set()
        assert self._event.is_set()
        del self._event  # remove this line can solve the issue too
        self.thread.join()

    @cached_property
    def _event(self):
        return Event()

    def run(self):
        from watchfiles import watch  # move this line to the top of the file to solve the issue

        for _ in watch(".", stop_event=self._event):
            ...


reloader = Reloader()

reloader.start()
reloader.stop()

print("done")

In the snippet above, both threading.Event and asyncio.Event will fail.

Watchfiles Output

"done" will never show

Operating System & Architecture

Windows-11-10.0.26100-SP0
10.0.26100

Environment

the normal way

Python & Watchfiles Version

python: 3.13.2 (main, Feb 5 2025, 19:16:35) [MSC v.1942 64 bit (AMD64)], watchfiles: 1.0.4

Rust & Cargo Version

No response