app reset fails due to improper I/O

[ReubenVandezande]

Description

My nicegui tests run with pytest leave .nfs files in the .nicegui folder and cause my tests to fail.

I run my nicegui tests on a system that produces .nfs files when a file is deleted before I/O is properly terminated. Annoyingly, these files cannot be deleted by the user and only get cleaned up after the process finishes execution. The only file in the cache is storage-user-*.json so I assume that is the file handle which gets closed improperly.

My workaround is to simply move the .nicegui cache folder to trick the app into behaving correctly.

@pytest.fixture
def user(user: User) -> User:
    yield user
    try:
        app.reset()
    except OSError:
        # This is necessary since once of the file handles opened
        # by nicegui isn't closed properly and leaves a .nfs file
        # We move the cache folder and then delete later.
        if list(app.storage.path.glob(".nfs*")):
            tmp_path = Path(".to_delete", '.nicegui')
            tmp_path.parent.mkdir(exist_ok=True)
            if tmp_path.exists():
                shutil.rmtree(tmp_path)

            shutil.move(app.storage.path, tmp_path)
        app.reset()

[rodja]

@ReubenVandezande thanks for bringing this up. Network File Systems bring in a whole new level of complexity. But it might have uncovered a small flaw in our setup. I just created pull request #4314 which simply flushes the data after writing. Maybe that is enough to fix it. A bit more complicated, but probably more "correct" would be the fix I tried to sketch in #4315. Could you please try both and share your findings?

[ReubenVandezande]

These files show up under high system loads. I'll need to find a way to 1. do that and 2. not annoy everyone else in the process.