Windows directory watcher stops working after some time #37233
Description
Original issue on the watcher package dart-lang/tools#1713, related issue in build_runner dart-lang/webdev#436.
I created a simple repro below that uses vanilla Directory.watch. You can run each of these scripts at the same time to repro, which exposes a few issues:
- If you start the watch script after the file modifying script is already running, then it won't see any events at all.
- After a while (few thousand events, but not consistent), the directory watcher script simply exits.
- The watcher script terminates in some weird way, I never see the
Stream closed!!message on stdout, but the process does exit. There is no unhandled exception that surfaces either.
File modification script, edits a single file in a loop:
import 'dart:io';
void main() async {
var i = 0;
var file = File('out.txt');
await file.create();
while (true) {
i++;
await file.writeAsString('$i');
}
}
Watcher script, logs watch events:
import 'dart:io';
main() async {
var i = 0;
await for (var event in Directory.current.watch(recursive: true)) {
print('$i: $event');
i++;
}
print('Stream closed!!');
}As a result of this we have to use a polling watcher, which doesn't perform well.