Some strange crash with chokidar watcher

[Omikhleia]

Observed on my Windows box: someObject.destroy() sometimes (but neither systematically nor even frequently) causes an abrupt exit with an "uncaughtException" trapped in 'on-exit.js', due to an EPERM error. The stack trace doesn't tell much beyond that and doesn't tell which file/directory caused it, but after having added try/catch's around all fs stuff in fs-db.js, it was still occurring - It only stopped (so far as it seems at least) when I commented out the chokidar watcher. (Sure, that's a pretty mean workaround, lol.)

Tracked here for the record, in any case it would be observed by others, but no investigation required yet, the point is maybe moot:

• It might be due to my modified fork, where I played with the directory structure and may have caused some havoc there (though I think I got the issue even before that. Will have to try to reproduce...)
• Or it might be Windows-specific, so well... ;)

[Omikhleia]

That's a chokidar known issue, apparently:
paulmillr/chokidar#324 (open since Jul 2015)

Still reproduced after forcing the upgrade to 1.6.0 (roomjs was requiring 1.4.x).

[Omikhleia]

Ah, pinpointed it, apparently.
As far as I can say, seems avoidable with chokidar (1.6.0 at least), assuming the calling code declares a .on("error", ...) handler

Thus:

• In fs-db.js, change this in setupWatcher():

    this.watcher.on('ready', () => {
      this.watcher
        .on('add', this.onFileAdded.bind(this))
        .on('change', this.onFileChanged.bind(this))
        .on('unlink', this.onFileRemoved.bind(this))
        // BEGIN PATCH
        .on('error', (error) => { 
            // Do some log here
        });
        // END PATCH
      this.emit('ready');

• and also fix the rmDir() method to gracefully accept errors

  rmDir(relpath) {
    const filepath = this.toFilepath(relpath);
    // BEGIN PATCH
    try {
      fs.rmdirSync(filepath);  
    } catch (err) { 
      // Do some log, possibly...
      // At least two observed cases here:
      // - ENOTEMPTY
      // - ENOENT
    }    
    // END PATCH
  }

The second patch is somewhat unrelated, it's notably triggered when deleting a directory from outside the game (so there might be a loophole elsewhere, chokidar notifiying roomjs, and then the object deletion triggering another fs-db action?), but also if the directory is not empty (e.g. I had the bad idea to put a non-game file in a directory, in the form of a readme.md :) - So it's probably still a reasonable safeguard to have a try/catch here.)

So far, no more random crashing observed.