on 'op' callback firing multiple times per each submitOp

[mdelbuono]

Hi I have the following code:

shareDoc.on('op', (ops, source) => {
    for (let op of ops) {
        this._dispatchOperation(op);
    }
});

The _dispatchOperation method gets called 4 times for each submitOp with the same ops object and source=true.

Is this by design or is it a bug?

In my case it is not what I want, therefore I modified the code as follows.

this._lastOps = null;
shareDoc.on('op', (ops, source) => {
    if (lodash.isEqual(ops, this._lastOps)) return;
    this._lastOps = ops;
    for (let op of ops) {
        this._dispatchOperation(op);
    }
});

Is this ok or the three op notifications that I am ignoring may be important?

[nickasd]

I'm experiencing the same issue but I'm not sure that they are related. In my case I noticed that the callback is fired for each doc.on('op', ...) call, even when calling doc.destroy() in between. In my opinion, either doc.destroy() should remove all registered callbacks, or there should be some method like doc.off('op').

[nickasd]

Thanks to #161 I discovered the method doc.removeListener('op', callback) which seems to do exactly what doc.destroy() should be doing (unregistering all observers). This should be mentioned in the README file.

[curran]

I encountered a similar issue and submitted a PR adding this documentation to the README 9 days ago #160 It has not yet been reviewed by @nateps or @rkstedman , who seem to be the only ones active on this project with permissions to merge pull requests.

[nickasd]

Thanks a lot, didn't see that.

[curran]

Totally understandable! I wish I could do more to push these PRs through in a timely manner. Maybe you could help me lobby for attention from the maintainers ;)

[nickasd]

If there's something I can do just tell me ... I'm quite new to GitHub.

[curran]

@nickasd Maybe make some noise over at #163? I feel like ShareDB is really awesome, but is suffering from absentee maintainers.

[ninjapapa]

I actually have to wrap doc.removeListener in doc.whenNothingPending to solve the problem.

In my code, it may happen that just after I call subscribe and fetch, I need to undo it right away. Since the attaching listener call, doc.on is inside the fetch's callback, so it can actually happen after the doc.removeListener get called. In that case doc.removeListener will do nothing, and two listener functions will be attached after the second time doc.fetch get called.

The following solved my problem:

      this.doc.whenNothingPending((err) => {
        this.doc.removeListener('op', this.handleSharedbUpdateCode);
      })