ondata not invoked when the results between calls don't change

[danielvanmil]

Hello,

With my query, for example:

  private readonly getItems = new ApolloQueryController(this, GetItemsDocument, {
    onData: () => {
     console.log("onData");
    },
    onError: () => {
      console.error("Cannot get data.");
    },
  });

The onData is not invoked when a next query result is the same as the previous one (in my case no items).
This seems expected behavior as the Appollo ObservableQuery code contains a check with a isDifferentFromLastResult:

    ObservableQuery.prototype.reportResult = function (result, variables) {
        var lastError = this.getLastError();
        if (lastError || this.isDifferentFromLastResult(result)) {
            if (lastError || !result.partial || this.options.returnPartialData) {
                this.updateLastResult(result, variables);
            }
            iterateObserversSafely(this.observers, 'next', result);
        }
    };

• Is this correct?
• Should this be documented as I would expect the onData handler to be invoked always?

Thanks.

[bennypowers]

Seems to me this is the correct behavior, that function should only be invoked when the data actually changes

[danielvanmil]

ok, but, should it then be called onDataChange maybe and how can I respond after the loading of the controller if needed?

[bennypowers]

you could dirty check in the host's updated callback

[danielvanmil]

@bennypowers : the dirty check seems a good solution/workaround for my issue. But it still seems to me a bit of doc could be added to make it more clear. Thanks!

[bennypowers]

you could send a docs PR