nz-code-editor's ControlValueAccessor triggers superfluous view→model updates

[Airblader]

Steps to reproduce

The ControlValueAccessor for nz-code-editor seems to have an issue where a model->view update will also trigger a view->model update, which can cause all kinds of issues like infinite loops when subscribing to form changes and then writing back into the control.

Environment	Info
ng-zorro-antd	9.1.2
Browser	Chrome

[Airblader]

FYI I couldn't provide a Stackblitz because I can't get nz-code-editor to work in there.

[wzhudev]

Fixed by #5872. Thanks for your issue and PR! 🥂

[Airblader]

@wendellhu95 My PR was a different issue, this issue is not fixed by that PR.

[Airblader]

I can't open a PR at the moment, but if someone wants to send the fix for this, I believe all that has to be done is change emitValue in code-editor.component.ts to this (but untested, so please double check):

  private emitValue(value: string): void {
    if (this.value === value) {
      // If the value didn't change there's no reason to send an update.
      // Specifically this may happen during an update from the model (writeValue) where sending an update to the model would actually be incorrect.
      return;
    }

    this.value = value;
    this.onChange(value);
  }

If you want to test this, essentially we need to make sure that calling writeValue does not trigger the onChange function.