instead of passing in undefined here, what about just passing in selectedOptions, as it was before, but having list_control.js (the business logic, not the component) override hasValue to check for an empty array, (or undefined too perhaps). Feels like this component having to understand what stageFilter would count as empty or not is leaking too much internal knowledge.

Can you add comments to explain the difference between reset and clear? It makes more sense when I see the UI but looking only at the code it's not obvious.

Also, clear indiscriminately changes _hasChanged to be true which can create some inconsistencies in a UX experience:

should this be using hasValue as the check? Also looks like this function only uses props.control so no need to pass in the entire props.

nit: can be shortened to just sliderValue (https://github.com/airbnb/javascript#es6-object-concise)

nit: could keep sliderValue as const via:

const sliderValue = control.hasValue() ?
  control.value :
  sliderValue = {
    min: control.min,
    max: control.min
  };

nit: could make this a bit more concise via changing above:

...
     minValue: control.hasValue() ? control.value.min : '',
     maxValue: control.hasValue() ? control.value.max : '',
...

imo it'd be clearer to do this.value = undefined; Can set ever be called outside of clear with undefined? If not, we could throw an error in set if newValue is not defined (or when we eventually typescript we could tell then we don't support undefined), and then we don't have to check this.hasValue(), just always assume there is a value.

We still need to support value being undefined to signal when the control is unset.

I can't seem to trigger set being called with undefined outside of this clear function when playing around with the control. Can you tell me the instance you are referring to? Or maybe we are misunderstanding each other. I understand we need to support the value being undefined, I just mean writing the code like this would be clearer imo:

set(newValue) {
  this.value = newValue;
  this._kbnFilter = this.filterManager.createFilter(this.value);
}

clear() {
  this.value = undefined;
  this._kbnFilter = null;
}

Then when this supports typescript we can do something like set(newValue: T) instead of set(newValue: T | undefined)

Here is a case where hasValue is needed. In the list control, when the list is cleared, set is called with []. In this case, _kbnFilter needs to be set to null since there is no filter value. This logic could move into filterManager.createFilter if that makes things easier to understand.

I think there is a bug here. Looks like I can't set an input control drop down to false. Should probably be a hard check for undefined. Could you add a test that would have caught this issue when you fix it?

The value can never be set to false. For list control, the value is either undefined or an array of objects with the shape label and value. I will create a test to show how the value gets set

Ah, okay. I suppose I am hitting another bug. I created a list drop down with true and false values for the sample flight data set and I get:

Uncaught (in promise) Error: 0 is not a valid boolean value for boolean field Cancelled
    at getConvertedValueForField (phrase.js:71)
    at buildPhraseFilter (phrase.js:31)
    at PhraseFilterManager.createFilter (phrase_filter_manager.js:72)
    at ListControl.set (control.js:154)
    at VisController._callee3$ (vis_controller.js:190)
    at tryCatch (runtime.js:65)
    at Generator.invoke [as _invoke] (runtime.js:303)
    at Generator.prototype.(anonymous function) [as next] (http://localhost:5601/xmb/bundles/vendors.bundle.js:218445:21)
    at step (vis_controller.js:41)
    at vis_controller.js:41
    at new Promise (<anonymous>)
    at VisController.<anonymous> (vis_controller.js:41)
    at VisController.stageFilter (vis_controller.js:218)
    at ListControl._this.handleOnChange (list_control.js:64)
    at EuiComboBox.onAddOption (combo_box.js:630)
    at onOptionClick (combo_box.js:621)

Once we have this typescripted we can enforce that set on the base class is only ever called with a certain type, but as it is now, it's not clear that set should only be called with an array type or undefined. But I suppose this is fine as is for this PR.

Would you mind creating a new issue for using boolean fields?