EmptyPlaceHolder causes IndexOutOfBoundsException on MaterialListValueBox#getValue

[jzaruba]

Selecting the very last item in the list and then calling MaterialListValueBox#getValue causes IndexOutOfBoundsException. This is because MaterialListValueBox#setEmptyPlaceHolder adds a new item into the list but does not add a new value into the array of the underlying model.

MaterialListValueBox#setEmptyPlaceHolder:

    public void setEmptyPlaceHolder(String value) {
        listBox.insertItem(value, 0);

        getOptionElement(0).setDisabled(true);
    }

I did not think this through at all, but maybe adding a null value at the 0-index of the underlying array could work? (Unless someone will beat me to it I shall look into it during this upcoming week.)

[jzaruba]

Are you working on this one? Otherwise I would make a fork. (I suppose release_2.0.1 would be the target branch...?)

Also it seems that calling MaterialListValueBox#clear probably annihilates the placeholder.

[jzaruba]

A pull request has been created with a fix.

Anyways, maybe a more clear solution/approach to the #emptyPlaceHolder thing would be not adding the placeholder into the #listBox at all... It serves no purpose there, it can not be selected, it looks weird when the list is opened/expanded (especially with multiple=true when it has now a disabled checkbox)
...we could avoid the #values.length != #listBox.length thing.
Maybe the placeholder could be displayed only when the MaterialListValueBox widget is not opened/expanded...?

[kevzlou7979]

@jzaruba Can you please add a test case for any new features to avoid regressions in the future.

[kevzlou7979]

Maybe the placeholder could be displayed only when the MaterialListValueBox widget is not opened/expanded...?

I don't think its necessary to hide it.

[jzaruba]

@kevzlou7979 I did not consider this one a new feature, rather a bug-fix.
(If you referred to #753 then ignore this comment.)