Required attribute on lightning:combobox ignored

Question

Browsers will prevent the form from submitting if there are any required input fields. This works well with lightning:input - the form won't submit until the fields with required=true are filled. However, setting this attribute on lightning:combobox does nothing - the form submits with an empty field.

Here is a component example with two fields in the form. Both are required. The form won't submit until you complete the Name field (lightning:input) but it will submit even if the Language field is left blank (lightning:combobox).

Any ideas on how to solve this without resorting to Java Script validation?

<aura:component access="global">
    <aura:attribute name="languageOptions" type="List" default="[
        {'label': 'English', 'value': 'English'},
        {'label': 'French', 'value': 'French'},
        {'label': 'Chinese', 'value': 'Chinese'},
    ]"/>

    <form onsubmit="{!c.handleSubmit}">
        <lightning:input required="true" label="Name" name="name" />
        <lightning:combobox required="true" label="Language" options="{!v.languageOptions}"/>
        <lightning:button variant="brand" type="submit" name="save" label="Save" />
    </form>
</aura:component>

Answer 1

Flexibility would be the ability to have either the component validate itself if it's empty and have a custom validation if necessary to override or replace the standard validation, like... you know, regular input.

Here... there's no Flexibility, the standard validation simply don't EXIST and we had to code our own validation ourselves.