title: Bootstrap Vue prevent / cancel event
body: <p>I have a page with a b-form-select control from Bootstrap Vue.
  When I change the value of this control I want to execute a function that can possibly cancel this event, and not change the value.</p>
  
  <p>To make things more complicated, my select is in a child component and the function I execute is in the parent.</p>
  
  <p>The child component </p>
  
  <pre><code>public values: any[] = [
    { name: 'default'},
    { name: 'forbidden'},
    { name: 'other option' },
  ]
  
  &lt;b-form-select :value="property" @change="$emit('onPropertyChange', arguments[0])"&gt;
     &lt;option v-for="(val, key) in values" :value="val" :key="key"&gt;{{val.Name}}&lt;/option&gt;
  &lt;/b-form-select&gt;
  </code></pre>
  
  <p>The parent component:</p>
  
  <pre><code>this.property = { name: 'default' }
  public onPropertyChange(newValue) {
    if (newValue.name === 'forbidden') {
      // Not changing this.property
    } else {
      // Changing it
      this.property = newValue
    }     
  }
  
  &lt;child :property="property" @onPropertyChange="onPropertyChange"&gt;&lt;/child&gt;
  </code></pre>
  
  <p>When I select 'forbidden' in the select. I see that the select box has changed to this value, but the property in the child and also the property in the parent still have the old value, which is what I want. How can I also have the select to have the old value?</p>
  
  <p>Bootstrap Vue does not seem to have a prevent modifier on the change event.
  I have also tried using the native event but that has the same issue.</p>
  
  <p>Am I doing something wrong?</p>