title: How to make optgroup selectable?
body: <p>Can you make an optgroup selectable?</p>
  <pre><code>&lt;mat-form-field class=&quot;h-1 text-xs w-full&quot;&gt;
      &lt;mat-select formControlName=&quot;source&quot;&gt;
          &lt;mat-option [value]=&quot;defaultSource&quot;&gt;All&lt;/mat-option&gt;
          &lt;mat-optgroup *ngFor=&quot;let source of sources&quot;
              [label]=&quot;source.source&quot;&gt;
              &lt;mat-option *ngFor=&quot;let subSource of source.subSources&quot;
                  [value]=&quot;{'source': source.source,'type': subSource.name}&quot;&gt;
                  {{ subSource.name }}
              &lt;/mat-option&gt;
          &lt;/mat-optgroup&gt;
      &lt;/mat-select&gt;
  &lt;/mat-form-field&gt;
  </code></pre>
  <p>I want to be able to select the top-level option and not just the children. Is it possible? Or is there a workaround for this?</p>