required=true not working as I would expect it to

[hut8]

I apologize in advance if I don't understand what required=true is supposed to do, but it seems to me like it should be the same as just adding the "required" attribute for other elements such as textarea.

When I do this:

<form name="myForm" novalidate>
  <textarea ng-model="someText" required>
  <button type="submit" class="btn btn-primary" ng-disabled="myForm.$invalid">Submit</button>
</form>

The submit button will be disabled until I put something in the textarea.

However if I do this:

<form name="myForm" novalidate>
    <div
      class="btn btn-primary btn-upload"
      url="/api/documents"
      param="file"
      required="true"
      upload-button>Upload</div>
  <button type="submit" class="btn btn-primary" ng-disabled="myForm.$invalid">Submit</button>
</form>

Then I can press "Submit" just fine even when there's no file selected.

Of course you'll see I added novalidate, but the point still stands, because even in the official AngularJS guide to forms (https://docs.angularjs.org/guide/forms) they always use novalidate on the form and everything works (as Angular then takes over the job of applying validations from the browser). Does this make sense?