Input grouping (FAPI #input_group_button) ajax (validation) problem

Hi,

I think there is a serious limitation (or bug, or maybe a misunderstanding) with a FAPI preprocess function and ajax calls.

I see it when i try to make a very simple form (one text field, on submit button) and grouping them with #input_group_button special key on field.

In _bootstrap_process_element() function, we can see

// Automatically inject the nearest button found after this element if
// #input_group_button exists.
if (!empty($element['#input_group_button'])) {
...
}

That's a really great "helper" than can make input grouping append (see example http://getbootstrap.com/components/#input-groups-buttons).

With that, I can do that

$form['input_text'] = array(
    '#title' => 'label',
    '#type' => 'textfield',
    '#size' => 15,
    '#required' => TRUE,
    '#attributes' => array(
      'class' => array(
        'col-xs'
      ),
    ),
    '#input_group_button' => true,
  );
  $form["submit"] = array(
    "#type" => "submit",
    '#value' => t('Search'),
    '#attributes' => array(
      'class' => array(
        'btn-blue'
      ),
    ),
    "#ajax" => array(
      "callback" => "_myformcallback_callback",
    ),
  );

But with that, Drupal ajax API was not called.

So I add #ajax to my text input

$form['input_text'] = array(
   // ...
    '#input_group_button' => true,
    "#ajax" => array(
      "callback" => "_myformcallback_callback",
    ),
  );

With that ajax (_myformcallback_callback) is called, when clicking on submit, or when pressing enter key in text input.
Nice but... The validation function IS called but errors are not "returned"

function myform_form_validate($form, &$form_state) {
  form_set_error('input_text', 'Error test');
  return $form_state;
}

At the consequence inside _myformcallback_callback function, form_get_errors(); remains empty and code continue to run as if the was no validation function (or no error).

If I comment #input_group_button all run fine (with validation) but output is not as desired (no grouping)

That's why I think it's a bootstrap bug. I know I can use preprocess or alter hook to get the desired output but this #input_group_button key is a good helper to do that !

Thanks for helping, and sorry for my bad English