form_profile2_form and form_profile2_TYPE_form alter functions called many, many times for user registration

HOOK_form_profile2_form_alter and HOOK_form_profile2_TYPE_form_alter functions are called repeatedly, whereas they should be called exactly once. In my situation, the alter function was adding a validation handler and the validation handler not working properly because it was being installed (and then called) many times.

In profile2.module:

function profile2_form_user_register_form_alter(&$form, &$form_state) {
  foreach (profile2_get_types() as $type_name => $profile_type) {
    if (!empty($profile_type->data['registration'])) {
      if (empty($form_state['profiles'][$type_name])) {
        $form_state['profiles'][$type_name] = profile2_create(array('type' => $type_name));
      }
      profile2_attach_form($form, $form_state);
      ...
    }
  }
}

function profile2_attach_form(&$form, &$form_state) {
  foreach ($form_state['profiles'] as $type => $profile) {
    $form['profile_' . $profile->type]['#tree'] = TRUE;
    $form['profile_' . $profile->type]['#parents'] = array('profile_' . $profile->type);
    field_attach_form('profile2', $profile, $form['profile_' . $profile->type], $form_state);
    ...
    // Provide a central place for modules to alter the profile forms, but
    // skip that in case the caller cares about invoking the hooks.
    // @see profile2_form().
    if (!isset($form_state['profile2_skip_hook'])) {
      $hooks[] = 'form_profile2_edit_' . $type . '_form';
      $hooks[] = 'form_profile2_form';
      drupal_alter($hooks, $form, $form_state);
    }
  }
  ...
}

So if there are 3 profiles, HOOK_form_profile_form_alter will be called:
1 times for the first call to profile_form_attach
1+2 times for the second call to profile_form_attach
1+2+3 times for the third call to profile_form_attach
----
10 times.

There are two causes of this bug. The first is simply that the $hooks array is appended to inside the loop. The second is that profile_form_attach calls the alter functions for all the profiles, not just the one added. Also note that the form is built repeatedly too.

The first bug could easily be fixed by accumulating an array of $hooks inside the loop, and then, if needed, adding the overall alter function and calling drupal_alter. In addition, inside the loop, the form could be built if it doesn't already exist. This could call the profile-specific alter function exactly once. However, it would still call the overall alter function once for every profile type -- a drastic improvement (3 versus 10 in the above example), but still not ideal.

To solve that, move the call the profile2_attach_form outside of the loop, attaching all the form elements at once. This would create all the profiles in $form_state, then attach them all at once, calling all the alters. Then (awkwardly) go back and make each profile form a field_set in a separate loop. This would also call field_attach_form only once for each profile, eliminating the redundant form building.

If these seems right, I will make a patch.