What happens to a render array after hook_form_alter() that does not happen after an AJAX callback?

Question

I have a multi-value field type in a content type. During hook_form_alter(), I add an #ajax property to the field.

Upon execution, the ajax callback loads a node's custom view mode and two form inputs from another content type into the div.

I am using field_default_form() to generate the form elements.

In order for these addons to persist through clicking the 'Add more' button, I use hook_form_alter() to call the same function that is called by the ajax callback, and I add them into the results/wrapper div.

My problem is that the form elements of the #ajax callback results are not rendered correctly. For example, they do not have a name or id for the <input> tag. One of the fields is an autocomplete field and autocomplete functionality does not get applied to the element.

However, the results of the 'add more' button, which calls hook_form_alter(), DOES render these elements correctly.

As far as I can tell, the render arrays are identical during generation. It seems to me like some additional processing happens after hook_form_alter() that does not happen after my #ajax callback.

I have tried adding #theme, #theme_wrapper, #after_build and #rebuild = TRUE keys to the resulting render array elements, but it does not appear to have any effect.

How can I get these elements to render correctly?

Answer 1

Since hook_form_alter() is returning the correct results, there is a way to use that to our advantage.

By calling drupal_rebuild_form() in our ajax callback, we can return the specific part of the resulting array that should fill in our wrapper div.

e.g.

function _send_item(&$form, &$form_state) {

    $delta   = $form_state['triggering_element']['#delta'];
    $lang    = $form_state['triggering_element']['#language'];

    $new_form = drupal_rebuild_form('mymodule_node_form', $form_state);

    return $new_form['mymodule_item_id'][$lang][$delta]['item_data'];
}