Drupal 7 -- #AJAX Refresh not displaying drupal_set_message errors - ajax

Question

The issue:
In Drupal 7's Form API, when using #AJAX to refresh fields, error messages from validation are not displayed until the entire page is refreshed. I see the field I refreshed highlighted in the error state, but the user does not see the associated message until it's too late (they've reloaded the page, or gone to another page).
I started to manually process the error stack in this manor: Drupal.org -- Filter out specific errors during validation, but I have a complex form, and a small budget of time to complete this task. There must be some way to refresh the stack & display the messages to the user without processing everything manually.
Note:
I'm using multi-commands with a callback, so utilizing this is an option for me.
$commands[] = ajax_command_replace("#my_wrapper", render($form['test']['field_a']));
$commands[] = ajax_command_replace("#another_wrapper", render($form['test']['field_b']));
return array('#type' => 'ajax', '#commands' => $commands);
Thoughts?

Answer 1

Solution:
Apparently, when you use the multi-callback approach, Drupal does not refresh messages for you. You can do this manually, as follows:
// Remove the old messages div, clearing existing messages.
$commands[] = ajax_command_remove('#messages');
// Append a new messages div with our latest errors and messages.
$commands[] = ajax_command_after('#header-region', '<div id="messages">' . theme('status_messages') . '</div>');
Simply add this to any callback commands[] array you have, and you're good to go.
Thanks to Drupal.org -- AJAX commands and Drupal Messages for the right direction!

Answer 2

thanks atomox! just a fuller example for those not onto multi comands yet:
$form['ld']['letterdrop_allocations_submit'] = array(
'#type' => 'submit',
'#value' => 'Letterdrop allocations update',
// '#name' => 'Letterdrop allocations update',
'#name' => 'agc_letterdrop_submit',
'#ajax' => array(
'callback' => 'agc_ems_form_letterdrop_submit_ajax',
),
);
...
function agc_ems_form_letterdrop_submit_ajax($form, &$form_state) {
drupal_set_message('here i am world', 'ok');
$commands = array();
$commands[] = ajax_command_replace('#messages',
'<div id="messages">' . theme('status_messages') . '</div>');
$commands[] = ajax_command_alert('submitted via handler');
return array(
'#type' => 'ajax',
'#commands' => $commands);
}
Also is a bit more concise and removes the assumptions that messages sit below the header region:
$commands[] = ajax_command_replace('#messages', '<div id="messages">' . theme('status_messages') . '</div>');