form api question -- cancel button to node/add form with required fields

The Leprechaun says this is a really easy task :)

First, you need to implement hook_form_alter() to alter the standard node form. In your hook_form_alter you need to add your custom submit handler as the the first element in the array of submit handers.

Next implement your custom submit handler.

If you look at the html source of the node form, you will notice the buttons all had a "name" attribute of "op". Therefore, you distinguish which button was clicked by inspecting the "value" attribute submitted:

function LUCKY_CHARMS_form_submit($form, &$form_state) {
    switch($form_state['values']['op']) {
        case 'Cancel' :
            drupal_set_message('Operation Cancelled');
            drupal_goto('magically/delicious');
        break;
....
    }
}

Again, the trick is to make sure you rearrange the submit handler array so that your handler is called first. In the example above, the Leprechaun redirects the user to the page who's path is mapped to "magically/delicious".

The Leprechaun says he hope this is useful.

There are two different options that you can do to avoid using jquery. If you're fine with a link (which IMO is better because it is the only easy way to get around required field validation):

/**
 * Implementation of hook_form_alter()
 */
function MODULENAME_form_alter(&$form, &$form_state, $form_id) {
  if ($form_id == 'NODETYPE_node_form') {
    $form['buttons']['cancel'] = array(
      '#type' => 'markup',
      '#value' => l(t('Cancel'), 'path/for/cancel'),
      '#weight' => 10,
    );
  }
}

This way will create a submit button, but it doesn't get around required field validation. There are ways to get around it (you have to remove all fields from being required - it's really ugly to say the least):

/**
 * Implementation of hook_form_alter()
 */
function MODULENAME_form_alter(&$form, &$form_state, $form_id) {
  if ($form_id == 'NODETYPE_node_form') {
    $form['buttons']['cancel'] = array(
      '#type' => 'submit',
      '#value' => t('Cancel'),
      '#validate' => array(''),
      '#submit' => array('my_submit_function'),
      '#weight' => 10,
    );
  }
}

function my_submit_function(&$form, &$form_state) {
  drupal_goto('path/for/cancel')
}

Both of these were tested against Drupal 6 just now and worked fine.

Hello. Did you check the link i've posted? It's step by step tutorial there. You need to define function and assign it to form #after_build property, like this

function module_name_form_alter(&$form, &$form_state, $form_id) {
  $form['cancel_button'] = array(
    '#type' => 'submit', 
    '#value' => t('Cancel'),
    '#submit'   => array('module_name_canel_button_submit'),
  );
  $form['#after_build'][] = 'module_name_form_after_build';
}

in this function you need to iterate through all form elements and recursively unset property $element['#needs_validation']

function module_name_form_after_build($form, &$form_state) {
  unset($form['#validate']);
  if($form_state['clicked_button']['#value'] == 'Cancel') {
    _module_name_disable_validation($form);
  }
  return $form;
}

function _module_name_disable_validation(&$element) {
  unset($element['#needs_validation']);
  foreach(element_children($element) as $key) {
    _module_name_disable_validation($element[$key]);
  }
}

these actions will skip required validation and you will be able to perform your button submit handler. Until you unset '#needs_validation' property and form #validate array, your submit button handler won't be called.

then in submit handler you can do whatever you want, for example redirect to another page with drupal_goto function.