Skipping form validation with a custom action button

Question

Related to my previous question -- I've got the button added to the form properly (thanks googletorp!), but now I'm having separate validation issues beyond just adding the button.

I have added a "Cancel" button to my custom content entity add/edit form, using hook_form_id_alter. When clicking this button I want it to leave the form completely and return to another admin-side page:

function mymodule_form_myform_alter(&$form, \Drupal\Core\Form\FormStateInterface $form_state, $form_id) {
    $form['actions']['cancel'] = array(
        '#type' => 'button',
        '#weight' => 10001,
        '#submit' => array('cancel_submit'),
        '#value' => t('Cancel'),
    );
}
function cancel_submit() {
    $response = new Symfony\Component\HttpFoundation\RedirectResponse(Url::fromUri('internal:/admin/mymodule/list', array('absolute' => true))->toString());
    $response->send();
}

I can't get this to work because it's still trying to validate the form.

In my form code, my validation code will only execute if if ($form_state->getValue('op') == 'Save') is true, and this evaluates to false for the Cancel button. However, while this is stopping my custom validation code from running, it isn't stopping built-in validation for fields that I defined as required in the Drupal interface. The cancel_submit function doesn't seem to be doing anything, and clicking the Cancel button just loads the form again with a validation error on a required field.

I also tried adding '#limit_validation_errors' => array(), to $form['actions']['cancel'] as recommended here, but this just refreshed the form without showing validation errors instead of redirecting where I want it to go, so I have no idea what this code is actually doing or if this is even applicable for Drupal 8.

I am not sure where to go from here.

Answer 1

To send a redirect response from a form use setRedirect() or setRedirectUrl():

  function cancel_submit(array &$form, FormStateInterface $form_state) {
    $form_state->setRedirectUrl($url);
  }

And add '#limit_validation_errors' => array() to the cancel button as already mentioned in the question to prevent validation errors.