How do I stop a node submission programmatically?

Question

i'm using Drupal 8. I would like to stop the user to submit a node when he tap save, and show some message. How can I do it programmatically?

Thanks!

Answer 1

You can hide the form submit button using hook_form_alter() and show a link Save and Publish on form. And include a jQuery snippet to show message, which will be triggered when user clicks on a link Save and Publish.

Answer 2

If you want to prevent form submission and show message, you can add form validation to your form (using hook_form_FORM_ID_alter):

function MYMODULE_form_node_MYNODETYPE_form_alter(&$form, &$form_state, $form_id) {
  $form['#validate'][] = '_node_MYNODETYPE_form_validate';
}

function _node_MYNODETYPE_form_validate($form, $form_state) {  
  // add some logic to show or not show message here
  $form_state->setErrorByName('field_MYFIELD', 'Message to show by my field');  
}

Answer 3

To avoid saving the results, you must remove (or override) the save function from the form. Try this:

function custom_module_form_alter(&$form, \Drupal\Core\Form\FormStateInterface $form_state, $form_id)
{    
        $form['actions']['submit']['#submit'][0] = "_custom_submit";
        unset($form['actions']['submit']['#submit'][1]); //Avoid save results    
}