minutes.module

<?php

use Drupal\Core\Form\FormStateInterface;
use Drupal\node\NodeInterface;

function minutes_form_alter(&$form, FormStateInterface $form_state, $form_id) {
  switch ($form_id) {
    case "node_minutes_form":
      _setup_minutes_entity_builder($form);
      break;
    case "node_minutes_edit_form":
      _hide_immutable_minutes_fields($form, $form_state);
      break;
    case "node_minutes_delete_form":
      _setup_minutes_entity_delete_callback($form);
      break;
  }
}

function _setup_minutes_entity_builder(&$form) {
  $form['title']['#access'] = FALSE;
  $form['#entity_builders'][] = '_minutes_node_builder';
}

function _setup_minutes_entity_delete_callback(&$form) {
  $form['#validate'][] = '_minutes_delete_validation';
}

function _hide_immutable_minutes_fields(&$form, $form_state) {
// These form the title .. and it's too late to change it now!
  $form['title']['#access'] = FALSE;
  $form['field_minutes_meeting']['#access'] = FALSE;
  // Hide the Minutes text field unless in Draft Status
  $minutes_node = $form_state->getFormObject()->getEntity();
  $minutes_status_id = $minutes_node->field_minutes_status->target_id;
  $referenced_tag = \Drupal::entityTypeManager()
    ->getStorage('taxonomy_term')
    ->load($minutes_status_id);
  $minutes_status = $referenced_tag->name->value;
  if ($minutes_status != 'Draft') {
    // We'll prevent agenda text edits unless in Draft status
    $form['body']['#access'] = FALSE;
  }
}

function _minutes_node_builder($entity_type, NodeInterface $node, &$form, FormStateInterface $form_state) {
  // Find the meeting date from the Meeting Node referenced by `field_minutes_meeting`
  if ($node->field_minutes_meeting->target_id) {
    $referenced_meeting_node = \Drupal::entityTypeManager()
      ->getStorage('node')
      ->load($node->field_minutes_meeting->target_id);
    $title_of_meeting = 'Minutes for ' . $referenced_meeting_node->getTitle();
    $node->setTitle($title_of_meeting);
  } else {
    $form_state->setErrorByName('field_minutes_meeting', 'Please choose a Meeting that already exists.');
    $node->setTitle('Error');
  }
} // end of minutes_node_builder

function _minutes_delete_validation(&$form, FormStateInterface $form_state) {
  $minutes_node = $form_state->getFormObject()->getEntity();
  $minutes_name = $minutes_node->getTitle();
  $minutes_node_id = $minutes_node->id();
  // Look for any Meetings referencing these Minutes
  $query = \Drupal::entityQuery('node')
    ->accessCheck(TRUE)
    ->condition('type', 'meeting')
    ->condition('field_meeting_minutes', $minutes_node_id);
  $nids = $query->execute();
  $count_nids = count($nids);
  if ($count_nids > 0) {
    $msg_stem = ($count_nids == 1) ? 'There is a Meeting that references "' : 'There are ' . $count_nids . ' Meetings that reference "';
    $form_state->setError($form, $msg_stem . $minutes_name . '". It cannot be deleted yet.');
  }
  $minutes_status_id = $minutes_node->field_minutes_status->target_id;
  $referenced_tag = \Drupal::entityTypeManager()
    ->getStorage('taxonomy_term')
    ->load($minutes_status_id);
  $minutes_status = $referenced_tag->name->value;
  if ($minutes_status != 'Draft') {
    // We'll prevent deleting Minutes unless in Draft status
    $form_state->setError($form, 'Please change the Minutes "Document status  to "Draft"  before attempting to delete.');
  }
}