Change JavaScript settings into a separate asset type

In order to optimize Drupal AJAX requests and the caching of CSS and JS aggregate files, JavaScript settings attached to Drupal render arrays were promoted to their own asset type.

Before

$build = array(
  …,
  '#attached' => array(
    'js' => array(
      array(
        'type' => 'setting',
          'data' => array('ckeditor' => array(
            'hiddenCKEditorConfig' => $config,
          )),
        ),
      ),
    ),
  ),
);

After

$build = [
  …,
  '#attached' => [
    'drupalSettings' => [
      'ckeditor' => ['hiddenCKEditorConfig' => $config],
    ]
  ],
];

hook_js_settings_build() has been added to allow modification of settings from library definitions, the results of this hook are cached.

An accompanying alter hook, hook_js_settings_alter() is also introduced. This means you no longer need to do crazy things in hook_js_alter().

Before

/**
 * Implements hook_js_alter().
 */
function user_js_alter(&$javascript) {
  // If >=1 JavaScript asset has declared a dependency on drupalSettings, the
  // 'settings' key will exist. Thus when that key does not exist, return early.
  if (!isset($javascript['settings'])) {
    return;
  }

  // Provide the user ID in drupalSettings to allow JavaScript code to customize
  // the experience for the end user, rather than the server side, which would
  // break the render cache.
  // Similarly, provide a permissions hash, so that permission-dependent data
  // can be reliably cached on the client side.
  $user = \Drupal::currentUser();
  $javascript['settings']['data'][] = array(
    'user' => array(
      'uid' => $user->id(),
      'permissionsHash' => \Drupal::service('user.permissions_hash')->generate($user),
    ),
  );
}

After

/**
 * Implements hook_js_settings_alter().
 */
function user_js_settings_alter(&$settings) {
  // Provide the user ID in drupalSettings to allow JavaScript code to customize
  // the experience for the end user, rather than the server side, which would
  // break the render cache.
  // Similarly, provide a permissions hash, so that permission-dependent data
  // can be reliably cached on the client side.
  $user = \Drupal::currentUser();
  $settings['user']['uid'] = $user->id();
  $settings['user']['permissionsHash'] = \Drupal::service('user.permissions_hash')->generate($user);
}