Notice: Trying to access array offset on value of type null in field_config_label_instance() (line 436 of /var/www/html/docroot/core/modules/field/field.module)

[alanmels]

Description of the bug

A single item configuration export page at admin/config/development/configuration/single/export is giving the notice in title.

Steps To Reproduce

To reproduce the behavior:

1. Go to admin/config/development/logging and set All messages to display.
2. Go to admin/config/development/configuration/single/export and see the reported notice.

Additional information

The offending line looks as $entity_label = $entity_type['label']; and the whole function as:

/**
 * Given a field array, display a unique label.
 */
function field_config_label_instance($instance, $config_name) {
  list($entity_type_name, $bundle, $field_name) = explode('.', str_replace('field.instance.', '', $config_name));
  $entity_type = entity_get_info($entity_type_name);
  $entity_label = $entity_type['label'];
  $bundle_label = isset($entity_type['bundles'][$bundle]['label']) ? $entity_type['bundles'][$bundle]['label'] : $bundle;
  return $entity_label . ' - ' . $bundle_label . ' - ' . $instance['label'];
}

Now, I've put the following check to find out which entity is causing the notice:

function field_config_label_instance($instance, $config_name) {
  list($entity_type_name, $bundle, $field_name) = explode('.', str_replace('field.instance.', '', $config_name));
  $entity_type = entity_get_info($entity_type_name);
  if (!isset($entity_type)) {
    sdpm($entity_type_name);
  }
  $entity_label = $entity_type['label'];
  $bundle_label = isset($entity_type['bundles'][$bundle]['label']) ? $entity_type['bundles'][$bundle]['label'] : $bundle;
  return $entity_label . ' - ' . $bundle_label . ' - ' . $instance['label'];
}

and it returned comment (which is not entity on Backdrop AFAIK) three times:

Running the same check condition for $config_name has given:

field.instance.comment.comment_node_card.comment_body
  field.instance.comment.comment_node_page.comment_body
  field.instance.comment.comment_node_post.comment_body

I'm not sure what's the best solution here, but changing the code as below makes the notice go away:

function field_config_label_instance($instance, $config_name) {
  list($entity_type_name, $bundle, $field_name) = explode('.', str_replace('field.instance.', '', $config_name));
  $entity_type = entity_get_info($entity_type_name);
  if (isset($entity_type)) {
    $entity_label = $entity_type['label'];
    $bundle_label = isset($entity_type['bundles'][$bundle]['label']) ? $entity_type['bundles'][$bundle]['label'] : $bundle;
    return $entity_label . ' - ' . $bundle_label . ' - ' . $instance['label'];
  }
}

Should I create a PR or another solution preventing the comment configuration from being fed to the function should be considered?

[indigoxela]

Possibly a duplicate of #5469

[alanmels]

Well, turning on the Comment module made the notice go away, so it's definitely the same issue. Closing this one.