Language code is missing from $context when hook_field_attach_view_alter() is invoked from field_view_field()

drupal_alter('field_attach_view', $result, $context) gets executed in function field_view_field() and in function field_attach_view().

Compared to function field_attach_view() the langcode is missing in $context in function field_view_field():

function field_attach_view($entity_type, EntityInterface $entity, $view_mode, $langcode = NULL) {

  // Let other modules alter the renderable array.
  $context = array(
    'entity_type' => $entity_type,
    'entity' => $entity,
    'view_mode' => $view_mode,
    'display' => $view_mode,
    'langcode' => $langcode,
  );
  drupal_alter('field_attach_view', $output, $context);
}

function field_view_field($entity_type, $entity, $field_name, $display = array(), $langcode = NULL) {

      // Invoke hook_field_attach_view_alter() to let other modules alter the
      // renderable array, as in a full field_attach_view() execution.
      $context = array(
        'entity_type' => $entity_type,
        'entity' => $entity,
        'view_mode' => '_custom',
        'display' => $display,
      );
      drupal_alter('field_attach_view', $result, $context);
}

This bug already exists in drupal 7 and breaks the indexing of nodes in apachesolr if the entity translation module is installed: #1820742: parameter $langcode of core function node_view() ignored
(The issues within Entity Translation have been fixed now, except this remaining bug in core.)

Attached you'll find a patch against drupal 8 where the bug still exists. After it gets committed a backport is required. But watch out, in drupal 7 the array key needs to be 'language' instead of 'langcode'.