Add child page link in book navigation does not insert parent into book outline

Specifically, book_node_prepare() expects bid and access which are both missing from the menu_link object returned by book_link_load().

Previously, book_link_load() did this:

<?php
function book_link_load($mlid) {
  if ($item = db_query("SELECT * FROM {menu_links} ml INNER JOIN {book} b ON b.mlid = ml.mlid LEFT JOIN {menu_router} m ON m.path = ml.router_path WHERE ml.mlid = :mlid", array(
      ':mlid' => $mlid,
    ))->fetchAssoc()) {
          var_dump($item);
    _menu_link_translate($item);
    return $item;
  }

  return FALSE;
}
?>

Now it just does this:

<?php
function book_link_load($mlid) {
  return entity_load('menu_link', $mlid);
}
?>

Some sample code, which fixes the issue. Whether it's the right approach is another story.

I'm not yet sure how we're checking menu_link access in D8, so just threw in TRUE for now.

<?php
function book_link_load($mlid) {
  if ($item = db_query("SELECT * FROM {book} b WHERE b.mlid = :mlid", array(
      ':mlid' => $mlid,
    ))->fetchAssoc()) {
    $book_link = entity_load('menu_link', $mlid);
    $book_link->bid = $item['bid'];
    $book_link->access = TRUE; // @todo Check access! Access was checked by _menu_link_translate() in D7.
    return $book_link;
  }
  return FALSE;
}
?>

Closing as duplicate of #2183779: Adding a child book page does not automatically select the parent book page in the Book outline vertical tab