_wp_menu_item_classes_by_context assumes $queried_object->ancestors is an array

[wpsmith]

Recently, on a site using ​CPT-onomies, I ran into an interesting error with _wp_menu_item_classes_by_context().

In this function, when setting the parent class, there is a large if statement that assumes that $queried_object->ancestors and $possible_taxonomy_ancestors[ $parent_item->object ] are arrays.

[wonderboymusic]

This function...

[nacin]

When are either of these not arrays?

For the first one, post objects always return get_post_ancestors(), which always returns an array. (It briefly did not: #22882.)

For the second one, that array must be set (the line above it) before it is treated as an array. It is set to be an array within the function.

[wpsmith]

Replying to nacin:

When are either of these not arrays?

In WP_Query::get_queried_object() it is initialized as null: $this->queried_object = null; in wp-includes/query.php.

[DrewAPicture]

#31630 was marked as a duplicate.