wp_update_nav_menu_item returns false instead of WP_Error for non-existent menu items

[mltsy]

Use case:
Calling wp_update_nav_menu_items with a non-existent menu_item_id as the first parameter

Expected return value: WP_Error object (as per the method's documentation)

Actual return value: Boolean false

Fix: wp-includes/nav-menu.php#L279 - This line should check for a false value first, and if $menu == false, set it equal to a new WP_Error object - then check is_wp_error($menu)

[mltsy]

Correction: the first parameter is a menu_id, not a menu_item_id. So this happens when you provide a non-existent menu_id.

The main reason this bug is important to fix is for the error message the WP_Error would provide, which should be something like "The specified menu ID does not exist in this site".

Without that, I had no idea why the method was failing, and had to go looking through the source code :)

[bootsz]

Assigns new WP_Error to $menu if $menu is false, and then returns the error.

[ocean90]

Hello mltsy and bootsz, thanks for the report and the patch.

I agree, the error handling can be improved here. Since we already returning WP_Error objects we easily can add one more, so the change is backward compatible.

We're doing similar checks on other places, like wp_insert_term() or is_object_in_term(), where we just declare the input as invalid. In 21652.2.patch​ I have used a similar phrase.

[SergeyBiryukov]

In 27251:

Consistently return a WP_Error object in case of an error in wp_update_nav_menu_item().

props bootsz, ocean90.
fixes #21652.