Position for first menu item on menu is 0 when it should be 1

[danielbachhuber]

When the first menu item is added to a menu and no position is explicitly set, its position is set as 0 instead of 1.

Offending line: https://core.trac.wordpress.org/browser/tags/3.9/src/wp-includes/nav-menu.php#L344

[danielbachhuber]

From ​https://github.com/wp-cli/wp-cli/pull/1182

[rohan013]

Change the default value menu-item-position to 1

[SergeyBiryukov]

When the first menu item is added to a menu and no position is explicitly set, its position is set as 0 instead of 1.

Could you describe the issue with more details, and why it should be 1?

[danielbachhuber]

Because 0 is an invalid menu position and it breaks things?

The historical context is in that pull request. I don't recall the exact specifics off the top of my head, but I vaguely remember that the positioning for a menu would be "0,2,3" without the hack (which broke other things).

[rohan013]

Fixed some errors

[chriscct7]

Patch is good, still needs unit tests

[birgire]

The position of menu items is stored as 0,2,3, ... in the menu_order field of the wp_posts table, as @danielbachhuber mentioned.

We note that it's not possible to test this behavior directly with wp_get_nav_menu_items(), because the position (menu_order) is adjusted from 0,2,3,... to 1,2,3,... with this part of that function:

$i = 1;
foreach ( $items as $k => $item ) {
    $items[$k]->{$args['output_key']} = $i++;
}

where $args['output_key'] is menu_order.

See here:

https://core.trac.wordpress.org/browser/tags/4.8.2/src/wp-includes/nav-menu.php#L657-L660

In 28140.3.patch​ we

• Adjust the patch in 28140.2.diff​ with 1 == (int) $args['menu-item-position'] instead of 0 == (int) $args['menu-item-position']

• Add a test to check if the position (menu_order) of two newly added menu items is 1 and then 2.
• Add a test to check if the position (menu_order) from wp_get_nav_menu_items() is 1 and 2.