ID, post_parent, menu_order on global $post object is a string in edit context; expecting int

[javorszky]

When I'm on an edit post screen, the ID, post_parent, menu_order attributes on the global $post object are strings. I expect them to be integers.

To quickly check, put this in a plugin:

<?php
add_action( 'add_meta_boxes', function(){
        add_meta_box( 'foo', 'bar', function( $post ) {
                var_dump($post->ID);
        });
});

Here's what's happening:

1. in wp-admin/post.php the edit case happens, and within that the post gets reloaded here: ​https://github.com/WordPress/WordPress/blob/4.9.5/wp-admin/post.php#L167
2. that function will run the post object through its own filter with filter edit here: ​https://github.com/WordPress/WordPress/blob/4.9.5/wp-includes/post.php#L552
3. because at the time $this->filter = "raw", and the $filter is edit, that will run the object through sanitize_post here ​https://github.com/WordPress/WordPress/blob/4.9.5/wp-includes/class-wp-post.php#L354
4. sanitize_post will, in turn, run all the fields through sanitize_post_field here: ​https://github.com/WordPress/WordPress/blob/4.9.5/wp-includes/post.php#L1940
5. and even though we have 3 fields set as int (​https://github.com/WordPress/WordPress/blob/4.9.5/wp-includes/post.php#L1973), by the time we get to this part (​https://github.com/WordPress/WordPress/blob/4.9.5/wp-includes/post.php#L2027-L2034), those three will be ran through esc_attr
6. esc_attr will feed it through _wp_specialchars here ​https://github.com/WordPress/WordPress/blob/4.9.5/wp-includes/formatting.php#L3978
7. which begins with $string = (string) $string; here ​https://github.com/WordPress/WordPress/blob/4.9.5/wp-includes/formatting.php#L912

The part that throws me off is that sanitize_post_field declares these three properties to be integers at the beginning of the function, so I sort of expected them to come out as integers on the other end.

[javorszky]

Related WooCommerce issue on ​https://github.com/woocommerce/woocommerce/issues/19704 (tldr: it being a string causes it to slow down due to WC expecting the prop to be an int)

[javorszky]

Original props goes to ​@alexrsoap for bumping into this and doing debugging that uncovered this.

[alexrsoap]

Replying to javorszky:

Original props goes to ​@alexrsoap for bumping into this and doing debugging that uncovered this.

Thanks for the props. Thanks to you for the legwork of verification and reporting.