Page ID of 0 passes is_page( 'ANYSLUG' ) check

[r-a-y]

For plugins using virtual pages like BuddyPress and bbPress, to avoid notices we override $wp_query to set the page ID to 0.

If we land on a page with our resetted page ID of 0, if a theme dev is using is_page( 'ANYSLUG' ) on this page, the check will always return true.

The problem is due to $wp_query->is_page() using in_array( $page_obj->ID, $page ):
source:/tags/4.1/src/wp-includes/query.php@:4349#L4338​

in_array( 0, array( 'ANYSLUG' ) always returns true.

My suggested fix would have been to use in_array()'s strict check - in_array( $page_obj->ID, $page, true ) - but that fails this test:
source:/tags/4.1/tests/phpunit/tests/canonical/pageOnFront.php@:51#L40​

So, I've opted to check the page ID before doing the in_array() check.

Attached is a unit test demonstrating the problem with the fix suggested above.

[SergeyBiryukov]

Duplicate of #24674.

[r-a-y]

Ugh! Apologies for the duplicate and thanks for pointing me to that ticket, SergeyBiryukov!