Canonical: Ensure a redirect for posts missing `postname` in a query with an ID.

If a site is using `/%post_id%/%postname%/` as permalink structure, and is missing the `postname`, the site  won't redirect to the appropriate URL. This change ensure that the redirect happens.

Fixes: #12456.
Props: Frank.Prendergast, dd32, Otto42, hlanggo, wonderboymusic, atimmer, seth17, calvin_ngan, Niresh12495, anbumz, SergeyBiryukov, donmhico.



Built from https://develop.svn.wordpress.org/trunk@47937


git-svn-id: http://core.svn.wordpress.org/trunk@47710 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/canonical.php

@@ -409,6 +409,17 @@ function redirect_canonical( $requested_url = null, $do_redirect = true ) {
 			}
 
 			$redirect['query'] = remove_query_arg( 'page', $redirect['query'] );
+		} elseif ( is_singular() && empty( get_query_var( 'name' ) ) && $post_id ) {
+			/*
+			 * Redirect example.org/%post_id%/ to canonical url.
+			 * @ticket 12456
+			 */
+			$redirect_url      = get_permalink( $post_id );
+			$redirect['query'] = _remove_qs_args_if_not_in_url(
+				$redirect['query'],
+				array( 'p', 'page_id', 'attachment_id', 'pagename', 'name', 'post_type' ),
+				$redirect_url
+			);
 		}
 
 		// Paging and feeds.

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.5-alpha-47936';
+$wp_version = '5.5-alpha-47937';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.