Canonical/Rewrite: sanity check posts that are paged with `<!--nextpage-->`. Page numbers past the max number of pages are returning the last page of content and causing infinite duplicate content.

Awesome rewrite bug: the `page` query var was being set to `'/4'` in `$wp`. When cast to `int`, it returns `0` (Bless you, PHP). `WP_Query` calls `trim( $page, '/' )` when setting its own query var. The few places that were checking `page`	before posts were queried now have sanity checks, so that these changes work without flushing rewrites.	

Adds/updates unit tests.

Props wonderboymusic, dd32.
See #11694.

Built from https://develop.svn.wordpress.org/trunk@34492


git-svn-id: http://core.svn.wordpress.org/trunk@34456 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/canonical.php

@@ -148,6 +148,13 @@ function redirect_canonical( $requested_url = null, $do_redirect = true ) {
 			}
 		}
 
+		if ( get_query_var( 'page' ) && $wp_query->post &&
+			false !== strpos( $wp_query->post->post_content, '<!--nextpage-->' ) ) {
+			$redirect['path'] = rtrim( $redirect['path'], (int) get_query_var( 'page' ) . '/' );
+			$redirect['query'] = remove_query_arg( 'page', $redirect['query'] );
+			$redirect_url = get_permalink( $wp_query->post->ID );
+		}
+
 	} elseif ( is_object($wp_rewrite) && $wp_rewrite->using_permalinks() ) {
 		// rewriting of old ?p=X, ?m=2004, ?m=200401, ?m=20040101
 		if ( is_attachment() && ! $redirect_url ) {
@@ -560,7 +567,7 @@ function redirect_guess_404_permalink() {
 			return false;
 		if ( get_query_var( 'feed' ) )
 			return get_post_comments_feed_link( $post_id, get_query_var( 'feed' ) );
-		elseif ( get_query_var( 'page' ) )
+		elseif ( get_query_var( 'page' ) && 1 < get_query_var( 'page' ) )
 			return trailingslashit( get_permalink( $post_id ) ) . user_trailingslashit( get_query_var( 'page' ), 'single_paged' );
 		else
 			return get_permalink( $post_id );

wp-includes/class-wp-rewrite.php

@@ -1071,8 +1071,10 @@ class WP_Rewrite {
 					$sub1 .= '?$';
 					$sub2 .= '?$';
 
-					//post pagination, e.g. <permalink>/2/
-					$match = $match . '(/[0-9]+)?/?$';
+					// Post pagination, e.g. <permalink>/2/
+					// Previously: '(/[0-9]+)?/?$', which produced '/2' for page.
+					// When cast to int, returned 0.
+					$match = $match . '(?:/([0-9]+))?/?$';
 					$query = $index . '?' . $query . '&page=' . $this->preg_index($num_toks + 1);
 				} else { //not matching a permalink so this is a lot simpler
 					//close the match and finalise the query

wp-includes/class-wp.php

@@ -587,7 +587,7 @@ class WP {
 	 * @global WP_Query $wp_query
  	 */
 	public function handle_404() {
-		global $wp_query;
+		global $wp_query, $wp;
 
 		// If we've already issued a 404, bail.
 		if ( is_404() )
@@ -596,16 +596,26 @@ class WP {
 		// Never 404 for the admin, robots, or if we found posts.
 		if ( is_admin() || is_robots() || $wp_query->posts ) {
 
-			// Only set X-Pingback for single posts.
+			$success = true;
 			if ( is_singular() ) {
 				$p = clone $wp_query->post;
+				// Only set X-Pingback for single posts that allow pings.
 				if ( $p && pings_open( $p ) ) {
 					@header( 'X-Pingback: ' . get_bloginfo( 'pingback_url' ) );
 				}
+
+				// check for paged content that exceeds the max number of pages
+				$next = '<!--nextpage-->';
+				if ( $p && false !== strpos( $p->post_content, $next ) && ! empty( $wp->query_vars['page'] ) ) {
+					$page = trim( $wp->query_vars['page'], '/' );
+					$success = (int) $page <= ( substr_count( $p->post_content, $next ) + 1 );
+				}
 			}
 
-			status_header( 200 );
-			return;
+			if ( $success ) {
+				status_header( 200 );
+				return;
+			}
 		}
 
 		// We will 404 for paged queries, as no posts were found.

wp-includes/rewrite-functions.php

@@ -256,6 +256,8 @@ function wp_resolve_numeric_slug_conflicts( $query_vars = array() ) {
 	} elseif ( 'monthnum' === $compare && isset( $query_vars['day'] ) ) {
 		$maybe_page = $query_vars['day'];
 	}
+	// Bug found in #11694 - 'page' was returning '/4'
+	$maybe_page = (int) trim( $maybe_page, '/' );
 
 	$post_page_count = substr_count( $post->post_content, '<!--nextpage-->' ) + 1;
 

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.4-alpha-34491';
+$wp_version = '4.4-alpha-34492';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.