Ticket #34890: 34890.2.diff

src/wp-includes/link-template.php

@@ -3502 +3502 @@
         $url = get_permalink( $id );
 
         $page = get_query_var( 'page' );
-        if ( $page ) {
-                $url = trailingslashit( $url ) . user_trailingslashit( $page, 'single_paged' );
+        if ( ( $page ) && ( 1 != $page ) ) {
+                if ( '' == get_option( 'permalink_structure' ) ) {
+                        $url = add_query_arg( 'page', $page, $url );
+                }
+                else {
+                        $url = trailingslashit( $url ) . user_trailingslashit( $page, 'single_paged' );
+                }
         }
 
         $cpage = get_query_var( 'cpage' );

tests/phpunit/tests/url.php

@@ -270 +270 @@
                 force_ssl_admin( $forced_admin );
         }
 
+        public function test_canonical_meta_tag() {
+                $now = time();
+                $post_id = self::factory()->post->create( array(
+                        'post_content' => rand_str() . "\n\n<!--nextpage-->\n\n" . rand_str(),
+                ) );
+
+                $this->set_permalink_structure( '' );
+
+                $url1 = add_query_arg( array(
+                        'page' => 2,
+                        'p'    => $post_id,
+                ), home_url() );
+                $url2 = add_query_arg( array(
+                        'p'    => $post_id,
+                        'page' => 2,
+                ), home_url() );
+
+                // Ensure the two URLs differ.
+                // If add_query_arg changes in the future and sorts by key, these
+                // tests will need to be rewritten to check different URLs return
+                // the same rel_canonical meta tag.
+                $this->assertNotEquals( ' ' . $url1, $url2 );
+
+                $this->go_to( $url1 );
+                ob_start();
+                rel_canonical();
+                $canonical1 = ob_get_clean();
+
+                $this->go_to( $url2 );
+                ob_start();
+                rel_canonical();
+                $canonical2 = ob_get_clean();
+
+                $this->assertEquals( $canonical1, $canonical2 );
+
+                $this->set_permalink_structure( '/%year%/%monthnum%/%day%/%postname%/' );
+
+                $permalink = get_permalink( $post_id );
+                $permalink_page_two = untrailingslashit( $permalink ) . '/2/';
+                $canonical3 = '<link rel="canonical" href="' . esc_url( $permalink_page_two ) . "\" />\n";
+
+                $this->go_to( $permalink_page_two );
+                ob_start();
+                rel_canonical();
+                $canonical4 = ob_get_clean();
+
+                $this->assertEquals( $canonical3, $canonical4 );
+        }
+
         public function test_get_adjacent_post() {
                 $now = time();
                 $post_id = self::factory()->post->create( array( 'post_date' => date( 'Y-m-d H:i:s', $now - 1 ) ) );