Ticket #47968: 47968.1.patch

src/wp-includes/class-wp.php

@@ -401 +401 @@
                 $headers       = array();
                 $status        = null;
                 $exit_required = false;
+                $date_format   = 'D, d M Y H:i:s';
 
                 if ( is_user_logged_in() ) {
                         $headers = array_merge( $headers, wp_get_nocache_headers() );
@@ -408 +409 @@
                         // Unmoderated comments are only visible for 10 minutes via the moderation hash.
                         $expires = 10 * MINUTE_IN_SECONDS;
 
-                        $headers['Expires']       = gmdate( 'D, d M Y H:i:s', time() + $expires );
+                        $headers['Expires']       = gmdate( $date_format, time() + $expires );
                         $headers['Cache-Control'] = sprintf(
                                 'max-age=%d, must-revalidate',
                                 $expires
@@ -447 +448 @@
                                         )
                                 )
                         ) {
-                                $wp_last_modified = mysql2date( 'D, d M Y H:i:s', get_lastcommentmodified( 'GMT' ), false );
+                                $wp_last_modified_post    = mysql2date( $date_format, get_lastpostmodified( 'GMT' ), false );
+                                $wp_last_modified_comment = mysql2date( $date_format, get_lastcommentmodified( 'GMT' ), false );
+
+                                if ( strtotime( $wp_last_modified_post ) > strtotime( $wp_last_modified_comment ) ) {
+                                        $wp_last_modified = $wp_last_modified_post;
+                                } else {
+                                        $wp_last_modified = $wp_last_modified_comment;
+                                }
                         } else {
-                                $wp_last_modified = mysql2date( 'D, d M Y H:i:s', get_lastpostmodified( 'GMT' ), false );
+                                $wp_last_modified = mysql2date( $date_format, get_lastpostmodified( 'GMT' ), false );
                         }
 
                         if ( ! $wp_last_modified ) {
-                                $wp_last_modified = gmdate( 'D, d M Y H:i:s' );
+                                $wp_last_modified = gmdate( $date_format );
                         }
 
                         $wp_last_modified .= ' GMT';

tests/phpunit/tests/feed/rss2.php

@@ -494 +494 @@
                 );
 
         }
+
+        /**
+         * Test that Last-Modified in headers is properly updated from posts and comments where appropriate.
+         *
+         * @ticket 47968
+         */
+        public function test_feed_last_modified_header() {
+                $last_week = gmdate( 'Y-m-d H:i:s', strtotime( '-1 week' ) );
+                $yesterday = gmdate( 'Y-m-d H:i:s', strtotime( '-1 day' ) );
+                $today     = gmdate( 'Y-m-d H:i:s' );
+
+                $post_id = $this->factory()->post->create(
+                        array(
+                                'post_date' => $last_week,
+                        )
+                );
+
+                $filter_post_modified_last_week = function( $headers ) use ( $last_week ) {
+                        $this->assertSame( strtotime( $headers['Last-Modified'] ), strtotime( $last_week ) );
+
+                        return $headers;
+                };
+
+                add_filter( 'wp_headers', $filter_post_modified_last_week );
+
+                // Last modified by a post last week.
+                $this->go_to( '/?feed=rss2' );
+
+                $this->factory()->comment->create(
+                        array(
+                                'comment_post_ID' => $post_id,
+                                'comment_date'    => $yesterday,
+                        )
+                );
+
+                // Last modified by a comment yesterday, however, we are calling a feed without comments, so Last-Modified is still from last week's post.
+                $this->go_to( '/?feed=rss2' );
+
+                remove_filter( 'wp_headers', $filter_post_modified_last_week );
+
+                $filter_comment_modified_yesterday = function( $headers ) use ( $yesterday ) {
+                        $this->assertSame( strtotime( $headers['Last-Modified'] ), strtotime( $yesterday ) );
+
+                        return $headers;
+                };
+
+                add_filter( 'wp_headers', $filter_comment_modified_yesterday );
+
+                // Last modified by a comment yesterday, we are calling a feed with comments, so Last-Modified is from yesterday's comment.
+                $this->go_to( '/?feed=rss2&withcomments=1' );
+
+                remove_filter( 'wp_headers', $filter_comment_modified_yesterday );
+
+                $this->factory()->post->create(
+                        array(
+                                'post_date' => $today,
+                        )
+                );
+
+                $filter_post_modified_today = function( $headers ) use ( $today ) {
+                        $this->assertSame( strtotime( $headers['Last-Modified'] ), strtotime( $today ) );
+
+                        return $headers;
+                };
+
+                add_filter( 'wp_headers', $filter_post_modified_today );
+
+                // Last modified by a post today, so that should be the Last-Modified datetime.
+                $this->go_to( '/?feed=rss2&withcomments=1' );
+
+                remove_filter( 'wp_headers', $filter_post_modified_today );
+        }
 }