From caf041d76e7f06274391a8c6d5f42d964bb2e71f Mon Sep 17 00:00:00 2001
From: Aaron Jorbin <jorbin@git.wordpress.org>
Date: Sun, 14 Jun 2015 18:36:14 +0000
Subject: [PATCH] Improve lastBuildDate timestamp in rss feeds

RSS feed timestamps should reflect the actual timestamps for those RSS feeds rather than the generic timestamp for all posts and all comments.

Props stevenkword.
Fixes #4575.




git-svn-id: https://develop.svn.wordpress.org/trunk@32765 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/feed-rss2-comments.php |  2 +-
 src/wp-includes/feed-rss2.php          |  2 +-
 src/wp-includes/feed.php               | 34 ++++++++++++++++++++++++++
 3 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/src/wp-includes/feed-rss2-comments.php b/src/wp-includes/feed-rss2-comments.php
index c8e8d498ea..73d92ce6cc 100644
--- a/src/wp-includes/feed-rss2-comments.php
+++ b/src/wp-includes/feed-rss2-comments.php
@@ -43,7 +43,7 @@ do_action( 'rss_tag_pre', 'rss2-comments' );
 	<atom:link href="<?php self_link(); ?>" rel="self" type="application/rss+xml" />
 	<link><?php (is_single()) ? the_permalink_rss() : bloginfo_rss("url") ?></link>
 	<description><?php bloginfo_rss("description") ?></description>
-	<lastBuildDate><?php echo mysql2date('r', get_lastcommentmodified('GMT')); ?></lastBuildDate>
+	<lastBuildDate><?php echo mysql2date('r', get_last_build_date_feed(), false ); ?></lastBuildDate>
 	<sy:updatePeriod><?php
 		/** This filter is documented in wp-includes/feed-rss2.php */
 		echo apply_filters( 'rss_update_period', 'hourly' );
diff --git a/src/wp-includes/feed-rss2.php b/src/wp-includes/feed-rss2.php
index c82fc63c56..08802e1e55 100644
--- a/src/wp-includes/feed-rss2.php
+++ b/src/wp-includes/feed-rss2.php
@@ -42,7 +42,7 @@ do_action( 'rss_tag_pre', 'rss2' );
 	<atom:link href="<?php self_link(); ?>" rel="self" type="application/rss+xml" />
 	<link><?php bloginfo_rss('url') ?></link>
 	<description><?php bloginfo_rss("description") ?></description>
-	<lastBuildDate><?php echo mysql2date('D, d M Y H:i:s +0000', get_lastpostmodified('GMT'), false); ?></lastBuildDate>
+	<lastBuildDate><?php echo mysql2date('D, d M Y H:i:s +0000', get_last_build_date_feed(), false); ?></lastBuildDate>
 	<language><?php bloginfo_rss( 'language' ); ?></language>
 	<sy:updatePeriod><?php
 		$duration = 'hourly';
diff --git a/src/wp-includes/feed.php b/src/wp-includes/feed.php
index a59fc5f50e..822abfbca0 100644
--- a/src/wp-includes/feed.php
+++ b/src/wp-includes/feed.php
@@ -87,6 +87,40 @@ function get_default_feed() {
 	return 'rss' == $default_feed ? 'rss2' : $default_feed;
 }
 
+/**
+ * Get the timestamp of the most recently modified post from WP_Query
+ *
+ * If viewing a comment feed, the date of the most recently modified
+ * comment will be returned.
+ *
+ * @since 4.3.0
+ *
+ * @return string Date ('Y-m-d H:i:s' for use with mysql2date() )
+ */
+function get_last_build_date_feed() {
+	global $wp_query, $wpdb;
+
+	if ( $wp_query->have_posts() ) {
+		$post_ids = array();
+		foreach( $wp_query->posts as $post ) {
+			$post_ids[] = $post->ID;
+			$post_times[] = $post->post_modified_gmt;
+		}
+		$postids = implode( "','", $post_ids );
+		$max_post_time = max( $post_times );
+
+		if( $wp_query->is_comment_feed() ) {
+			$max_comment_time = $wpdb->get_var( $wpdb->prepare( "SELECT MAX(comment_date_gmt) FROM $wpdb->comments WHERE comment_post_ID IN ('%s') AND comment_approved = '1'", $postids ) );
+
+			return max( $max_post_time, $max_comment_time );
+		}
+		return $max_post_time;
+	}
+
+	// Fallback to last time any post was modified or published.
+	return get_lastpostmodified( 'GMT' );
+}
+
 /**
  * Retrieve the blog title for the feed title.
  *