From b672d77e873f78f37f89e8549adbff2c1d95f03b Mon Sep 17 00:00:00 2001
From: whyisjake <whyisjake@git.wordpress.org>
Date: Tue, 8 Jun 2021 22:51:01 +0000
Subject: [PATCH] Permalinks: Limit pagination for posts with comments.

Additionally, redirect pages back to the source page if comments don't exist.

Props devrekli, carike, sumanm, mukesh27, chaion07, audrasjb, whyisjake, SergeyBiryukov.

Fixes #50233.

Built from https://develop.svn.wordpress.org/trunk@51118


git-svn-id: http://core.svn.wordpress.org/trunk@50727 1a063a9b-81f0-0310-95a4-ce76da25c4cd
---
 wp-includes/canonical.php | 12 ++++++++++--
 wp-includes/version.php   |  2 +-
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/wp-includes/canonical.php b/wp-includes/canonical.php
index 184fb756e8..0eba17d60d 100644
--- a/wp-includes/canonical.php
+++ b/wp-includes/canonical.php
@@ -27,6 +27,7 @@
  * or query in an attempt to figure the correct page to go to.
  *
  * @since 2.3.0
+ * @since 5.8.0 Checks comment page count to limit pagination.
  *
  * @global WP_Rewrite $wp_rewrite WordPress rewrite component.
  * @global bool       $is_IIS
@@ -504,8 +505,15 @@ function redirect_canonical( $requested_url = null, $do_redirect = true ) {
 				&& ( 'newest' === $default_comments_page && $cpage > 0
 					|| 'newest' !== $default_comments_page && $cpage > 1 )
 			) {
-				$addl_path  = ( ! empty( $addl_path ) ? trailingslashit( $addl_path ) : '' );
-				$addl_path .= user_trailingslashit( $wp_rewrite->comments_pagination_base . '-' . $cpage, 'commentpaged' );
+				// Checks comment page count to limit pagination.
+				$per_page = get_option( 'comments_per_page' );
+
+				// Get the total number of pages for comments.
+				$comments_total_pages = ceil( ( $wp_query->post->comment_count ) / $per_page );
+				if ( $cpage <= $comments_total_pages ) {
+					$addl_path  = ( ! empty( $addl_path ) ? trailingslashit( $addl_path ) : '' );
+					$addl_path .= user_trailingslashit( $wp_rewrite->comments_pagination_base . '-' . $cpage, 'commentpaged' );
+				}
 
 				$redirect['query'] = remove_query_arg( 'cpage', $redirect['query'] );
 			}
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 666012fd72..d3b8ebf284 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.8-alpha-51117';
+$wp_version = '5.8-alpha-51118';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.