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<title>[34729] trunk: Simplify pagination logic in `comments_template()`.</title>
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<dt style="float: left; width: 6em; font-weight: bold">Revision</dt> <dd><a style="font-weight: bold" href="https://core.trac.wordpress.org/changeset/34729">34729</a><script type="application/ld+json">{"@context":"http://schema.org","@type":"EmailMessage","description":"Review this Commit","action":{"@type":"ViewAction","url":"https://core.trac.wordpress.org/changeset/34729","name":"Review Commit"}}</script></dd>
<dt style="float: left; width: 6em; font-weight: bold">Author</dt> <dd>boonebgorges</dd>
<dt style="float: left; width: 6em; font-weight: bold">Date</dt> <dd>2015-10-01 03:10:13 +0000 (Thu, 01 Oct 2015)</dd>
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<pre style='padding-left: 1em; margin: 2em 0; border-left: 2px solid #ccc; line-height: 1.25; font-size: 105%; font-family: sans-serif'>Simplify pagination logic in `comments_template()`.

<a href="https://core.trac.wordpress.org/changeset/34561">[34561]</a> "fixed" the problem of newest-first comments showing fewer than
'per_page' comments on the post permalink when the total number of comments
was not divisible by 'per_page'. See <a href="https://core.trac.wordpress.org/ticket/29462">#29462</a>. But this fix caused numerous
other problems. First, comment pages reported by `get_page_of_comment()`
(which expects comment pages to be filled oldest-first) were no longer correct.
Second, and more seriously, the new logic caused comments to be shifted
between pages, making their permalinks non-permanent.

The current changeset reverts the changed behavior. In order to preserve the
performance improvements introduced in <a href="https://core.trac.wordpress.org/changeset/34561">[34561]</a>, an additional query must be
performed when 'default_comments_page=newest' and 'cpage=0' (ie, you're viewing
the post permalink). A nice side effect of this revert is that we no longer
need the hacks required to determine proper comment pagination, introduced in
<a href="https://core.trac.wordpress.org/changeset/34561">[34561]</a>.

See <a href="https://core.trac.wordpress.org/ticket/8071">#8071</a>. See <a href="https://core.trac.wordpress.org/ticket/34073">#34073</a>.</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunksrcwpincludescommenttemplatephp">trunk/src/wp-includes/comment-template.php</a></li>
<li><a href="#trunktestsphpunittestscommentcommentsTemplatephp">trunk/tests/phpunit/tests/comment/commentsTemplate.php</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunksrcwpincludescommenttemplatephp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/src/wp-includes/comment-template.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/src/wp-includes/comment-template.php        2015-10-01 02:09:41 UTC (rev 34728)
+++ trunk/src/wp-includes/comment-template.php  2015-10-01 03:10:13 UTC (rev 34729)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -1240,74 +1240,30 @@
</span><span class="cx" style="display: block; padding: 0 10px">                $per_page = (int) get_option( 'comments_per_page' );
</span><span class="cx" style="display: block; padding: 0 10px">        }
</span><span class="cx" style="display: block; padding: 0 10px"> 
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-        /*
-        * For legacy reasons, higher page numbers always mean more recent comments, regardless of sort order.
-        * Since we don't have full pagination info until after the query, we use some tricks to get the
-        * right comments for the current page.
-        *
-        * Abandon all hope, ye who enter here!
-        */
-       $flip_comment_order = $trim_comments_on_page= false;
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ $comment_args['order']  = 'ASC';
</ins><span class="cx" style="display: block; padding: 0 10px">         $comment_args['number'] = $per_page;
</span><span class="cx" style="display: block; padding: 0 10px">        $page = (int) get_query_var( 'cpage' );
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-        if ( 'newest' === get_option( 'default_comments_page' ) ) {
-               if ( $page ) {
-                       $comment_args['order'] = 'ASC';
</del><span class="cx" style="display: block; padding: 0 10px"> 
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-                        /*
-                        * We don't have enough data (namely, the total number of comments) to calculate an
-                        * exact offset. We'll fetch too many comments, and trim them as needed
-                        * after the query.
-                        */
-                       $offset = ( $page - 2 ) * $per_page;
-                       if ( 0 > $offset ) {
-                               // `WP_Comment_Query` doesn't support negative offsets.
-                               $comment_args['offset'] = 0;
-                       } else {
-                               $comment_args['offset'] = $offset;
-                       }
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+ if ( $page ) {
+               $comment_args['offset'] = ( $page - 1 ) * $per_page;
+       } elseif ( 'oldest' === get_option( 'default_comments_page' ) ) {
+               $comment_args['offset'] = 0;
+       } else {
+               // If fetching the first page of 'newest', we need a top-level comment count.
+               $top_level_query = new WP_Comment_Query();
+               $top_level_count = $top_level_query->query( array(
+                       'count'   => true,
+                       'orderby' => false,
+                       'post_id' => $post->ID,
+                       'parent'  => 0,
+               ) );
</ins><span class="cx" style="display: block; padding: 0 10px"> 
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-                        // Fetch double the number of comments we need.
-                       $comment_args['number'] += $per_page;
-                       $trim_comments_on_page = true;
-               } else {
-                       $comment_args['order'] = 'DESC';
-                       $comment_args['offset'] = 0;
-                       $flip_comment_order = true;
-               }
-       } else {
-               $comment_args['order'] = 'ASC';
-               if ( $page ) {
-                       $comment_args['offset'] = ( $page - 1 ) * $per_page;
-               } else {
-                       $comment_args['offset'] = 0;
-               }
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+         $comment_args['offset'] = ( ceil( $top_level_count / $per_page ) - 1 ) * $per_page;
</ins><span class="cx" style="display: block; padding: 0 10px">         }
</span><span class="cx" style="display: block; padding: 0 10px"> 
</span><span class="cx" style="display: block; padding: 0 10px">        $comment_query = new WP_Comment_Query( $comment_args );
</span><span class="cx" style="display: block; padding: 0 10px">        $_comments = $comment_query->comments;
</span><span class="cx" style="display: block; padding: 0 10px"> 
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-        // Delightful pagination quirk #1: `wp_list_comments()` expects the order to be wrong, so we make it wrong.
-       if ( $flip_comment_order ) {
-               $_comments = array_reverse( $_comments );
-       }
-
-       // Delightful pagination quirk #2: reverse chronological order requires page shifting.
-       if ( $trim_comments_on_page ) {
-               // Correct the value of max_num_pages, which is wrong because we manipulated the per_page 'number'.
-               $comment_query->max_num_pages = ceil( $comment_query->found_comments / $per_page );
-
-               // Identify the number of comments that should appear on page 1.
-               $page_1_count = $comment_query->found_comments - ( ( $comment_query->max_num_pages - 1 ) * $per_page );
-
-               // Use that value to shift the matched comments.
-               if ( 1 === $page ) {
-                       $_comments = array_slice( $_comments, 0, $page_1_count );
-               } else {
-                       $_comments = array_slice( $_comments, $page_1_count, $per_page );
-               }
-       }
-
</del><span class="cx" style="display: block; padding: 0 10px">         // Trees must be flattened before they're passed to the walker.
</span><span class="cx" style="display: block; padding: 0 10px">        $comments_flat = array();
</span><span class="cx" style="display: block; padding: 0 10px">        foreach ( $_comments as $_comment ) {
</span></span></pre></div>
<a id="trunktestsphpunittestscommentcommentsTemplatephp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/tests/phpunit/tests/comment/commentsTemplate.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/tests/phpunit/tests/comment/commentsTemplate.php    2015-10-01 02:09:41 UTC (rev 34728)
+++ trunk/tests/phpunit/tests/comment/commentsTemplate.php      2015-10-01 03:10:13 UTC (rev 34729)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -325,4 +325,88 @@
</span><span class="cx" style="display: block; padding: 0 10px">                $found_cids = array_map( 'intval', $matches[1] );
</span><span class="cx" style="display: block; padding: 0 10px">                $this->assertSame( array( $comment_1, $comment_2 ), $found_cids );
</span><span class="cx" style="display: block; padding: 0 10px">        }
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+
+       /**
+        * @ticket 8071
+        * @ticket 34073
+        * @ticket 29462
+        */
+       public function test_last_page_of_comments_should_be_full_when_default_comment_page_is_newest() {
+               $now = time();
+               $p = $this->factory->post->create();
+               $comment_1 = $this->factory->comment->create( array(
+                       'comment_post_ID' => $p,
+                       'comment_content' => '1',
+                       'comment_date_gmt' => date( 'Y-m-d H:i:s', $now - 100 ),
+               ) );
+               $comment_2 = $this->factory->comment->create( array(
+                       'comment_post_ID' => $p,
+                       'comment_content' => '2',
+                       'comment_date_gmt' => date( 'Y-m-d H:i:s', $now - 200 ),
+               ) );
+               $comment_3 = $this->factory->comment->create( array(
+                       'comment_post_ID' => $p,
+                       'comment_content' => '3',
+                       'comment_date_gmt' => date( 'Y-m-d H:i:s', $now - 300 ),
+               ) );
+
+               update_option( 'default_comments_page', 'newest' );
+               update_option( 'comment_order', 'desc' );
+
+               $link = add_query_arg( array(
+                       'cpage' => 1,
+                       'comments_per_page' => 2,
+               ), get_permalink( $p ) );
+
+               $this->go_to( $link );
+               $found = get_echo( 'comments_template' );
+
+               $comments = preg_match_all( '/id="comment-([0-9]+)"/', $found, $matches );
+
+               $found_cids = array_map( 'intval', $matches[1] );
+
+               $this->assertSame( array( $comment_2, $comment_3 ), $found_cids );
+       }
+
+       /**
+        * @ticket 8071
+        * @ticket 34073
+        * @ticket 29462
+        */
+       public function test_first_page_of_comments_should_have_remainder_when_default_comments_page_is_newest() {
+               $now = time();
+               $p = $this->factory->post->create();
+               $comment_1 = $this->factory->comment->create( array(
+                       'comment_post_ID' => $p,
+                       'comment_content' => '1',
+                       'comment_date_gmt' => date( 'Y-m-d H:i:s', $now - 100 ),
+               ) );
+               $comment_2 = $this->factory->comment->create( array(
+                       'comment_post_ID' => $p,
+                       'comment_content' => '2',
+                       'comment_date_gmt' => date( 'Y-m-d H:i:s', $now - 200 ),
+               ) );
+               $comment_3 = $this->factory->comment->create( array(
+                       'comment_post_ID' => $p,
+                       'comment_content' => '3',
+                       'comment_date_gmt' => date( 'Y-m-d H:i:s', $now - 300 ),
+               ) );
+
+               update_option( 'default_comments_page', 'newest' );
+               update_option( 'comment_order', 'desc' );
+
+               $link = add_query_arg( array(
+                       'cpage' => 2,
+                       'comments_per_page' => 2,
+               ), get_permalink( $p ) );
+
+               $this->go_to( $link );
+               $found = get_echo( 'comments_template' );
+
+               $comments = preg_match_all( '/id="comment-([0-9]+)"/', $found, $matches );
+
+               $found_cids = array_map( 'intval', $matches[1] );
+
+               $this->assertSame( array( $comment_1 ), $found_cids );
+       }
</ins><span class="cx" style="display: block; padding: 0 10px"> }
</span></span></pre>
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