wp-includes/comment.php:738 - Undefined property: WP_Query::$comments

[markjaquith]

get_comment_pages_count() can throw a notice. We use $wp_query->comments without checking it first.

Make sure it's not empty.

The patch is not correct. It does this:

- if ( !$comments || !is_array($comments) ) 
+ if ( ( !$comments || !is_array($comments) ) && !empty( $wp_query->comments ) ) 
    $comments = $wp_query->comments;
  if ( empty($comments) )
    return 0;

The patch defeats the is_array() check. For example, $comments=true, $wp_query->comments=null will not return 0.

Suggest:

- if ( !$comments || !is_array($comments) )
+ if ( empty($comments) || !is_array($comments) ) {
+   if (empty( $wp_query->comments ) )
+     return 0;
    $comments = $wp_query->comments;
+ }
- if ( empty($comments) )
-    return 0;

Replying to kitchin:

Suggest:

- if ( !$comments || !is_array($comments) )
+ if ( empty($comments) || !is_array($comments) ) {
+   if (empty( $wp_query->comments ) )
+     return 0;
    $comments = $wp_query->comments;
+ }
- if ( empty($comments) )
-    return 0;

Would you like to ​submit an updated patch?

Easiest place to see this bug is before the Loop. I put a note about that in the Codex, since then the function returns 0 with or without the bug fix. ​http://codex.wordpress.org/index.php?title=Function_Reference%2Fget_comment_pages_count&diff=128919&oldid=126895

A test for this bug is to set WP_DEBUG to true. In wp-content/themes/twentythirteen/single.php insert

  <?php printf('<pre>get_comment_pages_count=%s</pre>',
     get_comment_pages_count()); ?>

before and after the loop starts, at

  <?php comments_template(); ?>

And look at the Hello World post.
Expect 0 then 1, with 1 warning before the bug and no warnings after.
Another test is to make sure

  <?php printf('<pre>get_comment_pages_count=%s</pre>',
     get_comment_pages_count($GLOBALS['wp_query']->comments)); ?>

still works after the Loop. Expect 1.

But I didn't see anything similar in the unit tests as far as I could tell.

spacing