Paginate yearly archives for a custom post type

Question

Here's the code I'm using to create yearly archives for a custom post type:

function myquery_custom_post_rewrite( $rewrite_rules ) {
  $myqueryslug = 'customposttype';
  $month_archive = array( $myqueryslug . '/([0-9]{4})/?$' => 'index.php?year=' . $wp_rewrite->preg_index(1) . '&post_type=' . $myqueryslug . '&paged=' . $wp_rewrite->preg_index(3));
  $rewrite_rules = $month_archive + $rewrite_rules;
  return $rewrite_rules;
}
add_filter('rewrite_rules_array', 'myquery_custom_post_rewrite');

This works okay, except for the pagination. Trying to get to page 2 or any page other than 1 always shows a 404 page. Here's the URL I'm trying to use to get to pages other than 1:

http://mysite.com/customposttype/year/page/2

With the slug for my custom post type for customposttype and a year, like 2012, for year.

What am I doing wrong?

=============================

UPDATE: I got it working! Just in case anyone else needs it, here's the code that got it working:

function myquery_custom_post_rewrite( $rewrite_rules ) {
  $pagination_base = $GLOBALS['wp_rewrite']->pagination_base;
  $myqueryslug = 'customposttype';

  $year_archive = array(
    $myqueryslug . '/([0-9]{4})/' . $pagination_base . '/?([0-9]{1,})/?$' => 'index.php?post_type=' . $myqueryslug . '&year=$matches[1]&paged=$matches[2]',
    $myqueryslug . '/([0-9]{4})/?$' => 'index.php?post_type=' . $myqueryslug . '&year=$matches[1]',
  );
  $rewrite_rules = $year_archive + $rewrite_rules;
  return $rewrite_rules;
}
add_filter('rewrite_rules_array', 'myquery_custom_post_rewrite');

Answer 1

Your regex cannot work: $wp_rewrite->preg_index(3) doesn't match anything, because you capture only one part in '/([0-9]{4})/?$', not three.

Try to add the page parameter:

$pagination_base = $GLOBALS['wp_rewrite']->pagination_base;
$month_archive = array( 
    $myqueryslug . '/([0-9]{4})(' . $pagination_base . '/(\d+))?/?$' => 
        'index.php?year=' . $wp_rewrite->preg_index(1) 
        . '&post_type=' . $myqueryslug 
        . '&paged=' . $wp_rewrite->preg_index(3)
);

I haven't tested it, just see it as a hint for where to look.

Answer 2

Here's the code that worked:

function myquery_custom_post_rewrite( $rewrite_rules ) {
  $pagination_base = $GLOBALS['wp_rewrite']->pagination_base;
  $myqueryslug = 'customposttype';

  $year_archive = array(
    $myqueryslug . '/([0-9]{4})/' . $pagination_base . '/?([0-9]{1,})/?$' => 'index.php?post_type=' . $myqueryslug . '&year=$matches[1]&paged=$matches[2]',
    $myqueryslug . '/([0-9]{4})/?$' => 'index.php?post_type=' . $myqueryslug . '&year=$matches[1]',
  );
  $rewrite_rules = $year_archive + $rewrite_rules;
  return $rewrite_rules;
}
add_filter('rewrite_rules_array', 'myquery_custom_post_rewrite');