Drupal 7 Module Development

Chapter 4
into these lines:
'data' => array(
'#type' => 'link',
'#title' => $node->title,
'#href' => 'node/' . $node->nid,
),
system_element_info() defines the link element and we can see from its
declaration and examining its #pre_render callbacks that render elements
with a #type of link will be rendered into a link using l().
Unfortunately, the theme_item_list() function does not expect a render element
in its data key, so it will choke on these contents. Considering the push to make
everything alterable with render arrays, this seems like an oversight. If you
encounter a bug or inconsistency in Drupal (and you will!), you can contribute
simply by making a note of it and creating an issue in Drupal's issue queue. In fact, I
just created a new issue for this problem at http://drupal.org/node/891112.
In the meantime, we'll have to work around this problem rather then hacking Drupal
core. Fortunately, a close inspection of the render element properties available to us
(again, see Chapter 3) indicate that we can use a #pre_render callback to alter our
render element before it is passed to the element's theme function. Let's add one
to our $block['content']['list'] child element:
$block['content']['list'] = array(
'#theme' => 'item_list__single_blog',
'#items' => $items,
'#pre_render' => array('single_blog_item_list_child_render'),
);
Since drupal_render() will pass the entire child element to our #pre_render
callback, we just need to make sure our callback modifies the data element of
all our items.
/**
* Render the child elements of theme_item_list() before its
* data is themed.
*/
function single_blog_item_list_child_render($elements) {
foreach (array_keys($elements['#items']) AS $key) {
// Take the renderable array that we set in
// single_blog_block_view() and render it into the string
// that theme_item_list() expects.
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