Create a hook to alter generated link xml

Coming back to this, because the job I'm working on needed to make the sitemap like this because of our SEO team (grumbles):
https://support.google.com/webmasters/answer/2620865?hl=en

Having our sites for every region talk to each other is well outside the scope of this module, so I created my own custom solution to do it. Problem being though I was unable to output it as the method writeSitemapElement doesn't allow for attributes.

This patch adds the hook and allows writeSitemapElement to print out XML tags with attributes.

An example usage of

/**
 * Implements hook_xmlsitemap_item_extend().
 */
function CUSTOM_MODULE_xmlsitemap_item_extend($item) {
  $element = array();
  $element['#name'] = 'xhtml:link';
  $element['#attributes'] = array(
    'rel' => 'alternate',
    'hreflang' => $locale,
    'href' => $item['loc'],
  );
  $item['xhtml:link_' . $locale] = $element;
  return $item;
}

I clipped some of the example for space, mainly taking out the for loop that does it multiple times for each locale, but the result means I get an output like:

<url><loc>http://www.flightcentre.com.au/world-travel/australia</loc><lastmod>2014-04-01T03:47Z</lastmod><changefreq>yearly</changefreq>
<xhtml:link rel="alternate" hreflang="en-AU" href="http://www.mysite.com.au/world-travel/australia"/>
<xhtml:link rel="alternate" hreflang="en-NZ" href="http://www.mysite.co.nz/world-travel/australia"/></url>

Again I know the locale stuff is out of scope, this is just an example of what this hook and method rewrite allows.

Attached Xmlsitemap.patch shoud work for version 7.x-2.0-rc2
An example usage of hook_xmlsitemap_item_extend()

<?php

/*
 *
 * Implementation of hook_xmlsitemap_item_extend()
 *
 * @param $element
 * The current element array that will be turned to xml.
 *
 * @param
 * The link information from xmlsitemap. Contains useful keys, to look up other information e.g. nid
 *
 *
 * @Return the changed $element array
 * Refer - Refer https://support.google.com/webmasters/answer/183668?hl=en
 *
 */
function MODULE_NAME_xmlsitemap_item_extend($element, $link){
  // Check if we are dealing with a node
  if ($link['type'] != 'node') {
    return $element;
  }

  $node = node_load($link['id']);

  switch ($link['subtype']) {
    case 'video':
       $element['video:video']=array(
        'video:title' => 'Custom title',
        'video:description' => 'Custom Description',
        'video:thumbnail_loc' => 'Thumbnail URL',
        'video:player_loc' => 'Video player location',
      );
    break;
    
    default:
    break;
  }

return $element;
}
?>

Adding a base drupal_alter hook with minimal impact.
Our company need was to alter the URL's saved by the XMLwriter only, without adding extra data like "video" to the elements.
Altered the initial query (including extra columns), and added the element_alter to the drupal_alter() call.

Updated the patch to better comply with standards (added documentation to the API). Functionally the same patch, just a notation update from my previous submission.
This patch replaces my previous.

Here's my version of the patch started here. This patch adds two hooks, hook_xmlsitemap_root_attributes_alter() and hook_xmlsitemap_element_alter() which allow you to alter the XML that's about to be generated an add additional information.

This doesn't necessarily solve #451234: Support for extended sitemap formats (e.g. video, news, image, mobile) but it does make it pretty easy to write your own custom module that implements a couple of hooks and includes the required data. With this patch I had no problem adding the elements to my sitemap.

The code here is mostly the same as the patches above, but it adds documentation and better adherence to the Drupal coding standards. Thanks for the ideas about how to make this work everyone.

1. +++ b/xmlsitemap.xmlsitemap.inc
   @@ -73,6 +73,9 @@ class XMLSitemapWriter extends XMLWriter {
   +    drupal_alter('xmlsitemap_root_attributes', $attributes);
   

   We should probably be passing in $this->sitemap as an argument here, or possibly just $this. This way modules that want to add attributes can do so if they only apply to a specific sitemap context.

2. +++ b/xmlsitemap.xmlsitemap.inc
   @@ -173,6 +176,9 @@ class XMLSitemapIndexWriter extends XMLSitemapWriter {
   +    drupal_alter('xmlsitemap_root_attributes', $attributes);
   

   Same here.

Revised patch that ensure the sitemap object is passed through everywhere.

Committed #8 to 7.x-2.x.

Attached Xmlsitemap.patch shoud work for version 7.x-2.0-rc2. Added hook xmlsitemap_item_element_alter and xmlsitemap_more_attributes. By implementing the hooks mentioned above in custom module, we should be able to extend xmlsitemap for image and video.

To extend image sitemap.

/*
 *
 * Implementation of hook_xmlsitemap_item_element_alter()
 *
 * @param $element
 * The current link array that will be turned to xml.
 *
 * @param
 * The link information from xmlsitemap. Contains useful keys, to look up other information e.g. nid
 * Refer - https://support.google.com/webmasters/answer/178636?hl=en
 *
 */
function MODULE_NAME_xmlsitemap_item_element_alter(&$element, $link) {
  switch ($link['subtype']) {
    case 'image':
      $node = node_load($link['id']);
      $element['image:image']['image:loc'] = url(file_create_url($node->field_image_name['und'][0]['uri']));
      $element['image:image']['image:title'] = t($node->title);
      if($node->field_caption['und'][0]['value']) {
        $element['image:image']['image:caption'] = t(($node->field_caption_name['und'][0]['value']));
      }
    break;

    default:
    break;
  }
}

/*
 * Implementation of hook xmlsitemap_more_attributes()
 * returns array() of sitemap main attributes.
*/
function MODULE_NAME_xmlsitemap_more_attributes() {
  $attributes['xmlns:image'] = 'http://www.google.com/schemas/sitemap-image/1.1';
  return $attributes;
}

Just providing a little extra here ... We required the ability to "drop" the element from the sitemap if its not aliased.

I then simply used;

// In a "hook_xmlsitemap_element_alter()".
if ($link['type'] == 'node' && strpos($link['loc'], 'node/') === 0) {
  $element = array();
}

#8
// @todo Should this be moved to XMLSitemapWritier::writeSitemapElement()?

Yes, because I want to alter the operation when this element is added on xmlsitemap.xmlsitemap.inc file line 210. I would create a bacth but $link and $sitemap varaibles are not available inside writeSitemapElement() and changing the hook arguments would be an API change and this is probably not what we want.

$this->writeSitemapElement('sitemap', $element);

So maybe creating a new hook inside writeSitemapElement() would help ? Or making the hook dependant on the $name argument which is sent to writeSitemapElement as first parameter.

The reason behind this is that I need to change the new "chunk", "page" (call it whatever you want) element creation. Atm this is not possible cause the alter hook is not initialized.

EDIT:
It would also help if the hook is moved there and the default implementation is like this:

hook_xmlsitemap_element_alter(&$element, $link = '', $sitemap = '')

Instead of

hook_xmlsitemap_element_alter(&$element, $link, $sitemap)

This way it is still backward compatible but for those of us who want to alter other elements, it is then possible to use this hook every time an element is actually processed. (The $sitemap variable is also in $this actually, so it can be sent in the hook if needed.)

Forgot to mention earlier that this is for drupal 7
I created new patch which invokes the hook_xmlsitemap_element when generateXML is executed and before the element is sent to writeSitemapElement() It sends in empty link array on sitemap object from $this

Needed to add hook_xmlsitemap_element_alter for D8.

Based on @evanjenkins's patch in #16, I've also added in the change made by @pobster in #13.

One more patch here. The D7 patch exposed `type` and `subtype` to the hook, so I've added that here as well.

Thanks for the patch! Just one note, the D8 patch is missing hook_xmlsitemap_root_attributes_alter.

We need to move the discussion about supporting hook_element_alter() being able to skip the current link to a new feature request, this issue should be focused on ensuring that the Drupal 8 version supports the same functionality as the Drupal 7 version.

Revised patch which adds the missing hook_xmlsitemap_root_attributes_alter(), hook documentation, and small fixes.

@pobster: I think you still might be able to accomplish what you need just by using hook_xmlsitemap_link_alter(), and that way you avoid that link getting selected by the sitemap generation entirely, which would be better for performance. I don't see a need to support this additional feature in this patch.

/**
 * Implements hook_xmlsitemap_link_alter().
 *
 * Mark un-aliased nodes as unaccessible in the sitemap.
 */
function mymodule_xmlsitemap_link_alter(array &$link) {
  if ($link['type'] == 'node' && $link['access'] && strpos($link['loc'], 'node/') === 0) {
    $link['access'] = FALSE;
  }
}

Fixing some coding standards.

Tested and committed #22 to 8.x-1.x.