Add a default value for the node canonical URL

Check out this Drupal module from Joost de Valk:

http://yoast.com/canonical-url-links/

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I add a quick line to node.tpl.php using the code below:

	<?php drupal_set_html_head('<link rel="canonical" href="'.url('node/' . $node->nid, array('absolute' => TRUE)).'" />') ?>

Although it seems to work, at least only for nodes, is there any side effect using this code to generate canonical link url?

I agree, this is a tag that goes in the head and should be supported by the meta tags module. It should also be editable so we can set it to a custom location, not just what the path alias says it should be.

I am going to implement this in the version 6.x-1.x-dev.

This has been implemented in version 6.x-1.x-dev.

I moved to 6.x-1.x-dev to be able to use canonical url, but I don't like the way it works. It use canonical url by default, and if it is not specified while editing node, it says canonical - frontpage. And if I don't like that, I should set it on every single existing page and specify the url of the page which I'm editing as canonical (on page123 canonical should be: page123 to cancel default canonical: homepage).

The good behavior would be:
- when canonical url is specified, it is outputted in head
- if canonical is not specified, canonical meta tag is not present in the output

I guess that is caused by the fact the empty string is passed to url(), which returns the absolute URL of the front page.
That is not the desired thing, as an empty string should be interpreted as no canonical URL; there is always the way to mean the front page by using <front> (or something similar that is correctly interpreted by the function).

+1

If the canonical URL is equal to the actual URL, there is no reason to add the canonical meta tag.

The problem in the code is that it passed the empty string to the url() function, which returns the URL for the front page; that is not desired, and it must be changed. When I get the possibility to commit the code I changed, the problem will be fixed.

I committed the changed code; if the canonical URL is an empty string, it will not passed to url(), which then will not return the front page URL.

I think the feature request can be set to fixed, now. Thanks to everyone for making me notice the code problem.

I tried it now. There is nothing to select under "Tags to show on edit form" and under "Tags to output in html head".

Actually, there is nothing under 'Global meta tags' too. Something got broken in the last commit I have done, it seems.
I must verify the last commit, as I did it from a different PC, and this could have caused some problems.

Anyway, this is a different issue. I will open a new bug report.

See #497580: Settings page doesn't list any meta tag; the problem was caused by using a wrong name for the hook function that populates the meta tags list. I fixed the code, and committed the code in CVS. You have to wait until 12:00 PM GMT, before to get the new tarball archive.

Thanks for your report.

Thanks for fixing the "empty canonical" issue, but I am not sure dropping the tag completely is the best approach.

Why not have default behavior return the page's URL, cleaned up and stripped of junk, like extra parameters (e.g. page, destination, etc)?

In most cases canonical URL can and should be generated automagically.

I am not sure it's possible to use a default value that is valid for all the cases.
What do you think the default canonical URL used for nodes, taxonomy terms, views, panels, and the front page should be (one default value for each of the page types)?

I think we could have a special option to set "canonical default" with several possibilities:

1) Do not output the tag (existing behavior)
2) Simply cut off ALL query parameters, that would solve 90% problems with indexing pages like mydomain.com/my_node_list?page=15
3) Set up more elaborate options per entity type, whatever we figure out they should be. Maybe configurable with regexp or something...

Just adding Option 2 to Option 1, which you already implemented, should be a huge leap forward.

There is also the possibility to use the path alias as canonical URL; this could be an option more.

My idea is to follow this order:

• Verify if there is a path alias; if there is, use it as default value for the canonical URL.
• If there isn't a path alias, remove any arguments passed on the URL, and use the resulting URL as canonical URL.

The procedure is followed for all the nodes for which there isn't a canonical URL set by the user; when the user explicitly set the canonical URL, that value will be used instead.

The reported cases are automatically handled by Drupal, which will display the node with ID 237 in all the four cases (supposing that "new-node" is the path alias for the node with ID equal to 237). It's then enough to set the canonical URL for that node.

The code to generate a default canonical URL for user profile pages, nodes, taxonomy terms, and the front page has been added.
It's not possible to generate a default canonical URL for other cases because the module doesn't have settings for a generic path.

I am setting this report as fixed. If you need to have a settings page for a generic path, see #236833: Add more settings pages for the global meta tags.

Have you tested this with frontpage? I briefly looked at the code and do not think <front> will resolve to the correct path.

Confirmed by running dpm(drupal_get_path_alias('<front>'));.

The code does not perform a drupal_get_path_alias('<front>'). The executed code is the following:

      // ...
      case 'page':
        if (count($ids) == 1 && $ids[0] == '') {
          $value = '<front>';
        }
        break;
      // ...

The code does not change $path, in that case, but $value, which is the value used for the meta tags, and that is passed to url() (see the following code).

function nodewords_canonical_alter(&$tags, $type, $ids, $settings) {
  if (isset($tags['canonical'])) {
    $canonical_url = $tags['canonical'];
    
    if ($canonical_url[0] == '/') {
      $canonical_url = drupal_substr($canonical_url, 1);
    }
    
    $tags['canonical'] = !empty($canonical_url) ? check_url(url($canonical_url, array('absolute' => TRUE))) : '';
  }
}

In some Drupal installations, url('<front>') could return a wrong URL for the front page (or a value that could not be desired to use for that purpose); in that case, the administrator user can always set a different value, and the module will not overwrite the value set by the user. in fact, the first code I reported is executed only if there isn't a value already set for the meta tag.

function nodewords_canonical_prepare($type, $ids, $value, $settings) {
  if ($value == '<none>') {
    $path = '';
    
    switch ($type) {
      case 'node':
        // ...

'<none>' is the value set when the meta tag is not defined; differently, when the user set a empty string for the meta tag, the function will receive an empty string.

I am adding a tag so I can retrieve the features added after version 6.x-1.0 has been created.

Thanks for adding this feature, you've basically merged in the Canonical_URL module and fixed its deficiencies in one update :-)

Whoops... It seems I have added feature that were present in three different modules. In one case, the feature was added to replace the support for Views, and Panels; in the other two cases, I added the feature because there was a feature request.

I think it fits better in this module - as it is focused on managing all META and related tags, turning Nodewords into a one-stop-shop for all custom HTML HEAD tags isn't too far fetched to me and ultimately reduces the number of modules needed to run a site.

Will the canonical URL feature be added to the D5 build of this module? I am really looking forword to having this implemented! Would be awesome!