Provide a way to set a custom base URL for the index (headless CMS)

Hi codebymikey

Thank you for opening this issue and for taking the time to provide a merge request - the use case is clear and the overall approach is well thought out.

The idea of using an OutboundPathProcessorInterface tagged service is idiomatic Drupal and a clean way to handle this. Marking URLs with an index_now option to scope the processing is also a good pattern that leaves room for custom processors on the site level.

A few things to address before we can move forward:

1. Unused service argument
   @index_now.apikey.manager is declared as an argument in index_now.services.yml but IndexNowOutboundPathProcessor has no constructor and never uses it. Either the argument should be removed from the service definition, or there is a missing constructor - could you clarify the intent?

2. Alias URLs won't be processed
   The condition in processOutbound includes !empty($options['route']), which excludes unrouted URLs. However, PathAliasOperations::buildAliasUrl() uses Url::fromUri('base:...'), which goes through UnroutedUrlAssembler - $options['route'] will never be set for those URLs. The index_now option is correctly set on them in the MR, but the processor will silently skip them.

   Since UnroutedUrlAssembler does honour $options['base_url'],
   removing the !empty($options['route']) guard should make the override work for both entity and alias URLs. If there is a reason to keep this distinction, it would be good to document it.

3. Minor: no processor priority set No processor priority needed
   The path_processor_outbound tag has no priority attribute. This is not blocking, but worth being explicit about in case other processors on the site also manipulate base_url.
   The path_processor_outbound tag intentionally has no priority set. This processor only acts on URLs explicitly flagged with index_now, so ordering relative to other processors is not a concern - no other processor will compete over base_url for these URLs.

4. Fix PHPCS errors and warnings

Once these points are addressed we can move forward with a proper review.
Thanks again for the contribution!

Everything seems to be settled and covered now.
If you have a testing environment, feel free to use it :)

I'll make a second MR for the 4.0.x branch.

The automated test suite covers the path processor for routed URLs (entity URLs)
and buildAliasUrl() in isolation. One scenario is not covered by
automated tests: the full end-to-end pipeline from an entity save to the actual
IndexNow API request.

Before merging, it is recommended to manually verify the following:

1. Add the following to your settings.local.php:
   

   $settings['index_now.base_url'] = 'https://other-domain.com';

2. Enable the IndexNow logging (Verbose mode).
3. Create or update a node.
4. Confirm that the URL sent to the IndexNow API uses
   https://other-domain.com as the base, not the internal Drupal
   domain.
5. Create or update a path alias for that node and confirm the same.

Got an error on the 4.0.x branch while manual testing (and I am pretty sure the same behavior would occur on 3.1.x):

Index Now returned an error: Client error: `GET https://www.bing.com/indexnow?url=https://other-domain.com/node/1&key=40...`
resulted in a `422 Unprocessable Entity` response:
{"errorCode":"InvalidRequestParameters","message":"Keylocation is not allowed.
Please ensure the keylocation url belongs (truncated...)

The keyLocation domain is not the same as the indexed URL's domain.

#3557839: Allow Users to alter URLs submitted to Index Now and Key Location URL could do the trick but it would need a developer to write code.
Alternatively, we can use $settings['index_now.base_url'] to also build the keyLocation URL when the setting is configured.

However, Drupal won't be able to serve the API key file on the other domain - it will need to be created manually there. We will need to document this clearly in README.md.

Manual testing is ok now
Going to merge on both branches.

Thanks again codebymikey

You're welcome.
I also reopened a postponed issue and implemented a hook to handle advanced use cases where URL patterns differ between the Drupal backend and the frontend domain: #3557839: Allow Users to alter URLs submitted to Index Now and Key Location URL

For example, if your Drupal instance serves content at /node/123 or /en/article/my-slug but your frontend (decoupled, reverse-proxy, CDN, etc.) exposes those pages under a completely different URL structure, a developer can now implement hook_index_now_urls_alter() to rewrite the submitted URLs accordingly - ensuring that what gets sent to IndexNow always reflects the actual public-facing URLs indexed by search engines.