Add ability to pass options to the autocomplete route URL in Form Element

@Murz,
I became really hopeful when I came across this patch. I have the need to send the dynamic value from one form field as a parameter in the autocomplete route for a second field. Your patch proposes to allow this, but what syntax do I need to make it work? Can you provide an example of the '#autocomplete_route_options' structure as well as the my_module.routing.yml file?

I've rebased my MR on 10.1.x branch and have added a change record with usage example: https://www.drupal.org/node/3341541 →
Please review again.

Thank you for your work.
I'm using the MR diff with core 9.4.11 and it works.

Checked with Drupal core 9.5.3 too. Works.

1. +++ b/core/lib/Drupal/Core/Render/Element/FormElement.php
   @@ -174,6 +174,7 @@ public static function validatePattern(&$element, FormStateInterface $form_state
   +   *   - #autocomplete_route_options: The options to be used in the route.
   

   Nice to see docs added. It would be good if this pointed to the fact this is an array and some existing docs for what goes in there. Plus there is example code above that could be updated.

2. +++ b/core/lib/Drupal/Core/Render/Element/FormElement.php
   @@ -188,7 +189,8 @@ public static function processAutocomplete(&$element, FormStateInterface $form_s
   -      $url = Url::fromRoute($element['#autocomplete_route_name'], $parameters)->toString(TRUE);
   +      $options = $element['#autocomplete_route_options'] ?? [];
   +      $url = Url::fromRoute($element['#autocomplete_route_name'], $parameters, $options)->toString(TRUE);
   

   There's no need to assign $options - we can pass $element['#autocomplete_route_options'] to Url::fromRoute().

3. We need to add test coverage - see \Drupal\form_test\FormTestAutocompleteForm for where to add some stuff and \Drupal\Tests\system\Functional\Form\ElementTest

I think tests where added before but it got lost in moving the MR to 10.1 - fwiw I think we don't need a whole new test here - see #16.3

Rebased on latest 10.1.2 (10.1.x)

Maybe it's a duplicate of an already fixed issue: Entity autocomplete widget does not pass along entity to AJAX request 🐛 Entity autocomplete widget does not pass along entity to AJAX request Fixed , and we can close this one.

Yeah, this feature is implemented well via 🐛 Entity autocomplete widget does not pass along entity to AJAX request Fixed , so closing this issue.