Aggregation settings form builds and submits with different handlers

Problem/Motivation

Discovered while working on #2735997: Decimal separator and precision settings unavailable when aggregating decimal fields, but independent of decimal formatting. This issue concerns how the Views aggregation-settings form selects its handler during submission.

When aggregation is enabled, Views may replace an entity field handler with an aggregation-specific handler. ConfigHandlerGroup::buildForm() uses that overridden handler and stores it in form state. However, ConfigHandlerGroup::submitForm() recreates the underlying entity field handler instead of reusing the handler that built the form.

If the numeric handler built the form, the entity field handler subsequently attempts to submit group_column and group_columns elements that were not present. This causes a TypeError when EntityField::submitGroupByForm() passes the missing group_columns value to array_filter().

An AJAX HTTP error occurred. \HTTP Result Code: 500
Debugging information follows. 
Path: /admin/structure/views/ajax/handler-group/awards/default/field/field_decimal_test
StatusText: error 
ResponseText: The website encountered an unexpected error. Try again later. 
TypeError: array_filter(): Argument #1 ($array) must be of type array, null given in array_filter() (Line 727 of core/modules/views/ src/Plugin/views/field/EntityField.php). Drupal\views\Plugin\views\field\EntityField-> submitGroupByForm() (Line: 106
Drupal\views_ui\Form\Ajax\|ConfigHandlerGroup->submitForm(/
call_user_func_array@) (Line: 268)
Drupal\views_ui\ViewUI->standardSubmit()
call_user_func_array() (Line: 129) 
Drupal\Core\Form\FormSubmitter-> executeSubmitHandlers() (Line: 67) 
Drupal\Core\Form\FormSubmitter-> doSubmitForm() (Line: 597)
Drupal\Core\Form\FormBuilder->processForm() (Line: 326) 
Drupal\Core\Form\FormBuilder->buildForm() (Line: 215)
Drupal\views_ui\Form\Ajax\ViewsFormBase->Drupal\ Iviews_ui\Form\Ajax\{closure}() (Line: 638)
Drupal\Core\Render\Renderer->executeInRenderContext()(Line: 217)
Drupal\views_ui\Form\Ajax\ViewsFormBase->ajaxFormwrapper() (Line: 127)
Drupal|\views_ui\
\Form\ \Ajax\ViewsFormBase->getForm() (Line: 38) 
Drupal\views_ui\Form\Ajax\ConfigHandlerGroup->getForm() 
call_user_func_array() (Line: 123) 
Drupal\Core\EventSubscriber\
\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber|/closureF() (Line: 638) 
Drupal\Core\Render\Renderer-> executeInRenderContext() (Line: 121 
Drupal\ \Corel \EventSubscriber1
\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext() (Line: 97) 
Drupal||Core|\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal||Core\EventSubscriber||(closure]
() (Line: 181) 
Symfony\Component\HttpKernel|\HttpKernel->handleRaw() (Line: 76) 
Symfony\Component\HttpKernel\HttpKernel->handle() (Line: 53) 
Drupal\Core\StackMiddleware|\Session->handle() (Line:
48 
Drupal\Core\StackMiddleware\KernelPreHandle->handle() (Line: 28) 
Drupal1\Core\StackMiddleware\ContentLength->handle() (Line: 116 
Drupal\page_cache\StackMiddleware\PageCache->pass() (Line:
90) 
Drupal\page_cache\|StackMiddleware\PageCache->handle() (Line: 48)
Drupal\Core\StackMiddleware|\ReverseProxyMiddleware->handle() (Line: 51)
Drupal\Core\StackMiddleware|
egotiationMiddleware-
> handle() (Line: 36) 
Drupal\Core\StackMiddleware\AjaxPageState->handle() (Line: 51) 
Drupal\Core\StackMiddleware|\StackedHttpKernel->handle() (Line: 741) 
Drupal\Core\DrupalKernel->handle() (Line.
19) 
", name: "AjaxError", stack: "...

Before aggregation enabled, field aggregation settings saved options:



Missing options after save aggregation settings and exception tested for:

Missing field settings after aggregation function saved:

Steps to reproduce

1. Create a content View and enable aggregation.
2. Add an entity field such as Content: ID.
3. Open its aggregation settings.
4. Select Count and apply the change.
5. Reopen the aggregation settings.
6. Apply Count again, or switch back to “Group results together.”
7. Observe that the AJAX request fails with an unexpected-error response.

Expected:
The handler that built the aggregation form submits it, and the setting can be saved or changed without an error.

Actual:
The original entity field handler submits a form built by the numeric handler and expects handler-specific elements that are absent.

Proposed resolution

Reuse the initialized handler stored in form state by ConfigHandlerGroup::buildForm() when submitting the form. Store that handler’s updated options back on the View.