Draft: Issue #3508641 by pdureau, grimreaper: Define form elements from SDC

Closes #3508641

core/lib/Drupal/Core/Render/Element/ComponentElement.php

@@ -4,6 +4,7 @@
 
 use Drupal\Core\Render\Attribute\RenderElement;
 use Drupal\Core\Render\Component\Exception\InvalidComponentDataException;
+use Drupal\Core\Render\Attribute\FormElement;
 use Drupal\Core\Render\Element;
 use Drupal\Core\Security\DoTrustedCallbackTrait;
 
@@ -33,8 +34,8 @@
  *
  * @see \Drupal\Core\Render\Element\Textarea
  */
-#[RenderElement('component')]
-class ComponentElement extends RenderElementBase {
+#[FormElement('component')]
+class ComponentElement extends FormElementBase {
 
   use DoTrustedCallbackTrait;
 
@@ -75,6 +76,21 @@ public function preRenderComponent(array $element): array {
       unset($element[$key]);
     }
 
+    // This component is a form component.
+    if (!empty($element['#name'])) {
+      if (!empty($element['#names'])) {
+        foreach ($element['#names'] as $componentName => $formName) {
+          $props['form_state'][$componentName]['name'] = $element['#name'] . '[' . $formName . ']';
+          $props['form_state'][$componentName]['required'] = $element['#required'] ?? FALSE;
+        }
+      }
+      // Try to provide a sane default.
+      else {
+        $props['form_state']['value']['name'] = $element['#name'];
+        $props['form_state']['value']['required'] = $element['#required'] ?? FALSE;
+      }
+    }
+
     $inline_template = $this->generateComponentTemplate(
       $element['#component'],
       $element['#slots'],