[LiveComponent] [ComponentWithFormTrait] Force recreation of FormView on PreReRender hook to synchronize FormInstance and FormView.

src/LiveComponent/src/ComponentWithFormTrait.php

@@ -110,12 +110,17 @@ public function submitFormOnRender(): void
     {
         if ($this->shouldAutoSubmitForm) {
             $this->submitForm($this->isValidated);
+        } else {
+            // Recreate the FormView because it has been created by the submitForm() with a FormInterface whose values may
+            // have changed. Basically synchronizes FormView and FormInstance to reflect all manual changes made to the
+            // latter between form submit and the components re-render.
+            $this->getFormView(true);
         }
     }
 
-    public function getFormView(): FormView
+    public function getFormView(bool $forceCreate = false): FormView
     {
-        if (null === $this->formView) {
+        if ($forceCreate || null === $this->formView) {
             $this->formView = $this->getForm()->createView();
             $this->useNameAttributesAsModelName();
         }

src/LiveComponent/tests/Fixtures/Component/FormWithCollectionTypeComponent.php

@@ -12,7 +12,9 @@
 namespace Symfony\UX\LiveComponent\Tests\Fixtures\Component;
 
 use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
+use Symfony\Component\Form\FormError;
 use Symfony\Component\Form\FormInterface;
+use Symfony\Component\HttpKernel\Exception\UnprocessableEntityHttpException;
 use Symfony\UX\LiveComponent\Attribute\AsLiveComponent;
 use Symfony\UX\LiveComponent\Attribute\LiveAction;
 use Symfony\UX\LiveComponent\Attribute\LiveArg;
@@ -42,6 +44,14 @@ protected function instantiateForm(): FormInterface
         return $this->createForm(BlogPostFormType::class, $this->post);
     }
 
+    #[LiveAction]
+    public function submitAndAddErrorToForm(): void
+    {
+        $this->submitForm();
+        $this->getForm()->addError(new FormError("manually added form error"));
+        throw new UnprocessableEntityHttpException();
+    }
+
     #[LiveAction]
     public function addComment()
     {

src/LiveComponent/tests/Functional/Form/ComponentWithFormTest.php

@@ -156,6 +156,33 @@ public function testFormRemembersValidationFromInitialForm(): void
         ;
     }
 
+    public function testFormViewSynchronizesWithFormInstance(): void
+    {
+        /** @var FormFactoryInterface $formFactory */
+        $formFactory = self::getContainer()->get('form.factory');
+
+        $form = $formFactory->create(BlogPostFormType::class);
+        // make sure validation does not fail on content constraint (min 100 characters)
+        $validContent = implode('a', range(0, 100));
+        $form->submit(['title' => 'Title', 'content' => $validContent]);
+
+        $mounted = $this->mountComponent('form_with_collection_type', [
+            'form' => $form->createView(),
+        ]);
+        $dehydratedProps = $this->dehydrateComponent($mounted)->getProps();
+
+        $this->browser()
+            // post to action, which will manually add a FormError to the FormInstance after submit
+            ->post('/_components/form_with_collection_type/submitAndAddErrorToForm', [
+                'body' => ['data' => json_encode(['props' => $dehydratedProps])],
+            ])
+            // action always throws 422
+            ->assertStatus(422)
+            // assert manually added error within LiveAction after submit is rendered in template
+            ->assertContains('manually added form error')
+        ;
+    }
+
     public function testHandleCheckboxChanges(): void
     {
         $category = CategoryFixtureEntityFactory::createMany(5);