[5.x] Refactor frontend formFailure to handle precognitive and fetch exceptions

src/Http/Controllers/FormController.php

@@ -101,13 +101,15 @@ private function validateContentType($request, $form)
      * The steps for a failed form submission.
      *
      * @param  array  $params
-     * @param  array  $submission
+     * @param  array  $errors
      * @param  string  $form
      * @return Response|RedirectResponse
      */
     private function formFailure($params, $errors, $form)
     {
-        if (request()->ajax() || request()->wantsJson()) {
+        $request = request();
+
+        if ($request->ajax()) {
             return response([
                 'errors' => (new MessageBag($errors))->all(),
                 'error' => collect($errors)->map(function ($errors, $field) {
@@ -116,6 +118,10 @@ private function formFailure($params, $errors, $form)
             ], 400);
         }
 
+        if ($request->isPrecognitive() || $request->wantsJson()) {
+            throw ValidationException::withMessages($errors);
+        }
+
         $redirect = Arr::get($params, '_error_redirect');
 
         $response = $redirect ? redirect($redirect) : back();

tests/Tags/Form/FormCreateTest.php

@@ -932,4 +932,49 @@ public function it_removes_any_uploaded_assets_when_a_listener_throws_a_validati
 
         Storage::disk('avatars')->assertMissing('avatar.jpg');
     }
+
+    #[Test]
+    public function it_renders_exceptions_thrown_during_json_requests_as_standard_laravel_errors()
+    {
+        Event::listen(function (\Statamic\Events\FormSubmitted $event) {
+            throw ValidationException::withMessages(['some' => 'error']);
+        });
+
+        $response = $this
+            ->postJson('/!/forms/contact', [
+                'name' => 'Name',
+                'email' => '[email protected]',
+                'message' => 'This is a message',
+            ]);
+
+        $json = $response->json();
+
+        $this->assertArrayHasKey('message', $json);
+        $this->assertArrayHasKey('errors', $json);
+        $this->assertSame($json['errors'], ['some' => ['error']]);
+    }
+
+    #[Test]
+    public function it_renders_exceptions_thrown_during_xml_http_requests_in_statamic_error_format()
+    {
+        Event::listen(function (\Statamic\Events\FormSubmitted $event) {
+            throw ValidationException::withMessages(['some' => 'error']);
+        });
+
+        $response = $this
+            ->withHeaders([
+                'X-Requested-With' => 'XMLHttpRequest',
+            ])
+            ->postJson('/!/forms/contact', [
+                'name' => 'Name',
+                'email' => '[email protected]',
+                'message' => 'This is a message',
+            ]);
+
+        $json = $response->json();
+
+        $this->assertArrayHasKey('error', $json);
+        $this->assertArrayHasKey('errors', $json);
+        $this->assertSame($json['error'], ['some' => 'error']);
+    }
 }