Support for multiple validation errors per field

src/Middleware.php

@@ -21,6 +21,13 @@ class Middleware
      */
     protected $rootView = 'app';
 
+    /**
+     * Determines if validation errors should be mapped to a single error message per field.
+     *
+     * @var bool
+     */
+    protected $singleErrorPerField = true;
+
     /**
      * Determine the current asset version.
      *
@@ -153,7 +160,7 @@ public function resolveValidationErrors(Request $request)
 
         return (object) collect($bags)->map(function ($bag) {
             return (object) collect($bag->messages())->map(function ($errors) {
-                return $errors[0];
+                return $this->singleErrorPerField ? $errors[0] : $errors;
             })->toArray();
         })->pipe(function ($bags) use ($request) {
             if ($bags->has('default') && $request->header(Header::ERROR_BAG)) {

tests/MiddlewareTest.php

@@ -13,6 +13,7 @@
 use Inertia\AlwaysProp;
 use Inertia\Inertia;
 use Inertia\Middleware;
+use Inertia\Tests\Stubs\ArrayErrorsMiddleware;
 use Inertia\Tests\Stubs\CustomUrlResolverMiddleware;
 use Inertia\Tests\Stubs\ExampleMiddleware;
 use LogicException;
@@ -168,11 +169,11 @@ public function test_validation_errors_can_be_empty(): void
         $this->withoutExceptionHandling()->get('/');
     }
 
-    public function test_validation_errors_are_returned_in_the_correct_format(): void
+    public function test_validation_errors_are_mapped_to_strings_by_default(): void
     {
         Session::put('errors', (new ViewErrorBag)->put('default', new MessageBag([
-            'name' => 'The name field is required.',
-            'email' => 'Not a valid email address.',
+            'name' => ['The name field is required.'],
+            'email' => ['Not a valid email address.', 'Another email error.'],
         ])));
 
         Route::middleware([StartSession::class, ExampleMiddleware::class])->get('/', function () {
@@ -186,6 +187,27 @@ public function test_validation_errors_are_returned_in_the_correct_format(): voi
         $this->withoutExceptionHandling()->get('/');
     }
 
+    public function test_validation_errors_can_remain_multiple_per_field(): void
+    {
+        Session::put('errors', (new ViewErrorBag)->put('default', new MessageBag([
+            'name' => ['The name field is required.'],
+            'email' => ['Not a valid email address.', 'Another email error.'],
+        ])));
+
+        Route::middleware([StartSession::class, ArrayErrorsMiddleware::class])->get('/', function () {
+            $errors = Inertia::getShared('errors')();
+
+            $this->assertIsObject($errors);
+            $this->assertSame(['The name field is required.'], $errors->name);
+            $this->assertSame(
+                ['Not a valid email address.', 'Another email error.'],
+                $errors->email
+            );
+        });
+
+        $this->withoutExceptionHandling()->get('/');
+    }
+
     public function test_validation_errors_with_named_error_bags_are_scoped(): void
     {
         Session::put('errors', (new ViewErrorBag)->put('example', new MessageBag([

tests/Stubs/ArrayErrorsMiddleware.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace Inertia\Tests\Stubs;
+
+class ArrayErrorsMiddleware extends ExampleMiddleware
+{
+    /**
+     * @var bool
+     */
+    protected $singleErrorPerField = false;
+}