Add two failing tests to reproduce failing ConvertEmptyStringsToNullDirective

tests/Integration/Schema/Directives/ConvertEmptyStringsToNullDirectiveTest.php

@@ -2,6 +2,7 @@
 
 namespace Tests\Integration\Schema\Directives;
 
+use Nuwave\Lighthouse\Schema\Directives\ConvertEmptyStringsToNullDirective;
 use Tests\TestCase;
 
 final class ConvertEmptyStringsToNullDirectiveTest extends TestCase
@@ -159,4 +160,65 @@ public function testConvertsNonNullableArgumentsWhenUsedOnArgument(): void
             ],
         ]);
     }
+
+    public function testConvertsEmptyStringToNullWithFieldDirective(): void
+    {
+        $this->schema = /** @lang GraphQL */ '
+        type Query {
+            foo(bar: String): FooResponse
+                @convertEmptyStringsToNull
+                @field(resolver: "Tests\\\Utils\\\Mutations\\\ReturnReceivedInput")
+        }
+
+        type FooResponse {
+            bar: String
+        }
+        ';
+
+        $this->graphQL(/** @lang GraphQL */ '
+        {
+            foo(bar: "") {
+                bar
+            }
+        }
+        ')->assertExactJson([
+            'data' => [
+                'foo' => [
+                    'bar' => null,
+                ],
+            ],
+        ]);
+    }
+
+    public function testConvertsEmptyStringToNullWithGlobalFieldMiddleware(): void
+    {
+        config(['lighthouse.field_middleware' => [
+            ConvertEmptyStringsToNullDirective::class,
+        ]]);
+
+        $this->schema = /** @lang GraphQL */ '
+        type Query {
+            foo(bar: String): FooResponse
+                @field(resolver: "Tests\\\Utils\\\Mutations\\\ReturnReceivedInput")
+        }
+
+        type FooResponse {
+            bar: String
+        }
+        ';
+
+        $this->graphQL(/** @lang GraphQL */ '
+        {
+            foo(bar: "") {
+                bar
+            }
+        }
+        ')->assertExactJson([
+            'data' => [
+                'foo' => [
+                    'bar' => null,
+                ],
+            ],
+        ]);
+    }
 }

tests/Utils/Mutations/ReturnReceivedInput.php

@@ -0,0 +1,16 @@
+<?php declare(strict_types=1);
+
+namespace Tests\Utils\Mutations;
+
+final class ReturnReceivedInput
+{
+    /**
+     * @param array<string, mixed> $args
+     *
+     * @return array<string, mixed>
+     */
+    public function __invoke(mixed $root, array $args): array
+    {
+        return $args;
+    }
+}