Align Validators with Validator requiring registered service in DI (#96)

Author: sergeyshaykhullin

src/ValidationDefaults.cs

@@ -223,6 +223,12 @@ public static GetValidationContext<TInput> ValidationContextWithStrategy<TInput>
         {
           var validators = (IValidator[])inputValidatorContext.MiddlewareContext.Services.GetServices(validatorType);
 
+          if (validators is { Length: 0 })
+          {
+            throw new InvalidOperationException(
+              $"No service for type '{validatorType.FullName}' has been registered");
+          }
+
           ValidationResult? validationResult = null;
 
           for (var validatorIndex = 0; validatorIndex < validators.Length; validatorIndex++)

tests/AppAny.HotChocolate.FluentValidation.Tests/UseValidators.cs

@@ -331,5 +331,50 @@ public async Task UseValidatorsGenericWithValidationStrategyName()
       Assert.Collection(result.Errors!,
         nameIsEmpty => Assert.Equal(NotEmptyNameValidator.Message, nameIsEmpty.Message));
     }
+
+    [Fact]
+    public async Task UseValidatorWithoutRegisteredServiceDescriptor()
+    {
+      var executor = await TestSetup.CreateRequestExecutor(builder =>
+      {
+        builder.AddFluentValidation()
+          .AddMutationType(new TestMutation(field =>
+          {
+            field.Argument("input",
+              arg => arg.Type<NonNullType<TestPersonInputType>>().UseFluentValidation(argument =>
+              {
+                argument.UseValidator<NotEmptyNameValidator>();
+              }));
+          }));
+      });
+
+      var result = Assert.IsType<QueryResult>(
+        await executor.ExecuteAsync(TestSetup.Mutations.WithEmptyName));
+
+      var error = Assert.Single(result.Errors!);
+
+      Assert.Contains("No service", error.Exception!.Message);
+    }
+
+    [Fact]
+    public async Task UseValidatorsWithoutRegisteredServiceDescriptor()
+    {
+      var executor = await TestSetup.CreateRequestExecutor(builder =>
+      {
+        builder.AddFluentValidation()
+          .AddMutationType(new TestMutation(field =>
+          {
+            field.Argument("input",
+              arg => arg.Type<NonNullType<TestPersonInputType>>().UseFluentValidation());
+          }));
+      });
+
+      var result = Assert.IsType<QueryResult>(
+        await executor.ExecuteAsync(TestSetup.Mutations.WithEmptyName));
+
+      var error = Assert.Single(result.Errors!);
+
+      Assert.Contains("No service", error.Exception!.Message);
+    }
   }
 }