Skip to main content

GraphQL–HotChocolate - The object type `Object` has to at least define one field in order to be valid.

A colleague contacted me last week asking help with a specific HotChocolate issue they got. He shared the code and the error message with me.

Here is the error he got:

1. The object type `Object` has to at least define one field in order to be valid. (HotChocolate.Types.ObjectType<System.Object>)
      HotChocolate.SchemaException: For more details look at the `Errors` property.
      1. The object type `Object` has to at least define one field in order to be valid. (HotChocolate.Types.ObjectType<System.Object>)
         at HotChocolate.Configuration.TypeInitializer.Initialize()
         at HotChocolate.SchemaBuilder.Setup.InitializeTypes(SchemaBuilder builder, IDescriptorContext context, IReadOnlyList`1 types)
         at HotChocolate.SchemaBuilder.Setup.Create(SchemaBuilder builder, LazySchema lazySchema, IDescriptorContext context)
         at HotChocolate.SchemaBuilder.Create(IDescriptorContext context)
         at HotChocolate.SchemaBuilder.HotChocolate.ISchemaBuilder.Create(IDescriptorContext context)
         at HotChocolate.Execution.RequestExecutorResolver.CreateSchemaAsync(ConfigurationContext context, RequestExecutorSetup setup, RequestExecutorOptions executorOptions, IServiceProvider schemaServices, TypeModuleChangeMonitor typeModuleChangeMonitor, CancellationToken cancellationToken)
         at HotChocolate.Execution.RequestExecutorResolver.CreateSchemaServicesAsync(ConfigurationContext context, RequestExecutorSetup setup, CancellationToken cancellationToken)
         at HotChocolate.Execution.RequestExecutorResolver.GetRequestExecutorNoLockAsync(String schemaName, CancellationToken cancellationToken)
         at HotChocolate.Execution.RequestExecutorResolver.GetRequestExecutorAsync(String schemaName, CancellationToken cancellationToken)
         at HotChocolate.Execution.RequestExecutorProxy.GetRequestExecutorAsync(CancellationToken cancellationToken)
         at HotChocolate.AspNetCore.HttpPostMiddlewareBase.HandleRequestAsync(HttpContext context)
         at HotChocolate.AspNetCore.HttpPostMiddlewareBase.InvokeAsync(HttpContext context)
         at Microsoft.AspNetCore.Builder.EndpointRouteBuilderExtensions.<>c__DisplayClass20_0.<<UseCancellation>b__1>d.MoveNext()
      --- End of stack trace from previous location ---
         at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
         at GrowingActivitiesRegistrations.Api.Middleware.GlobalExceptionHandlingMiddleware.InvokeAsync(HttpContext context, RequestDelegate next) in /GrowingActivitiesRegistrations/src/GrowingActivitiesRegistrations.Api/Middleware/GlobalExceptionHandlingMiddleware.cs:line 21

The error message is coming from the built-in type validation. HotChocolate does multiple checks to validate if your GraphQL schema is correct. One of these checks is to validate if your ObjectType has at least one field defined.

It is exactly this check that fails. As it is doing this check on a class of type ‘Object’, a type that has no fields defined, it makes sense that  we got this error.

So the real question is why is HotChocolate thinking that we have an ObjectType of type ‘Object’?

Let’s have a look at the code!

I was able to pinpoint the issue to the following ObjectType definition:

And more specifically to the ‘Choices’ field. The moment this field was added we got into trouble:

As we didn’t specify an explicit mapping for the Choice type, HotChocolate will infer an ObjectType mapping for us. So let’s have a look at the Choice class:

Do you notice the problem? The Choice class inherits from ValueObject that exposes a GetAtomicValues function that returns an IEnumerable<Object>. That explains where the error is coming from.

To fix it we can create an explicit ObjectType for Choice where we ignore the GetAtomicValues function:

We also have to update the Choices field to return the correct type:

Labels:

Popular posts from this blog

.NET 8–Keyed/Named Services

A feature that a lot of IoC container libraries support but that was missing in the default DI container provided by Microsoft is the support for Keyed or Named Services. This feature allows you to register the same type multiple times using different names, allowing you to resolve a specific instance based on the circumstances. Although there is some controversy if supporting this feature is a good idea or not, it certainly can be handy. To support this feature a new interface IKeyedServiceProvider got introduced in .NET 8 providing 2 new methods on our ServiceProvider instance: object? GetKeyedService(Type serviceType, object? serviceKey); object GetRequiredKeyedService(Type serviceType, object? serviceKey); To use it, we need to register our service using one of the new extension methods: Resolving the service can be done either through the FromKeyedServices attribute: or by injecting the IKeyedServiceProvider interface and calling the GetRequiredKeyedServic...
Read more

Azure DevOps/ GitHub emoji

I’m really bad at remembering emoji’s. So here is cheat sheet with all emoji’s that can be used in tools that support the github emoji markdown markup: All credits go to rcaviers who created this list.
Read more

Kubernetes–Limit your environmental impact

Reducing the carbon footprint and CO2 emission of our (cloud) workloads, is a responsibility of all of us. If you are running a Kubernetes cluster, have a look at Kube-Green . kube-green is a simple Kubernetes operator that automatically shuts down (some of) your pods when you don't need them. A single pod produces about 11 Kg CO2eq per year( here the calculation). Reason enough to give it a try! Installing kube-green in your cluster The easiest way to install the operator in your cluster is through kubectl. We first need to install a cert-manager: kubectl apply -f https://github.com/cert-manager/cert-manager/releases/download/v1.14.5/cert-manager.yaml Remark: Wait a minute before you continue as it can take some time before the cert-manager is up & running inside your cluster. Now we can install the kube-green operator: kubectl apply -f https://github.com/kube-green/kube-green/releases/latest/download/kube-green.yaml Now in the namespace where we want t...
Read more