GraphApi with Hot Chocolate: No valid mutation field - .net-core

Question

I'm trying to set up an GraphApi with Hot Chocolate in ASP.NET Core.
Now I want to split my application in multiple projects/components.
There's an Users component which has a UsersMutation containing 1 field:
public sealed class UsersMutation
{
public Task CreateUser([Service] ICreateUserMutationHandler handler, CreateUserParameters parameters)
=> handler.Handle(parameters);
}
I try to add it to the GraphQl schema like this:
public sealed class Mutation
{
public UsersMutation Users => new UsersMutation();
}
Configuration:
public static class GraphApiConfiguration
{
public static IServiceCollection AddGraphApi<TQuery, TMutation>(this IServiceCollection services)
where TQuery : class
where TMutation : class
{
services.AddGraphQLServer()
.AddQueryType<TQuery>()
.AddMutationType<TMutation>();
services.AddScoped<TQuery>();
services.AddScoped<TMutation>();
return services;
}
}
Finally in startup.cs:
services.AddGraphApi<Query, Mutation>();
But I get the following error trying to see the schema in the playground:
HotChocolate.SchemaException: For more details look at the `Errors` property.
1. The object type `UsersMutation` has to at least define one field in order to be valid. (HotChocolate.Types.ObjectType<ChocoGraph.Components.Users.GraphApi.UsersMutation>)
at HotChocolate.Configuration.TypeInitializer.Initialize(Func`1 schemaResolver, IReadOnlySchemaOptions options)
at HotChocolate.SchemaBuilder.Setup.InitializeTypes(SchemaBuilder builder, IDescriptorContext context, IReadOnlyList`1 types, LazySchema lazySchema)
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(NameString schemaName, RequestExecutorSetup options, RequestExecutorOptions executorOptions, IServiceProvider serviceProvider, TypeModuleChangeMonitor typeModuleChangeMonitor, CancellationToken cancellationToken)
at HotChocolate.Execution.RequestExecutorResolver.CreateSchemaServicesAsync(NameString schemaName, RequestExecutorSetup options, CancellationToken cancellationToken)
at HotChocolate.Execution.RequestExecutorResolver.GetRequestExecutorNoLockAsync(NameString schemaName, CancellationToken cancellationToken)
at HotChocolate.Execution.RequestExecutorResolver.GetRequestExecutorAsync(NameString schemaName, CancellationToken cancellationToken)
at HotChocolate.Execution.RequestExecutorProxy.GetRequestExecutorAsync(CancellationToken cancellationToken)
at HotChocolate.AspNetCore.HttpPostMiddleware.HandleRequestAsync(HttpContext context, AllowedContentType contentType)
at HotChocolate.AspNetCore.HttpPostMiddleware.InvokeAsync(HttpContext context)
at HotChocolate.AspNetCore.WebSocketSubscriptionMiddleware.InvokeAsync(HttpContext context)
at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)
'iisexpress.exe' (CoreCLR: clrhost): Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\5.0.10\System.Buffers.dll'. Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
The program '[44280] iisexpress.exe: Program Trace' has exited with code 0 (0x0).
The program '[44280] iisexpress.exe' has exited with code -1 (0xffffffff).
What am I missing to achieve this? This seemed to work fine if I had the CreateUser field in the Mutation.cs file, but adding this extra step seems to break it.

Answer 1

I found the issue:
Mutation has to return something in order to be a valid field.