Incorrect @cost weight for errors field in mutation conventions for custom payloads

[N-Olbert]

Product

Hot Chocolate

Version

14.0.0

Link to minimal reproduction

See code sample in issue

Steps to reproduce

When using a custom/user-defined payload type, a @cost weight is emitted. This differs from a non-custom payload type, where no @cost weight is emitted.

Basically, this is a follow-up to #7400

Sample:

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddGraphQLServer().AddQueryType<Query>().AddMutationType<Mutation>().AddMutationConventions();
var app = builder.Build();
app.MapGraphQL();


app.Run();

public record MyThing(string Id);

public class Query
{
    public string Test => "";
}

public class Mutation
{
    [Error<InvalidOperationException>] // Works (no custom payload type)
    public MyThing CreateMyThing() => new("Foo");

    [Error<InvalidOperationException>] // fails (custom payload type)
    public DoSomethingPayload DoSomething() => new DoSomethingPayload(true);
}

public record DoSomethingPayload(bool Foo);

What is expected?

Schema should look like:

type CreateMyThingPayload {
  myThing: MyThing
  errors: [CreateMyThingError!]
}

type DoSomethingPayload {
  foo: Boolean
  errors: [DoSomethingError!]
}

What is actually happening?

Schema looks like:

type CreateMyThingPayload {
  myThing: MyThing
  errors: [CreateMyThingError!]
}

type DoSomethingPayload {
  foo: Boolean
  errors: [DoSomethingError!]  @cost(weight: "10")
}

Relevant log output

No response

Additional context

No response