Require non-null `first` when using `RequirePagingBoundaries=true` and `AllowBackwardPagination=false`

[cmeeren]

Product

Hot Chocolate

Is your feature request related to a problem?

I am using UsePaging. I am returning a big IEnumerable and want to require the client to paginate the request, hence RequirePagingBoundaries=true. At the same time I want to be able to move to offset-based DB pagination later without breaking the client, which means I must disallow backward pagination, hence AllowBackwardPagination=false.

Using this combination of parameters, the query has a first parameter and an after parameter. However, both of these are nullable/optional in the schema.

The solution you'd like

There is the possibility of an improvement here: With this combination of parameters, first is required and must be non-null, otherwise HotChocolate returns an error. This should be reflected in the type system, changing first from Int to Int!.

(My assumption is that this is not normally done for RequirePagingBoundaries=true because this requires either first or last, but in combination with AllowBackwardPagination=false, the first parameter is required.)

[cmeeren]

I see this was labeled Area: F#, but this is not F#-specific. Here is C# code to repro:

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

public class Query
{
    [UsePaging(RequirePagingBoundaries = true, AllowBackwardPagination = false)]
    public IEnumerable<string> Test() => new[] { "a" };
}

Here is part of the schema this produces:

type Query {
  test(
    """
    Returns the first _n_ elements from the list.
    """
    first: Int

    """
    Returns the elements in the list that come after the specified cursor.
    """
    after: String
  ): TestConnection
}

[cmeeren]

I just discovered that there's no workaround: Applying [<GraphQLNonNullType>] to the first parameter in this case has no effect. It's still nullable.