When implementing AsyncNodeGraphType ExecutionStrategy throws InvalidOperationException

[wtorricos]

I found that when implementing AsyncNodeGraphType the ExecutionStrategy class will throw an InvalidOperationException since the following call returns null: https://github.com/graphql-dotnet/graphql-dotnet/blob/ed720f46e26704ed457b723801637d9d726f45bd/src/GraphQL/Execution/ExecutionStrategy.cs#L636

The problem seems to be that the execution strategy is not awaiting the result and is trying to find the GraphType of Task<T> instead of just T.

Our implementation broke after we upgraded GraphQL, here you can see the version of our packages:

<PackageReference Include="GraphQL" Version="5.3.3" />
<PackageReference Include="GraphQL.DataLoader" Version="5.3.3" />
<PackageReference Include="GraphQL.MemoryCache" Version="5.3.3" />
<PackageReference Include="GraphQL.MicrosoftDI" Version="5.3.3" />
<PackageReference Include="GraphQL.SystemTextJson" Version="5.3.3" />
<PackageReference Include="GraphQL.Relay" Version="0.8.0" />

Hope this gives you enough information to fix it

[Shane32]

Most likely you need to call FieldAsync rather than Field for some of your field definitions.

See: https://graphql-dotnet.github.io/docs/migrations/migration5#32-valuetask-execution-pipeline-support-changes

[Shane32]

I'd further guess that the field type in this case is an interface or union, and what happened is that IsTypeOf returned false for the Task<T> returned value, causing the type to be null. With this change here in proposed PR graphql-dotnet/graphql-dotnet#3270 : https://github.com/graphql-dotnet/graphql-dotnet/pull/3270#discussion_r939766433 the code will use the interface type and not cause a null reference exception. Then you would at least see a better exception than what is seen currently, but it would not solve your issue.

Without seeing more of your code, this is just a guess, of course.

[wtorricos]

Thank you for the reply.

Regarding FieldAsync, I don't think that's the problem as even some really simple types are failing, we have many like the one below:

public sealed class CharacterType : AsyncNodeGraphType<CharacterModel>
{
    public CharacterType()
    {
        Name = "Character";

        Id(characterModel => characterModel.Id);

        Field<NonNullGraphType<StringGraphType>>()
            .Name("name")
            .Resolve(context => context.Source.Name ?? "None");
    }

    public override async Task<CharacterModel> GetById(IResolveFieldContext<object> context, string id)
    {
        var characterService = context.RequestServices.GetRequiredService<CharacterService>();
        Guid characterId = Guid.Parse(id);
        return characterService.GetByIdAsync(characterId, context.CancellationToken);
    }
}

The workaround that is working at the moment is to extend NodeGraphType instead of AsyncNodeGraphType

[Shane32]

Right I see. AsyncNodeGraphType<T> (which is in the relay project) inherits from NodeGraphType<Task<T>>, and when you call Id it calls Field instead of FieldAsync. The relay project's AsyncNodeGraphType needs to be fixed so that it does not call Field but instead calls FieldAsync.

[Shane32]

See faulty code here: (when used by the derived AsyncNodeGraphType -- the code is fine as NodeGraphType)

https://github.com/graphql-dotnet/relay/blob/5ad6b1c6367a2cfd83894a1f2f1f761a62c36b4d/src/GraphQL.Relay/Types/NodeGraphType.cs#L91..L98

There's nobody that actively works on this project, but if you'd like to open a pull request @tico321 I would be happy to review it, and when merged, issue an updated release.

[wtorricos]

Thank you for the fast response, I'll try to take a look over the weekend

[wtorricos]

Supporting NodeGraphType as well as AsyncNodeGraphtype seems to be a little bit trickier than what I thought, using FieldAsync wan't enough, but I found that awaiting the result in QueryGraphType fixes the problem. https://github.com/graphql-dotnet/relay/blob/7e5d8e4a6365194b68f282239b31f36137ace5aa/src/GraphQL.Relay/Types/QueryGraphType.cs#L24 Since I'm only using AsyncNodeGraphType I'm going to use the following class in my project until I can find a way to make it work with both Node and AsyncNode.

public class AsyncQueryGraphType : ObjectGraphType
{
    public AsyncQueryGraphType()
    {
        Name = "Query";

        Field<NodeInterface>()
            .Name("node")
            .Description("Fetches an object given its global Id")
            .Argument<NonNullGraphType<IdGraphType>>("id", "The global Id of the object")
            .ResolveAsync(ResolveObjectFromGlobalId);
    }

    private async Task<object> ResolveObjectFromGlobalId(IResolveFieldContext<object> context)
    {
        var globalId = context.GetArgument<string>("id");
        var parts = Node.FromGlobalId(globalId);
        var node = context.Schema.AllTypes[parts.Type];
        var getById = node!.GetType().GetMethod("GetById");

        dynamic awaitable = getById!.Invoke(node, new object[] { context, parts.Id });
        await awaitable!;
        return awaitable.GetAwaiter().GetResult();
    }
}

Having said that please let me know if you have any suggestions that may work and I'll take a look when I have some time.