Incompatible with GraphQL.Server Metrics/Instrumentation

[AzureMarker]

When using GraphQL.Conventions with GraphQL.Server, the following error occurs during the first GraphQL request:

GraphQL Error: Unable to cast object of type 'GraphQL.Instrumentation.InstrumentFieldsMiddleware' to type 'GraphQL.Types.IGraphType'.
   at GraphQL.Conventions.Adapters.GraphTypeAdapter.DeriveTypeFromTypeInfo(Type type)
   at GraphQL.FuncServiceProvider.GetService(Type type) in /_/src/GraphQL/DI/FuncServiceProvider.cs:line 27
   at GraphQL.Types.Schema.System.IServiceProvider.GetService(Type serviceType) in /_/src/GraphQL/Types/Schema.cs:line 107
   at GraphQL.Instrumentation.FieldMiddlewareBuilderExtensions.<>c__DisplayClass3_0.<Use>b__0(ISchema schema, FieldMiddlewareDelegate next) in /_/src/GraphQL/Instrumentation/FieldMiddlewareBuilderExtensions.cs:line 62
   at GraphQL.Instrumentation.FieldMiddlewareBuilder.Build(FieldMiddlewareDelegate start, ISchema schema) in /_/src/GraphQL/Instrumentation/FieldMiddlewareBuilder.cs:line 57
   at GraphQL.Instrumentation.FieldMiddlewareBuilder.ApplyTo(ISchema schema) in /_/src/GraphQL/Instrumentation/FieldMiddlewareBuilder.cs:line 77
   at GraphQL.DocumentExecuter.ExecuteAsync(ExecutionOptions options) in /_/src/GraphQL/Execution/DocumentExecuter.cs:line 74

GraphQL.Server.GraphQLOptions.Metrics is enabled by default. This eventually results in a call to provider.GetService(middleware), where provider.GetService is a reference to GraphTypeAdapter.DeriveTypeFromTypeInfo. This function falls back to Activator.CreateInstance, but casts to IGraphType. This cast causes the above error.

I think I found a workaround by disabling GraphQL.Server's metrics and manually adding InstrumentFieldsMiddleware to the GraphQLEngine via WithMiddleware. I'm not sure this is a good/valid fix though. A proper fix might be to remove the cast since the function is only used as the implementation of GetService, which only requires object? as a return type.

Details: ConfigureServices and Configure methods

Here are my ConfigureServices and Configure methods in Startup (link to file in git repo):

        public void ConfigureServices(IServiceCollection services) {
            // Infer the schema using GraphQL.Conventions
            var engine = new GraphQLEngine()
                .WithQuery<Query>()
                .BuildSchema();
            var schema = engine.GetSchema();

            services.AddControllers();
            services.AddSingleton(schema);
            services.AddWebSockets(_ => { });
            services
                .AddGraphQL((options, provider) => {
                    var logger = provider.GetRequiredService<ILogger<Startup>>();
                    options.UnhandledExceptionDelegate = ctx =>
                        logger.LogError(
                            "GraphQL Error: {Error}\n{Stacktrace}",
                            ctx.OriginalException.Message,
                            ctx.OriginalException.StackTrace
                        );
                })
                .AddWebSockets()
                .AddSystemTextJson();
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env) {
            if (env.IsDevelopment()) {
                app.UseDeveloperExceptionPage();
            }

            app.UseRouting();
            app.UseEndpoints(endpoints => { endpoints.MapControllers(); });
            app.UseWebSockets();
            app.UseGraphQLWebSockets<ISchema>();
            app.UseGraphiQLServer(new GraphiQLOptions { Path = "/graphiql" });
            app.UseGraphQL<ISchema>();
        }

[tlil]

Hey @Mcat12 - apologies for my late response.

Thanks for the above report. It does indeed look like there's a mismatch in return types for DeriveTypeFromTypeInfo(). I've attempted a fix on branch fix/issue-211 (#212). Could you please take it for a spin and see if the changed signature resolves the issue for you? The test suite seems unaffected.

[AzureMarker]

That does seem to fix the error, although I've since changed to the GraphType approach instead of using this library (I think I ran into some issues with passing through GraphQL Server's context; I tested this fix on a previous revision).

[tlil]

No probs. Thanks for checking. 👍

[tlil]

If you recall any context around the other issues that you ran into, feel free to elaborate and I can have a look into it.