[samples/aspdotnet] minimal apis with async result throw runtime Exception

[bacongobbler]

Given a minimal API endpoint such as the following:

app.MapPost("/", async ([FromServices] IMyService myService) =>
{
    app.Logger.LogInformation("doing something");
    await myService.DoSomething();
    app.Logger.LogInformation("completed something");
    return "";
});

Results in an error at runtime:

Unhandled exception. System.AggregateException: One or more errors occurred. (JsonTypeInfo metadata for type 'System.Threading.Tasks.Task`1[System.String]' was not provided by TypeInfoResolver of type '[SpinHttpWorld.wit.exports.wasi.http.v0_2_0.AppJsonSerializerContext, Microsoft.AspNetCore.OpenApi.OpenApiJsonSchemaContext]'. If using source generation, ensure that all root types passed to the serializer have been annotated with 'JsonSerializableAttribute', along with any types that might be serialized polymorphically.)

I am assuming that the async result from the request handler needs to be handled by WasiHttpServer before passing it along to the resolver.

[dicej]

Yeah, I ran into this yesterday. After some experimentation, I found that this worked, at least:

        app.MapGet(
            "/hellosql",
            async context =>
            {
                await HelloSql();
            }
        );

// ...
    private static async Task<string> HelloSql()
    {
        // ...
    }

That was inspired by https://learn.microsoft.com/en-us/aspnet/core/fundamentals/minimal-apis?view=aspnetcore-8.0#endpoint-defined-outside-of-programcs, along with https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.builder.endpointroutebuilderextensions.mapget?view=aspnetcore-8.0#microsoft-aspnetcore-builder-endpointroutebuilderextensions-mapget(microsoft-aspnetcore-routing-iendpointroutebuilder-system-string-microsoft-aspnetcore-http-requestdelegate) and https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.http.requestdelegate?view=aspnetcore-8.0.

The Map* functions are heavily overloaded, and I'm guessing sometimes they need type hints in order to make sure you're using the right one, at least when NativeAOT is in the mix.

[bacongobbler]

That does appear to work. Thank you!

Here's the updated sample:

app.MapPost("/", async context =>
{
    var myService = context.RequestServices.GetRequiredService<IMyService>();
    app.Logger.LogInformation("doing something");
    await myService.DoSomething();
    app.Logger.LogInformation("completed something");
    context.Response.StatusCode = StatusCodes.Status204NoContent;
});

[bacongobbler]

I'll keep this open for now with a note to document this for others.