Blazor: Grpc.Core.RpcException: Status(StatusCode="Cancelled", Detail="No grpc-status found on response.")

Throwing RpcException on the server always results in

Grpc.Core.RpcException: Status(StatusCode=“Cancelled”, Detail=“No grpc-status found on response.”)

being raised in a Blazor webassembly client.

What version of gRPC and what language are you using?

2.34.0 C#

What operating system (Linux, Windows,…) and version?

Windows 10

What runtime / compiler are you using (e.g. .NET Core SDK version dotnet --info)

.NET 5

What did you do?

(see here for demo project)

Created a GRPC service from the VS template, enabled Cors, enabled Grpc-Web. Changed the Kestrel endpoints protocol in appsettings.json from Http2 to Http.

GreeterService.cs

public override Task<HelloReply> SayHello(HelloRequest request, ServerCallContext context)
{
    throw new RpcException(new Status(StatusCode.AlreadyExists, "already exists detail"));
}

Created a Blazor web-assembly project.

Index.razor

@page "/"
@inject GrpcGreeter.Greeter.GreeterClient Client
<button @onclick="CallSayHello">Call Say Hello</button>
@code {
    private async Task CallSayHello()
    {
        await Client.SayHelloAsync(new GrpcGreeter.HelloRequest() { Name = "Mark" });        
    }
}

Program.cs

builder.Services.AddScoped(services =>
{
    var httpClient = new HttpClient(new GrpcWebHandler(GrpcWebMode.GrpcWeb, new HttpClientHandler()));
    var channel = GrpcChannel.ForAddress(ServerAddress, new GrpcChannelOptions { HttpClient = httpClient });
    return new GrpcGreeter.Greeter.GreeterClient(channel);
});

I have confirmed the correct error is being generated by the server with grpcurl…

grpcurl -d “{"name":"Mark"}” localhost:6001 greet.Greeter/SayHello ERROR: Code: AlreadyExists Message: already exists detail

Also, Fiddler reports the response from the Blazor request as

HTTP/1.1 200 OK Date: Thu, 24 Dec 2020 11:42:48 GMT Content-Type: application/grpc-web Server: Kestrel Content-Length: 0 Access-Control-Allow-Credentials: true Access-Control-Allow-Origin: https://localhost:44326 Grpc-Status: 6 Grpc-Message: already exists detail

What did you expect to see?

The server generated RpcException passed to the client.

What did you see instead?

Grpc.Core.RpcException: Status(StatusCode=“Cancelled”, Detail=“No grpc-status found on response.”)

[JamesNK]

See https://github.com/grpc/grpc-dotnet/blob/3518cd757002f5a685f34d277e876850b7637ecc/examples/Spar/Server/Startup.cs#L44

[HppZ]

same error in UWP client app. how to config grpc-status header?