CORS not supported on a Dart server

[Levi-Lesches]

When using package:grpc on a Dart server, you make a Server and then call server.serve(). This server cannot handle CORS requests in the way package:shelf can, and so all requests from the Flutter side are broken.

grpc version: v3.1.0

Repro steps

// LoginService is a regular rpc service
void main() async {
  final server = Server([LoginService()]);
  await server.serve(port: 9000);
  print("Server running on http://localhost:9000");
}

Expected result: Sending requests to this server works

Actual result:

gRPC Error (code: 2, codeName: UNKNOWN, message: HTTP request completed without a status (potential CORS issue)

[mraleph]

Note that the server implementation only talks gRPC native protocol, does not support gRPC-Web clients directly. Hence no CORS support or anything like that. You need a proxy in between which would convert gRPC-Web to gRPC.

[Levi-Lesches]

Yes, I saw that elsewhere. Would it be possible to provide, in this package or another, native Dart support for gRPC-Web without the need for a separate proxy?

[mraleph]

It is definitely possible and I think we will accept a PR implementing gRPC-Web server.