Response with code != OK triggers both success and error callbacks

[evanj]

It is possible for gRPC responses to both have a code set to something that is not OK, and still have a response. For example, the following Python server code will return that payload, using the official gRPC implementation:

context.set_code(grpc.StatusCode.ABORTED)
context.set_details('error details')
return interop_pb2.EchoResponse(arg='message')

On the wire, this returns first the correctly serialized response object, then a headers block with grpc-status: 10 and grpc-message: error details.

When using grpc-web with this end point, the client calls the callback TWICE: First with the response message, then a second time with the error. The official NodeJS client, and the other gRPC clients I've tried this with, treat this as a gRPC error, and ignore the response message.

[adamkewley]

Having this issue with a grpc-web implementation also. Means client-side callbacks are getting called with response and error. The data sent down the wire includes a bogus response followed by an error. Python server-side also.

[adamkewley]

As a followup, once we identified that the issue we were having was because of this double-messaging thing, we dropped into the server side and made sure that context.abort(code, details) was called server-side, rather than setting the code and responding like above. The python documentation for abort is here:

https://grpc.github.io/grpc/python/grpc.html#service-side-context

[stanley-cheung]

This should be fixed by #847 and #858 in version 1.2.0. Now the callbacks behavior should align with the grpc-node implementations. A response with a non-OK status will be treated as an error. The response will not be returned to align with other grpc client implementations.