grpc: Fix cardinality violations in client streaming and unary RPCs.

stream.go

@@ -1167,7 +1167,7 @@
 	} else if err != nil {
 		return toRPCErr(err)
 	}
-	return toRPCErr(errors.New("grpc: client streaming protocol violation: get <nil>, want <EOF>"))
+	return status.Errorf(codes.Internal, "cardinality violation: expected <EOF> for non server-streaming RPCs, but received another message")
 }
 
 func (a *csAttempt) finish(err error) {
@@ -1491,7 +1491,7 @@
 	} else if err != nil {
 		return toRPCErr(err)
 	}
-	return toRPCErr(errors.New("grpc: client streaming protocol violation: get <nil>, want <EOF>"))
+	return status.Errorf(codes.Internal, "cardinality violation: expected <EOF> for non server-streaming RPCs, but received another message")
 }
 
 func (as *addrConnStream) finish(err error) {

test/end2end_test.go

@@ -3739,6 +3739,39 @@ func (s) TestClientStreaming_ReturnErrorAfterSendAndClose(t *testing.T) {
 	}
 }
 
+// Tests that a client receives a cardinality violation error for client-streaming
+// RPCs if the server call SendMsg multiple times.
+func (s) TestClientStreaming_ServerHandlerSendMsgAfterSendMsg(t *testing.T) {
+	ss := stubserver.StubServer{
+		StreamingInputCallF: func(stream testgrpc.TestService_StreamingInputCallServer) error {
+			if err := stream.SendMsg(&testpb.StreamingInputCallResponse{}); err != nil {
+				t.Errorf("stream.SendMsg(_) = %v, want <nil>", err)
+			}
+			if err := stream.SendMsg(&testpb.StreamingInputCallResponse{}); err != nil {
+				t.Errorf("stream.SendMsg(_) = %v, want <nil>", err)
+			}
+			return nil
+		},
+	}
+	if err := ss.Start(nil); err != nil {
+		t.Fatal("Error starting server:", err)
+	}
+	defer ss.Stop()
+
+	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
+	defer cancel()
+	stream, err := ss.Client.StreamingInputCall(ctx)
+	if err != nil {
+		t.Fatalf(".StreamingInputCall(_) = _, %v, want <nil>", err)
+	}
+	if err := stream.Send(&testpb.StreamingInputCallRequest{}); err != nil {
+		t.Fatalf("stream.Send(_) = %v, want <nil>", err)
+	}
+	if _, err := stream.CloseAndRecv(); status.Code(err) != codes.Internal {
+		t.Fatalf("stream.CloseAndRecv() = %v, want error with status code %s", err, codes.Internal)
+	}
+}
+
 func (s) TestExceedMaxStreamsLimit(t *testing.T) {
 	for _, e := range listTestEnv() {
 		testExceedMaxStreamsLimit(t, e)