[#620] object: Send status response for server-side streams

Previously status responses were wrapped in the gRPC error and thus
couldn't be correctly handled on client.

Introduced in c2617baf63, thanks @ale64bit for having found.

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

pkg/services/object/sign.go

@@ -49,7 +49,11 @@ func NewSignService(key *ecdsa.PrivateKey, svc ServiceServer) *SignService {
 }
 
 func (s *getStreamSigner) Send(resp *object.GetResponse) error {
-	if err := s.sigSvc.SignResponse(resp, nil); err != nil {
+	return s.send(resp, nil)
+}
+
+func (s *getStreamSigner) send(resp *object.GetResponse, err error) error {
+	if err := s.sigSvc.SignResponse(resp, err); err != nil {
 		return err
 	}
 	return s.GetObjectStream.Send(resp)
@@ -62,10 +66,14 @@ func (s *SignService) Get(req *object.GetRequest, stream GetObjectStream) error
 		return stream.Send(resp)
 	}
 
-	return s.svc.Get(req, &getStreamSigner{
+	w := &getStreamSigner{
 		GetObjectStream: stream,
 		sigSvc:          s.sigSvc,
-	})
+	}
+	if err := s.svc.Get(req, w); err != nil {
+		return w.send(new(object.GetResponse), err)
+	}
+	return nil
 }
 
 func (s *putStreamSigner) Send(ctx context.Context, req *object.PutRequest) error {
@@ -124,7 +132,11 @@ func (s *SignService) PutSingle(ctx context.Context, req *object.PutSingleReques
 
 func (s *searchStreamSigner) Send(resp *object.SearchResponse) error {
 	s.nonEmptyResp = true
-	if err := s.sigSvc.SignResponse(resp, nil); err != nil {
+	return s.send(resp, nil)
+}
+
+func (s *searchStreamSigner) send(resp *object.SearchResponse, err error) error {
+	if err := s.sigSvc.SignResponse(resp, err); err != nil {
 		return err
 	}
 	return s.SearchStream.Send(resp)
@@ -142,15 +154,15 @@ func (s *SignService) Search(req *object.SearchRequest, stream SearchStream) err
 		sigSvc:       s.sigSvc,
 	}
 	err := s.svc.Search(req, ss)
-	if err == nil && !ss.nonEmptyResp {
+	if err != nil || !ss.nonEmptyResp {
 		// The higher component does not write any response in the case of an empty result (which is correct).
 		// With the introduction of status returns at least one answer must be signed and sent to the client.
 		// This approach is supported by clients who do not know how to work with statuses (one could make
 		// a switch according to the protocol version from the request, but the costs of sending an empty
 		// answer can be neglected due to the gradual refusal to use the "old" clients).
-		return stream.Send(new(object.SearchResponse))
+		return ss.send(new(object.SearchResponse), err)
 	}
-	return err
+	return nil
 }
 
 func (s *SignService) Delete(ctx context.Context, req *object.DeleteRequest) (*object.DeleteResponse, error) {
@@ -163,7 +175,11 @@ func (s *SignService) Delete(ctx context.Context, req *object.DeleteRequest) (*o
 }
 
 func (s *getRangeStreamSigner) Send(resp *object.GetRangeResponse) error {
-	if err := s.sigSvc.SignResponse(resp, nil); err != nil {
+	return s.send(resp, nil)
+}
+
+func (s *getRangeStreamSigner) send(resp *object.GetRangeResponse, err error) error {
+	if err := s.sigSvc.SignResponse(resp, err); err != nil {
 		return err
 	}
 	return s.GetObjectRangeStream.Send(resp)
@@ -176,10 +192,14 @@ func (s *SignService) GetRange(req *object.GetRangeRequest, stream GetObjectRang
 		return stream.Send(resp)
 	}
 
-	return s.svc.GetRange(req, &getRangeStreamSigner{
+	w := &getRangeStreamSigner{
 		GetObjectRangeStream: stream,
 		sigSvc:               s.sigSvc,
-	})
+	}
+	if err := s.svc.GetRange(req, w); err != nil {
+		return w.send(new(object.GetRangeResponse), err)
+	}
+	return nil
 }
 
 func (s *SignService) GetRangeHash(ctx context.Context, req *object.GetRangeHashRequest) (*object.GetRangeHashResponse, error) {