fix: remove mandatory attrs response in MRD

storage/grpc_reader_multi_range.go

@@ -115,7 +115,9 @@ func (c *grpcStorageClient) NewMultiRangeDownloader(ctx context.Context, params
 			manager.wg.Wait()
 			return nil, manager.permanentErr
 		}
-		mrd.Attrs = manager.attrs
+		if manager.attrs != nil {
+			mrd.Attrs = *manager.attrs
+		}
 		return mrd, nil
 	case <-ctx.Done():
 		cancel()
@@ -220,7 +222,7 @@ type multiRangeDownloaderManager struct {
 	waiters        []chan struct{}
 	readSpec       *storagepb.BidiReadObjectSpec
 	lastReadHandle []byte
-	attrs          ReaderObjectAttrs
+	attrs          *ReaderObjectAttrs
 	attrsReady     chan struct{}
 	attrsOnce      sync.Once
 	spanCtx        context.Context
@@ -487,8 +489,8 @@ func (m *multiRangeDownloaderManager) handleAddCmd(ctx context.Context, cmd *mrd
 	}
 	m.readIDCounter++
 
-	// Attributes should be ready if we are processing Add commands
-	if req.offset < 0 {
+	// Convert to positive offset only if attributes are available.
+	if m.attrs != nil && req.offset < 0 {
 		err := m.convertToPositiveOffset(req)
 		if err != nil {
 			return
@@ -517,23 +519,20 @@ func (m *multiRangeDownloaderManager) convertToPositiveOffset(req *rangeRequest)
 	if req.offset >= 0 {
 		return nil
 	}
-	objSize := m.attrs.Size
-	if objSize <= 0 {
-		err := errors.New("storage: cannot resolve negative offset without object size")
-		m.failRange(req, err)
-		return err
+	var objSize int64
+	if m.attrs != nil {
+		objSize = m.attrs.Size
 	}
-	if req.length != 0 {
-		err := fmt.Errorf("storage: negative offset with non-zero length is not supported (offset: %d, length: %d)", req.origOffset, req.origLength)
+	if objSize <= 0 {
+		err := errors.New("storage: cannot resolve negative offset with object size as 0")
 		m.failRange(req, err)
 		return err
 	}
-	start := objSize + req.offset
-	if start < 0 {
-		start = 0
-	}
+	start := max(objSize+req.offset, 0)
 	req.offset = start
-	req.length = objSize - start
+	if req.length == 0 {
+		req.length = objSize - start
+	}
 	return nil
 }
 
@@ -573,15 +572,12 @@ func (m *multiRangeDownloaderManager) processSessionResult(result mrdSessionResu
 		if meta := resp.GetMetadata(); meta != nil {
 			obj := newObjectFromProto(meta)
 			attrs := readerAttrsFromObject(obj)
-			m.attrs = attrs
-
+			m.attrs = &attrs
 			for _, req := range m.pendingRanges {
 				if req.offset < 0 {
 					_ = m.convertToPositiveOffset(req)
 				}
 			}
-		} else {
-			m.handleStreamEnd(mrdSessionResult{err: errors.New("storage: first response from BidiReadObject stream missing metadata")})
 		}
 	})
 

storage/integration_test.go

@@ -528,9 +528,10 @@ func TestIntegration_MRDCallbackReturnsDataLength(t *testing.T) {
 func TestIntegration_MRDWithReadHandle(t *testing.T) {
 	multiTransportTest(skipAllButZonal(context.Background(), "Bidi Read API test"), t, func(t *testing.T, ctx context.Context, bucket string, _ string, client *Client) {
 		const (
-			dataSize = 1000
-			offset   = 0
-			limit    = 100
+			dataSize       = 1000
+			offset         = 0
+			limit          = 100
+			negativeOffset = -200
 		)
 
 		// Generate random content for testing.
@@ -562,7 +563,7 @@ func TestIntegration_MRDWithReadHandle(t *testing.T) {
 		}
 
 		// Perform the read operation.
-		var res1, res2 multiRangeDownloaderOutput
+		var res1, res2, res3, res4 multiRangeDownloaderOutput
 		mrd.Add(&res1.buf, offset, limit, func(x, y int64, err error) {
 			res1.offset = x
 			res1.limit = y
@@ -573,14 +574,28 @@ func TestIntegration_MRDWithReadHandle(t *testing.T) {
 			res2.limit = y
 			res2.err = err
 		})
+		mrd2.Add(&res3.buf, negativeOffset, limit, func(x, y int64, err error) {
+			res3.offset = x
+			res3.limit = y
+			res3.err = err
+		})
+		mrd2.Add(&res4.buf, negativeOffset, 0, func(x, y int64, err error) {
+			res4.offset = x
+			res4.limit = y
+			res4.err = err
+		})
 
 		mrd.Wait()
 		mrd2.Wait()
+
 		if res1.err != nil {
 			t.Fatalf("mrd.Add callback returned error: %v", res1.err)
 		}
 		if res2.err != nil {
-			t.Fatalf("mrd2.Add callback returned error: %v", res2.err)
+			t.Fatalf("mrd2.Add callback returned error for res2: %v", res2.err)
+		}
+		if res3.err != nil {
+			t.Fatalf("mrd2.Add callback returned error for res3: %v", res3.err)
 		}
 
 		// Validate results for mrd with read handle.
@@ -593,6 +608,16 @@ func TestIntegration_MRDWithReadHandle(t *testing.T) {
 			t.Errorf("mrd2 downloaded content mismatch. got %d bytes, want %d bytes", len(got), len(want))
 		}
 
+		want = content[max(0, dataSize+negativeOffset):min(dataSize, max(0, dataSize+negativeOffset)+limit)]
+		if got := res3.buf.Bytes(); !bytes.Equal(got, want) {
+			t.Errorf("mrd2 downloaded content mismatch. got %v bytes, want %v bytes. %v", got, want, content)
+		}
+
+		want = content[max(0, dataSize+negativeOffset):]
+		if got := res4.buf.Bytes(); !bytes.Equal(got, want) {
+			t.Errorf("mrd2 downloaded content mismatch. got %v bytes, want %v bytes. %v", got, want, content)
+		}
+
 		if err := mrd.Close(); err != nil {
 			t.Fatalf("Error while closing reader: %v", err)
 		}