fix(storage/transfermanager): correct Attrs.StartOffset for sharded d…

…ownloads (#10512)

Because the download is in pieces, the StartOffset may be incorrect.

storage/transfermanager/downloader.go

@@ -419,6 +419,12 @@ func (d *Downloader) gatherShards(in *DownloadObjectInput, outs <-chan *Download
 	if len(errs) != 0 {
 		shardOut.Err = fmt.Errorf("download shard errors:\n%w", errors.Join(errs...))
 	}
+	if shardOut.Attrs != nil {
+		shardOut.Attrs.StartOffset = 0
+		if in.Range != nil {
+			shardOut.Attrs.StartOffset = in.Range.Offset
+		}
+	}
 	d.addResult(in, shardOut)
 }
 

storage/transfermanager/integration_test.go

@@ -423,6 +423,10 @@ func TestIntegration_DownloaderSynchronous(t *testing.T) {
 			if got, want := got.Attrs.Size, tb.objectSizes[got.Object]; want != got {
 				t.Errorf("expected object size %d, got %d", want, got)
 			}
+
+			if got, want := got.Attrs.StartOffset, int64(0); want != got {
+				t.Errorf("expected start offset %d, got %d", want, got)
+			}
 		}
 
 		if len(results) != len(objects) {