[Prafyl]

when a class with its own Streamer is stored with tree->Branch("lv", &lv) (TLorentzVector, TVector3, TGraph, TMatrixD, TVectorD ...) ROOT doesnt split it and writes each entry with the class streamer, so every entry starts with version and bytecount. jsroot ran the member streamers directly without reading that header, so all values came out shifted, for TLorentzVector fE was the same garbage number in every entry.

for branches with fType -1 it now uses buf.classStreamer(), which reads the header and still handles classes like TDatime that have none. this also fixes Branch("oa", "TObjArray", &arr) which threw a RangeError, and TList which came back empty.

added demo/node/tree_tobject_test made with ROOT 6.40, it fails on current dev and passes with the fix.

this was assisted by ai

[linev]

I closed and open again PR to restart CI jobs

[linev]

I can confirm that correspondent code exists in ROOT
In TTreeReaderValue.cxx, line 771

      } else if (brElement->GetType() == -1 && brElement->GetTypeName()) {
         dict = TDictionary::GetDictionary(brElement->GetTypeName());
         ResolveTypedef();
         return brElement->GetTypeName();
      }

Thanks for fixing it!