[ntuple] Use name of first TTree when importing unnamed TChain

Fixes issue #13088.
root-project · Jul 24, 2023 · 46f2e5f · 46f2e5f
1 parent 492dc79
commit 46f2e5f
Show file tree

Hide file tree

Showing 2 changed files with 55 additions and 28 deletions.
diff --git a/tree/ntupleutil/v7/src/RNTupleImporter.cxx b/tree/ntupleutil/v7/src/RNTupleImporter.cxx
@@ -24,6 +24,7 @@
 #include <ROOT/RStringView.hxx>
 
 #include <TBranch.h>
+#include <TChain.h>
 #include <TClass.h>
 #include <TDataType.h>
 #include <TLeaf.h>
@@ -110,7 +111,15 @@ std::unique_ptr<ROOT::Experimental::RNTupleImporter>
 ROOT::Experimental::RNTupleImporter::Create(TTree *sourceTree, std::string_view destFileName)
 {
    auto importer = std::unique_ptr<RNTupleImporter>(new RNTupleImporter());
-   importer->fNTupleName = sourceTree->GetName();
+
+   if (sourceTree->IsA() == TChain::Class() && std::strcmp(sourceTree->GetName(), "") == 0) {
+      if (sourceTree->LoadTree(0) != 0)
+         throw RException(R__FAIL("failure retrieving first tree from provided chain"));
+      importer->fNTupleName = sourceTree->GetTree()->GetName();
+   } else {
+      importer->fNTupleName = sourceTree->GetName();
+   }
+
    importer->fSourceTree = sourceTree;
 
    // If we have IMT enabled, its best use is for parallel page compression

diff --git a/tree/ntupleutil/v7/test/ntuple_importer.cxx b/tree/ntupleutil/v7/test/ntuple_importer.cxx
@@ -59,46 +59,64 @@ TEST(RNTupleImporter, CreateFromTree)
 
 TEST(RNTupleImporter, CreateFromChain)
 {
-   FileRaii fileGuard1("test_ntuple_create_from_chain_1.root");
+   FileRaii treeFileGuard("test_ntuple_create_from_chain_1.root");
    {
-      std::unique_ptr<TFile> file(TFile::Open(fileGuard1.GetPath().c_str(), "RECREATE"));
-      auto tree = std::make_unique<TTree>("tree", "");
+      std::unique_ptr<TFile> file(TFile::Open(treeFileGuard.GetPath().c_str(), "RECREATE"));
+
+      auto tree1 = std::make_unique<TTree>("tree1", "");
       Int_t a = 42;
-      // For single-leaf branches, use branch name, not leaf name
-      tree->Branch("a", &a);
-      tree->Fill();
-      tree->Write();
+      tree1->Branch("a", &a);
+      tree1->Fill();
+      tree1->Write();
+
+      auto tree2 = std::make_unique<TTree>("tree2", "");
+      a = 43;
+      tree2->Branch("a", &a);
+      tree2->Fill();
+      tree2->Write();
    }
 
-   FileRaii fileGuard2("test_ntuple_create_from_chain_2.root");
+   FileRaii chainFileGuard("test_ntuple_create_from_chain_2.root");
    {
-      std::unique_ptr<TFile> file(TFile::Open(fileGuard2.GetPath().c_str(), "RECREATE"));
-      auto tree = std::make_unique<TTree>("tree", "");
-      Int_t a = 43;
-      // For single-leaf branches, use branch name, not leaf name
-      tree->Branch("a", &a);
-      tree->Fill();
-      tree->Write();
+      std::unique_ptr<TFile> file(TFile::Open(chainFileGuard.GetPath().c_str(), "RECREATE"));
+
+      TChain namedChain("tree");
+      namedChain.Add((treeFileGuard.GetPath() + "?#tree1").c_str());
+      namedChain.Add((treeFileGuard.GetPath() + "?#tree2").c_str());
+      namedChain.Write();
    }
 
-   TChain *chain = new TChain("tree");
-   chain->Add(fileGuard1.GetPath().c_str());
-   chain->Add(fileGuard2.GetPath().c_str());
+   std::unique_ptr<TFile> file(TFile::Open(chainFileGuard.GetPath().c_str()));
+   auto namedChain = file->Get<TChain>("tree");
 
-   auto importer = RNTupleImporter::Create(chain, fileGuard1.GetPath());
-   importer->SetIsQuiet(true);
-   EXPECT_THROW(importer->Import(), ROOT::Experimental::RException);
-   importer->SetNTupleName("ntuple");
-   importer->Import();
+   auto importer1 = RNTupleImporter::Create(namedChain, chainFileGuard.GetPath());
+   importer1->SetIsQuiet(true);
+   EXPECT_THROW(importer1->Import(), ROOT::Experimental::RException);
+   importer1->SetNTupleName("ntuple");
+   importer1->Import();
 
-   auto reader = RNTupleReader::Open("ntuple", fileGuard1.GetPath());
-   auto viewA = reader->GetView<std::int32_t>("a");
+   auto reader1 = RNTupleReader::Open("ntuple", chainFileGuard.GetPath());
+   auto viewA = reader1->GetView<std::int32_t>("a");
 
-   EXPECT_EQ(2U, reader->GetNEntries());
+   EXPECT_EQ(2U, reader1->GetNEntries());
    EXPECT_EQ(42, viewA(0));
    EXPECT_EQ(43, viewA(1));
 
-   EXPECT_THROW(importer->Import(), ROOT::Experimental::RException);
+   EXPECT_THROW(importer1->Import(), ROOT::Experimental::RException);
+
+   TChain unnamedChain;
+   unnamedChain.Add((treeFileGuard.GetPath() + "?#tree1").c_str());
+   unnamedChain.Add((treeFileGuard.GetPath() + "?#tree2").c_str());
+
+   auto importer2 = RNTupleImporter::Create(&unnamedChain, chainFileGuard.GetPath());
+   importer2->SetIsQuiet(true);
+   importer2->Import();
+
+   // Without explicitly setting the name of the imported chain, we expect it to be equal to the name of the first tree
+   // in the chain.
+   std::unique_ptr<RNTupleReader> reader2;
+   EXPECT_NO_THROW(reader2 = RNTupleReader::Open("tree1", chainFileGuard.GetPath()));
+   EXPECT_EQ(2U, reader2->GetNEntries());
 }
 
 TEST(RNTupleImporter, Simple)