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[tree] Clear error when calling CopyTree on a chain with friends #21260

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Merged
dpiparo merged 1 commit into from
Feb 21, 2026
Merged

[tree] Clear error when calling CopyTree on a chain with friends #21260

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1 change: 1 addition & 0 deletions tree/tree/inc/TChain.h
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Original file line number Diff line number Diff line change
Expand Up @@ -86,6 +86,7 @@ class TChain : public TTree {
TFriendElement *AddFriend(TTree* chain, const char* alias = "", bool warn = false) override;
void Browse(TBrowser*) override;
virtual void CanDeleteRefs(bool flag = true);
virtual TTree *CopyTree(const char* selection, Option_t* option = "", Long64_t nentries = kMaxEntries, Long64_t firstentry = 0) override;
virtual void CreatePackets();
void DirectoryAutoAdd(TDirectory *) override;
Long64_t Draw(const char* varexp, const TCut& selection, Option_t* option = "", Long64_t nentries = kMaxEntries, Long64_t firstentry = 0) override;
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18 changes: 18 additions & 0 deletions tree/tree/src/TChain.cxx
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Expand Up @@ -751,6 +751,24 @@ void TChain::CanDeleteRefs(bool flag /* = true */)
fCanDeleteRefs = flag;
}

////////////////////////////////////////////////////////////////////////////////
/// Copy a tree with selection.
///
/// See the documentation of TTree::CopyTree
///
/// ### Known limitations for TChain
/// - This method is not supported if used on an instance with friends

TTree* TChain::CopyTree(const char* selection, Option_t* option /* = 0 */, Long64_t nentries /* = TTree::kMaxEntries */, Long64_t firstentry /* = 0 */)
{
// A clear error for ROOT-10778
if (GetListOfFriends()) {
Error("CopyTree","TChain::CopyTree is not supported if the TChain instance has friends.");
return nullptr;
}
return this->TTree::CopyTree(selection, option, nentries, firstentry);
}

////////////////////////////////////////////////////////////////////////////////
/// Initialize the packet descriptor string.

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13 changes: 13 additions & 0 deletions tree/tree/test/TChainRegressions.cxx
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Expand Up @@ -6,10 +6,23 @@
#include <TSystem.h>
#include <TTree.h>

#include "ROOT/TestSupport.hxx"
#include "gtest/gtest.h"

class TTreeCache;

// ROOT-10778
TEST(TChain, CopyTreeWithFriends)
{
TChain ch1("chain1");
TChain ch2("chain2");
ch1.AddFriend(&ch2);
ROOT::TestSupport::CheckDiagsRAII diags;
diags.requiredDiag(kError, "TChain::CopyTree",
"TChain::CopyTree is not supported if the TChain instance has friends.");
ch1.CopyTree("");
}

// https://its.cern.ch/jira/browse/ROOT-7973
TEST(TChain, WrongCacheReadTwoTrees)
{
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