DefinePerSample is not supported for RDataSource

[vepadulano]

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Description

RLoopManager::RunDataSource is lacking the logic to update the sample information which is present in the equivalent runners for the empty data source or the TTree data source. This notably prevents using DefinePerSample effectively when the input data source is an RNTuple.

$: ./repro.out
+-----+-----------+
| Row | file_name |
+-----+-----------+
| 0   | ""        |
+-----+-----------+
| 1   | ""        |
+-----+-----------+
| 2   | ""        |
+-----+-----------+
| 3   | ""        |
+-----+-----------+
| 4   | ""        |
+-----+-----------+
| 5   | ""        |
+-----+-----------+
| 6   | ""        |
+-----+-----------+
| 7   | ""        |
+-----+-----------+
| 8   | ""        |
+-----+-----------+
| 9   | ""        |
+-----+-----------+
| 10  | ""        |
+-----+-----------+
| 11  | ""        |
+-----+-----------+
| 12  | ""        |
+-----+-----------+
| 13  | ""        |
+-----+-----------+
| 14  | ""        |
+-----+-----------+

Reproducer

#include <ROOT/RNTupleDS.hxx>
#include <ROOT/RNTupleWriter.hxx>
#include <ROOT/RNTupleModel.hxx>
#include <TFile.h>
#include <ROOT/RNTuple.hxx>
#include <ROOT/RNTupleReader.hxx>
#include <ROOT/RVec.hxx>

#include <iostream>

using RNTupleModel = ROOT::Experimental::RNTupleModel;
using RNTupleWriter = ROOT::Experimental::RNTupleWriter;

void create_definepersample(const std::string &ntpl_name, const std::vector<std::string> &filenames)
{
    for (const auto &fn : filenames)
    {
        auto model = RNTupleModel::Create();
        auto fldX = model->MakeField<ULong64_t>("x");
        auto ntpl = RNTupleWriter::Recreate(std::move(model), ntpl_name, fn);
        for (ULong64_t entry = 0; entry < 10; entry++)
        {
            *fldX = entry;
            ntpl->Fill();
        }
    }
}

int main()
{
    std::vector<std::string> filenames{
        "sample1.root",
        "sample2.root",
        "sample3.root"};
    std::string ntpl_name = "Events";
    create_definepersample(ntpl_name, filenames);
    ROOT::RDataFrame df{ntpl_name, filenames};
    auto df1 = df.DefinePerSample("file_name", [](unsigned int, const ROOT::RDF::RSampleInfo &si) {
      return si.AsString();
    });
    df1.Display<std::string>({"file_name"}, 30)->Print();
}

ROOT version

Any

Installation method

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Operating system

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Additional context

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