[DF] Add test for I/O of nested RVecs

root/dataframe/CMakeLists.txt

@@ -216,3 +216,6 @@ ROOTTEST_ADD_TEST(test_progressiveCSV
                   COPY_TO_BUILDDIR test_progressiveCSV.csv
                   OUTREF test_progressiveCSV.ref
                   DEPENDS ${GENERATE_EXECUTABLE_TEST})
+
+# need the '+' to autogenerate required dictionaries with ACLiC
+ROOTTEST_ADD_TEST(test_nested_rvec_snapshot MACRO test_nested_rvec_snapshot.C+)

root/dataframe/test_nested_rvec_snapshot.C

@@ -0,0 +1,55 @@
+#include <ROOT/RDataFrame.hxx>
+#include <ROOT/RVec.hxx>
+using namespace ROOT::VecOps;
+
+struct TwoInts {
+   int a, b;
+};
+
+#ifdef __CLING__
+#pragma link C++ class ROOT::VecOps::RVec<TwoInts>+;
+#pragma link C++ class ROOT::VecOps::RVec<ROOT::VecOps::RVec<TwoInts>>+;
+#pragma link C++ class ROOT::VecOps::RVec<ROOT::VecOps::RVec<int>>+;
+#pragma link C++ class ROOT::VecOps::RVec<ROOT::VecOps::RVec<ROOT::VecOps::RVec<int>>>+;
+#endif
+
+void test_nested_rvec_snapshot()
+{
+   const auto fname = "snapshot_nestedrvecs.root";
+
+   auto df = ROOT::RDataFrame(1)
+                .Define("vv",
+                        [] {
+                           return RVec<RVec<int>>{{1, 2}, {3, 4}};
+                        })
+                .Define("vvv",
+                        [] {
+                           return RVec<RVec<RVec<int>>>{{{1, 2}, {3, 4}}, {{5, 6}, {7, 8}}};
+                        })
+                .Define("vvti", [] {
+                   return RVec<RVec<TwoInts>>{{{1, 2}, {3, 4}}};
+                });
+
+   auto check = [](ROOT::RDF::RNode d) {
+      d.Foreach(
+         [](const RVec<RVec<int>> &vv, const RVec<RVec<RVec<int>>> &vvv, const RVec<RVec<TwoInts>> &vvti) {
+            R__ASSERT(All(vv[0] == RVec<int>{1, 2}));
+            R__ASSERT(All(vv[1] == RVec<int>{3, 4}));
+            R__ASSERT(All(vvv[0][0] == RVec<int>{1, 2}));
+            R__ASSERT(All(vvv[0][1] == RVec<int>{3, 4}));
+            R__ASSERT(All(vvv[1][0] == RVec<int>{5, 6}));
+            R__ASSERT(All(vvv[1][1] == RVec<int>{7, 8}));
+            R__ASSERT(vvti[0][0].a == 1 && vvti[0][0].b == 2 && vvti[0][1].a == 3 && vvti[0][1].b == 4);
+         },
+         {"vv", "vvv", "vvti"});
+   };
+
+   // compiled
+   auto out_df1 =
+      df.Snapshot<RVec<RVec<int>>, RVec<RVec<RVec<int>>>, RVec<RVec<TwoInts>>>("t", fname, {"vv", "vvv", "vvti"});
+   check(*out_df1);
+
+   // jitted
+   auto out_df2 = df.Snapshot("t", fname, {"vv", "vvv", "vvti"});
+   check(*out_df2);
+}