[RDF] Fix varied Defines not showing up in Snapshots.

RActionSnapshot did not create the varied versions of Defines.
Therefore, Defines that implicitly depended on a variation were
identical to nominal, and did not get snapshot.
Here, the computation graph is JITted and the variations of Defines are
created when the snapshot action gets created.

Fix root-project#20506

Author: hageboeck

tree/dataframe/inc/ROOT/RDF/RActionSnapshot.hxx

@@ -74,9 +74,6 @@ class R__CLING_PTRCHECK(off) RActionSnapshot final : public RActionBase {
       const auto &prevVariations = nominalPrevNode->GetVariations();
       fPrevNodes.reserve(1 + currentVariations.size());
 
-      // Need to populate parts of the computation graph for which we have empty shells, e.g. RJittedFilters
-      if (!currentVariations.empty())
-         fLoopManager->Jit();
       for (const auto &variation : currentVariations) {
          if (IsStrInVec(variation, prevVariations)) {
             fPrevNodes.emplace_back(
@@ -105,7 +102,19 @@ public:
          fIsDefine.push_back(colRegister.IsDefineOrAlias(columns[i]));
 
       if constexpr (std::is_same_v<Helper, SnapshotHelperWithVariations>) {
+         // Need to populate parts of the computation graph for which we have empty shells, e.g. RJittedFilters and
+         // varied Defines
+         if (!GetVariations().empty())
+            fLoopManager->Jit();
+
          AppendVariedPrevNodes();
+
+         for (auto i = 0u; i < nColumns; ++i) {
+            if (fIsDefine[i]) {
+               auto define = colRegister.GetDefine(columns[i]);
+               define->MakeVariations(GetVariations());
+            }
+         }
       }
    }