fix: add support for Long64_t (#2023)

* fix: add test

* test: column of a Long64_t type

* test: check form of an output ak array

* fix: specialize type_to_name

header-only/awkward/utils.h

@@ -62,6 +62,14 @@ namespace awkward {
     return "int64";
   }
 
+  /// @brief Returns `int64` string when the primitive type
+  /// is a 64-bit signed integer.
+  template <>
+  const std::string
+  type_to_name<Long64_t>() {
+    return "int64";
+  }
+
   /// @brief Returns `uint8` string when the primitive type
   /// is an 8-bit unsigned integer.
   template <>

tests/test_2023-from-rdataframe.py

@@ -0,0 +1,24 @@
+# BSD 3-Clause License; see https://github.com/scikit-hep/awkward-1.0/blob/main/LICENSE
+
+import numpy as np  # noqa: F401
+import pytest
+
+import awkward as ak
+import awkward._connect.cling
+import awkward._lookup
+
+ROOT = pytest.importorskip("ROOT")
+
+
+compiler = ROOT.gInterpreter.Declare
+
+
+def test_rdf_column_of_Long64_t_type():
+    data_frame = ROOT.RDataFrame(10).Define("x", "(Long64_t)(gRandom->Rndm()*1000.)")
+    assert data_frame.GetColumnType("x") == "Long64_t"
+
+    ak_array = ak.from_rdataframe(
+        data_frame,
+        columns="x",
+    )
+    assert ak_array.layout.form == ak.forms.NumpyForm("int64")