(#391) RangetSetND: add missing autostep when folding

When folding specific nD-RangeSets which were triggering a
special heuristic, we were creating new RangeSets without copying
the current autostep value.

Thanks to D. Martinet for debugging it!

Closes #391.

Change-Id: I0c6eb21b508cec458d05cf63183de70367ba3e35

Author: Aurelien Degremont

lib/ClusterShell/RangeSet.py

@@ -1131,7 +1131,8 @@ def _fold_multivariate_expand(self):
         if len(self._veclist) * (len(self._veclist) - 1) / 2 > max_length * 10:
             # *** nD full expand is preferred ***
             pads = self.pads()
-            self._veclist = [[RangeSet.fromone(i, pad=pads[axis])
+            self._veclist = [[RangeSet.fromone(i, pad=pads[axis],
+                                               autostep=self.autostep)
                               for axis, i in enumerate(tvec)]
                              for tvec in set(self._iter())]
             return

tests/RangeSetNDTest.py

@@ -158,6 +158,11 @@ def test_folding(self):
                      "0-2; 1-2; 0-4\n3; 1-2; 0-5\n", 42)
         self._testRS([["0-2", "1-2", "0-4"], ["1-3", "1-3", "0-4"]],
                      "1-2; 1-3; 0-4\n0,3; 1-2; 0-4\n3; 3; 0-4\n", 55)
+
+        # triggers full expand heuristic
+        veclist = [item for x in range(0, 22, 2) for item in [(x,0), (x,1)]]
+        self._testRS(veclist, "0-20/2; 0-1\n", 22)
+
         # the following test triggers folding loop protection
         self._testRS([["0-100", "50-200"], ["2-101", "49"]],
                      "0-100; 50-200\n2-101; 49\n", 15351)