added test for issue GH 8866

Author: jamalsenouci

pandas/core/groupby.py

@@ -245,7 +245,6 @@ def _set_grouper(self, obj, sort=False):
             return self.grouper
         else:
             self._set_basegrouper(obj)
-            return self.grouper
 
     def _set_timegrouper(self, obj, sort=False):
         """
@@ -350,6 +349,7 @@ def is_in_obj(gpr):
         grouper = BaseGrouper(ax, grouping)
         self.obj = obj
         self.grouper = grouper
+        return self.grouper
 
     def _get_binner_for_grouping(self, obj):
         raise NotImplementedError

pandas/tests/test_groupby.py

@@ -3677,6 +3677,16 @@ def test_timegrouper_get_group(self):
                 dt = pd.Timestamp(t)
                 result = grouped.get_group(dt)
                 assert_frame_equal(result, expected)
+                
+    def test_grouper_with_nondatetime(self):
+        # GH 8866
+        s = Series(np.arange(8),index=pd.MultiIndex.from_product([list('ab'),
+                   range(2),pd.date_range('20130101',periods=2)],
+                   names=['one','two','three']))
+
+        expected = Series(data = [6,22], index=pd.Index(['a','b'], name='one'))
+        result = s.groupby(pd.Grouper(level='one')).sum()
+        assert_series_equal(result,expected)
 
     def test_cumcount(self):
         df = DataFrame([['a'], ['a'], ['a'], ['b'], ['a']], columns=['A'])