Fix computation of union of empty and nonempty Selector instances.

neurokernel · Feb 12, 2015 · d39af3b · d39af3b
1 parent 4c73c1f
commit d39af3b
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Showing 2 changed files with 15 additions and 2 deletions.
diff --git a/neurokernel/plsel.py b/neurokernel/plsel.py
@@ -190,8 +190,12 @@ def union(cls, *sels):
         out = cls('')
         tmp = set()
         for s in sels:
-            tmp = tmp.union(s.expanded)
-        out._expanded = tuple(sorted(tmp))
+            if s.nonempty:
+                tmp = tmp.union(s.expanded)
+        if tmp:
+            out._expanded = tuple(sorted(tmp))
+        else:
+            out._expanded = ((),)
         try:
             out._max_levels = max([s.max_levels for s in sels if s.nonempty])
         except ValueError:

diff --git a/tests/test_plsel.py b/tests/test_plsel.py
@@ -144,6 +144,15 @@ def test_selector_union_nonempty(self):
         assert c.max_levels == 2
         assert c.str == '/x/0,/x/1,/x/2,/x/3,/x/4'
 
+    def test_selector_union_empty_nonempty(self):
+        a = Selector('')
+        b = Selector('/x[0:3]')
+        c = Selector.union(a, b)
+        assert len(c) == 3
+        assert c.expanded == (('x', 0), ('x', 1), ('x', 2))
+        assert c.max_levels == 2
+        assert c.str == '/x/0,/x/1,/x/2'
+
 class test_path_like_selector(TestCase):
     def setUp(self):
         self.df = df.copy()