Fix OD item lookup evaluating subobject's length (fixes #588) (#589)

If the lookup by name returns an object (not None), the boolean
expression still checks whether that object is equivalent to boolean
True.  This needlessly calls the object's __len__() method, while what
we're interested in is just whether an object was found.

Author: sveinse

canopen/objectdictionary/__init__.py

@@ -133,7 +133,9 @@ def __getitem__(
         self, index: Union[int, str]
     ) -> Union[ODArray, ODRecord, ODVariable]:
         """Get object from object dictionary by name or index."""
-        item = self.names.get(index) or self.indices.get(index)
+        item = self.names.get(index)
+        if item is None:
+            item = self.indices.get(index)
         if item is None:
             if isinstance(index, str) and '.' in index:
                 idx, sub = index.split('.', maxsplit=1)

test/test_od.py

@@ -249,6 +249,18 @@ def test_get_item_dot(self):
         self.assertEqual(test_od["Test Array.Test Variable"], member1)
         self.assertEqual(test_od["Test Array.Test Variable 2"], member2)
 
+    def test_get_item_index(self):
+        test_od = od.ObjectDictionary()
+        array = od.ODArray("Test Array", 0x1000)
+        test_od.add_object(array)
+        item = test_od[0x1000]
+        self.assertIsInstance(item, od.ODArray)
+        self.assertIs(item, array)
+        item = test_od["Test Array"]
+        self.assertIsInstance(item, od.ODArray)
+        self.assertIs(item, array)
+
+
 class TestArray(unittest.TestCase):
 
     def test_subindexes(self):