Always return tuple for MultiSelection

issue11282
review361021002

CHANGELOG

@@ -1,3 +1,4 @@
+* Always return tuple for MultiSelection
 * Use default selectors instead of select
 * Add batch option to push queue tasks
 * Support ref value for reference field

trytond/model/fields/multiselection.py

@@ -55,7 +55,7 @@ class MultiSelection(SelectionMixin, Field):
                 self.selection, RPC(instantiate=instantiate))
 
     def get(self, ids, model, name, values=None):
-        lists = {id: None for id in ids}
+        lists = {id: () for id in ids}
         for value in values or []:
             data = value[name]
             if data:

trytond/tests/test_field_multiselection.py

@@ -29,7 +29,7 @@ class FieldMultiSelectionTestCase(unittest.TestCase):
                     }])
 
         self.assertEqual(selection.selects, ('bar', 'foo'))
-        self.assertEqual(selection_none.selects, None)
+        self.assertEqual(selection_none.selects, ())
 
     @with_transaction()
     def test_create_not_in(self):
@@ -67,7 +67,7 @@ class FieldMultiSelectionTestCase(unittest.TestCase):
                     'dyn_selects': None,
                     }])
 
-        self.assertEqual(selection.dyn_selects, None)
+        self.assertEqual(selection.dyn_selects, ())
 
     @with_transaction()
     def test_create_dynamic_not_in(self):
@@ -100,7 +100,7 @@ class FieldMultiSelectionTestCase(unittest.TestCase):
                     'static_selects': None,
                     }])
 
-        self.assertEqual(selection.static_selects, None)
+        self.assertEqual(selection.static_selects, ())
 
     @with_transaction()
     def test_create_static_not_in(self):
@@ -183,7 +183,7 @@ class FieldMultiSelectionTestCase(unittest.TestCase):
                     'selects': None,
                     }])
 
-        self.assertEqual(selection.selects_string, None)
+        self.assertEqual(selection.selects_string, [])
 
     @with_transaction()
     def test_search_equals(self):