Use string version for selection values in error message

trytond/trytond/model/model.py

@@ -244,11 +244,15 @@ class Model(URLMixin, PoolBase, metaclass=ModelMeta):
         IrModelField = pool.get('ir.model.field')
 
         def format_value(value):
+            ffield = getattr(cls, field, None)
             if isinstance(value, Model):
                 try:
                     return value.rec_name
                 except Exception:
                     return str(value.id)
+            elif ffield and ffield._type in {'selection', 'multiselection'}:
+                selection = ffield.get_selection(cls, field, record)
+                return ffield.get_selection_string(selection, value)
             else:
                 return str(value)
 

trytond/trytond/tests/model.py

@@ -10,6 +10,15 @@ class Model(ModelSQL):
     'Model'
     __name__ = 'test.model'
     name = fields.Char('Name')
+    selection = fields.Selection([
+            ('foo', "Foo"),
+            ('bar', "Bar"),
+            (None, ""),
+            ], "Selection")
+    multiselection = fields.MultiSelection([
+            ('foo', "Foo"),
+            ('bar', "Bar"),
+            ], "MultiSelection")
 
 
 class ModelParent(Model):

trytond/trytond/tests/test_model.py

@@ -204,6 +204,34 @@ class ModelTestCase(unittest.TestCase):
                 'model': "Model", 'field': "Name",
                 'record': record.id, 'value': "Test"})
 
+    @with_transaction()
+    def test_names_value_selection(self):
+        "test __names__ with selection value"
+        pool = Pool()
+        Model = pool.get('test.model')
+
+        record = Model(selection='foo')
+        names = Model.__names__(field='selection', record=record)
+
+        self.assertEqual(
+            names, {
+                'model': "Model", 'field': "Selection",
+                'record': record.id, 'value': "Foo"})
+
+    @with_transaction()
+    def test_names_value_multiselection(self):
+        "test __names__ with multiselection value"
+        pool = Pool()
+        Model = pool.get('test.model')
+
+        record = Model(multiselection=['foo', 'bar'])
+        names = Model.__names__(field='multiselection', record=record)
+
+        self.assertEqual(
+            names, {
+                'model': "Model", 'field': "MultiSelection",
+                'record': record.id, 'value': "Foo, Bar"})
+
     @with_transaction()
     def test_names_value_list(self):
         "Test __names__ with value as list"