Fix Enum field, which allows unrestricted values

For some reason, the Enum field allows valid_values to be None, which disables
all the is-this-a-valid-value checking, thus defeating the entire purpose of
the type. This patch removes that possibility so that we don't let anything
creep into the RPC-affecting API that would be unrestricted.

The change that introduced this was I7848f8b934c169a76b1cfd875f7905273f9f914b

Closes-Bug: #1441243
Change-Id: Ia33994402cca5b4569d72860ab5da675134f5a95

nova/objects/fields.py

@@ -254,18 +254,25 @@ class String(FieldType):
 
 
 class Enum(String):
-    def __init__(self, valid_values=None, **kwargs):
+    def __init__(self, valid_values, **kwargs):
+        try:
+            length = len(valid_values)
+        except TypeError:
+            raise ValueError('valid_values is not a sequence'
+                             ' of permitted values')
+        if length == 0:
+            raise ValueError('valid_values may not be empty')
         self._valid_values = valid_values
         super(Enum, self).__init__(**kwargs)
 
     def coerce(self, obj, attr, value):
-        if self._valid_values and value not in self._valid_values:
+        if value not in self._valid_values:
             msg = _("Field value %s is invalid") % value
             raise ValueError(msg)
         return super(Enum, self).coerce(obj, attr, value)
 
     def stringify(self, value):
-        if self._valid_values and value not in self._valid_values:
+        if value not in self._valid_values:
             msg = _("Field value %s is invalid") % value
             raise ValueError(msg)
         return super(Enum, self).stringify(value)
@@ -592,7 +599,7 @@ class StringField(AutoTypedField):
 
 
 class EnumField(AutoTypedField):
-    def __init__(self, valid_values=None, **kwargs):
+    def __init__(self, valid_values, **kwargs):
         self.AUTO_TYPE = Enum(valid_values=valid_values)
         super(EnumField, self).__init__(**kwargs)
 
@@ -674,7 +681,7 @@ class ListOfStringsField(AutoTypedField):
 
 
 class ListOfEnumField(AutoTypedField):
-    def __init__(self, valid_values=None, **kwargs):
+    def __init__(self, valid_values, **kwargs):
         self.AUTO_TYPE = List(Enum(valid_values=valid_values))
         super(ListOfEnumField, self).__init__(**kwargs)
 

nova/tests/unit/objects/test_fields.py

@@ -108,6 +108,12 @@ class TestEnum(TestField):
         field2 = fields.EnumField(valid_values=['foo', 'bar1'])
         self.assertNotEqual(str(field1), str(field2))
 
+    def test_without_valid_values(self):
+        self.assertRaises(ValueError, fields.EnumField, 1)
+
+    def test_with_empty_values(self):
+        self.assertRaises(ValueError, fields.EnumField, [])
+
 
 class TestInteger(TestField):
     def setUp(self):