don't convert (unindexed) ascii str to bytes

src/google/appengine/ext/ndb/model.py

@@ -2741,8 +2741,9 @@ def _db_get_value(self, v, p):
         sval = modelclass._from_pb(pb)
       elif meaning != entity_pb2.Property.BYTESTRING:
         try:
-          sval.decode('ascii')
-
+          decoded = sval.decode('ascii')
+          if meaning == entity_pb2.Property.TEXT:
+            sval = six.ensure_str(decoded, encoding='ascii')
         except UnicodeDecodeError:
           try:
             sval = six.text_type(sval.decode('utf-8'))

tests/google/appengine/ext/ndb/polymodel_test.py

@@ -143,9 +143,18 @@ class Mammal(Animal):
     self.assertEqual(cat1.naps, 18)
     self.assertEqual(cat1.sound, b'purr')
 
-  def testExpandoPoly(self):
-
+    # un-indexed properties retain str type regardless of encoding:
+    Mammal._default_indexed = False
+    cat = Mammal(name='Clémentine', naps=18, sound=b'meow', action='stretch')
+    cat1 = cat.put().get(use_cache=False)
+    self.assertFalse(cat1 is cat)
+    self.assertEqual(cat1, cat)
+    self.assertEqual(cat1.name, 'Clémentine')
+    self.assertEqual(cat1.naps, 18)
+    self.assertEqual(cat1.sound, b'meow')
+    self.assertEqual(cat1.action, 'stretch')
 
+  def testExpandoPoly(self):
 
     class Animal(model.Expando, PolyModel):
       pass
@@ -162,6 +171,18 @@ class Mammal(Animal):
     self.assertEqual(18, actual.naps)
     self.assertEqual(b'purr', actual.sound)
 
+    # un-indexed properties retain str type regardless of encoding:
+    Mammal._default_indexed = False
+    expected = Mammal(name='Clémentine', naps=18, sound=b'meow', action='stretch')
+    actual = expected.put().get()
+
+    self.assertIsNot(expected, actual)
+    self.assertEqual(expected, actual)
+    self.assertEqual('Clémentine', actual.name)
+    self.assertEqual(18, actual.naps)
+    self.assertEqual(b'meow', actual.sound)
+    self.assertEqual('stretch', actual.action)
+
   def testInheritance(self):
 
     class NamedThing(model.Model):