Child property with Polymodel doesn't work

[stepanovsh]

Hi. We're trying to create new models on AppEngine Standard with PY3 runtime and have some problems with child Models if we use Polymodel

Models example

from google.cloud import ndb
from google.cloud.ndb import polymodel


class Foo(ndb.Model):
    timestamp = ndb.DateTimeProperty()


class TestPolymodel(polymodel.PolyModel):
    test_string = ndb.StringProperty(required=True)
    test_boolean = ndb.BooleanProperty()
    test_auto_now = ndb.DateTimeProperty(auto_now=True)
    test_auto_add = ndb.DateTimeProperty(auto_now_add=True)


class TestModel(TestPolymodel):
    test_key = ndb.KeyProperty(kind='Foo')
    test_strchild = ndb.StringProperty(required=True)
    test_boolchild = ndb.BooleanProperty()

When we try to save these models to datastore all information saved properly but when we try to retrieve them we received None values for child model keys

Code example

from google.cloud import ndb

ndb_client = ndb.Client()

with ndb_client.context(): 
    test_model = TestModel.get_by_id(5632763172487168)
    print(test_model.to_dict())

Print result

{'class_': ['TestPolymodel', 'TestModel'],
 'test_auto_add': datetime.datetime(2019, 8, 29, 8, 42, 25, 246185),
 'test_auto_now': datetime.datetime(2019, 8, 29, 8, 42, 25, 246191),
 'test_boolchild': None,
 'test_boolean': True,
 'test_key': None,
 'test_strchild': None,
 'test_string': 'test_string'}

But if we move some property to TestPolymodel class we can retrieve them

Models example

class TestPolymodel(polymodel.PolyModel):
    test_string = ndb.StringProperty(required=True)
    test_boolean = ndb.BooleanProperty()
    test_auto_now = ndb.DateTimeProperty(auto_now=True)
    test_auto_add = ndb.DateTimeProperty(auto_now_add=True)
    test_strchild = ndb.StringProperty(required=True)


class TestModel(TestPolymodel):
    test_key = ndb.KeyProperty(kind='Foo')
    test_boolchild = ndb.BooleanProperty()

with ndb_client.context(): 
    test_model = TestModel.get_by_id(5632763172487168)
    print(test_model.to_dict())

Print result

{'class_': ['TestPolymodel', 'TestModel'],
 'test_auto_add': datetime.datetime(2019, 8, 29, 8, 42, 25, 246185),
 'test_auto_now': datetime.datetime(2019, 8, 29, 8, 42, 25, 246191),
 'test_boolchild': None,
 'test_boolean': True,
 'test_key': None,
 'test_strchild': 'test_strchild',
 'test_string': 'test_string'}

As you can see we received the correct value for test_strchild

Thanks!

[cguardia]

Thanks a lot for you report. We'll take a look.