fix: correct inconsistent behavior with regards to namespaces (#662)

In the constructor for `Key`, `None` and the empty string `""` were
being treated as distinct namespaces, despite both being synonyms for
the default namespace.

In ancestor queries, the namespace for the query is now taken properly
from the ancestor key.

Fixes #661

Author: Chris Rossi

packages/google-cloud-ndb/google/cloud/ndb/key.py

@@ -1367,6 +1367,9 @@ def _parse_from_args(
         # Offload verification of parent to ``google.cloud.datastore.Key()``.
         parent_ds_key = parent._key
 
+    if namespace == "":
+        namespace = None
+
     return google.cloud.datastore.Key(
         *flat, parent=parent_ds_key, project=project, namespace=namespace
     )

packages/google-cloud-ndb/google/cloud/ndb/query.py

@@ -1267,7 +1267,10 @@ def __init__(self, config=None, context=None, **kwargs):
                 self.project = context.client.project
 
             if self.namespace is None:
-                self.namespace = context.get_namespace()
+                if self.ancestor is None:
+                    self.namespace = context.get_namespace()
+                else:
+                    self.namespace = self.ancestor.namespace()
 
 
 class Query(object):

packages/google-cloud-ndb/tests/system/test_misc.py

@@ -501,3 +501,27 @@ class SomeKind(ndb.Model):
     assert entity.children[1].bar is False
     assert entity.children[2].foo == "i'm in jail!"
     assert entity.children[2].bar is False
+
+
+@pytest.mark.usefixtures("client_context")
+def test_parent_and_child_in_default_namespace(dispose_of):
+    """Regression test for #661
+
+    https://github.com/googleapis/python-ndb/issues/661
+    """
+
+    class SomeKind(ndb.Model):
+        pass
+
+    class OtherKind(ndb.Model):
+        foo = ndb.IntegerProperty()
+
+    parent = SomeKind(namespace="")
+    parent_key = parent.put()
+    dispose_of(parent_key._key)
+
+    child = OtherKind(parent=parent_key, namespace="", foo=42)
+    child_key = child.put()
+    dispose_of(child_key._key)
+
+    assert OtherKind.query(ancestor=parent_key).get().foo == 42

packages/google-cloud-ndb/tests/unit/test_key.py

@@ -210,7 +210,25 @@ def test_constructor_with_namespace():
         assert key._key == google.cloud.datastore.Key(
             "Kind", 1337, project="testing", namespace="foo"
         )
-        assert key._reference is None
+        assert key.namespace() == "foo"
+
+    @staticmethod
+    @pytest.mark.usefixtures("in_context")
+    def test_constructor_with_default_namespace_as_empty_string(context):
+        context.client.namespace = "DiffNamespace"
+        key = key_module.Key("Kind", 1337, namespace="")
+
+        assert key._key == google.cloud.datastore.Key("Kind", 1337, project="testing")
+        assert key.namespace() is None
+
+    @staticmethod
+    @pytest.mark.usefixtures("in_context")
+    def test_constructor_with_default_namespace_as_None(context):
+        context.client.namespace = "DiffNamespace"
+        key = key_module.Key("Kind", 1337, namespace=None)
+
+        assert key._key == google.cloud.datastore.Key("Kind", 1337, project="testing")
+        assert key.namespace() is None
 
     @pytest.mark.usefixtures("in_context")
     def test_constructor_with_parent(self):