fix: ignore datastore properties that are not mapped to NDB properties (#470)

During deserialization from Datastore, since NDB properties can be
arbitrarily mapped to Datastore properties of different names, it is
possible for a Datastore entity to have a property with the same name as
an NDB property, but that isn't the Datastore property mapped to that
NDB property. This fix prevents the unmapped Datastore property from
accidentally clobbering the NDB property of the same name.

Fixes #461.

Author: Chris Rossi

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

@@ -5964,8 +5964,27 @@ def _code_name_from_stored_name(cls, name):
         """Return the code name from a property when it's different from the
         stored name. Used in deserialization from datastore."""
         if name in cls._properties:
-            if name != cls._properties[name]._code_name:
-                name = cls._properties[name]._code_name
+            return cls._properties[name]._code_name
+
+        # If name isn't in cls._properties but there is a property with that
+        # name, it means that property has a different codename, and returning
+        # this name will potentially clobber the real property.  Take for
+        # example:
+        #
+        # class SomeKind(ndb.Model):
+        #     foo = ndb.IntegerProperty(name="bar")
+        #
+        # If we are passed "bar", we know to translate that to "foo", becasue
+        # the datastore property, "bar", is the NDB property, "foo". But if we
+        # are passed "foo", here, then that must be the datastore property,
+        # "foo", which isn't even mapped to anything in the NDB model.
+        #
+        prop = getattr(cls, name, None)
+        if prop:
+            # Won't map to a property, so this datastore property will be
+            # effectively ignored.
+            return " "
+
         return name
 
     @classmethod

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

@@ -20,9 +20,11 @@
 
 import pytest
 
+import test_utils.system
+
 from google.cloud import ndb
 
-from . import eventually, length_equals
+from . import eventually, length_equals, KIND
 
 USE_REDIS_CACHE = bool(os.environ.get("REDIS_CACHE_URL"))
 
@@ -295,3 +297,21 @@ def save_entity():
 
     assert retrieved.foo == 42
     assert retrieved.bar == "none"
+
+
+@pytest.mark.usefixtures("client_context")
+def test_crosswired_property_names(ds_entity):
+    """Regression test for #461.
+
+    https://github.com/googleapis/python-ndb/issues/461
+    """
+    entity_id = test_utils.system.unique_resource_id()
+    ds_entity(KIND, entity_id, foo=42, bar=43)
+
+    class SomeKind(ndb.Model):
+        bar = ndb.IntegerProperty(name="foo")
+
+    key = ndb.Key(KIND, entity_id)
+    entity = key.get()
+
+    assert entity.bar == 42