Return empty str for permissive, none, properties

In Kilo, a patch landed to allow glance for returning None values. While
this was not an issue for the base and registered properties in the
`schema-image.json` file, it did break backwards compatibility for the
custom images created in V1 that have a vulue equal to None.

In order to restore compatibility, this changes returns empty strings
for those custom properties that exist in the database but that are not
part of the V2 schema. This strategy will help migrating such properties
when updates to the image data happens and it'll be a noop for just
reads.

We can't use a schema migration because we don't know off hand which of
the properties in the database are the ones that would need to be
migrated.

While we could skip this properties entirely, this patch prefers to send
the empty string back as a way to create awareness on the fact that
there's an empty property in the database. Since we didn't use to return
these properties, we can assume they weren't being used.

Closes-bug: #1419823
Change-Id: I59bb27a892fe9485fc98a612ca0148a84123f5a2
(cherry picked from commit ccea7b6856)

glance/schema.py

@@ -47,6 +47,22 @@ class Schema(object):
         for key, value in six.iteritems(obj):
             if self._filter_func(self.properties, key):
                 filtered[key] = value
+
+            # NOTE(flaper87): This exists to allow for v1, null properties,
+            # to be used with the V2 API. During Kilo, it was allowed for the
+            # later to return None values without considering that V1 allowed
+            # for custom properties to be None, which is something V2 doesn't
+            # allow for. This small hack here will set V1 custom `None` pro-
+            # perties to an empty string so that they will be updated along
+            # with the image (if an update happens).
+            #
+            # We could skip the properties that are `None` but that would bring
+            # back the behavior we moved away from. Note that we can't consider
+            # doing a schema migration because we don't know which properties
+            # are "custom" and which came from `schema-image` if those custom
+            # properties were created with v1.
+            if key not in self.properties and value is None:
+                filtered[key] = ''
         return filtered
 
     @staticmethod

glance/tests/functional/__init__.py

@@ -85,6 +85,7 @@ class Server(object):
         self.server_module = None
         self.stop_kill = False
         self.use_user_token = False
+        self.send_identity_credentials = False
 
     def write_conf(self, **kwargs):
         """
@@ -322,6 +323,7 @@ metadata_encryption_key = %(metadata_encryption_key)s
 registry_host = 127.0.0.1
 registry_port = %(registry_port)s
 use_user_token = %(use_user_token)s
+send_identity_credentials = %(send_identity_credentials)s
 log_file = %(log_file)s
 image_size_cap = %(image_size_cap)d
 delayed_delete = %(delayed_delete)s
@@ -346,6 +348,7 @@ image_property_quota=%(image_property_quota)s
 image_tag_quota=%(image_tag_quota)s
 image_location_quota=%(image_location_quota)s
 location_strategy=%(location_strategy)s
+allow_additional_image_properties = True
 [oslo_policy]
 policy_file = %(policy_file)s
 policy_default_rule = %(policy_default_rule)s

glance/tests/functional/v2/test_images.py

@@ -68,6 +68,37 @@ class TestImages(functional.FunctionalTest):
         base_headers.update(custom_headers or {})
         return base_headers
 
+    def test_v1_none_properties_v2(self):
+        self.api_server.deployment_flavor = 'noauth'
+        self.api_server.use_user_token = True
+        self.api_server.send_identity_credentials = True
+        self.registry_server.deployment_flavor = ''
+        # Image list should be empty
+        self.start_servers(**self.__dict__.copy())
+
+        # Create an image (with two deployer-defined properties)
+        path = self._url('/v1/images')
+        headers = self._headers({'content-type': 'application/octet-stream'})
+        headers.update(test_utils.minimal_headers('image-1'))
+        # NOTE(flaper87): Sending empty string, the server will use None
+        headers['x-image-meta-property-my_empty_prop'] = ''
+
+        response = requests.post(path, headers=headers)
+        self.assertEqual(201, response.status_code)
+        data = jsonutils.loads(response.text)
+        image_id = data['image']['id']
+
+        # NOTE(flaper87): Get the image using V2 and verify
+        # the returned value for `my_empty_prop` is an empty
+        # string.
+        path = self._url('/v2/images/%s' % image_id)
+        response = requests.get(path, headers=self._headers())
+        self.assertEqual(200, response.status_code)
+        image = jsonutils.loads(response.text)
+        self.assertEqual('', image['my_empty_prop'])
+
+        self.stop_servers()
+
     def test_image_lifecycle(self):
         # Image list should be empty
         self.start_servers(**self.__dict__.copy())