Support that an extension extends a sub-resource

The neutron.api.extensions code assumes that the resource to update are
base resources and updates its dictionary. When the resource
is a sub-resource, ie. a {'parent': ... , 'parameters': {..} } dictionary,
the result of the update is that the content of 'parameters' is
overwritten.

The correct thing to do here, in the case where the extended resource is
a sub-resource, is to update the content of parameters with the new/changed
attributes.

This change also removes a workaround that was made in
the qos-bw-limit-direction extension, and which after the change in API
extension code, is not needed anymore.

Needed-By: I263e1ee6cf4e1a91be91a4a78f4a160f64d33cc6
Change-Id: I4cb61481205c3689c41e62670cec113adb2a0362
Closes-Bug: 1722842

neutron/api/extensions.py

@@ -345,7 +345,16 @@ class ExtensionManager(object):
                     continue
                 extended_attrs = ext.get_extended_resources(version)
                 for res, resource_attrs in extended_attrs.items():
-                    attr_map.setdefault(res, {}).update(resource_attrs)
+                    res_to_update = attr_map.setdefault(res, {})
+                    if self._is_sub_resource(res_to_update):
+                        # in the case of an existing sub-resource, we need to
+                        # update the parameters content rather than overwrite
+                        # it, and also keep the description of the parent
+                        # resource unmodified
+                        res_to_update['parameters'].update(
+                            resource_attrs['parameters'])
+                    else:
+                        res_to_update.update(resource_attrs)
                 processed_exts[ext_name] = ext
                 del exts_to_process[ext_name]
             if len(processed_exts) == processed_ext_count:
@@ -369,6 +378,12 @@ class ExtensionManager(object):
         for ext in processed_exts.values():
             ext.update_attributes_map(attr_map)
 
+    def _is_sub_resource(self, resource):
+        return ('parent' in resource and
+                isinstance(resource['parent'], dict) and
+                'member_name' in resource['parent'] and
+                'parameters' in resource)
+
     def _check_faulty_extensions(self, faulty_extensions):
         """Raise for non-default faulty extensions.
 

neutron/extensions/qos_bw_limit_direction.py

@@ -37,17 +37,14 @@ OPTIONAL_EXTENSIONS = None
 # The resource attribute map for the extension.
 SUB_RESOURCE_ATTRIBUTE_MAP = {
     qos_apidef.BANDWIDTH_LIMIT_RULES: {
-        'parameters': dict(
-            qos_apidef.SUB_RESOURCE_ATTRIBUTE_MAP[
-                qos_apidef.BANDWIDTH_LIMIT_RULES]['parameters'],
-            **{'direction': {
+        'parameters': {
+            'direction': {
                 'allow_post': True,
                 'allow_put': True,
                 'is_visible': True,
                 'default': common_constants.EGRESS_DIRECTION,
                 'validate': {
                     'type:values': common_constants.VALID_DIRECTIONS}}}
-        )
     }
 }
 

neutron/tests/unit/api/test_extensions.py

@@ -669,6 +669,67 @@ class ExtensionManagerTest(base.BaseTestCase):
         self.assertNotIn('ext1-attr', attr_map['ext2'])
         self.assertNotIn('ext2-attr', attr_map['ext1'])
 
+    def test_extension_extends_sub_resource(self):
+        """Unit test for bug 1722842
+
+        Check that an extension can extend a sub-resource
+        """
+        RESOURCE = "test_resource"
+        SUB_RESOURCE_NAME = "test_sub_resource"
+        INITIAL_PARAM = "dummy_param1"
+        ADDITIONAL_PARAM = "dummy_param2"
+
+        SUB_RESOURCE = {
+            'parent': {'member_name': RESOURCE},
+            'parameters': {
+                INITIAL_PARAM: {'allow_post': False,
+                                'allow_put': False,
+                                'validate': {'type:uuid': None},
+                                'is_visible': True}
+            }
+        }
+
+        class BaseExtension(ext_stubs.StubExtension):
+
+            def get_extended_resources(self, version):
+                return {
+                     SUB_RESOURCE_NAME: SUB_RESOURCE
+                }
+
+        class ExtensionExtendingASubresource(ext_stubs.StubExtension):
+
+            def get_extended_resources(self, version):
+                return {
+                    SUB_RESOURCE_NAME: {
+                        'parameters': {
+                            ADDITIONAL_PARAM: {'allow_post': False,
+                                               'allow_put': False,
+                                               'validate': {'type:uuid': None},
+                                               'is_visible': True}
+                        }
+                    }
+                }
+
+            def get_required_extensions(self):
+                return ['base_extension']
+
+        ext_mgr = extensions.ExtensionManager('')
+        attr_map = {}
+        ext_mgr.add_extension(BaseExtension('base_extension'))
+        ext_mgr.add_extension(
+            ExtensionExtendingASubresource())
+        ext_mgr.extend_resources("2.0", attr_map)
+
+        # check that the parent descriptor is untouched
+        self.assertEqual(SUB_RESOURCE['parent'],
+                         attr_map[SUB_RESOURCE_NAME]['parent'])
+        # check that the initial attribute is still here
+        self.assertIn(INITIAL_PARAM,
+                      attr_map[SUB_RESOURCE_NAME]['parameters'])
+        # check that the new attribute is here as well
+        self.assertIn(ADDITIONAL_PARAM,
+                      attr_map[SUB_RESOURCE_NAME]['parameters'])
+
 
 class PluginAwareExtensionManagerTest(base.BaseTestCase):