Empty fields processed correctly in plugin adapters

Before this patch all empty but existing plugin metadata properties was
removed from output as well as `tasks` field that was not respecting
not null constraint at DB level.

As a minor patch payload missing InvalidFileFormat error was added.

Change-Id: I6a21e347fefb7a9a30be562b7fb3e4a8c5c61a36
Partial-Bug: 1616722
Closes-Bug: 1626855

nailgun/nailgun/errors/__init__.py

@@ -20,6 +20,7 @@ from .api import *
 from .deployment import *
 from .disk import *
 from .extension import *
+from .files import *
 from .mongodb import *
 from .network import *
 from .network_template import *

nailgun/nailgun/errors/files.py

@@ -0,0 +1,25 @@
+# coding: utf-8
+
+# Copyright 2016 Mirantis, Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from .base import NailgunException
+
+
+class InvalidFileFormat(NailgunException):
+    message = "Invalid file format: {}, supported formats are: {}"
+
+    def __init__(self, path, supported_formats, *args, **kwargs):
+        super(InvalidFileFormat, self).__init__(*args, **kwargs)
+        self.message = self.message.format(path, ', '.join(supported_formats))

nailgun/nailgun/objects/plugin.py

@@ -38,6 +38,16 @@ class Plugin(NailgunObject):
 
     @classmethod
     def create(cls, data):
+        """Create plugin.
+
+        WARNING: don't pass keys with none to non nullable fields.
+
+        :param data: data
+        :type data: dict
+
+        :return: plugin instance
+        :rtype: models.Plugin
+        """
         graphs = {}
         for graph in data.pop("graphs", []):
             graphs[graph.pop('type')] = graph

nailgun/nailgun/plugins/adapters.py

@@ -48,11 +48,8 @@ class PluginAdapterBase(object):
     def attributes_processors(self):
         return {
             'attributes_metadata':
-                lambda data:
-                    (data.get('attributes', None) or {})
-                    if data else data,
-            'tasks':
-                lambda data: data or []
+                lambda data: (data or {}).get('attributes', {}),
+            'tasks': lambda data: data or []
         }
 
     @abc.abstractmethod
@@ -66,17 +63,24 @@ class PluginAdapterBase(object):
         :rtype: dict
         """
         data_tree, report = self.loader.load()
+
         if report.is_failed():
             logger.error(report.render())
             logger.error('Problem with loading plugin {0}'.format(
                 self.plugin_path))
             return data_tree
+
         for field in data_tree:
             if field in self.attributes_processors:
                 data_tree[field] = \
                     self.attributes_processors[field](data_tree.get(field))
 
-        data_tree = {k: v for k, v in six.iteritems(data_tree) if v}
+        data_tree = {
+            k: v
+            for k, v in six.iteritems(data_tree)
+            if v is not None
+        }
+
         return data_tree
 
     @property
@@ -321,6 +325,7 @@ class PluginAdapterV1(PluginAdapterBase):
                 if isinstance(role, list) and 'controller' in role:
                     role.append('primary-controller')
             return tasks
+        return []
 
     def get_tasks(self):
         tasks = self.plugin.tasks