Adds model mixin for {to,from}_dict functionality

Implements ModelDictMixin, which is an alternative to DictBase that does
not force a module to have an "extra" field. It also gets away from the
idea that we need to keep a list of attibutes, named `attributes`, on
each model definition.

Change-Id: Id2c208ee9be4cc17b1b6444c5e0558952571163b
Fixes-bug: #1265071

keystone/common/sql/core.py

@@ -144,6 +144,19 @@ class DictBase(models.ModelBase):
         return getattr(self, key)
 
 
+class ModelDictMixin(object):
+
+    @classmethod
+    def from_dict(cls, d):
+        """Returns a model instance from a dictionary."""
+        return cls(**d)
+
+    def to_dict(self):
+        """Returns the model's attributes as a dictionary."""
+        names = (column.name for column in self.__table__.columns)
+        return dict((name, getattr(self, name)) for name in names)
+
+
 @contextlib.contextmanager
 def transaction(expire_on_commit=False):
     """Return a SQLAlchemy session in a scoped transaction."""

keystone/tests/core.py

@@ -55,7 +55,7 @@ from keystone.common import kvs
 from keystone.common.kvs import core as kvs_core
 from keystone.common import sql
 from keystone.common.sql import migration_helpers
-from keystone.common import utils
+from keystone.common import utils as common_utils
 from keystone import config
 from keystone import exception
 from keystone import notifications
@@ -132,12 +132,12 @@ def checkout_vendor(repo, rev):
                 return revdir
 
         if not os.path.exists(revdir):
-            utils.git('clone', repo, revdir)
+            common_utils.git('clone', repo, revdir)
 
         os.chdir(revdir)
-        utils.git('checkout', '-q', 'master')
-        utils.git('pull', '-q')
-        utils.git('checkout', '-q', rev)
+        common_utils.git('checkout', '-q', 'master')
+        common_utils.git('pull', '-q')
+        common_utils.git('checkout', '-q', rev)
 
         # write out a modified time
         with open(modcheck, 'w') as fd:

keystone/tests/unit/common/test_sql_core.py

@@ -0,0 +1,52 @@
+# 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 sqlalchemy.ext import declarative
+import testtools
+
+from keystone.common import sql
+from keystone.tests import utils
+
+
+ModelBase = declarative.declarative_base()
+
+
+class TestModel(ModelBase, sql.ModelDictMixin):
+    __tablename__ = 'testmodel'
+    id = sql.Column(sql.String(64), primary_key=True)
+    text = sql.Column(sql.String(64), nullable=False)
+
+
+class TestModelDictMixin(testtools.TestCase):
+
+    def test_creating_a_model_instance_from_a_dict(self):
+        d = {'id': utils.new_uuid(), 'text': utils.new_uuid()}
+        m = TestModel.from_dict(d)
+        self.assertEqual(m.id, d['id'])
+        self.assertEqual(m.text, d['text'])
+
+    def test_creating_a_dict_from_a_model_instance(self):
+        m = TestModel(id=utils.new_uuid(), text=utils.new_uuid())
+        d = m.to_dict()
+        self.assertEqual(m.id, d['id'])
+        self.assertEqual(m.text, d['text'])
+
+    def test_creating_a_model_instance_from_an_invalid_dict(self):
+        d = {'id': utils.new_uuid(), 'text': utils.new_uuid(), 'extra': None}
+        self.assertRaises(TypeError, TestModel.from_dict, d)
+
+    def test_creating_a_dict_from_a_model_instance_that_has_extra_attrs(self):
+        expected = {'id': utils.new_uuid(), 'text': utils.new_uuid()}
+        m = TestModel(id=expected['id'], text=expected['text'])
+        m.extra = 'this should not be in the dictionary'
+        self.assertEqual(m.to_dict(), expected)

keystone/tests/utils.py

@@ -0,0 +1,20 @@
+# 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.
+
+"""Useful utilities for tests."""
+
+import uuid
+
+
+def new_uuid():
+    """Return a string UUID."""
+    return uuid.uuid4().hex