Introduce API Decorators

Decorators will be used for backwards compatibility with
API v1. Will be needed when doing translations for alignment
of V2 API with LBaaSv2

Change-Id: If98e4dd2b667149b7404a6378e798537684d405d
Co-Authored-By: Brandon Logan <brandon.logan@rackspace.com>
Co-Authored-By: Sindhu Devale <sindhu.devale@intel.com>

octavia/common/decorators.py

@@ -0,0 +1,54 @@
+#    Copyright 2016
+#    All Rights Reserved.
+#
+#    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.
+
+"""Decorators to provide backwards compatibility for V1 API."""
+
+
+def rename_kwargs(**renamed_kwargs):
+    """Renames a class's variables and maintains backwards compatibility.
+
+    :param renamed_kwargs: mapping of old kwargs to new kwargs.  For example,
+    to say a class has renamed variable foo to bar the decorator would
+    be used like: rename_kwargs(foo='bar')
+
+    """
+
+    def wrap(cls):
+        def __getattr__(instance, name):
+            if name in renamed_kwargs:
+                return getattr(instance, renamed_kwargs[name])
+            return getattr(instance, name)
+
+        def __setattr__(instance, name, value):
+            if name in renamed_kwargs:
+                instance.__dict__[renamed_kwargs[name]] = value
+            else:
+                instance.__dict__[name] = value
+
+        def wrapped_cls(*args, **kwargs):
+            # Handle cases of inner classes being called with self
+            # For example: self.TestClass(1, a=1)
+            if (args and hasattr(args[0], '__class__') and
+                    hasattr(args[0].__class__, cls.__name__)):
+                args = args[1:] if args else tuple()
+            for old_kwarg, new_kwarg in renamed_kwargs.items():
+                if old_kwarg in kwargs:
+                    kwargs[new_kwarg] = kwargs[old_kwarg]
+                    del kwargs[old_kwarg]
+            cls.__getattr__ = __getattr__
+            cls.__setattr__ = __setattr__
+            return cls(*args, **kwargs)
+        return wrapped_cls
+    return wrap

octavia/tests/unit/common/test_decorator.py

@@ -0,0 +1,56 @@
+#    Copyright 2016
+#    All Rights Reserved.
+#
+#    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.
+
+
+"""Test for the decorator which provides backward compatibility for V1 API."""
+
+import octavia.common.decorators as dec
+import octavia.tests.unit.base as base
+
+
+class TestDecorator(base.TestCase):
+
+    @dec.rename_kwargs(a='z')
+    class TestClass(object):
+        def __init__(self, x, z=None):
+            self.x = x
+            self.z = z
+
+    @dec.rename_kwargs(a='z')
+    class TestClassDupe(object):
+        def __init__(self, x, z=None):
+            self.x = x
+            self.z = z
+
+    def test_get(self):
+        obj = self.TestClass(1, a=3)
+        self.assertEqual(1, obj.x)
+        self.assertEqual(3, obj.z)
+        self.assertEqual(obj.z, obj.a)
+
+    def test_set(self):
+        obj = self.TestClass(1, a=3)
+        obj.a = 5
+        self.assertEqual(1, obj.x)
+        self.assertEqual(5, obj.z)
+        self.assertEqual(obj.z, obj.a)
+
+    def test_similar_classes(self):
+        obj = self.TestClass(1, z=5)
+        obj2 = self.TestClassDupe(2, z=10)
+        self.assertEqual(5, obj.z)
+        self.assertEqual(10, obj2.z)
+        self.assertEqual(obj.z, obj.a)
+        self.assertEqual(obj2.z, obj2.a)