Merge lp:~brian.curtin/ubuntu-sso-client/py3-metaclass into lp:ubuntu-sso-client

[Brian Curtin]

- Switch to Python 2 and 3 safe usage of a metaclass for IPC

The IPC code makes use of a metaclass, and due to Python 3's changes to metaclasses, we need a version-safe way to continue using it. The easiest way is by using a base class that was created by calling the metaclass directly, which we get from a trivial function.

This is the same as what six.with_metaclass does.

[Alejandro J. Cura (alecu)]

Nice branch!

Since the new "meta_base" function seems like it might be useful elsewhere, should it be moved to a more common module?

Or perhaps it makes sense that we should start depending on six, since it's being used for the protobuf port to python 3, and it may help us with other porting.

Anyway, I think we should discuss separately from this branch.

review: Approve

[Alejandro J. Cura (alecu)]

Sorry, I didn't notice that lint gave this error:

ubuntu_sso/utils/tests/test_ipc.py:
    508: [W0232, RemoteMetaTestCase.test_remote_calls_renamed.TestClass] Class has no __init__ method

review: Needs Fixing

[lp:~brian.curtin/ubuntu-sso-client/py3-metaclass]

992. By Brian Curtin on 2012-08-14

Get rid of a warning about __init__ not existing

[Alejandro J. Cura (alecu)]

+1

review: Approve

[Eric Casteleijn (thisfred)]

review: Approve

=== modified file 'ubuntu_sso/utils/ipc.py'
--- ubuntu_sso/utils/ipc.py	2012-06-22 16:51:06 +0000
+++ ubuntu_sso/utils/ipc.py	2012-08-14 20:40:23 +0000
@@ -172,10 +172,16 @@
         return super(RemoteMeta, mcs).__new__(mcs, name, bases, attrs)
 
 
-class RemoteService(Referenceable, SignalBroadcaster):
+def meta_base(meta):
+    """A function to return a metaclass which is called directly.
+    This is safe for both Python 2 and 3."""
+    return meta("MetaBase", (object,), {})
+
+
+class RemoteService(meta_base(RemoteMeta),
+                    Referenceable, SignalBroadcaster):
     """A remote service that provides the methods listed in remote_calls."""
 
-    __metaclass__ = RemoteMeta
     remote_calls = []
 
 

=== modified file 'ubuntu_sso/utils/tests/test_ipc.py'
--- ubuntu_sso/utils/tests/test_ipc.py	2012-04-30 16:15:46 +0000
+++ ubuntu_sso/utils/tests/test_ipc.py	2012-08-14 20:40:23 +0000
@@ -505,16 +505,16 @@
         """The remote_calls are renamed."""
         test_token = object()
 
-        class TestClass(object):
+        # pylint: disable=W0232
+        class TestClass(ipc.meta_base(ipc.RemoteMeta)):
             """A class for testing."""
 
-            __metaclass__ = ipc.RemoteMeta
-
             remote_calls = ['test_method']
 
             def test_method(self):
                 """Fake call."""
                 return test_token
+        # pylint: enable=W0232
 
         tc = TestClass()
         self.assertEquals(tc.test_method(), test_token)