Bug in Python API "!=" doesn't behave as expected for base.Resource objects

[Chris Geroux]

The result of some OpenStack objects, for example a server or a volume, do not compare with None as expected. For example if a server has been found and is clearly not None (e.g. I can print out its name) the test "server!=None" will be False. This really isn't the expected behavior. I can worked around this by using the "server is not None" but this would make bugs appear very easily if I slip back into "!=" which is my usual habit, and could be other's habit as well. I have attached a simple script which should reproduce the bug.

[Matt Riedemann (mriedem)]

When you say 'objects' do you mean nova.objects.* objects? The attachment doesn't load for me.

[Matt Riedemann (mriedem)]

I'm not really clear on this one, especially with the attachment not loading for me. But:

>>> from nova.objects import instance as instance_obj
>>> import uuid
>>> instance = instance_obj.Instance(uuid=str(uuid.uuid4()))
>>> instance.uuid
'2d066a8c-303a-48eb-8d65-f9233c77c08b'
>>> instance is None
False
>>> instance == None
False
>>> instance != None
True
>>>

[Matt Riedemann (mriedem)]

The script loads now, and I see you're talking about novaclient, not nova.

[Matt Riedemann (mriedem)]

What version of novaclient?

This is the base class for novaclient resource objects:

https://github.com/openstack/python-novaclient/blob/master/novaclient/base.py#L118

And it implements __eq__:

https://github.com/openstack/python-novaclient/blob/master/novaclient/base.py#L202

[Matt Riedemann (mriedem)]

OK I guess I see the point here:

>>> from novaclient.v2 import servers
>>> server = servers.Server(manager=None, info={'id': 1, 'name': 'test'})
>>> server
<Server: test>
>>> server is None
False
>>> server == None
False
>>> server != None
False
>>> server is not None
True
>>>

[Chris Geroux (cgeroux)]

I know there are a few ways to implement things, v2/v3 etc. and what I attached was only run in a very specific situation so I could easily see how it might not work with a different openstack setup. What I do in principle is a little more complex to handle v2/v3 authentication but I wanted to keep the number of code lines short.

Even so it looks like you identified the issue with the line "server!=None" producing the "False" result even when the "server is not None". I suspected it had to do with an implementation of the "__eq__" for base.py. I am assuming that other projects such as "cinder" etc. also use the same or very similar "base.py" definition for "__eq__".

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/409549

[Akshil Verma (akshilv)]

Hi Guys,
I am new to openstack and took this bug as my first contribution to openstack. I have one doubt.
I have made the necessary changes and the code review has been accepted. Do I change the status to Fix committed or will that happen automatically?

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/409549
Committed: https://git.openstack.org/cgit/openstack/python-novaclient/commit/?id=78e621faf757e3bf4bd8475c29090bb1c83bc0cd
Submitter: Jenkins
Branch: master

commit 78e621faf757e3bf4bd8475c29090bb1c83bc0cd
Author: Akshil Verma <email address hidden>
Date: Sun Dec 11 13:37:25 2016 -0600

    Fixed the __ne__ implementation in base.Resource

    Any object of Resource class or its child class do not compare with
    None as expected. For example if a server has been found and is
    clearly not None, the test "server!=None" will be False.

    This was occuring because the __eq__ implementation was returning the
    'NotImplemented' keyword and the __ne__ implementation was returning
    the not of __eq__, which in this case will return False as the
    expected python behavior for a the not of NotImplemented is False.

    Changed the __ne__ implementation to return the correct boolean value
    and added the test case that fails with the older implementation and
    passes in the current fix.

    Change-Id: I6bf5a6e9c9eed4bbcf6678467df19dfea560b4de
    Closes-Bug: #1648207

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/python-novaclient 7.1.0 release.