Public bug reported:
I found this the hard way while working on a patch that added a keyword
argument to the signature of
nova.virt.libvirt.volume.LibvirtBaseVolumeDriver.disconnect_volume.
I had missed updating some of the volume drivers and
LibvirtBaseVolumeDriverSubclassSignatureTestCase.test_signatures should
have caught it ... but it didn't because it was not actually checking
any signatures.
After some digging, I found that SubclassSignatureTestCase has not worked
properly since we dropped support for python 2.7. The reason is the use of the
inspect.ismethod() function; in python 2.7
it returned true if the object was a bound or an unbound method [2] but as of
python 3, it only returns true if the object is a bound method [2].
So in this code [3]:
# the base class. It's redundant for us to test these, but as
# they'll always pass it's not worth the complexity to filter them out.
for (name, method) in inspect.getmembers(cls, inspect.ismethod):
inspect.getmembers(cls, inspect.ismethod) never returns any methods
because none of them are bound.
As of python 3, we need to use inspect.isfunction() instead.
[1] https://docs.python.org/2.7/library/inspect.html#inspect.ismethod
[2] https://docs.python.org/3.5/library/inspect.html#inspect.ismethod
[3] https://github.com/openstack/nova/blob/b3fdd7c/nova/test.py#L718
** Affects: nova
Importance: Undecided
Assignee: melanie witt (melwitt)
Status: In Progress
** Tags: testing
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https://bugs.launchpad.net/bugs/2019772
Title:
nova.test.SubclassSignatureTestCase no longer works
Status in OpenStack Compute (nova):
In Progress
Bug description:
I found this the hard way while working on a patch that added a
keyword argument to the signature of
nova.virt.libvirt.volume.LibvirtBaseVolumeDriver.disconnect_volume.
I had missed updating some of the volume drivers and
LibvirtBaseVolumeDriverSubclassSignatureTestCase.test_signatures
should have caught it ... but it didn't because it was not actually
checking any signatures.
After some digging, I found that SubclassSignatureTestCase has not worked
properly since we dropped support for python 2.7. The reason is the use of the
inspect.ismethod() function; in python 2.7
it returned true if the object was a bound or an unbound method [2] but as of
python 3, it only returns true if the object is a bound method [2].
So in this code [3]:
# the base class. It's redundant for us to test these, but as
# they'll always pass it's not worth the complexity to filter them
out.
for (name, method) in inspect.getmembers(cls, inspect.ismethod):
inspect.getmembers(cls, inspect.ismethod) never returns any methods
because none of them are bound.
As of python 3, we need to use inspect.isfunction() instead.
[1] https://docs.python.org/2.7/library/inspect.html#inspect.ismethod
[2] https://docs.python.org/3.5/library/inspect.html#inspect.ismethod
[3] https://github.com/openstack/nova/blob/b3fdd7c/nova/test.py#L718
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