tests - Python 3.12 - TypeError: Object of type _SentinelObject is not JSON serializable

[James Page]

Executing unit tests with Python 3.12 results in some test failures which I think are todo with the way the unit tests mock the __json__ method in the tools module:

neutron.tests.unit.api.v2.test_base.RegistryNotificationTest.test_networks_create_bulk_registry_publish
-------------------------------------------------------------------------------------------------------

Captured traceback:
~~~~~~~~~~~~~~~~~~~
    Traceback (most recent call last):

      File "/home/jamespage/src/upstream/openstack/neutron/neutron/tests/base.py", line 178, in func
    return f(self, *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^

      File "/home/jamespage/src/upstream/openstack/neutron/neutron/tests/unit/api/v2/test_base.py", line 1300, in test_networks_create_bulk_registry_publish
    self._test_registry_publish('create', 'network', input)

      File "/home/jamespage/src/upstream/openstack/neutron/neutron/tests/unit/api/v2/test_base.py", line 1269, in _test_registry_publish
    res = self.api.post_json(
          ^^^^^^^^^^^^^^^^^^^

No tests were successful during the run
      File "/home/jamespage/src/upstream/openstack/neutron/.tox/py312/lib/python3.12/site-packages/webtest/utils.py", line 34, in wrapper
    return self._gen_request(method, url, **kw)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

      File "/home/jamespage/src/upstream/openstack/neutron/.tox/py312/lib/python3.12/site-packages/webtest/app.py", line 749, in _gen_request
    return self.do_request(req, status=status,
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

      File "/home/jamespage/src/upstream/openstack/neutron/.tox/py312/lib/python3.12/site-packages/webtest/app.py", line 646, in do_request
    self._check_status(status, res)

      File "/home/jamespage/src/upstream/openstack/neutron/.tox/py312/lib/python3.12/site-packages/webtest/app.py", line 675, in _check_status
    raise AppError(

    webtest.app.AppError: Bad response: 500 Internal Server Error (not 200 OK or 3xx redirect for http://localhost/networks)
b'{"NeutronError": {"type": "HTTPInternalServerError", "message": "Request Failed: internal server error while processing your request.", "detail": ""}}'

Captured pythonlogging:
~~~~~~~~~~~~~~~~~~~~~~~
       ERROR [neutron.pecan_wsgi.hooks.translation] POST failed.
Traceback (most recent call last):
  File "/home/jamespage/src/upstream/openstack/neutron/.tox/py312/lib/python3.12/site-packages/pecan/core.py", line 682, in __call__
    self.invoke_controller(controller, args, kwargs, state)
  File "/home/jamespage/src/upstream/openstack/neutron/.tox/py312/lib/python3.12/site-packages/pecan/core.py", line 603, in invoke_controller
    result = self.render(template, result)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jamespage/src/upstream/openstack/neutron/.tox/py312/lib/python3.12/site-packages/pecan/core.py", line 414, in render
    return renderer.render(template, namespace)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jamespage/src/upstream/openstack/neutron/.tox/py312/lib/python3.12/site-packages/pecan/templating.py", line 23, in render
    return encode(namespace)
           ^^^^^^^^^^^^^^^^^
  File "/home/jamespage/src/upstream/openstack/neutron/.tox/py312/lib/python3.12/site-packages/pecan/jsonify.py", line 154, in encode
    return _instance.encode(obj)
           ^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/json/encoder.py", line 200, in encode
    chunks = self.iterencode(o, _one_shot=True)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/json/encoder.py", line 258, in iterencode
    return _iterencode(o, 0)
           ^^^^^^^^^^^^^^^^^
  File "/home/jamespage/src/upstream/openstack/neutron/.tox/py312/lib/python3.12/site-packages/pecan/jsonify.py", line 148, in default
    return jsonify(obj)
           ^^^^^^^^^^^^
  File "/usr/lib/python3.12/functools.py", line 909, in wrapper
    return dispatch(args[0].__class__)(*args, **kw)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jamespage/src/upstream/openstack/neutron/.tox/py312/lib/python3.12/site-packages/pecan/jsonify.py", line 143, in jsonify
    return _default.default(obj)
           ^^^^^^^^^^^^^^^^^^^^^
  File "/home/jamespage/src/upstream/openstack/neutron/.tox/py312/lib/python3.12/site-packages/pecan/jsonify.py", line 129, in default
    return JSONEncoder.default(self, obj)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/json/encoder.py", line 180, in default
    raise TypeError(f'Object of type {o.__class__.__name__} '
TypeError: Object of type _SentinelObject is not JSON serializable

Digging in I can see all of the plugin child calls being updated, however I don't see them actually called under Python 3.12.

This issue impacts the following unit tests:

FAIL: neutron.tests.unit.api.v2.test_base.RegistryNotificationTest.test_network_create_registry_publish
FAIL: neutron.tests.unit.api.v2.test_base.RegistryNotificationTest.test_network_update_registry_publish
FAIL: neutron.tests.unit.api.v2.test_base.RegistryNotificationTest.test_networks_create_bulk_registry_publish
FAIL: neutron.tests.unit.api.v2.test_base.NotificationTest.test_network_create_notifier
FAIL: neutron.tests.unit.api.v2.test_base.NotificationTest.test_network_update_notifier
FAIL: neutron.tests.unit.api.v2.test_base.QuotaTest.test_create_network_quota_without_limit
FAIL: neutron.tests.unit.extensions.test_providernet.ProvidernetExtensionTestCase.test_network_create_with_provider_attrs
FAIL: neutron.tests.unit.extensions.test_providernet.ProvidernetExtensionTestCase.test_network_update_with_provider_attrs

[Miguel Lavalle (minsel)]

@James Page,

Do you intend to fix this issue?

[James Page (james-page)]

@minsel

I spent some time investigating and can see the same set of mocks and associated dunder methods being created between 3.11 and 3.12 but under 3.12 I don't see them being used which has me scratching my head.

I will pickup investigation again if time permits.

[Miguel Lavalle (minsel)]

@James Page,

In that case I'll indicate in the weekly report that this bug is in need of an owner

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/neutron/+/908255

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/neutron/+/908255
Committed: https://opendev.org/openstack/neutron/commit/4df5f2f41baede43b3e87ff8b716a7e6c773fbea
Submitter: "Zuul (22348)"
Branch: master

commit 4df5f2f41baede43b3e87ff8b716a7e6c773fbea
Author: Rodolfo Alonso Hernandez <email address hidden>
Date: Wed Feb 7 08:15:03 2024 +0000

    [UT] Fix ``APIv2TestBase`` derived test classes

    The method test calling ``_post_request`` with create or update
    operations, were not properly patching the ML2 plugin
    ``create_network`` and `update_network`` methods. With
    Python3.12, the mock object passed (instead of a dictionary with a
    reduced network definition) don't have a ``__json__`` method and
    fails during the encoding.

    NOTE: this has been manually tested with Python3.12. Currently this
    patch cannot be tested in the CI.

    Closes-Bug: #2051928
    Change-Id: Ie30af0c655d2f27d9039ff7933e81603047da6f4

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/neutron 24.0.0.0rc1 release candidate.