Steps to reproduce:

Ran the integration_patch unit tests in a clean chroot:

python -m build --wheel --no-isolation
python -m venv --system-site-packages test-env
test-env/bin/python -m installer dist/*.whl
test-env/bin/python -m pytest tests/test_integration_patch.py

For context, the quoted command lines are part of the AUR PKGBUILD, which I maintain.

Actual results:

Since v2.14.0, the test_git_patch_with_commit and test_hg_patch_with_commit tests each have a ~ 1-in-4 chance of failing randomly with a message that says:

mozphab.exceptions.NotFoundError: Repository TEST not found

Example output:

========================================================= test session starts ==========================================================
platform linux -- Python 3.14.4, pytest-9.0.3, pluggy-1.6.0
rootdir: /build/moz-phab/src/review-2.14.0
configfile: pytest.ini
collected 4 items                                                                                                                      

tests/test_integration_patch.py ..F.                                                                                             [100%]

=============================================================== FAILURES ===============================================================
______________________________________________________ test_git_patch_with_commit ______________________________________________________

m_call_conduit = <MagicMock name='call' id='139871424556944'>, m_get_diffs = <MagicMock name='get_diffs' id='139871423013152'>
m_get_revs = <MagicMock name='get_revisions' id='139871423013488'>, in_process = None
git_repo_path = PosixPath('/tmp/pytest-of-builduser/pytest-0/test_git_patch_with_commit0/git-repo')

    @mock.patch("mozphab.conduit.ConduitAPI.get_revisions")
    @mock.patch("mozphab.conduit.ConduitAPI.get_diffs")
    @mock.patch("mozphab.conduit.ConduitAPI.call")
    def test_git_patch_with_commit(
        m_call_conduit,
        m_get_diffs,
        m_get_revs,
        in_process,
        git_repo_path,
    ):
        sha = git_out("rev-parse", "HEAD").rstrip("\n")
        diff_1 = copy.deepcopy(DIFF_1)
        diff_1["fields"]["refs"][0]["identifier"] = sha
        m_get_revs.return_value = [REV_1]
        m_get_diffs.return_value = {"PHID-DIFF-1": diff_1}
        m_call_conduit.side_effect = [
            {},
            {"data": [{"phid": "PHID-REPO-1", "fields": {"vcs": "git"}}]},
            PATCH_1_DIFF,
        ]
    
>       mozphab.main(["patch", "D1", "--apply-to", "here"], is_development=True)

/build/moz-phab/src/review-2.14.0/tests/test_integration_patch.py:163: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
/build/moz-phab/src/review-2.14.0/mozphab/mozphab.py:167: in main
    sys.exit(1)
/build/moz-phab/src/review-2.14.0/mozphab/mozphab.py:127: in main
    args.func(repo, args)
/build/moz-phab/src/review-2.14.0/mozphab/commands/patch.py:241: in patch
    vcs_future.result()
/usr/lib/python3.14/concurrent/futures/_base.py:443: in result
    return self.__get_result()
           ^^^^^^^^^^^^^^^^^^^
/usr/lib/python3.14/concurrent/futures/_base.py:395: in __get_result
    raise self._exception
/usr/lib/python3.14/concurrent/futures/thread.py:86: in run
    result = ctx.run(self.task)
             ^^^^^^^^^^^^^^^^^^
/usr/lib/python3.14/concurrent/futures/thread.py:73: in run
    return fn(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^
/build/moz-phab/src/review-2.14.0/mozphab/git.py:937: in check_vcs
    if self.is_cinnabar_required and not self.is_cinnabar_installed:
       ^^^^^^^^^^^^^^^^^^^^^^^^^
/build/moz-phab/src/review-2.14.0/mozphab/git.py:78: in is_cinnabar_required
    return self.vcs != self.phab_vcs
                       ^^^^^^^^^^^^^
/build/moz-phab/src/review-2.14.0/mozphab/repository.py:302: in phab_vcs
    self._phab_vcs = self.phab_repo["fields"]["vcs"]
                     ^^^^^^^^^^^^^^
/build/moz-phab/src/review-2.14.0/mozphab/repository.py:239: in phab_repo
    self._phab_repo = conduit.get_repository_by_callsign(self.call_sign)
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
/build/moz-phab/src/review-2.14.0/mozphab/conduit.py:708: in get_repository_by_callsign
    return self.repository_search_single("callsigns", call_sign)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <mozphab.conduit.ConduitAPI object at 0x7f365b0ade80>, constraint = 'callsigns', value = 'TEST'

    def repository_search_single(self, constraint: str, value: str) -> dict:
        """Get the information about a single repository from Phabricator.
    
        Takes a `constraint` to be passed to `diffusion.repository.search`
        and a `value` to be passed as the value of `constraint`. `value`
        must be a single element and will be passed in a list to Conduit.
        """
        api_call_args = {"constraints": {constraint: [value]}, "limit": 1}
        data = self.call("diffusion.repository.search", api_call_args)
        if not data.get("data"):
>           raise NotFoundError("Repository %s not found" % value)
E           mozphab.exceptions.NotFoundError: Repository TEST not found

/build/moz-phab/src/review-2.14.0/mozphab/conduit.py:724: NotFoundError
---------------------------------------------------------- Captured log call -----------------------------------------------------------
ERROR    moz-phab:mozphab.py:161 Traceback (most recent call last):
  File "/build/moz-phab/src/review-2.14.0/mozphab/mozphab.py", line 127, in main
    args.func(repo, args)
    ~~~~~~~~~^^^^^^^^^^^^
  File "/build/moz-phab/src/review-2.14.0/mozphab/commands/patch.py", line 241, in patch
    vcs_future.result()
    ~~~~~~~~~~~~~~~~~^^
  File "/usr/lib/python3.14/concurrent/futures/_base.py", line 443, in result
    return self.__get_result()
           ~~~~~~~~~~~~~~~~~^^
  File "/usr/lib/python3.14/concurrent/futures/_base.py", line 395, in __get_result
    raise self._exception
  File "/usr/lib/python3.14/concurrent/futures/thread.py", line 86, in run
    result = ctx.run(self.task)
  File "/usr/lib/python3.14/concurrent/futures/thread.py", line 73, in run
    return fn(*args, **kwargs)
  File "/build/moz-phab/src/review-2.14.0/mozphab/git.py", line 937, in check_vcs
    if self.is_cinnabar_required and not self.is_cinnabar_installed:
       ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/build/moz-phab/src/review-2.14.0/mozphab/git.py", line 78, in is_cinnabar_required
    return self.vcs != self.phab_vcs
                       ^^^^^^^^^^^^^
  File "/build/moz-phab/src/review-2.14.0/mozphab/repository.py", line 302, in phab_vcs
    self._phab_vcs = self.phab_repo["fields"]["vcs"]
                     ^^^^^^^^^^^^^^
  File "/build/moz-phab/src/review-2.14.0/mozphab/repository.py", line 239, in phab_repo
    self._phab_repo = conduit.get_repository_by_callsign(self.call_sign)
                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^
  File "/build/moz-phab/src/review-2.14.0/mozphab/conduit.py", line 708, in get_repository_by_callsign
    return self.repository_search_single("callsigns", call_sign)
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^
  File "/build/moz-phab/src/review-2.14.0/mozphab/conduit.py", line 724, in repository_search_single
    raise NotFoundError("Repository %s not found" % value)
mozphab.exceptions.NotFoundError: Repository TEST not found
======================================================= short test summary info ========================================================
FAILED tests/test_integration_patch.py::test_git_patch_with_commit - mozphab.exceptions.NotFoundError: Repository TEST not found
===================================================== 1 failed, 3 passed in 4.52s ======================================================

Sometimes both fail, sometimes one of them fails, sometimes both pass.
Reverting to v2.13.0 fixes the issue for me.

Expected results:

========================================================= test session starts ==========================================================
platform linux -- Python 3.14.4, pytest-9.0.3, pluggy-1.6.0
rootdir: /build/moz-phab/src/review-2.14.0
configfile: pytest.ini
collected 4 items                                                                                                                      

tests/test_integration_patch.py ....                                                                                             [100%]

========================================================== 4 passed in 8.63s ===========================================================

Possibly regressed by 2031283?

(Feel free to unlink if I’m mistaken.)

(In reply to Claudia Pellegrino from comment #1)

Possibly regressed by 2031283?

(Feel free to unlink if I’m mistaken.)

I think that's right. Thank you for the report. :)

We previously used a list-based side effect. Now that calls are
parallelized, if one call completes before another, the wrong
mocked result is returned in the test. Switch to a function
based side-effect instead, using the diff ID as the key, so the
returned value is always correct.

@Connor Sheehan [:sheehan] Thanks for the patch.

The modified test has about the same breakage rate than before. I just got 5 failures out of 16 attempts, see log.

I updated the patch with fixes for a few more tests. Can you give it another try for me?

Yay, that did it! 16 passed out of 16 attempts.

Thanks for the fix!

(In reply to Claudia Pellegrino from comment #7)

Yay, that did it! 16 passed out of 16 attempts.

Thanks for the fix!

Thank you for verifying! I'll close out this bug once the patch is reviewed and landed. :)

Authored by https://github.com/cgsheeh
https://github.com/mozilla-conduit/review/commit/b36ad964127d3eefbf00265c5df8922f319ee52a
[main] tests: use function-based side-effect for threaded Conduit calls (Bug 2036007) r=sylvestre