workflow_state xtrigger and CLI command do not work across users

[ColemanTom]

Description

>>> import workflow_state
>>> from workflow_state import workflow_state as ws
>>> ws('a', 'b', '20240101T1200Z', cylc_run_dir='/home/another_user')
Traceback (most recent call last):
  File "/home/user/miniconda3/envs/cylc-dev/lib/python3.11/site-packages/cylc/flow/workflow_files.py", line 872, in infer_latest_run
    id_ = str(path.relative_to(cylc_run_dir))
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/miniconda3/envs/cylc-dev/lib/python3.11/pathlib.py", line 730, in relative_to
    raise ValueError("{!r} is not in the subpath of {!r}"
ValueError: '/home/another_user/a' is not in the subpath of '/home/548/tc2375/cylc-run' OR one path is relative and the other is absolute.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/548/tc2375/cylc/cylc/flow/xtriggers/workflow_state.py", line 87, in workflow_state
    _, workflow = infer_latest_run(Path(cylc_run_dir, workflow))
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/miniconda3/envs/cylc-dev/lib/python3.11/site-packages/cylc/flow/workflow_files.py", line 874, in infer_latest_run
    raise ValueError(f"{path} is not in the cylc-run directory")
ValueError: /home/another_user/a is not in the cylc-run directory



>>> from pathlib import Path
>>> a=Path('/home/tc2375')
>>> a.relative_to('/home/another_user')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/user/miniconda3/envs/cylc-dev/lib/python3.11/pathlib.py", line 730, in relative_to
    raise ValueError("{!r} is not in the subpath of {!r}"
ValueError: '/home/tc2375' is not in the subpath of '/home/another_user' OR one path is relative and the other is absolute.
>>>

Reproducible Example

See above. The relative_to method does not work for across user checking.
You can do similar from the command line interface, but make sure to use the --debug flag otherwise the error message is misleading/unhelpful.

Expected Behaviour

Should be able to use workflow_state across different users.

[hjoliver]

Thanks @ColemanTom I think you're right. We must be lacking a test for this. My last manual test, it seems that it worked because I had a workflow of the same name in my own run-dir.

Looks like some of the new Cylc 8 "workflow_files" code assumes owner-only run-dirs...

[hjoliver]

We'd better fix this for 8.3.0 - it would be a show-stopper for Cylc 8 migration at some sites (mine included).

[hjoliver]

Closed by #6031