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Description
a detailed description of the bug or problem you are having, MWE
I have parametrized tests that take input data from a config, e.g., a list of matrices. It may happen that there is no input parameter at all, i.e., empty list of parameters, see below
import pytest
parameters = []
@pytest.mark.parametrize(
"matrix",
parameters,
ids=lambda matrix: matrix.id,
)
def test_foo(matrix):
return True
Now, I'd like to just collect matrices there are, i.e.
pytest dev.py --collect-only
but it fails as it tries to create at least a single instance for test_foo. The reason is that ids is a callable and it's called with NotSetType.
===================================================================================================================================================== test session starts =====================================================================================================================================================
platform linux -- Python 3.11.3, pytest-8.3.3, pluggy-1.5.0
benchmark: 5.1.0 (defaults: timer=time.perf_counter disable_gc=False min_rounds=5 min_time=0.000005 max_time=1.0 calibration_precision=10 warmup=False warmup_iterations=100000)
rootdir: ...
configfile: ...
plugins: monitor-1.6.1, benchmark-5.1.0
collected 0 items / 1 error
=========================================================================================================================================================== ERRORS ============================================================================================================================================================
___________________________________________________________________________________________________________________________________________________ ERROR collecting dev.py ___________________________________________________________________________________________________________________________________________________
dev.py:9: in <lambda>
ids=lambda matrix: matrix.id,
E AttributeError: 'NotSetType' object has no attribute 'id'
The above exception was the direct cause of the following exception:
.venv/lib/python3.11/site-packages/pluggy/_hooks.py:513: in __call__
return self._hookexec(self.name, self._hookimpls.copy(), kwargs, firstresult)
.venv/lib/python3.11/site-packages/pluggy/_manager.py:120: in _hookexec
return self._inner_hookexec(hook_name, methods, kwargs, firstresult)
.venv/lib/python3.11/site-packages/_pytest/python.py:245: in pytest_pycollect_makeitem
return list(collector._genfunctions(name, obj))
.venv/lib/python3.11/site-packages/_pytest/python.py:462: in _genfunctions
self.ihook.pytest_generate_tests.call_extra(methods, dict(metafunc=metafunc))
.venv/lib/python3.11/site-packages/pluggy/_hooks.py:574: in call_extra
return self._hookexec(self.name, hookimpls, kwargs, firstresult)
.venv/lib/python3.11/site-packages/pluggy/_manager.py:120: in _hookexec
return self._inner_hookexec(hook_name, methods, kwargs, firstresult)
.venv/lib/python3.11/site-packages/_pytest/python.py:115: in pytest_generate_tests
metafunc.parametrize(*marker.args, **marker.kwargs, _param_mark=marker)
.venv/lib/python3.11/site-packages/_pytest/python.py:1236: in parametrize
ids = self._resolve_parameter_set_ids(
.venv/lib/python3.11/site-packages/_pytest/python.py:1355: in _resolve_parameter_set_ids
return id_maker.make_unique_parameterset_ids()
.venv/lib/python3.11/site-packages/_pytest/python.py:897: in make_unique_parameterset_ids
resolved_ids = list(self._resolve_ids())
.venv/lib/python3.11/site-packages/_pytest/python.py:932: in _resolve_ids
yield "-".join(
.venv/lib/python3.11/site-packages/_pytest/python.py:933: in <genexpr>
self._idval(val, argname, idx)
.venv/lib/python3.11/site-packages/_pytest/python.py:939: in _idval
idval = self._idval_from_function(val, argname, idx)
.venv/lib/python3.11/site-packages/_pytest/python.py:961: in _idval_from_function
raise ValueError(msg) from e
E ValueError: dev.py::test_foo: error raised while trying to determine id of parameter 'matrix' at position 0
=================================================================================================================================================== short test summary info ===================================================================================================================================================
ERROR dev.py - ValueError: dev.py::test_foo: error raised while trying to determine id of parameter 'matrix' at position 0
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
I found a nasty workaround
import pytest
parameters = []
@pytest.mark.parametrize(
"matrix",
parameters,
ids=(lambda matrix: matrix.id) if parameters else None,
)
def test_foo(matrix):
return True
which returns
...
plugins: monitor-1.6.1, benchmark-5.1.0
collected 1 item
<Dir bigplan-algorithm>
<Module dev.py>
<Function test_foo[matrix0]>
...
While the problem might seem a bit artificial, it's a scenario in my case. I have no control on what data are in the config, I just need to test the thing without failures. The workaround is doable but I would don't like writing these for each single case, and frankly, don't understand why ids are invoked at all.
output of pip list from the virtual environment you are using
igplan-algorithm>
<Module dev.py>
<Function test_foo[matrix0]>
================================================================================================================================================== 1 test collected in 0.01s ==================================================================================================================================================
> pip list
Package Version
------------------------ --------------
pytest 8.3.3
pytest-benchmark 5.1.0
pytest-monitor 1.6.1
pytest-xdist 3.6.1
20.04.1-Ubuntu