_LazyValueCaseParamValue is injected instead of the case function result

[smarie]

When at least two "basic" cases are present next to each other in a set of cases where there is at least a fixture case (parameterized case or case requiring a fixture), then the case function is not called and a _LazyValueCaseParamValue is wrongly injected.

Reproducible example:

import pytest
from pytest_cases import fixture, parametrize_with_cases

class DataCases:
    def data_dummy(self):
        return 1

    def data_dummy2(self):
        return 1

    @pytest.mark.parametrize("a", [False])
    def data_dummy3(self, a):
        return 1

@fixture
@parametrize_with_cases("dset", cases=DataCases, prefix="data_", debug=True)
def dataset(dset):
    assert dset == 1
    yield dset

def test_foo(dataset):
    pass

yields

============================= test session starts =============================
collecting ... Case function DataCases.data_dummy > 1 lazy_value() with id dummy and additional marks None
Case function DataCases.data_dummy2 > 1 lazy_value() with id dummy2 and additional marks None
Case function DataCases.data_dummy3 > Creating fixture 'dummy3' in <module 'test_case_fixture' from 'C:\\_dev\\python_ws\\_Libs_Schneider\\CIPP_docs\\tests\\test_case_fixture.py'>
Case function DataCases.data_dummy3 > fixture_ref('dummy3') with marks ()
Fixture references found. Creating references and fixtures...
 - Creating new fixture 'dataset_dset_is_P0toP1' to handle parameters 0 to 1
Creating parametrized fixture 'dataset_dset_is_P0toP1' returning [_LazyValueCaseParamValue(valuegetter=functools.partial(<function DataCases.data_dummy at 0x00000164FDBCB510>, <test_case_fixture.DataCases object at 0x00000164FDD82668>), _id='dummy', _marks=(), cached_value_context=None, cached_value=None), _LazyValueCaseParamValue(valuegetter=functools.partial(<function DataCases.data_dummy2 at 0x00000164FDBCB488>, <test_case_fixture.DataCases object at 0x00000164FDD82748>), _id='dummy2', _marks=(), cached_value_context=None, cached_value=None)]
 - Creating reference to existing fixture 'dummy3'
Creating final union fixture 'dataset_dset' with alternatives ['dataset_dset_is_P0toP1', 'dummy3']
Creating final test function wrapper with signature dataset(dataset_dset)
collected 3 items

test_case_fixture.py::test_foo[dummy] ERROR
test setup failed
_LazyValueCaseParamValue(valuegetter=functools.partial(<function DataCases.data_dummy at 0x00000164FDBCB510>, <test_case_fixture.DataCases object at 0x00000164FDD82668>), _id='dummy', _marks=(), cached_value_context=None, cached_value=None) != 1

Expected :1
Actual   :_LazyValueCaseParamValue(valuegetter=functools.partial(<function DataCases.data_dummy at 0x00000164FDBCB510>, <test_case_fixture.DataCases object at 0x00000164FDD82668>), _id='dummy', _marks=(), cached_value_context=None, cached_value=None)
<Click to see difference>

dset = _LazyValueCaseParamValue(valuegetter=functools.partial(<function DataCases.data_dummy at 0x00000164FDBCB510>, <test_case_fixture.DataCases object at 0x00000164FDD82668>), _id='dummy', _marks=(), cached_value_context=None, cached_value=None)

    @fixture
    @parametrize_with_cases("dset", cases=DataCases, prefix="data_", debug=True)
    def dataset(dset):
>       assert dset == 1
E       AssertionError: assert _LazyValueCaseParamValue(valuegetter=functools.partial(<function DataCases.data_dummy at 0x00000164FDBCB510>, <test_case_fixture.DataCases object at 0x00000164FDD82668>), _id='dummy', _marks=(), cached_value_context=None, cached_value=None) == 1
E         +_LazyValueCaseParamValue(valuegetter=functools.partial(<function DataCases.data_dummy at 0x00000164FDBCB510>, <test_case_fixture.DataCases object at 0x00000164FDD82668>), _id='dummy', _marks=(), cached_value_context=None, cached_value=None)
E         -1

[smarie]

The bug does not happen when the cases are used to parametrize the test (not a fixture).
The following works:

import pytest
from pytest_cases import parametrize_with_cases

class DataCases:
    def data_dummy(self):
        return 1

    def data_dummy2(self):
        return 1

    @pytest.mark.parametrize("a", [False])
    def data_dummy3(self, a):
        return 1

@parametrize_with_cases("dset", cases=DataCases, prefix="data_", debug=True)
def test_foo(dset):
    assert dset == 1

[smarie]

Decoding what happens in the original (failing) example:

• @parametrize_with_cases creates the dummy3 fixture for case 3 and lazy_values for the first 2 cases and calls @parametrize
• @parametrize creates the dataset_dset_is_P0toP1 fixture, parametrized with the first two lazy values
• @parametrize creates the "union" fixture dataset_dset with alternatives ['dataset_dset_is_P0toP1', 'dummy3']
• @parametrize creates a wrapper around def dataset(dset), that has the signature def dataset(dataset_dset). This is the function that will be decorated by @fixture (instead of the original function)

We can see this in the debug log enabled using debug = True :

Case function DataCases.data_dummy > 1 lazy_value() with id dummy and additional marks None
Case function DataCases.data_dummy2 > 1 lazy_value() with id dummy2 and additional marks None
Case function DataCases.data_dummy3 > Creating fixture 'dummy3' in <module 'tests.cases.issues.test_issue_274' from 'C:\\_dev\\python_ws\\_Libs_OpenSource\\python-pytest-cases\\tests\\cases\\issues\\test_issue_274.py'>
Case function DataCases.data_dummy3 > fixture_ref('dummy3') with marks ()
Fixture references found. Creating references and fixtures...
 - Creating new fixture 'dataset_dset_is_P0toP1' to handle parameters 0 to 1
Creating parametrized fixture 'dataset_dset_is_P0toP1' returning [_LazyValueCaseParamValue(valuegetter=functools.partial(<function DataCases.data_dummy at 0x000001F6C607BCA0>, <tests.cases.issues.test_issue_274.DataCases object at 0x000001F6C60815E0>), _id='dummy', _marks=(), cached_value_context=None, cached_value=None), _LazyValueCaseParamValue(valuegetter=functools.partial(<function DataCases.data_dummy2 at 0x000001F6C607BE50>, <tests.cases.issues.test_issue_274.DataCases object at 0x000001F6C6081D60>), _id='dummy2', _marks=(), cached_value_context=None, cached_value=None)]
 - Creating reference to existing fixture 'dummy3'
Creating final union fixture 'dataset_dset' with alternatives ['dataset_dset_is_P0toP1', 'dummy3']
Creating final test function wrapper with signature dataset(dataset_dset)