fix: add get_launch_test_fixture_scope for pytest compatibility

[wep21]

Description

Fixes #947

Is this user-facing behavior change?

Did you use Generative AI?

codex 5.3

Additional Information

before

❯ PYTHONPATH=launch_pytest:launch_testing:launch:../ament_index/ament_index_python/ uvx --with pytest --with osrf_pycommon --with typing_extensions --with pyyaml --with lark pytest /Users/daisuke/workspace/launch/launch_pytest/test/launch_pytest/tools/test_process.py::test_sync_process_tools -q
E                                                                                                                                                  [100%]
========================================================================= ERRORS =========================================================================
_______________________________________________________ ERROR at setup of test_sync_process_tools ________________________________________________________
file /Users/daisuke/workspace/launch/launch_pytest/test/launch_pytest/tools/test_process.py, line 65
  @pytest.mark.launch(fixture=launch_description)
  def test_sync_process_tools(dut, launch_context):
E       fixture 'launch_context' not found
>       available fixtures: LineMatcher, _config_for_test, _pytest, _sys_snapshot, cache, capfd, capfdbinary, caplog, capsys, capsysbinary, capteesys, doctest_namespace, dut, launch_description, linecomp, monkeypatch, pytestconfig, pytester, record_property, record_testsuite_property, record_xml_attribute, recwarn, subtests, testdir, tmp_path, tmp_path_factory, tmpdir, tmpdir_factory
>       use 'pytest --fixtures [testpath]' for help on them.

/Users/daisuke/workspace/launch/launch_pytest/test/launch_pytest/tools/test_process.py:65
==================================================================== warnings summary ====================================================================
launch_pytest/test/launch_pytest/tools/test_process.py:49
  /Users/daisuke/workspace/launch/launch_pytest/test/launch_pytest/tools/test_process.py:49: PytestUnknownMarkWarning: Unknown pytest.mark.launch - is this a typo?  You can register custom marks to avoid this warning - for details, see https://docs.pytest.org/en/stable/how-to/mark.html
    @pytest.mark.launch(fixture=launch_description)

launch_pytest/test/launch_pytest/tools/test_process.py:65
  /Users/daisuke/workspace/launch/launch_pytest/test/launch_pytest/tools/test_process.py:65: PytestUnknownMarkWarning: Unknown pytest.mark.launch - is this a typo?  You can register custom marks to avoid this warning - for details, see https://docs.pytest.org/en/stable/how-to/mark.html
    @pytest.mark.launch(fixture=launch_description)

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
================================================================ short test summary info =================================================================
ERROR launch_pytest/test/launch_pytest/tools/test_process.py::test_sync_process_tools
2 warnings, 1 error in 0.12s

~/workspace/launch rolling
❯ PYTHONPATH=launch_pytest:launch_testing:launch:../ament_index/ament_index_python \
      uvx --with pytest --with osrf_pycommon --with typing_extensions --with pyyaml --with lark \
      pytest -p launch_pytest.plugin \
      /Users/daisuke/workspace/launch/launch_pytest/test/launch_pytest/tools/test_process.py::test_sync_process_tools -q

================================================================== ERRORS ==================================================================
________________________________________ ERROR collecting test/launch_pytest/tools/test_process.py _________________________________________
../../.cache/uv/archive-v0/LH_vSsIIXaIhCxrT9it7P/lib/python3.14/site-packages/pluggy/_hooks.py:512: in __call__
    return self._hookexec(self.name, self._hookimpls.copy(), kwargs, firstresult)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
../../.cache/uv/archive-v0/LH_vSsIIXaIhCxrT9it7P/lib/python3.14/site-packages/pluggy/_manager.py:120: in _hookexec
    return self._inner_hookexec(hook_name, methods, kwargs, firstresult)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
launch_pytest/launch_pytest/plugin.py:239: in pytest_pycollect_makeitem
    scope = fixture._pytestfixturefunction.scope
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
E   AttributeError: 'FixtureFunctionDefinition' object has no attribute '_pytestfixturefunction'. Did you mean: '_fixture_function'?
========================================================= short test summary info ==========================================================
ERROR launch_pytest/test/launch_pytest/tools/test_process.py - AttributeError: 'FixtureFunctionDefinition' object has no attribute '_pytestfixturefunction'. Did you mean: '_fixture_function'?
1 error in 0.06s
ERROR: found no collectors for /Users/daisuke/workspace/launch/launch_pytest/test/launch_pytest/tools/test_process.py::test_sync_process_tools

after

❯ PYTHONPATH=launch_pytest:launch_testing:launch:../ament_index/ament_index_python \
      uvx --with pytest --with osrf_pycommon --with typing_extensions --with pyyaml --with lark \
      pytest -p launch_pytest.plugin \
      /Users/daisuke/workspace/launch/launch_pytest/test/launch_pytest/tools/test_process.py::test_sync_process_tools -q
.                                                                                                                                    [100%]
============================================================= warnings summary =============================================================
test/launch_pytest/tools/test_process.py::test_sync_process_tools
  /Users/daisuke/workspace/launch/launch_pytest/launch_pytest/fixture.py:75: DeprecationWarning: 'asyncio.get_event_loop_policy' is deprecated and slated for removal in Python 3.16
    loop = asyncio.get_event_loop_policy().new_event_loop()

test/launch_pytest/tools/test_process.py::test_sync_process_tools
  /Users/daisuke/workspace/launch/launch_pytest/launch_pytest/fixture.py:76: DeprecationWarning: 'asyncio.get_event_loop_policy' is deprecated and slated for removal in Python 3.16
    policy = asyncio.get_event_loop_policy()

test/launch_pytest/tools/test_process.py::test_sync_process_tools
  /Users/daisuke/workspace/launch/launch_pytest/launch_pytest/fixture.py:87: DeprecationWarning: 'asyncio.set_event_loop_policy' is deprecated and slated for removal in Python 3.16
    asyncio.set_event_loop_policy(None)

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
1 passed, 3 warnings in 5.04s

[wep21]

@claraberendsen could you review this PR?

[claraberendsen]

Thanks @wep21 for setting this up ❤️ . Checking if it solves the build regression on Resolute.

@sloretz I would appreciate your review here of the implementation.