Installing latest flake8 breaks ament_flake8 on humble: ValueError: 'string' is not callable

[Ryanf55]

Installing latest flake8 breaks ament_flake8. While flake8 3.7.9 works, upgrading to the latest of 7.2.0 causes tests in ros2/launch on humble branch, commit b4a2c06a41a9c34435548180221fdb7429b539c1 to fail.

Found in ArduPilot/ardupilot#30369 (comment)

Perhaps this is an unsupported combo?

colcon test --packages-select launch --pytest-args " -k" " test_flake8" " -v" --event-handlers=console_cohesion+
Starting >>> launch  
--- output: launch                   
============================= test session starts ==============================
platform linux -- Python 3.10.12, pytest-6.2.5, py-1.10.0, pluggy-0.13.0 -- /usr/bin/python3
cachedir: /home/ryan/Dev/ros2_ws/src/launch/build/launch/.pytest_cache
rootdir: /home/ryan/Dev/ros2_ws/src/launch/launch, configfile: pytest.ini
plugins: launch-pytest-1.0.7, ament-xmllint-0.12.11, ament-black-0.2.6, ament-lint-0.12.11, ament-copyright-0.12.11, launch-testing-ros-0.19.8, launch-testing-1.0.7, ament-mypy-0.12.11, ament-flake8-0.12.11, ament-pep257-0.12.11, anyio-4.6.2.post1, mock-3.6.1, cov-3.0.0, colcon-core-0.18.4, timeout-2.1.0
collecting ... 
collected 242 items / 241 deselected / 1 selected                              

test/test_flake8.py::test_flake8 FAILED                                  [100%]

=================================== FAILURES ===================================
_________________________________ test_flake8 __________________________________
test/test_flake8.py:22: in test_flake8
    rc, errors = main_with_errors(argv=[])
/opt/ros/humble/lib/python3.10/site-packages/ament_flake8/main.py:88: in main_with_errors
    report = generate_flake8_report(
/opt/ros/humble/lib/python3.10/site-packages/ament_flake8/main.py:267: in generate_flake8_report
    style = get_flake8_style_guide(flake8_argv)
/opt/ros/humble/lib/python3.10/site-packages/ament_flake8/main.py:186: in get_flake8_style_guide
    application.plugins, application.options = parse_args(argv)
/home/ryan/.local/lib/python3.10/site-packages/flake8/options/parse_args.py:51: in parse_args
    option_manager.register_plugins(plugins)
/home/ryan/.local/lib/python3.10/site-packages/flake8/options/manager.py:259: in register_plugins
    add_options(self)
/usr/lib/python3/dist-packages/flake8_import_order/flake8_linter.py:44: in add_options
    register_opt(
/usr/lib/python3/dist-packages/flake8_import_order/flake8_linter.py:98: in register_opt
    parser.add_option(*args, **kwargs)
/home/ryan/.local/lib/python3.10/site-packages/flake8/options/manager.py:281: in add_option
    self._current_group.add_argument(*option_args, **option_kwargs)
/usr/lib/python3.10/argparse.py:1447: in add_argument
=============================== warnings summary ===============================
test/test_flake8.py::test_flake8
  Warning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html

test/test_flake8.py::test_flake8
  Warning: Deprecated call to `pkg_resources.declare_namespace('mpl_toolkits')`.
  Implementing implicit namespace packages (as specified in PEP 420) is preferred to `pkg_resources.declare_namespace`. See https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-namespace-packages

-- Docs: https://docs.pytest.org/en/stable/warnings.html
    raise ValueError('%r is not callable' % (type_func,))
E   ValueError: 'string' is not callable
- generated xml file: /home/ryan/Dev/ros2_ws/src/launch/build/launch/pytest.xml -
=========================== short test summary info ============================
FAILED test/test_flake8.py::test_flake8 - ValueError: 'string' is not callable
================ 1 failed, 241 deselected, 2 warnings in 0.52s =================
---
--- stderr: launch
=============================== warnings summary ===============================
test/test_flake8.py::test_flake8
  Warning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html

test/test_flake8.py::test_flake8
  Warning: Deprecated call to `pkg_resources.declare_namespace('mpl_toolkits')`.
  Implementing implicit namespace packages (as specified in PEP 420) is preferred to `pkg_resources.declare_namespace`. See https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-namespace-packages

-- Docs: https://docs.pytest.org/en/stable/warnings.html
---
Finished <<< launch [0.84s]	[ with test failures ]

Summary: 1 package finished [0.92s]
  1 package had stderr output: launch
  1 package had test failures: launch

[christophebedard]

Yeah, the general expectation is that the version available from the Ubuntu system packages is used. For Humble (Ubuntu 22.04), that's 4.0.1: https://packages.ubuntu.com/jammy/python3-flake8. For example, we use flake8 4.0.1 for Humble on Windows too: https://github.com/ros2/ros2/blob/fa23142b2cd5ec27f455b2e417ae7862ea04308a/pixi.toml#L55.

PRs that make ament_flake8 work with other versions of flake8 can be considered, depending on the complexity/added maintenance burden of the change. You might want to look at ament_flake8 PRs after Humble; perhaps it's just a matter of backporting one of them.

[christophebedard]

Yeah, the general expectation is that the version available from the Ubuntu system packages is used.

To add to this, the expectation is that you install dependencies (e.g., <exec_depend>python3-flake8</exec_depend>) using rosdep, which installs the python3-flake8 system package on Ubuntu. If you use pip or some other package manager to install some other version of flake8, you might run into issues like this one.

[Yadunund]

@Ryanf55 as Chrisophe has stated using non-system versions of dependencies is unsupported.

Having said that, you're welcome to submit a pull request to update the code formatting as long as the changes also comply with flake8 from system packages.