[Epic][CI] Upgrade flake8 to version 7.1.1

[MortalHappiness]

What happened + What you expected to happen

While running the pre-commit hook of flake8, the following error occurs if Python version is 3.12. It's because the version of flake8 is too old.

flake8...................................................................Failed
- hook id: flake8
- exit code: 1

Traceback (most recent call last):
  File "/home/mortalhappiness/.cache/pre-commit/repo785be_6i/py_env-python3.12/bin/flake8", line 8, in <module>
    sys.exit(main())
             ^^^^^^
  File "/home/mortalhappiness/.cache/pre-commit/repo785be_6i/py_env-python3.12/lib/python3.12/site-packages/flake8/main/cli.py", line 22, in main
    app.run(argv)
  File "/home/mortalhappiness/.cache/pre-commit/repo785be_6i/py_env-python3.12/lib/python3.12/site-packages/flake8/main/application.py", line 363, in run
    self._run(argv)
  File "/home/mortalhappiness/.cache/pre-commit/repo785be_6i/py_env-python3.12/lib/python3.12/site-packages/flake8/main/application.py", line 350, in _run
    self.initialize(argv)
  File "/home/mortalhappiness/.cache/pre-commit/repo785be_6i/py_env-python3.12/lib/python3.12/site-packages/flake8/main/application.py", line 330, in initialize
    self.find_plugins(config_finder)
  File "/home/mortalhappiness/.cache/pre-commit/repo785be_6i/py_env-python3.12/lib/python3.12/site-packages/flake8/main/application.py", line 153, in find_plugins
    self.check_plugins = plugin_manager.Checkers(local_plugins.extension)
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/mortalhappiness/.cache/pre-commit/repo785be_6i/py_env-python3.12/lib/python3.12/site-packages/flake8/plugins/manager.py", line 356, in __init__
    self.manager = PluginManager(
                   ^^^^^^^^^^^^^^
  File "/home/mortalhappiness/.cache/pre-commit/repo785be_6i/py_env-python3.12/lib/python3.12/site-packages/flake8/plugins/manager.py", line 238, in __init__
    self._load_entrypoint_plugins()
  File "/home/mortalhappiness/.cache/pre-commit/repo785be_6i/py_env-python3.12/lib/python3.12/site-packages/flake8/plugins/manager.py", line 254, in _load_entrypoint_plugins
    eps = importlib_metadata.entry_points().get(self.namespace, ())
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'EntryPoints' object has no attribute 'get'

Versions / Dependencies

Python 3.12

Reproduction script

If python version is 3.9 -> no error

If python version is 3.12 -> has error

Upgrade the following packages to the newest version solves this issue:

• flake8==7.1.1
• flake8-comprehensions==3.15.0
• flake8-quotes==3.4.0
• flake8-bugbear==24.8.19

Issue Severity

Low: It annoys or frustrates me.

flake8 upgrade subtasks tracking:

Thanks for @CheyuWu 's comment here https://github.com/ray-project/ray/issues/48022#issuecomment-2414051046

pycodestyle

• [ ] #48058
• [x] #48059
• [ ] #48060
• [ ] #48061

pyflakes

• [ ] #48062
• [ ] #48063

flake8-bugbear

https://github.com/PyCQA/flake8-bugbear

• [x] #48065
• [x] #48066
• [x] #48067
• [ ] #48068
• [ ] #48069
• [ ] #48070
• [ ] #48071
• [ ] #48072
• [ ] #48073
• [ ] #48074
• [ ] #48075
• [ ] #48076

flake8-comprehensions

https://github.com/adamchainz/flake8-comprehensions

• [ ] #48077
• [ ] #48078
• [ ] #48079
• [ ] #48080

CI upgrade

• [ ] #48508
• [ ] #48022

Cleanup

• [ ] #48147

Notes for contributors

• Use the following command to filter files that need to be fixed for single rule:

  flake8 --select E721 --extend-exclude python/ray/core/generated,python/ray/serve/generated/,python/ray/cloudpickle/,python/ray/_private/runtime_env/_clonevirtualenv.py,doc/external/,python/ray/dashboard/client/node_modules

  Replace E721 with the rule that you want to fix.

• Please note that the pre-commit hook still need to be run, but flake8 will fail, preventing you from committing. The temporary workaround is as follows:
  1. Perform a normal git add and commit.
  2. At this point, the pre-commit hook will be executed. Ideally, only flake8 should fail, and everything else should pass.
  3. Use git commit -n to bypass the pre-commit hook and commit.
  4. Use git commit --amend --no-edit --signoff to sign off the commit from the previous step.

[CheyuWu]

@MortalHappiness I'd like to help with this!

[jjyao]

@MortalHappiness we should explore replacing flake8 with https://github.com/astral-sh/ruff if we want to do the upgrade.

[MortalHappiness]

@jjyao Do you mean to replace flake8 completely with ruff?

[jjyao]

Yes. Reasoning is that ruff is drop-in replacement for flake8 so upgrading flake8 and switching to ruff should require the similar amount of efforts.