Possible False Positive: too-many-arguments (PLR0913) considers `self` and `cls`

[Bibo-Joshi]

• List of keywords you searched for before creating this issue. Write them down here so that others can find this issue more easily and help provide feedback.

  • "PRL0913"
  • "too-many-arguments"
  • "self"
  • "cls"
  • "false positve"

• A minimal code snippet that reproduces the bug.

  class DemoClass:
      def __init__(self, one, two, three, four, five):
          pass
  
      @classmethod
      def bar(cls, one, two, three, four, five):
          pass
  
      @staticmethod
      def foo(one, two, three, four, five):
          pass

• The command you invoked (e.g., ruff /path/to/file.py --fix), ideally including the --isolated flag.

  ruff check foo.py --isolated --select PLR0913

  This produles the following output:

  (.venv) ~\PycharmProjects\test git:[dev]
  ruff check foo.py --isolated --select PLR0913
  foo.py:2:9: PLR0913 Too many arguments in function definition (6 > 5)
    |
  1 | class DemoClass:
  2 |     def __init__(self, one, two, three, four, five):
    |         ^^^^^^^^ PLR0913
  3 |         pass
    |
  
  foo.py:6:9: PLR0913 Too many arguments in function definition (6 > 5)
    |
  5 |     @classmethod
  6 |     def bar(cls, one, two, three, four, five):
    |         ^^^ PLR0913
  7 |         pass
    |
  
  Found 2 errors.

  Apparently, ruff considers self and cls when computing the number of arguments. However, these arguments are mandatory anyway, are not visible to the consumer of these methods and don't introduce any maintenance overhead. I propose that ruff ignores them.

• The current Ruff settings (any relevant sections from your pyproject.toml). used --isolated flag above

• The current Ruff version (ruff --version): ruff 0.5.1

[MichaReiser]

I'm not arguing whether the behavior is correct. But what I understand from Pylint's source code is that it also counts self and cls

https://github.com/pylint-dev/pylint/blob/a48cd4c6a872b6565bc58030b74585812f327f36/pylint/checkers/design_analysis.py#L536-L553

One important difference is that pylint supports a configuration (Regex) to ignore arguments.

[dhruvmanila]

FWIW, Pylint considers this as false-positive in pylint-dev/pylint#8675 and I think that makes sense. The implementation should also consider decorators like @staticmethod and @classmethod when determining whether to count self / cls.

[Bibo-Joshi]

That was lightning fast. Awesome, thanks :)