Ignore trailing commas not working for function arguments

[sparxastronomy]

Summary

I have the following function block:

def compute_profiles(
        x: np.ndarray, 
        y: np.ndarray, 
        window_size: int, 
        type: str = "median", 
        return_xbins: bool = False
) -> tuple[np.ndarray, np.ndarray, np.ndarray, np.ndarray]:

However ruff ignores the trailing commas, and formats it to even though skip-magic-trailing-comma = false

def compute_profiles(
    x: np.ndarray, y: np.ndarray, window_size: int, type: str = "median", return_xbins: bool = False
) -> tuple[np.ndarray, np.ndarray, np.ndarray, np.ndarray]:

The problem only appears for functions, for regular arrays the problem does not appear.

My configuration is:

[tool.ruff]
extend-include = ["*.ipynb"]
preview = true
line-length = 120
indent-width = 4

[tool.ruff.format]
preview = true
quote-style = "double"
indent-style = "space"
line-ending = "auto"
skip-magic-trailing-comma = false
docstring-code-format = true
docstring-code-line-length = "dynamic"

[tool.ruff.lint]
select = [
    "E", # pycodestyle (error)
    "F", # pyflakes
    "B", # bugbear
    "B9",
    "C4", # flake8-comprehensions
    "SIM", # flake8-simplify
    "I", # isort
    "UP", # pyupgrade
    "PIE", # flake8-pie
    "PGH", # pygrep-hooks
    "PYI", # flake8-pyi
    "RUF",
]
ignore = [
    # only relevant if you run a script with `python -0`,
    # which seems unlikely for any of the scripts in this repo
    "B011",
    # Leave it to the formatter to split long lines and
    # the judgement of all of us.
    "E501",
    "RUF052",
    "E201",
    "E241"
]

fixable = ["A", "B", "C", "D", "E", "F"]
unfixable = []

[tool.ruff.lint.pydocstyle]
convention = "google"

I am using the latest version of Ruff extension on VSCode.

Version

v2025.14.0 (VScode)

[MichaReiser]

Hi @sparxastronomy

I don't see a trailing comma in your example code. The trailing comma must come after the last argument's default value:

def compute_profiles(
        x: np.ndarray, 
        y: np.ndarray, 
        window_size: int, 
        type: str = "median", 
        return_xbins: bool = False,
) -> tuple[np.ndarray, np.ndarray, np.ndarray, np.ndarray]: ...

Ruff should then split the arguments across multiple lines when using skip-magic-trailing-comma=false (default)

https://play.ruff.rs/10014487-0683-40d5-9eed-968075bce9b5

[sparxastronomy]

Thanks @MichaReiser for point out the missing commas. I thought the last comma was not needed.