extend-immutable-calls: how to configure?

[DavidVujic]

I haven't been able to make the recently released feature extend-immutable-calls to work.

Have I configured it wrong?

I have verified that flake8 recognizes the config, by setting the line-length to 10 and verified flake8 warnings about line length.

flake8 --version

4.0.1 (flake8-bugbear: 21.11.29, mccabe: 0.6.1, pycodestyle: 2.8.0, pyflakes: 2.4.0) CPython 3.10.0 on
Darwin

example.py

import fastapi


def example_fn(data: str = fastapi.Header(None)):
    pass

setup.cfg

[flake8]
max-line-length = 120
extend-immutable-calls = ["fastapi.Header"]

flake8 --show-source

./example.py:4:28: B008 Do not perform function calls in argument defaults.  The call is performed only once at function definition time. All calls to your function will reuse the result of that definition-time function call.  If this is intended, assign the function call to a module-level variable and use that variable as a default value.
def example_fn(data: str = fastapi.Header(None)):
                           ^

[aberres]

Same problem here - I tried to silence pathlib.Path.

[sco1]

You want:

[flake8]
max-line-length = 120
extend-immutable-calls = fastapi.Header

[cooperlees]

Do we feel we should add anything more to the README here? I'd accept a PR if so. Otherwise do we close?

[sco1]

Even though it's just ConfigParser doing it's thing, it wouldn't hurt to add an example to the README (see also: #215).

I'm happy to include in #218 if you feel it's appropriate.

[aberres]

Ah, great thanks.

And the matching happens by name, right?

So in the following case I would need extend-immutable-calls = Path to silence the warning.

from pathlib import Path

def foo(bar=Path()):
   ...

[aberres]

And as we are here already: Would it make sense to add a hint to this parameter to the error message of B008?

[DavidVujic]

Great, thank you for clarifying!

I had thought that the values should be defined as a (Python) array. Now, when typing something like this (for more than one fastAPI thing to allow), everything works as expected:

extend-immutable-calls = fastapi.Header, fastapi.Depends

[cooperlees]

Please at least add to the README to make it clearer. The message, I’d you can make a sane suggestion in code please do too. Thanks!

[copdips]

Great, thank you for clarifying!

I had thought that the values should be defined as a (Python) array. Now, when typing something like this (for more than one fastAPI thing to allow), everything works as expected:

extend-immutable-calls = fastapi.Header, fastapi.Depends

You can use list format like this:

extend-immutable-calls =
    fastapi.Header,
    fastapi.Depends,

[npip99]

If anyone is using pyproject.toml,

[tool.ruff.lint.flake8-bugbear]
extend-immutable-calls = [
    # Whitelisted default arguments
    "fastapi.Header",
    "fastapi.Depends",
]