flake8-force-keyword-arguments

A flake8 plugin that is looking for function calls and forces to use keyword arguments if there are more than X (default=2) arguments. And it can ignore positional only or variable arguments functions such as setattr() or Logger.info(). The plugin inspects given modules (via --kwargs-inspect-module, --kwargs-inspect-module-extend) to get signature and to determine whether it is positional only or variable arguments function. The inspection runs only once at the start of the flake8 command and remembers ignore list through runtime.

Installation

pip install flake8-force-keyword-arguments

Usage

Run your flake8 checker as usual.

Example:

flake8 your_module.py

Option

• --kwargs-max-positional-arguments: How many positional arguments are allowed (default: 2)
• --kwargs-ignore-function-pattern: Ignore pattern list (default: ('^logger.(:?log|debug|info|warning|error|exception|critical)$', 'setattr$', 'delattr$', 'getattr$'))
• --kwargs-ignore-function-pattern-extend: Extend ignore pattern list.
• --kwargs-inspect-module: Inspect module level constructor of classes or functions to gather positional only callables and ignore it on lint. Note that methods are not subject to inspection. (default: ('builtins',))
• --kwargs-inspect-module-extend: Extend --kwargs-inspect-module
• --kwargs-inspect-qualifier-option {only_name,only_with_qualifier,both}: For detected positional only callables by inspection, option to append the qualifier or not. e.g. In case builtins.setattr(), both will register builtins.setattr and setattr as positional only function. only_name will register setattr and only_with_qualifier will register builtins.setattr. (default: QualifierOption.BOTH)

Example

code: test.py

from functools import partial

def one_argument(one):
    pass

def two_arguments(one, two):
    pass

def pos_only_arguments(one, two, three, /):  # python 3.8 or higher required
    pass

def variable_arguments(*args):
    pass

variadic = lambda *args: None
curried = partial(variadic, 1)

one_argument(1)
one_argument(one=1)
two_arguments(1, 2)
two_arguments(one=1, two=2)
pos_only_arguments(1, 2, 3)
variadic(1, 2, 3)
curried(2, 3)

Command

flake8 test.py --select FKA1 --kwargs-inspect-module-extend test

test.py:20:1: FKA100 two_arguments's call uses 2 positional arguments, use keyword arguments.

flake8 test.py --select FKA1 --kwargs-inspect-module-extend test --kwargs-ignore-function-pattern-extend ^two_arguments$

No error

flake8 test.py --select FKA1

test.py:16:11: FKA100 partial's call uses 2 positional arguments, use keyword arguments.
test.py:20:1: FKA100 two_arguments's call uses 2 positional arguments, use keyword arguments.
test.py:22:1: FKA100 pos_only_arguments's call uses 3 positional arguments, use keyword arguments.
test.py:23:1: FKA100 variadic's call uses 3 positional arguments, use keyword arguments.
test.py:24:1: FKA100 curried's call uses 2 positional arguments, use keyword arguments.

Limitation

Currently it only inspects given modules and can not inspect (static, class or normal) methods. Because inspection carries import, it is not safe to inspect all possible packages. And method case, the plugin can inspect methods signature and also can determine whether it is positional only or not. But it can not use the information on lint time. Because python is a dynamic typed language and flake8 is basically a static analyzer. That is, flake8 can not get type information of logger.debug(). So even if I know that logging.Logger::debug() is a variadic function, I can not assure that logger is a instance of Logger.

Error codes