[pycodestyle] Whitespace after decorator (E204)

[jkauerl]

Summary

This is the implementation for the new rule of pycodestyle (E204). It follows the guidlines described in the contributing site, and as such it has a new file named whitespace_after_decorator.rs, a new test file called E204.py, and as such invokes the function in the AST statement checker for functions and functions in classes. Linking #2402 because it has all the pycodestyle rules.

Test Plan

The file E204.py, has a decorator defined called wrapper, and this decorator is used for 2 cases. The first one is when a function which has a decorator is called in the file, and the second one is when there is a class and 2 methods are defined for the class with a decorator attached it.

Test file:

def foo(fun):
    def wrapper():
        print('before')
        fun()
        print('after')
    return wrapper

# No error
@foo
def bar():
    print('bar')

# E204
@ foo
def baz():
    print('baz')

class Test:
    # No error
    @foo
    def bar(self):
        print('bar')

    # E204
    @ foo
    def baz(self):
        print('baz')

I am still new to rust and any suggestion is appreciated. Specially with the way im using native ruff utilities.

[charliermarsh]

Thanks! I added a fix too.