Ensure that B006 autofixes are inserted after imports

[hoxbro]

Summary

Fixes #7616 by ensuring that B006 fixes are inserted after module imports.

I have created a new test file, B006_5.py. This is mainly because I have been working on this on and off, and the merge conflicts were easier to handle in a separate file. If needed, I can move it into another file.

Test Plan

cargo test

[codspeed-hq]

CodSpeed Performance Report

Merging #7629 will not alter performance

_{Comparing Hoxbro:fix_b006_import (7d27160) with main (2aef46c)}

Summary

✅ 25 untouched benchmarks

[github-actions]

PR Check Results

Ecosystem

✅ ecosystem check detected no changes.

[konstin]

Do you also need to handle the locator.full_line_end(statement.end()) == locator.text_len() case from above here?

[hoxbro]

I will take a look at it later today.

[hoxbro]

This should now be handled.

[hoxbro]

This line was added when implementing the locator.full_line_end(statement.end()) == locator.text_len() case.

I can see something similar happens when doing it with docstrings on 0.0.291.

This will:

def t(foo=[]):
    """Docstring"""

a = 2

will be fixed to

def t(foo=None):
    """Docstring"""
    if foo is None:
        foo = []

a = 2

Whereas

def t(foo=[]):
    """Docstring"""

will be fixed to

def t(foo=None):
    """Docstring"""

    if foo is None:
        foo = []

[charliermarsh]

@hoxbro - I collapsed these two cases -- I think semantically they're the same? We want to skip docstrings and imports, and find the first opportunity to insert after them. (If there's no such opportunity, we insert at the start of the function.)

[charliermarsh]

Of course, please let me know if I've misunderstood or messed something up -- happy to fix in a follow-up.

[hoxbro]

No, that sounds right to me.