ANN201 false positive when functions are defined within functions

[sumnerevans]

Describe the bug
When an outer function returns None, but a function which is defined within it returns something that isn't None, the outer function is falsly marked with an ANN2** error.

Edit: Note this happens even when suppress-none-returning = True.

To Reproduce
Minimal code example to reproduce the behavior:

def foo():
    def bar() -> int:
        return 1

    print(bar())


foo()

When running with --supress-none-returning:

$ flake8 --suppress-none-returning test.py
test.py:1:11: ANN201 Missing return type annotation for public function

Version Information

$ flake8 --version
3.7.9 (flake8-annotations: 2.0.0, flake8-comprehensions: 3.2.2, flake8-print: 3.1.4, flake8_pep3101: 1.2.1, import-order: 0.18.1, mccabe: 0.6.1, pycodestyle: 2.5.0, pyflakes: 2.1.1) CPython 3.8.1 on Linux

As well as your Python version:

$ python -V
Python 3.8.1

[sco1]

This isn’t a false positive, foo should be annotated here as it implicitly returns None.

[sumnerevans]

Sorry, meant to mention that this happens even when suppress-none-returning = True. I've edited the original description to reflect this.

[sco1]

Well I know why this is happening but it's looking like the fix is going to be challenging.

While the return node visitor approach is an elegant one for most cases, it breaks for nested functions because it is visiting the return nodes without any knowledge of their containing function. In the code snippet above, for example, the return node ends up being visited twice, once for bar, as expected, and the other for foo, since the return node is in the body of the foo function node.

Conceptually, this is simply fixed by skipping nested function nodes, but the actual implementation of the fix doesn't seem to be a simple one.

[sco1]

Hi @sumnerevans, these issues should be fixed now by v2.0.1. Please let us know if we've missed anything!

[sumnerevans]

Thanks for getting to this so quickly! Just upgraded, and this issue appears to be fixed.