fwalk: incorrect boolean test for non-fd arguments

[dubiousjim]

BPO	42053
Nosy	@serhiy-storchaka, @AliyevH, @akulakov
PRs	bpo-42053: fixed fwalk incorrect boolean test for non-fd arguments #27524 bpo-42053: Remove misleading check in os.fwalk() #27669

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2021-08-08.18:04:38.130>
created_at = <Date 2020-10-16.17:31:45.463>
labels = ['type-bug', 'library', '3.11']
title = 'fwalk: incorrect boolean test for non-fd arguments'
updated_at = <Date 2021-08-08.18:04:38.130>
user = 'https://bugs.python.org/dubiousjim'

bugs.python.org fields:

activity = <Date 2021-08-08.18:04:38.130>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2021-08-08.18:04:38.130>
closer = 'serhiy.storchaka'
components = ['Library (Lib)']
creation = <Date 2020-10-16.17:31:45.463>
creator = 'dubiousjim'
dependencies = []
files = []
hgrepos = []
issue_num = 42053
keywords = ['patch']
message_count = 5.0
messages = ['378725', '398676', '398679', '399223', '399226']
nosy_count = 4.0
nosy_names = ['serhiy.storchaka', 'dubiousjim', 'AliyevH', 'andrei.avk']
pr_nums = ['27524', '27669']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue42053'
versions = ['Python 3.11']

[dubiousjim]

[Lib/os.py](https://github.com/python/cpython/blob/main/Lib/os.py) has at line 464, in definition of fwalk:

if not isinstance(top, int) or not hasattr(top, '__index__'):

If I understand this test correctly, it should be requiring that the name/fd is NEITHER an int NOR has an __index__ method. As written, anything which fails the left-hand side (and so is an int) will probably have an __index__ method, so the right-hand side is idle.

Proposed fix: change or to and.

[akulakov]

dubiousjim: I agree, it should be and or have the form not (isinstance(..) or hasattr(..)).

If you would like to make the patch, I can review.

[akulakov]

By the way I confirmed that fixing this doesn't break any tests (perhaps unsurprising ;) )

[serhiy-storchaka]

I confirm that fwalk() does not support integer first argument. This check is misleading.

[serhiy-storchaka]

New changeset 2b496e7 by Serhiy Storchaka in branch 'main':
bpo-42053: Remove misleading check in os.fwalk() (GH-27669)
2b496e7