The tempfile._infer_return_type function cannot infer the type of os.PathLike objects.

[rekyungmin]

BPO	45192
Nosy	@ambv, @miss-islington, @akulakov, @rekyungmin
PRs	bpo-45192: Fix a bug that infers the type of an os.PathLike[bytes] object as str #28323 [3.10] bpo-45192: Fix a bug that infers the type of an os.PathLike[bytes] object as str (GH-28323) #29111 [3.9] bpo-45192: Fix a bug that infers the type of an os.PathLike[bytes] object as str (GH-28323) #29112

^{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 = None
created_at = <Date 2021-09-14.05:44:04.045>
labels = ['type-bug', '3.8', '3.9', '3.10', '3.7', 'library']
title = 'The tempfile._infer_return_type function cannot infer the type of os.PathLike objects.'
updated_at = <Date 2021-10-20.21:27:38.952>
user = 'https://github.com/rekyungmin'

bugs.python.org fields:

activity = <Date 2021-10-20.21:27:38.952>
actor = 'lukasz.langa'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2021-09-14.05:44:04.045>
creator = 'rekyungmin'
dependencies = []
files = []
hgrepos = []
issue_num = 45192
keywords = ['patch']
message_count = 6.0
messages = ['401754', '401755', '404139', '404523', '404528', '404529']
nosy_count = 4.0
nosy_names = ['lukasz.langa', 'miss-islington', 'andrei.avk', 'rekyungmin']
pr_nums = ['28323', '29111', '29112']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue45192'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8', 'Python 3.9', 'Python 3.10']

[rekyungmin]

The tempfile module has been updated to accept an object implementing os.PathLike protocol for path-related parameters as of Python 3.6 (e.g. dir parameter). An os.PathLike object represents a filesystem path as a str or bytes object (i.e. def __fspath__(self) -> Union[str, bytes]:). However, if an object implementing os.PathLike[bytes] is passed as a dir argument, a TypeError is raised. This bug occurs because the tempfile._infer_return_type function considers all objects other than bytes as str type.

[rekyungmin]

for example:

from typing import Union


class FakePath:
    def __init__(self, path):
        self.path = path

    def __fspath__(self) -> Union[str, bytes]:
        return self.path


if __name__ == "__main__":
    from tempfile import TemporaryDirectory

    # You need to create `existing_path` directory

    with TemporaryDirectory(dir=FakePath("existing_path")) as str_path:
        print(str_path)  # 'existing_path/...'

    with TemporaryDirectory(dir=FakePath(b"existing_path")) as byte_path:
        print(byte_path)  # expected b'existing_path/...' but raised TypeError

[akulakov]

This is a duplicate of bpo-29447, so if this is merged, the other issue should also be closed as fixed.

[ambv]

New changeset 6270d3e by Kyungmin Lee in branch 'main':
bpo-45192: Fix a bug that infers the type of an os.PathLike[bytes] object as str (GH-28323)
6270d3e

[ambv]

New changeset d33fae7 by Miss Islington (bot) in branch '3.9':
bpo-45192: Fix a bug that infers the type of an os.PathLike[bytes] object as str (GH-28323) (GH-29112)
d33fae7