configparser.ConfigParser.read() has undocumented/unexpected behaviour when given a bytestring path.

[DavidCEllis]

BPO	29627
Nosy	@ambv, @DavidCEllis
PRs	bpo-31307: Allow use of bytes object as a single argument in ConfigParser.read #3420
Superseder	bpo-31307: ConfigParser.read silently fails if filenames argument is a byte string

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

Show more details

GitHub fields:

assignee = None
closed_at = <Date 2017-09-05.17:52:56.707>
created_at = <Date 2017-02-23.00:08:04.932>
labels = ['3.7', 'type-bug', 'library']
title = 'configparser.ConfigParser.read() has undocumented/unexpected behaviour when given a bytestring path.'
updated_at = <Date 2017-09-07.12:06:28.067>
user = 'https://github.com/DavidCEllis'

bugs.python.org fields:

activity = <Date 2017-09-07.12:06:28.067>
actor = 'vxgmichel'
assignee = 'none'
closed = True
closed_date = <Date 2017-09-05.17:52:56.707>
closer = 'lukasz.langa'
components = ['Library (Lib)']
creation = <Date 2017-02-23.00:08:04.932>
creator = 'David Ellis'
dependencies = []
files = []
hgrepos = []
issue_num = 29627
keywords = []
message_count = 1.0
messages = ['288394']
nosy_count = 2.0
nosy_names = ['lukasz.langa', 'David Ellis']
pr_nums = ['3420']
priority = 'normal'
resolution = 'duplicate'
stage = 'resolved'
status = 'closed'
superseder = '31307'
type = 'behavior'
url = 'https://bugs.python.org/issue29627'
versions = ['Python 3.5', 'Python 3.6', 'Python 3.7']

[DavidCEllis]

Related:
#242
https://bugs.python.org/issue29623

In the discussion over my PR for bpo-29623 it became clear that bytestring paths were also unsupported and it was suggested that that should be a separate issue (currently the PR adds checks for both types).

There is some possible odd behaviour as when given a bytestring path the method attempts to open the integer file descriptors for each character in the bytestring. This will most likely fail silently but if it does find an actual file descriptor it will attempt to read and then close the file.

Example from the discussion on the PR:

>>> import os
>>> import configparser
>>> k = os.open('/home/david/develop/cpython/Lib/test/cfgparser.1', os.O_RDONLY)
>>> k
3
>>> c = configparser.ConfigParser()
>>> c.read(b'\x03') 
[3]
>>> list(c)
['DEFAULT', 'Foo Bar']
>>> os.close(k)  # File has already been closed
OSError: [Errno 9] Bad file descriptor

Currently bytestrings do work correctly when provided as part of a list.