Title: pathlib.PurePath.with_suffix() does not allow removing the suffix
Type: behavior Stage: resolved
Components: Library (Lib) Versions: Python 3.5, Python 3.4
Status: closed Resolution: fixed
Dependencies: Superseder:
Assigned To: Nosy List: july, pitrou, python-dev, serhiy.storchaka
Priority: normal Keywords: patch

Created on 2014-02-16 13:28 by july, last changed 2014-07-07 01:39 by pitrou. This issue is now closed.

File name Uploaded Description Edit
pathlib-with_suffix-test.diff july, 2014-02-16 13:28 proposed tests review
pathlib-with_suffix.diff july, 2014-02-16 13:30 proposed fix review
Messages (5)
msg211316 - (view) Author: July Tikhonov (july) * Date: 2014-02-16 13:28
The changeset ef2b2ddd27c8 restricted the argument of Path.with_suffix() too much, and caused some strange behavior.

Case 1: removing suffix completely is disallowed now.
The following code worked before the fix:

>>> pathlib.PurePath('a', 'b.c').with_suffix('')

but now fails with ValueError:

>>> pathlib.PurePath('a', 'b.c').with_suffix('')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/july/source/python/Lib/", line 760, in with_suffix
    raise ValueError("Invalid suffix %r" % (suffix))
ValueError: Invalid suffix ''

It was the only one obvious way of removing the suffix, and I think it should remain so. (BTW: There is a XXX note in the code questioning if Path.with_suffix(None) should remove the suffix.)

Case 2: while the output is now always a correct Path, the suffix can still contain separator.
The following code produced incorrect path before the fix:

>>> pathlib.PurePath('a', 'b.c').with_suffix('./.s/.')
('a', 'b./.s/.')

Now, the produced path is correct, but the code itself is still allowed:

>>> pathlib.PurePath('a', 'b.c').with_suffix('./.s/.')

while I would expect it to fail with ValueError.

Attached: proposed test patch.
msg211317 - (view) Author: July Tikhonov (july) * Date: 2014-02-16 13:30
Proposed patch attached.
msg211766 - (view) Author: Antoine Pitrou (pitrou) * (Python committer) Date: 2014-02-20 23:39
Thank you! Unfortunately, it is too late for 3.4, but I will make sure the fix is included in 3.4.1 (and 3.5).
msg222428 - (view) Author: Roundup Robot (python-dev) Date: 2014-07-07 01:38
New changeset 0d84855861ff by Antoine Pitrou in branch '3.4':
Issue #20639: calling Path.with_suffix('') allows removing the suffix again.
msg222430 - (view) Author: Antoine Pitrou (pitrou) * (Python committer) Date: 2014-07-07 01:39
Sorry for the delay! The patch is now applied. Thank you for contributing!
Date User Action Args
2014-07-07 01:39:34pitrousetstatus: open -> closed
resolution: fixed
messages: + msg222430

stage: patch review -> resolved
2014-07-07 01:38:47python-devsetnosy: + python-dev
messages: + msg222428
2014-02-20 23:39:58pitrousetnosy: + serhiy.storchaka

messages: + msg211766
stage: patch review
2014-02-16 13:30:25julysetfiles: + pathlib-with_suffix.diff

messages: + msg211317
2014-02-16 13:28:50julycreate