Issues with handling the -W option

[serhiy-storchaka]

BPO	39056
Nosy	@serhiy-storchaka, @miss-islington
PRs	bpo-39056: Fix handling invalid warning category in the -W option. #17618 [3.8] bpo-39056: Fix handling invalid warning category in the -W option. (GH-17618) #17831 [3.7] bpo-39056: Fix handling invalid warning category in the -W option. (GH-17618) #17832

^{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 2020-01-05.13:33:25.031>
created_at = <Date 2019-12-15.18:43:32.999>
labels = ['3.7', '3.8', 'type-bug', 'library', '3.9']
title = 'Issues with handling the -W option'
updated_at = <Date 2020-01-05.13:33:25.030>
user = 'https://github.com/serhiy-storchaka'

bugs.python.org fields:

activity = <Date 2020-01-05.13:33:25.030>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2020-01-05.13:33:25.031>
closer = 'serhiy.storchaka'
components = ['Library (Lib)']
creation = <Date 2019-12-15.18:43:32.999>
creator = 'serhiy.storchaka'
dependencies = []
files = []
hgrepos = []
issue_num = 39056
keywords = ['patch']
message_count = 4.0
messages = ['358439', '359333', '359338', '359339']
nosy_count = 2.0
nosy_names = ['serhiy.storchaka', 'miss-islington']
pr_nums = ['17618', '17831', '17832']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue39056'
versions = ['Python 3.7', 'Python 3.8', 'Python 3.9']

[serhiy-storchaka]

There are some issues with handling the -W option:

1. A traceback is printed for some invalid category names.

$ ./python -Wignore::0
'import warnings' failed; traceback:
Traceback (most recent call last):
  File "/home/serhiy/py/cpython/Lib/warnings.py", line 542, in <module>
    _processoptions(sys.warnoptions)
  File "/home/serhiy/py/cpython/Lib/warnings.py", line 208, in _processoptions
    _setoption(arg)
  File "/home/serhiy/py/cpython/Lib/warnings.py", line 224, in _setoption
    category = _getcategory(category)
  File "/home/serhiy/py/cpython/Lib/warnings.py", line 271, in _getcategory
    if not issubclass(cat, Warning):
TypeError: issubclass() arg 1 must be a class

$ ./python -Wignore::0a 
'import warnings' failed; traceback:
Traceback (most recent call last):
  File "/home/serhiy/py/cpython/Lib/warnings.py", line 542, in <module>
    _processoptions(sys.warnoptions)
  File "/home/serhiy/py/cpython/Lib/warnings.py", line 208, in _processoptions
    _setoption(arg)
  File "/home/serhiy/py/cpython/Lib/warnings.py", line 224, in _setoption
    category = _getcategory(category)
  File "/home/serhiy/py/cpython/Lib/warnings.py", line 256, in _getcategory
    cat = eval(category)
  File "<string>", line 1
    0a
     ^
SyntaxError: unexpected EOF while parsing

$ ./python -Wignore::=
'import warnings' failed; traceback:
Traceback (most recent call last):
  File "/home/serhiy/py/cpython/Lib/warnings.py", line 542, in <module>
    _processoptions(sys.warnoptions)
  File "/home/serhiy/py/cpython/Lib/warnings.py", line 208, in _processoptions
    _setoption(arg)
  File "/home/serhiy/py/cpython/Lib/warnings.py", line 224, in _setoption
    category = _getcategory(category)
  File "/home/serhiy/py/cpython/Lib/warnings.py", line 264, in _getcategory
    m = __import__(module, None, None, [klass])
ValueError: Empty module name

In normal case Python just complains:

$ ./python -Wignore::unknown
Invalid -W option ignored: unknown warning category: 'unknown'

2. For non-ascii warning names Python complains about a module and strips the last character:

$ ./python -Wignore::Wärning
Invalid -W option ignored: invalid module name: 'Wärnin'

3. The re module is always imported is the -W option is used, even if this is not needed.

[serhiy-storchaka]

New changeset 41ec17e by Serhiy Storchaka in branch 'master':
bpo-39056: Fix handling invalid warning category in the -W option. (GH-17618)
41ec17e

[miss-islington]

New changeset e1caa49 by Miss Islington (bot) in branch '3.8':
bpo-39056: Fix handling invalid warning category in the -W option. (GH-17618)
e1caa49

[miss-islington]

New changeset 43fbc70 by Miss Islington (bot) in branch '3.7':
bpo-39056: Fix handling invalid warning category in the -W option. (GH-17618)
43fbc70