wildcard imports should normalise names in `__all__`

[christiankolen]

BPO	44981
Nosy	@ericvsmith, @stevendaprano, @serhiy-storchaka, @FFY00

^{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 = None
created_at = <Date 2021-08-22.20:55:35.168>
labels = ['type-feature', '3.11']
title = 'wildcard imports should normalise names in `__all__`'
updated_at = <Date 2021-08-24.02:17:14.953>
user = 'https://bugs.python.org/christiankolen'

bugs.python.org fields:

activity = <Date 2021-08-24.02:17:14.953>
actor = 'steven.daprano'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2021-08-22.20:55:35.168>
creator = 'christian.kolen'
dependencies = []
files = []
hgrepos = []
issue_num = 44981
keywords = []
message_count = 8.0
messages = ['400106', '400110', '400111', '400112', '400143', '400154', '400155', '400193']
nosy_count = 5.0
nosy_names = ['eric.smith', 'steven.daprano', 'serhiy.storchaka', 'FFY00', 'christian.kolen']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue44981'
versions = ['Python 3.11']

[christiankolen]

With Python 3.9.6 on macOS,

In a file all_bug.py,

__all__ = ("ϵ",)
ϵ = "ϵ"

Then run from all_bug import *, resulted in

AttributeError: module 'all_bug' has no attribute 'ϵ'

This happens with some other unicode characters as well, but not all. I can provide them if needed.

Removing the __all__ line will successfully import ϵ and be used.

[ericvsmith]

Python normalizes identifiers with NFKC (see PEP-3131):

>>> e0 = "ϵ"
>>> import unicodedata
>>> e1 = unicodedata.normalize("NFKC", e0)
>>> e0 == e1
False
>>> unicodedata.name(e0)
'GREEK LUNATE EPSILON SYMBOL'
>>> unicodedata.name(e1)
'GREEK SMALL LETTER EPSILON'

If you use GREEK SMALL LETTER EPSILON as your identifier, you should be okay.

[stevendaprano]

Eric, I think you may have been too hasty to close this as "not a bug".

It has tripped people up before. See bpo-41542 which has also been closed (I also think prematurely).

We normalise variable names with NFKC, so we should normalise the values in __all__ as well, at least when doing an import.

Note that this is different from bpo-42680 where the right answer is just to document. We shouldn't normalise strings as dict keys.

[ericvsmith]

I'd be okay with changing it to a 3.11 enhancement to normalize elements of __all__, or maybe a request to change the documentation.

[stevendaprano]

Okay, reopening the ticket with a new description.

from module import * should use the same NFKC normalisation on the names in __all__.

To be clear, I don't propose that __all__ should be modified.