PYTHONCASEOK is ignored on Windows

[eryksun]

BPO	27083
Nosy	@brettcannon, @rhettinger, @pfmoore, @tjguk, @brianherman, @vadmium, @zware, @serhiy-storchaka, @eryksun, @zooba

^{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 = 'https://github.com/brettcannon'
closed_at = <Date 2016-07-16.18:20:12.418>
created_at = <Date 2016-05-22.06:45:31.981>
labels = ['easy', 'type-bug', 'library', 'OS-windows']
title = 'PYTHONCASEOK is ignored on Windows'
updated_at = <Date 2016-07-16.18:20:12.417>
user = 'https://github.com/eryksun'

bugs.python.org fields:

activity = <Date 2016-07-16.18:20:12.417>
actor = 'brett.cannon'
assignee = 'brett.cannon'
closed = True
closed_date = <Date 2016-07-16.18:20:12.418>
closer = 'brett.cannon'
components = ['Library (Lib)', 'Windows']
creation = <Date 2016-05-22.06:45:31.981>
creator = 'eryksun'
dependencies = []
files = []
hgrepos = []
issue_num = 27083
keywords = ['easy']
message_count = 13.0
messages = ['266057', '266302', '270227', '270499', '270500', '270506', '270507', '270508', '270509', '270537', '270544', '270576', '270578']
nosy_count = 11.0
nosy_names = ['brett.cannon', 'rhettinger', 'paul.moore', 'tim.golden', 'Brian.Herman', 'python-dev', 'martin.panter', 'zach.ware', 'serhiy.storchaka', 'eryksun', 'steve.dower']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue27083'
versions = ['Python 3.5', 'Python 3.6']

[eryksun]

importlib ignores the PYTHONCASEOK environment variable on Windows. _relax_case checks for b'PYTHONCASEOK' in os.environ, which is never true because os.environ is Unicode. On Windows, _make_relax_case should return a function that instead checks for 'PYTHONCASEOK'.

The following test demonstrates that case-insensitive imports otherwise appear to work correctly in 3.5:

    >>> import sys, importlib, glob
    >>> glob.glob('*.py')
    ['Test.py']

    >>> importlib._bootstrap_external._relax_case()
    False
    >>> import test
    >>> test.__file__
    'C:\\Program Files\\Python35\\lib\\test\\__init__.py'

patched:

    >>> src = "_relax_case = lambda: 'PYTHONCASEOK' in _os.environ"
    >>> exec(src, vars(importlib._bootstrap_external))
    >>> importlib._bootstrap_external._relax_case()
    True
    >>> del sys.modules['test']
    >>> import test
    this is a test
    >>> test.__file__
    'C:\\Temp\\test.py'

It would be better if __file__ were the actual filename "Test.py" instead of "test.py".

[serhiy-storchaka]

Did you forgot to upload a patch?

[brianherman]

In python 3.6 from hg it has been fixed.

>>> glob.glob('*.py')
['setup.py', 'test.py']
>>> import test
>>> test.__file__
'C:\\Users\\brian\\Desktop\\cpython\\test.py'
>>>

[python-dev]

New changeset bedcb9ec3f26 by Brett Cannon in branch '3.5':
Issue bpo-27083: Respect the PYTHONCASEOK environment variable under
https://hg.python.org/cpython/rev/bedcb9ec3f26

New changeset 777da58794ca by Brett Cannon in branch 'default':
Merge for bpo-27083
https://hg.python.org/cpython/rev/777da58794ca

[brettcannon]

I fixed this by simply checking for both b'PYTHONCASEOK' and 'PYTHONCASEOK'. Thanks for the bug report, Eryk!

[serhiy-storchaka]

Comparing bytes with str can emit a warning or raise an exception. Checking for b'PYTHONCASEOK' in os.environ looks as a bug to me.

[brettcannon]

There's no direct comparison to trigger a warning; it's just seeing if a key in a dict exists.

And b'PYTHONCASEOK' is not a bug as that's required for OS X (remember this is technically posix.environ, not os.environ).