subprocess.Popen(..., env={}) fails to pass empty env.

[Yhg1s]

BPO	12383
Nosy	@Yhg1s, @gpshead, @vstinner, @ned-deily, @bitdancer
PRs	bpo-12383: Refactor subprocess test_empty_env #1874 bpo-12383: subprocess test_empty_env typo fix. #1877 bpo-12383: Also ignore __PYVENV_LAUNCHER__ #3278
Files	subprocess.diff.txt: subprocess.diff

^{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/gpshead'
closed_at = <Date 2017-05-30.23:34:55.810>
created_at = <Date 2011-06-21.14:36:01.494>
labels = ['type-bug', 'library']
title = 'subprocess.Popen(..., env={}) fails to pass empty env.'
updated_at = <Date 2017-09-04.04:00:24.461>
user = 'https://github.com/Yhg1s'

bugs.python.org fields:

activity = <Date 2017-09-04.04:00:24.461>
actor = 'ned.deily'
assignee = 'gregory.p.smith'
closed = True
closed_date = <Date 2017-05-30.23:34:55.810>
closer = 'gregory.p.smith'
components = ['Library (Lib)']
creation = <Date 2011-06-21.14:36:01.494>
creator = 'twouters'
dependencies = []
files = ['22419']
hgrepos = []
issue_num = 12383
keywords = ['patch', 'needs review']
message_count = 19.0
messages = ['138787', '138788', '138789', '138790', '138791', '138792', '138794', '138796', '138797', '138798', '138800', '138831', '138837', '138867', '294789', '294793', '294797', '294799', '301205']
nosy_count = 7.0
nosy_names = ['twouters', 'gregory.p.smith', 'vstinner', 'ned.deily', 'Arfrever', 'r.david.murray', 'python-dev']
pr_nums = ['1874', '1877', '3278']
priority = 'high'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue12383'
versions = ['Python 3.2', 'Python 3.3']

[Yhg1s]

The addition of the _posixsubprocess module in 3.2 introduced a change of behaviour when passing an empty dict (or other false value besides None) as env:

python3.1 -c 'import subprocess; print(subprocess.Popen(["env"], env={}, stdout=subprocess.PIPE).communicate())'
(b'', None)

python3.2 -c 'import subprocess; print(subprocess.Popen(["env"], env={}, stdout=subprocess.PIPE).communicate())'
(b'LC_MONETARY=C\nSHELL=/bin/bash\nTERM=scr....', None)

The test for 'env' being the default (None) is not explicit enough.

[python-dev]

New changeset b5963fceddad by Victor Stinner in branch '3.2':
Close bpo-12383: Fix subprocess module with env={}: don't copy the environment
http://hg.python.org/cpython/rev/b5963fceddad

New changeset 10ecf8576eb2 by Victor Stinner in branch 'default':
(merge 3.2) Close bpo-12383: Fix subprocess module with env={}: don't copy the
http://hg.python.org/cpython/rev/10ecf8576eb2

[vstinner]

The addition of the _posixsubprocess module in 3.2 introduced
a change of behaviour when passing an empty dict
(or other false value besides None) as env: ...

This bug was introduced by the commit (768722b2ae0a) introducing _posixsubprocess.

[vstinner]

Thanks for the fix, I added an unit test.

[bitdancer]

The test appears to be failing on the buildbots:

http://www.python.org/dev/buildbot/all/builders/x86%20Ubuntu%20Shared%203.2/builds/370

[gpshead]

That failure is likely due to the environment being empty causing the subprocess to be unable to run. Notice this error message further up:

test_empty_env (test.test_subprocess.ContextManagerTests) ... /srv/buildbot/buildarea/3.2.bolen-ubuntu/build/python: error while loading shared libraries: libpython3.2dm.so.1.0: cannot open shared object file: No such file or directory
FAIL

Looking at the environment at the top of the buildbot run log I'm not sure what it would be.

[vstinner]

On Mac OS X, the failure is different:

======================================================================
FAIL: test_empty_env (test.test_subprocess.ProcessTestCase)
----------------------------------------------------------------------

Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.parc-tiger-1/build/Lib/test/test_subprocess.py", line 400, in test_empty_env
    self.assertEqual(stdout.strip(), b"0")
AssertionError: b'1' != b'0'

http://www.python.org/dev/buildbot/all/builders/PPC%20Tiger%203.x/builds/2059/steps/test/logs/stdio

[Arfrever]

Maybe test_empty_env() should pass LD_LIBRARY_PATH to child process.

[python-dev]

New changeset 8d46e84cd812 by Victor Stinner in branch '3.2':
Issue bpo-12383: skip test_empty_env() if compiled is compiled in shared mode
http://hg.python.org/cpython/rev/8d46e84cd812

[python-dev]

New changeset d1d5a7392e39 by Victor Stinner in branch 'default':
(merge 3.2) Issue bpo-12383: skip test_empty_env() if compiled is compiled in
http://hg.python.org/cpython/rev/d1d5a7392e39