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bpo-35755: shutil.which() uses os.confstr("CS_PATH") (GH-12858) 

shutil.which() and distutils.spawn.find_executable() now use
os.confstr("CS_PATH") if available instead of os.defpath, if the PATH
environment variable is not set.

Don't use os.confstr("CS_PATH") nor os.defpath if the PATH
environment variable is set to an empty string to mimick Unix 'which'
command behavior.

Changes:

* find_executable() now starts by checking for the executable in the
  current working directly case. Add an explicit
  "if not path: return None".
* Add tests for PATH='' (empty string), PATH=':' and for PATHEXT.
This commit is contained in:
Victor Stinner 2019-04-17 16:26:36 +02:00 committed by GitHub
parent 71ce03df9c
commit 228a3c99bd
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
5 changed files with 155 additions and 18 deletions
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39
Lib/distutils/spawn.py
View File

@ -172,21 +172,32 @@ def find_executable(executable, path=None):
A string listing directories separated by 'os.pathsep'; defaults to
os.environ['PATH']. Returns the complete filename or None if not found.
"""
if path is None:
path = os.environ.get('PATH', os.defpath)
paths = path.split(os.pathsep)
base, ext = os.path.splitext(executable)
_, ext = os.path.splitext(executable)
if (sys.platform == 'win32') and (ext != '.exe'):
executable = executable + '.exe'
if not os.path.isfile(executable):
for p in paths:
f = os.path.join(p, executable)
if os.path.isfile(f):
# the file exists, we have a shot at spawn working
return f
return None
else:
if os.path.isfile(executable):
return executable
if path is None:
path = os.environ.get('PATH', None)
if path is None:
try:
path = os.confstr("CS_PATH")
except (AttributeError, ValueError):
# os.confstr() or CS_PATH is not available
path = os.defpath
# bpo-35755: Don't use os.defpath if the PATH environment variable is
# set to an empty string to mimick Unix which command behavior
# PATH='' doesn't match, whereas PATH=':' looks in the current directory
if not path:
return None
paths = path.split(os.pathsep)
for p in paths:
f = os.path.join(p, executable)
if os.path.isfile(f):
# the file exists, we have a shot at spawn working
return f
return None

47
Lib/distutils/tests/test_spawn.py
View File

@ -87,11 +87,52 @@ class SpawnTestCase(support.TempdirManager,
rv = find_executable(dont_exist_program , path=tmp_dir)
self.assertIsNone(rv)
# test os.defpath: missing PATH environment variable
# PATH='': no match, except in the current directory
with test_support.EnvironmentVarGuard() as env:
with mock.patch('distutils.spawn.os.defpath', tmp_dir):
env.pop('PATH')
env['PATH'] = ''
with unittest.mock.patch('distutils.spawn.os.confstr',
return_value=tmp_dir, create=True), \
unittest.mock.patch('distutils.spawn.os.defpath',
tmp_dir):
rv = find_executable(program)
self.assertIsNone(rv)
# look in current directory
with test_support.change_cwd(tmp_dir):
rv = find_executable(program)
self.assertEqual(rv, program)
# PATH=':': explicitly looks in the current directory
with test_support.EnvironmentVarGuard() as env:
env['PATH'] = os.pathsep
with unittest.mock.patch('distutils.spawn.os.confstr',
return_value='', create=True), \
unittest.mock.patch('distutils.spawn.os.defpath', ''):
rv = find_executable(program)
self.assertIsNone(rv)
# look in current directory
with test_support.change_cwd(tmp_dir):
rv = find_executable(program)
self.assertEqual(rv, program)
# missing PATH: test os.confstr("CS_PATH") and os.defpath
with test_support.EnvironmentVarGuard() as env:
env.pop('PATH', None)
# without confstr
with unittest.mock.patch('distutils.spawn.os.confstr',
side_effect=ValueError,
create=True), \
unittest.mock.patch('distutils.spawn.os.defpath',
tmp_dir):
rv = find_executable(program)
self.assertEqual(rv, filename)
# with confstr
with unittest.mock.patch('distutils.spawn.os.confstr',
return_value=tmp_dir, create=True), \
unittest.mock.patch('distutils.spawn.os.defpath', ''):
rv = find_executable(program)
self.assertEqual(rv, filename)

13
Lib/shutil.py
View File

@ -1309,9 +1309,20 @@ def which(cmd, mode=os.F_OK | os.X_OK, path=None):
use_bytes = isinstance(cmd, bytes)
if path is None:
path = os.environ.get("PATH", os.defpath)
path = os.environ.get("PATH", None)
if path is None:
try:
path = os.confstr("CS_PATH")
except (AttributeError, ValueError):
# os.confstr() or CS_PATH is not available
path = os.defpath
# bpo-35755: Don't use os.defpath if the PATH environment variable is
# set to an empty string to mimick Unix which command behavior
# PATH='' doesn't match, whereas PATH=':' looks in the current directory
if not path:
return None
if use_bytes:
path = os.fsencode(path)
path = path.split(os.fsencode(os.pathsep))

68
Lib/test/test_shutil.py
View File

@ -1619,6 +1619,57 @@ class TestWhich(unittest.TestCase):
rv = shutil.which(self.file)
self.assertEqual(rv, self.temp_file.name)
def test_environ_path_empty(self):
# PATH='': no match
with support.EnvironmentVarGuard() as env:
env['PATH'] = ''
with unittest.mock.patch('os.confstr', return_value=self.dir, \
create=True), \
support.swap_attr(os, 'defpath', self.dir), \
support.change_cwd(self.dir):
rv = shutil.which(self.file)
self.assertIsNone(rv)
def test_environ_path_cwd(self):
expected_cwd = os.path.basename(self.temp_file.name)
if sys.platform == "win32":
curdir = os.curdir
if isinstance(expected_cwd, bytes):
curdir = os.fsencode(curdir)
expected_cwd = os.path.join(curdir, expected_cwd)
# PATH=':': explicitly looks in the current directory
with support.EnvironmentVarGuard() as env:
env['PATH'] = os.pathsep
with unittest.mock.patch('os.confstr', return_value=self.dir, \
create=True), \
support.swap_attr(os, 'defpath', self.dir):
rv = shutil.which(self.file)
self.assertIsNone(rv)
# look in current directory
with support.change_cwd(self.dir):
rv = shutil.which(self.file)
self.assertEqual(rv, expected_cwd)
def test_environ_path_missing(self):
with support.EnvironmentVarGuard() as env:
env.pop('PATH', None)
# without confstr
with unittest.mock.patch('os.confstr', side_effect=ValueError, \
create=True), \
support.swap_attr(os, 'defpath', self.dir):
rv = shutil.which(self.file)
self.assertEqual(rv, self.temp_file.name)
# with confstr
with unittest.mock.patch('os.confstr', return_value=self.dir, \
create=True), \
support.swap_attr(os, 'defpath', ''):
rv = shutil.which(self.file)
self.assertEqual(rv, self.temp_file.name)
def test_empty_path(self):
base_dir = os.path.dirname(self.dir)
with support.change_cwd(path=self.dir), \
@ -1633,6 +1684,23 @@ class TestWhich(unittest.TestCase):
rv = shutil.which(self.file)
self.assertIsNone(rv)
@unittest.skipUnless(sys.platform == "win32", 'test specific to Windows')
def test_pathext(self):
ext = ".xyz"
temp_filexyz = tempfile.NamedTemporaryFile(dir=self.temp_dir,
prefix="Tmp2", suffix=ext)
os.chmod(temp_filexyz.name, stat.S_IXUSR)
self.addCleanup(temp_filexyz.close)
# strip path and extension
program = os.path.basename(temp_filexyz.name)
program = os.path.splitext(program)[0]
with support.EnvironmentVarGuard() as env:
env['PATHEXT'] = ext
rv = shutil.which(program, path=self.temp_dir)
self.assertEqual(rv, temp_filexyz.name)
class TestWhichBytes(TestWhich):
def setUp(self):

6
Misc/NEWS.d/next/Library/2019-04-16-17-50-39.bpo-35755.Fg4EXb.rst Normal file
View File

@ -0,0 +1,6 @@
:func:`shutil.which` and :func:`distutils.spawn.find_executable` now use
``os.confstr("CS_PATH")`` if available instead of :data:`os.defpath`, if the
``PATH`` environment variable is not set. Moreover, don't use
``os.confstr("CS_PATH")`` nor :data:`os.defpath` if the ``PATH`` environment
variable is set to an empty string to mimick Unix ``which`` command
behavior.