sys.executable generating canonical path

[alvesjnr]

BPO	14088
Nosy	@pitrou, @vstinner, @ned-deily, @merwok, @akheron, @iritkatriel
Files	canonical_path.diff sys_executable_realpath.patch

^{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 = None
closed_at = None
created_at = <Date 2012-02-22.16:36:56.658>
labels = ['type-bug', 'library', '3.9', '3.10', '3.11']
title = 'sys.executable generating canonical path'
updated_at = <Date 2021-08-31.21:58:44.018>
user = 'https://bugs.python.org/alvesjnr'

bugs.python.org fields:

activity = <Date 2021-08-31.21:58:44.018>
actor = 'vstinner'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2012-02-22.16:36:56.658>
creator = 'alvesjnr'
dependencies = []
files = ['24604', '24607']
hgrepos = []
issue_num = 14088
keywords = ['patch']
message_count = 15.0
messages = ['153970', '153993', '154008', '154009', '154010', '154012', '154015', '154019', '154108', '154448', '400435', '400618', '400619', '400651', '400787']
nosy_count = 7.0
nosy_names = ['pitrou', 'vstinner', 'ned.deily', 'eric.araujo', 'petri.lehtinen', 'alvesjnr', 'iritkatriel']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue14088'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']

[alvesjnr]

Hi all,

As it is my first time here, I'll try to explay step-by-step why I'm providing this path, and why I think that it is changing something that I believe that is not correct.

First of all, I was trying to run one individual test, as the dev guide says:

./python -m test -v test_sys

but, instead of run this test from the root directory of the project, I run it from ./Lib/test, so I did:

../../python -m test -v test_sys

and it returned an error. The reason is that my sys.executable was not an abspath. When I went to see why it is different, I get this value to sys.executable:

sys.executable -> '/home/antonio/Projects/cpython/Lib/test/../../python'

I'm not sure if I'm thinking write, but for me don't look nice to have this value as sys.executable, once the real path should be:

'/home/antonio/Projects/cpython/python'

So I'm providing a paatch that do exactly this.

Hope you enjoy

[pitrou]

This is unfortunately wrong since it will fail in the face of symlinks.
(if "foo" is a symlink to another directory, then "foo/../bar" is not the same thing as "bar")

[vstinner]

We can use realpath() if the function is available. Something similar is already done for sys.argv[0]. We should also use GetFullPathNameW() on Windows.

[vstinner]

See also the issue bpo-13402.

[pitrou]

We can use realpath() if the function is available. Something similar
is already done for sys.argv[0]. We should also use GetFullPathNameW()
on Windows.

GetFullPathName() is an abspath() equivalent. For realpath() you want
GetFinalPathNameByHandle(), aka. _nt.getfinalpathname().

[vstinner]

GetFullPathName() is an abspath() equivalent. For realpath() you
want GetFinalPathNameByHandle(), aka. _nt.getfinalpathname().

Ah? ntpath.realpath() uses nt._getfullpathname(). Is it a bug in ntpath?

[pitrou]

Ah? ntpath.realpath() uses nt._getfullpathname(). Is it a bug in ntpath?

Probably:

# realpath is a no-op on systems without islink support
realpath = abspath

[vstinner]

> Is it a bug in ntpath?
Probably

Ok, I opened the issue bpo-14094.

[merwok]

I wonder if the doc for sys.executable should mention that .. segments may be present.

[akheron]

Éric Araujo wrote:

I wonder if the doc for sys.executable should mention that ..
segments may be present.

Once this is fixed, it should say that .. segments may be present if
there's realpath() is not available.

[iritkatriel]

This is still unresolved:

iritkatriel@Irits-MBP Lib % pwd
/Users/iritkatriel/src/cpython-1/Lib
iritkatriel@Irits-MBP Lib % ../python.exe -m test -v test_sys

[snipped]

======================================================================
FAIL: test_executable (test.test_sys.SysModuleTest)
----------------------------------------------------------------------

Traceback (most recent call last):
  File "/Users/iritkatriel/src/cpython-1/Lib/test/test_sys.py", line 692, in test_executable
    self.assertEqual(os.path.abspath(sys.executable), sys.executable)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: '/Users/iritkatriel/src/cpython-1/python.exe' != '/Users/iritkatriel/src/cpython-1/Lib/../python.exe'
- /Users/iritkatriel/src/cpython-1/python.exe
+ /Users/iritkatriel/src/cpython-1/Lib/../python.exe
?                                  +++++++