On Windows os.path.abspath(" ") == " "

While that's not a valid Windows path, similar invalid paths like "" or "?" etc all produce an absolute path.

Tested on 2.7 and 3.6

The generic abspath implementation could be moved into the genericpath module, where it will be common to both posixpath and ntpath:

    def abspath(path):
        """Return an absolute path."""
        path = os.fspath(path)
        if not isabs(path):
            if isinstance(path, bytes):
                cwd = os.getcwdb()
            else:
                cwd = os.getcwd()
            path = join(cwd, path)
        return normpath(path)

Then replace it in ntpath if nt._getfullpathname is defined, but with a fallback to the generic implementation if OSError is raised (e.g. for " "):

try:
    from nt import _getfullpathname
except ImportError:
    pass
else:
    def abspath(path):
        """Return an absolute path."""
        try:
            return _getfullpathname(path)
        except OSError:
            return genericpath.abspath(path)

This _getfullpathname version also skips the redundant fspath and normpath calls.

New changeset d2e902e by Steve Dower (Franz Wöllert) in branch 'master':
bpo-31047: Fix ntpath.abspath for invalid paths (GH-8544)
d2e902e

New changeset 5753b13 by Miss Islington (bot) in branch '3.7':
bpo-31047: Fix ntpath.abspath for invalid paths (GH-8544)
5753b13

New changeset b0bf51b by Steve Dower in branch '3.6':
bpo-31047: Fix ntpath.abspath for invalid paths (GH-8544)
b0bf51b

I think this caused a behavior change:

Before (Python 3.6.6):
>>> from os.path import abspath
>>> abspath('/abc/')
'C:\\abc'

After (Python 3.6.7):
>>> abspath('/abc/')
'C:\\abc\\'

This causes a test failure in Django's safe_join() function: https://github.com/django/django/blob/10d82c85aa5f8bd6adff0db49798dd368455cdcf/django/utils/_os.py#L24-L47

https://github.com/django/django/blob/10d82c85aa5f8bd6adff0db49798dd368455cdcf/tests/utils_tests/test_os_utils.py#L10

Traceback (most recent call last):
  File "C:\Jenkins\workspace\django-windows\database\sqlite3\label\windows\python\Python36\tests\utils_tests\test_os_utils.py", line 10, in test_base_path_ends_with_sep
    drive, path = os.path.splitdrive(safe_join("/abc/", "abc"))
  File "C:\Jenkins\workspace\django-windows\database\sqlite3\label\windows\python\Python36\django\utils\_os.py", line 46, in safe_join
    'component ({})'.format(final_path, base_path))
django.core.exceptions.SuspiciousFileOperation: The joined path (C:\abc\abc) is located outside of the base path component (C:\abc\)

Agreed, it no longer matches os.normpath()'s declared behavior by not trimming the end separator.

It's obviously too late for the current release (I'd hope Django is one of the projects running tests against RC's, but I guess not :( ), but I think we can fix it for the next updates on all versions.

Patches welcome.

New changeset d03b775 by Steve Dower (Tim Graham) in branch 'master':
bpo-31047: Fix ntpath.abspath to trim ending separator (GH-10082)
d03b775

New changeset a7ffb66 by Steve Dower in branch '3.7':
[3.7] bpo-31047: Fix ntpath.abspath to trim ending separator (GH-10082)
a7ffb66

New changeset 4aa1fda by Steve Dower in branch '3.6':
bpo-31047: Fix ntpath.abspath to trim ending separator (GH-10082)
4aa1fda

Thanks, Tim!