bpo-38671: Make sure to return an absolute path in pathlib._WindowsFlavour.resolve()

Lib/pathlib.py

@@ -15,7 +15,7 @@
 
 
 if os.name == 'nt':
- from nt import _getfinalpathname
+ from nt import _getfinalpathname, _getfullpathname
 else:
  _getfinalpathname = None
 
@@ -189,26 +189,26 @@ def compile_pattern(self, pattern):
  def resolve(self, path, strict=False):
  s = str(path)
  if not s:
- return path._accessor.getcwd()
+ s = path._accessor.getcwd()
+ if _getfinalpathname is None:
+ return None # Means fallback on absolute
+ if strict:
+ return self._ext_to_normal(_getfinalpathname(s))
+ s = path = _getfullpathname(s)
  previous_s = None
- if _getfinalpathname is not None:
- if strict:
- return self._ext_to_normal(_getfinalpathname(s))
+ tail_parts = [] # End of the path after the first one not found
+ while True:
+ try:
+ s = self._ext_to_normal(_getfinalpathname(s))
+ except FileNotFoundError:
+ previous_s = s
+ s, tail = os.path.split(s)
+ tail_parts.append(tail)
+ if previous_s == s:
+ # Root reached, fallback to _getfullpathname()
+ return path
  else:
- tail_parts = [] # End of the path after the first one not found
- while True:
- try:
- s = self._ext_to_normal(_getfinalpathname(s))
- except FileNotFoundError:
- previous_s = s
- s, tail = os.path.split(s)
- tail_parts.append(tail)
- if previous_s == s:
- return path
- else:
- return os.path.join(s, *reversed(tail_parts))
- # Means fallback on absolute
- return None
+ return os.path.join(s, *reversed(tail_parts))
 
  def _split_extended_path(self, s, ext_prefix=ext_namespace_prefix):
  prefix = ''

Lib/test/test_pathlib.py

@@ -1799,6 +1799,16 @@ def test_resolve_dot(self):
  # Non-strict
  self.assertEqual(r.resolve(strict=False), p / '3' / '4')
 
+ def test_resolve_nonexist_relative_issue38671(self):
+ p = self.cls('non', 'exist')
+
+ old_cwd = os.getcwd()
+ os.chdir(BASE)
+ try:
+ self.assertEqual(p.resolve(), self.cls(BASE, p))
+ finally:
+ os.chdir(old_cwd)
+
  def test_with(self):
  p = self.cls(BASE)
  it = p.iterdir()

Misc/NEWS.d/next/Library/2019-12-28-02-50-12.bpo-38671.xT4R0P.rst

@@ -0,0 +1,2 @@
+Ensure pathlib.Path.resolve(strict=False) returns an absolute path on
+Windows when the path is relative and does not exist.