Issue #19887: Improve the Path.resolve() algorithm to support certain symlink chains.
Original patch by Serhiy.
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@ -254,42 +254,47 @@ class _PosixFlavour(_Flavour):
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def resolve(self, path):
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sep = self.sep
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def split(p):
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return [x for x in p.split(sep) if x]
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def absparts(p):
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# Our own abspath(), since the posixpath one makes
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# the mistake of "normalizing" the path without resolving the
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# symlinks first.
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if not p.startswith(sep):
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return split(os.getcwd()) + split(p)
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else:
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return split(p)
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parts = absparts(str(path))[::-1]
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accessor = path._accessor
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resolved = cur = ""
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symlinks = {}
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while parts:
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part = parts.pop()
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cur = resolved + sep + part
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if cur in symlinks and symlinks[cur] <= len(parts):
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# We've already seen the symlink and there's not less
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# work to do than the last time.
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raise RuntimeError("Symlink loop from %r" % cur)
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try:
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target = accessor.readlink(cur)
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except OSError as e:
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if e.errno != EINVAL:
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raise
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# Not a symlink
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resolved = cur
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else:
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# Take note of remaining work from this symlink
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symlinks[cur] = len(parts)
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if target.startswith(sep):
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# Symlink points to absolute path
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resolved = ""
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parts.extend(split(target)[::-1])
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return resolved or sep
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seen = {}
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def _resolve(path, rest):
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if rest.startswith(sep):
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path = ''
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for name in rest.split(sep):
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if not name or name == '.':
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# current dir
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continue
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if name == '..':
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# parent dir
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path, _, _ = path.rpartition(sep)
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continue
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newpath = path + sep + name
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if newpath in seen:
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# Already seen this path
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path = seen[newpath]
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if path is not None:
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# use cached value
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continue
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# The symlink is not resolved, so we must have a symlink loop.
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raise RuntimeError("Symlink loop from %r" % newpath)
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# Resolve the symbolic link
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try:
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target = accessor.readlink(newpath)
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except OSError as e:
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if e.errno != EINVAL:
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raise
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# Not a symlink
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path = newpath
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else:
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seen[newpath] = None # not resolved symlink
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path = _resolve(path, target)
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seen[newpath] = path # resolved symlink
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return path
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# NOTE: according to POSIX, getcwd() cannot contain path components
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# which are symlinks.
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base = '' if path.is_absolute() else os.getcwd()
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return _resolve(base, str(path)) or sep
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def is_reserved(self, parts):
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return False
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@ -1620,6 +1620,59 @@ class _BasePathTest(object):
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# 'bin'
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self.assertIs(p.parts[2], q.parts[3])
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def _check_complex_symlinks(self, link0_target):
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# Test solving a non-looping chain of symlinks (issue #19887)
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P = self.cls(BASE)
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self.dirlink(os.path.join('link0', 'link0'), join('link1'))
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self.dirlink(os.path.join('link1', 'link1'), join('link2'))
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self.dirlink(os.path.join('link2', 'link2'), join('link3'))
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self.dirlink(link0_target, join('link0'))
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# Resolve absolute paths
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p = (P / 'link0').resolve()
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self.assertEqual(p, P)
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self.assertEqual(str(p), BASE)
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p = (P / 'link1').resolve()
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self.assertEqual(p, P)
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self.assertEqual(str(p), BASE)
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p = (P / 'link2').resolve()
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self.assertEqual(p, P)
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self.assertEqual(str(p), BASE)
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p = (P / 'link3').resolve()
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self.assertEqual(p, P)
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self.assertEqual(str(p), BASE)
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# Resolve relative paths
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old_path = os.getcwd()
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os.chdir(BASE)
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try:
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p = self.cls('link0').resolve()
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self.assertEqual(p, P)
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self.assertEqual(str(p), BASE)
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p = self.cls('link1').resolve()
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self.assertEqual(p, P)
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self.assertEqual(str(p), BASE)
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p = self.cls('link2').resolve()
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self.assertEqual(p, P)
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self.assertEqual(str(p), BASE)
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p = self.cls('link3').resolve()
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self.assertEqual(p, P)
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self.assertEqual(str(p), BASE)
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finally:
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os.chdir(old_path)
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@with_symlinks
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def test_complex_symlinks_absolute(self):
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self._check_complex_symlinks(BASE)
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@with_symlinks
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def test_complex_symlinks_relative(self):
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self._check_complex_symlinks('.')
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@with_symlinks
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def test_complex_symlinks_relative_dot_dot(self):
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self._check_complex_symlinks(os.path.join('dirA', '..'))
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class PathTest(_BasePathTest, unittest.TestCase):
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cls = pathlib.Path
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