path_info: don't forget to override as_posix method

dvc/path_info.py

@@ -36,6 +36,15 @@ def __new__(cls, *args):
     def from_posix(cls, s):
         return cls(PosixPathInfo(s))
 
+    def as_posix(self):
+        f = self._flavour
+        # Unlike original implementation [1] that uses `str()` we actually need
+        # to use `fspath`, because we've overriden `__str__` method to return
+        # relative paths, which will break original `as_posix`.
+        #
+        # [1] https://github.com/python/cpython/blob/v3.7.0/Lib/pathlib.py#L692
+        return self.fspath.replace(f.sep, "/")
+
     def __str__(self):
         path = self.__fspath__()
         return relpath(path)
@@ -94,10 +103,6 @@ def __fspath__(self):  # noqa: F811
         def with_name(self, name):
             return pathlib.PurePath.with_name(self, name.encode(fs_encoding))
 
-        def as_posix(self):
-            f = self._flavour
-            return str(self).replace(f.sep, "/")
-
 
 class WindowsPathInfo(PathInfo, pathlib.PureWindowsPath):
     pass

tests/unit/test_path_info.py

@@ -1,7 +1,11 @@
 import pytest
 import copy
 
-from dvc.path_info import URLInfo, CloudURLInfo
+from dvc.utils.compat import pathlib
+from dvc.path_info import PathInfo, URLInfo, CloudURLInfo
+
+
+TEST_DEPTH = len(pathlib.Path(__file__).parents) + 1
 
 
 @pytest.mark.parametrize("cls", [URLInfo, CloudURLInfo])
@@ -42,3 +46,32 @@ def test_url_info_deepcopy(cls):
     u1 = cls("ssh://user@test.com:/test1/test2/test3")
     u2 = copy.deepcopy(u1)
     assert u1 == u2
+
+
+@pytest.mark.parametrize(
+    "path, as_posix, osname",
+    [
+        ("/some/abs/path", "/some/abs/path", "posix"),
+        ("some/rel/path", "some/rel/path", "posix"),
+        ("../some/rel/path", "../some/rel/path", "posix"),
+        ("windows\\relpath", "windows/relpath", "nt"),
+        ("..\\windows\\rel\\path", "../windows/rel/path", "nt"),
+        # These ones are to test that no matter how layered this relpath is,
+        # we don't accidentally round it over. E.g. how
+        #
+        #  import os
+        #  os.chdir("/")
+        #  os.path.relpath("../../path")
+        #
+        # results in "path".
+        ("\\".join([".."] * TEST_DEPTH), "/".join([".."] * TEST_DEPTH), "nt"),
+        (
+            "/".join([".."] * TEST_DEPTH),
+            "/".join([".."] * TEST_DEPTH),
+            "posix",
+        ),
+    ],
+)
+def test_path_info_as_posix(mocker, path, as_posix, osname):
+    mocker.patch("os.name", osname)
+    assert PathInfo(path).as_posix() == as_posix