3.13 support for Windows (#10667)

python/cpython#113829 changed `os.path.isabs` on Windows to not consider a path starting a single backslash to be an absolute path.

We do a lot of naive `posixpath` to `ntpath` conversions, and it broke DVC in multiple places. DVC is likely broken in many other places, and these bugs are difficult to identify.

In this commit, I have tried to fix in the places where the tests failed. And mostly by trying to imitate pre-3.13 behaviour.
Some of the changes may not be correct but keeps the old behaviour in place.

Also re-enabled the CI for all Python versions supported for Windows.

.github/workflows/tests.yaml

@@ -69,6 +69,30 @@ jobs:
         - os: windows-latest
           pyv: "3.9"
           pytestargs: "--splitting-algorithm=least_duration --splits 4 --group 4"
+        - os: windows-latest
+          pyv: "3.10"
+          pytestargs: "--splitting-algorithm=least_duration --splits 4 --group 1"
+        - os: windows-latest
+          pyv: "3.10"
+          pytestargs: "--splitting-algorithm=least_duration --splits 4 --group 2"
+        - os: windows-latest
+          pyv: "3.10"
+          pytestargs: "--splitting-algorithm=least_duration --splits 4 --group 3"
+        - os: windows-latest
+          pyv: "3.10"
+          pytestargs: "--splitting-algorithm=least_duration --splits 4 --group 4"
+        - os: windows-latest
+          pyv: "3.11"
+          pytestargs: "--splitting-algorithm=least_duration --splits 4 --group 1"
+        - os: windows-latest
+          pyv: "3.11"
+          pytestargs: "--splitting-algorithm=least_duration --splits 4 --group 2"
+        - os: windows-latest
+          pyv: "3.11"
+          pytestargs: "--splitting-algorithm=least_duration --splits 4 --group 3"
+        - os: windows-latest
+          pyv: "3.11"
+          pytestargs: "--splitting-algorithm=least_duration --splits 4 --group 4"
         - os: windows-latest
           pyv: "3.12"
           pytestargs: "--splitting-algorithm=least_duration --splits 4 --group 1"
@@ -81,6 +105,18 @@ jobs:
         - os: windows-latest
           pyv: "3.12"
           pytestargs: "--splitting-algorithm=least_duration --splits 4 --group 4"
+        - os: windows-latest
+          pyv: "3.13"
+          pytestargs: "--splitting-algorithm=least_duration --splits 4 --group 1"
+        - os: windows-latest
+          pyv: "3.13"
+          pytestargs: "--splitting-algorithm=least_duration --splits 4 --group 2"
+        - os: windows-latest
+          pyv: "3.13"
+          pytestargs: "--splitting-algorithm=least_duration --splits 4 --group 3"
+        - os: windows-latest
+          pyv: "3.13"
+          pytestargs: "--splitting-algorithm=least_duration --splits 4 --group 4"
     steps:
     - uses: actions/checkout@v4
       with:

dvc/config.py

@@ -1,6 +1,8 @@
 """DVC config objects."""
 
+import ntpath
 import os
+import posixpath
 import re
 from contextlib import contextmanager
 from functools import partial
@@ -268,12 +270,17 @@ class Config(dict):
         if re.match(r"\w+://", path):
             return path
 
+        if os.name == "nt" and posixpath.isabs(path) and ntpath.sep not in path:
+            return path
+
         if os.path.isabs(path):
             return path
 
         # on windows convert slashes to backslashes
         # to have path compatible with abs_conf_dir
         if os.path.sep == "\\" and "/" in path:
+            if path.startswith("/"):
+                path = path.replace("/", "\\\\", 1)
             path = path.replace("/", "\\")
 
         expanded = os.path.expanduser(path)
@@ -305,6 +312,9 @@ class Config(dict):
         if os.path.expanduser(path) != path:
             return localfs.as_posix(path)
 
+        if os.name == "nt" and posixpath.isabs(path) and ntpath.sep not in path:
+            return path
+
         if isinstance(path, RelPath) or not os.path.isabs(path):
             path = relpath(path, conf_dir)
             return localfs.as_posix(path)

dvc/fs/dvc.py

@@ -732,9 +732,10 @@ class DVCFileSystem(FileSystem):
         return self.fs.repo_url
 
     def from_os_path(self, path: str) -> str:
-        if os.path.isabs(path):
+        if os.path.isabs(path) or (
+            os.name == "nt" and posixpath.isabs(path) and ntpath.sep not in path
+        ):
             path = os.path.relpath(path, self.repo.root_dir)
-
         return as_posix(path)
 
     def close(self):

tests/unit/test_ignore.py

@@ -168,8 +168,9 @@ def test_match_ignore_from_file(
 ):
     from dvc.fs import localfs
 
+    root = r"\\" if os.name == "nt" else "/"
     dvcignore_path = os.path.join(
-        os.path.sep, "full", "path", "to", "ignore", "file", ".dvcignore"
+        root, "full", "path", "to", "ignore", "file", ".dvcignore"
     )
     dvcignore_dirname = os.path.dirname(dvcignore_path)