Handle cross-mount paths in find_parents

pylsp/_utils.py

@@ -96,7 +96,11 @@ def find_parents(root, path, names):
     # Split the relative by directory, generate all the parent directories, then check each of them.
     # This avoids running a loop that has different base-cases for unix/windows
     # e.g. /a/b and /a/b/c/d/e.py -> ['/a/b', 'c', 'd']
-    dirs = [root] + os.path.relpath(os.path.dirname(path), root).split(os.path.sep)
+    try:
+        dirs = [root] + os.path.relpath(os.path.dirname(path), root).split(os.path.sep)
+    except ValueError:
+        log.warning("Path %r not in %r", path, root)
+        return []
 
     # Search each of /a/b/c, /a/b, /a
     while dirs:

test/test_utils.py

@@ -2,6 +2,7 @@
 # Copyright 2021- Python Language Server Contributors.
 
 import multiprocessing
+import ntpath
 import os
 import sys
 import time
@@ -197,6 +198,19 @@ def test_find_parents(tmpdir) -> None:
     ]
 
 
+def test_find_parents_handles_cross_mount_paths(monkeypatch) -> None:
+    monkeypatch.setattr(_utils.os, "path", ntpath)
+
+    assert (
+        _utils.find_parents(
+            r"\\server\share1",
+            r"\\server\share2\path.py",
+            ["test.cfg"],
+        )
+        == []
+    )
+
+
 def test_merge_dicts() -> None:
     assert _utils.merge_dicts(
         {"a": True, "b": {"x": 123, "y": {"hello": "world"}}},