fix(pathlib): avoid zero-inode samefile matches

Author: aryansk

src/_pytest/pathlib.py

@@ -1095,4 +1095,10 @@ def samefile_nofollow(p1: Path, p2: Path) -> bool:
 
     Unlike Path.samefile(), does not resolve symlinks.
     """
-    return os.path.samestat(p1.lstat(), p2.lstat())
+    s1, s2 = p1.lstat(), p2.lstat()
+    # Some network filesystems report a zero inode for every path. In that
+    # case samestat() cannot distinguish different files and would make every
+    # collected path match the requested one.
+    if not s1.st_ino or not s2.st_ino:
+        return False
+    return os.path.samestat(s1, s2)

testing/test_pathlib.py

@@ -39,6 +39,7 @@
 from _pytest.pathlib import resolve_pkg_root_and_module_name
 from _pytest.pathlib import safe_exists
 from _pytest.pathlib import scandir
+from _pytest.pathlib import samefile_nofollow
 from _pytest.pathlib import spec_matches_module_path
 from _pytest.pathlib import symlink_or_skip
 from _pytest.pathlib import visit
@@ -570,6 +571,20 @@ def test_samefile_false_negatives(tmp_path: Path, monkeypatch: MonkeyPatch) -> N
     assert getattr(module, "foo")() == 42
 
 
+@pytest.mark.parametrize("inodes", [(0, 0), (0, 1), (1, 0)])
+def test_samefile_nofollow_rejects_zero_inodes(
+    inodes: tuple[int, int], monkeypatch: MonkeyPatch
+) -> None:
+    stats = [unittest.mock.Mock(st_ino=inode) for inode in inodes]
+    lstat = unittest.mock.Mock(side_effect=stats)
+    samestat = unittest.mock.Mock(return_value=True)
+    monkeypatch.setattr(Path, "lstat", lstat)
+    monkeypatch.setattr(os.path, "samestat", samestat)
+
+    assert not samefile_nofollow(Path("first"), Path("second"))
+    samestat.assert_not_called()
+
+
 def test_scandir_with_non_existent_directory() -> None:
     # Test with a directory that does not exist
     non_existent_dir = "path_to_non_existent_dir"