Only adapt the separators for the non-current fs

pyfakefs/fake_pathlib.py

@@ -62,12 +62,18 @@ def init_module(filesystem):
         # but points to the os-specific path module (posixpath/ntpath)
         fake_posix_os = FakeOsModule(filesystem)
         fake_posix_path = fake_posix_os.path
+        if filesystem.is_windows_fs:
+            # The POSIX path separators must be set if running under Windows
+            fake_posix_path.sep = "/"
+            fake_posix_path.altsep = None
+        fake_posix_path = fake_posix_os.path
         FakePathlibModule.PurePosixPath._flavour = fake_posix_path
-        # The Windows path separators must be customized.
         fake_nt_os = FakeOsModule(filesystem)
         fake_nt_path = fake_nt_os.path
-        fake_nt_path.sep = "\\"
-        fake_nt_path.altsep = "/"
+        if not filesystem.is_windows_fs:
+            # The Windows path separators must be set if running under POSIX
+            fake_nt_path.sep = "\\"
+            fake_nt_path.altsep = "/"
         FakePathlibModule.PureWindowsPath._flavour = fake_nt_path
 
 
@@ -399,10 +405,11 @@ class _FakeWindowsFlavour(_FakeFlavour):
 
         def __init__(self, *args, **kwargs):
             super().__init__(*args, **kwargs)
-            # Because this class is used with pure Windows paths,
+            # If this class is used with pure Windows paths under POSIX,
             # the separators must be filesystem-independent.
-            self.sep = "\\"
-            self.altsep = "/"
+            if not self.filesystem.is_windows_fs:
+                self.sep = "\\"
+                self.altsep = "/"
 
         def is_reserved(self, parts):
             """Return True if the path is considered reserved under Windows."""
@@ -480,6 +487,14 @@ class _FakePosixFlavour(_FakeFlavour):
 
         pathmod = posixpath
 
+        def __init__(self, *args, **kwargs):
+            super().__init__(*args, **kwargs)
+            # If this class is used with pure POSIX paths under Windows,
+            # the separators must be filesystem-independent.
+            if self.filesystem.is_windows_fs:
+                self.sep = "/"
+                self.altsep = None
+
         def is_reserved(self, parts):
             return False
 

pyfakefs/pytest_tests/pytest_reload_pandas_test.py

@@ -4,23 +4,23 @@
 
 from pathlib import Path
 
-import pandas as pd
 import pytest
 
 try:
+    import pandas as pd
     import parquet
 except ImportError:
     parquet = None
 
 
-@pytest.mark.skipif(parquet is None, reason="parquet not installed")
+@pytest.mark.skipif(parquet is None, reason="pandas or parquet not installed")
 def test_1(fs):
     dir_ = Path(__file__).parent / "data"
     fs.add_real_directory(dir_)
     pd.read_parquet(dir_ / "test.parquet")
 
 
-@pytest.mark.skipif(parquet is None, reason="parquet not installed")
+@pytest.mark.skipif(parquet is None, reason="pandas or parquet not installed")
 def test_2():
     dir_ = Path(__file__).parent / "data"
     pd.read_parquet(dir_ / "test.parquet")

pyfakefs/tests/fake_pathlib_test.py

@@ -1296,12 +1296,21 @@ def test_windows_pure_path_parsing(self):
             pathlib.PureWindowsPath(path).stem,
         )
 
-        path = r"C:/Windows/cmd.exe"
+        path = "C:/Windows/cmd.exe"
         self.assertEqual(
             fake_pathlib.FakePathlibModule.PureWindowsPath(path).stem,
             pathlib.PureWindowsPath(path).stem,
         )
 
+    def test_posix_pure_path_parsing(self):
+        """Verify faked pure POSIX paths use filesystem-independent separators."""
+
+        path = "/foo/bar"
+        self.assertEqual(
+            fake_pathlib.FakePathlibModule.PurePosixPath(path).stem,
+            pathlib.PurePosixPath(path).stem,
+        )
+
 
 if __name__ == "__main__":
     unittest.main(verbosity=2)