explicit state/hash for pathlib paths

sisyphus/hash.py

@@ -1,5 +1,6 @@
 import enum
 import hashlib
+import pathlib
 from inspect import isclass, isfunction, ismemberdescriptor
 
 
@@ -43,6 +44,13 @@ def get_object_state(obj):
     Comment: Maybe obj.__reduce__() is a better idea? is it stable for hashing?
     """
 
+    if isinstance(obj, pathlib.PurePath):
+        # pathlib paths have a somewhat technical internal state
+        # ('_drv', '_root', '_parts', '_str', '_hash', '_pparts', '_cached_cparts'),
+        # so we don't want to rely on this, but instead just use the string representation as state.
+        # https://github.com/rwth-i6/sisyphus/pull/208#issuecomment-2405560718
+        return str(obj)
+
     if hasattr(obj, "__getnewargs_ex__"):
         args = obj.__getnewargs_ex__()
     elif hasattr(obj, "__getnewargs__"):

tests/hash_unittest.py

@@ -47,6 +47,12 @@ def test_functools_partial(self):
             ),
         )
 
+    def test_pathlib_Path(self):
+        from pathlib import Path
+
+        obj = Path("/etc/passwd")
+        self.assertEqual(sis_hash_helper(obj), b"(PosixPath, (str, '/etc/passwd'))")
+
 
 if __name__ == "__main__":
     unittest.main()