Fix zpath when passing pathlib.Path

src/monty/os/path.py

@@ -5,6 +5,7 @@
 from __future__ import annotations
 
 import os
+from pathlib import Path
 from typing import TYPE_CHECKING
 
 from monty.fnmatch import WildCard
@@ -14,7 +15,7 @@
     from typing import Callable, Literal, Optional, Union
 
 
-def zpath(filename: str) -> str:
+def zpath(filename: str | Path) -> str:
     """
     Returns an existing (zipped or unzipped) file path given the unzipped
     version. If no path exists, returns the filename unmodified.
@@ -23,10 +24,10 @@ def zpath(filename: str) -> str:
         filename: filename without zip extension
 
     Returns:
-        filename with a zip extension (unless an unzipped version
-        exists). If filename is not found, the same filename is returned
-        unchanged.
+        str: filename with a zip extension (unless an unzipped version exists).
+            If filename is not found, the same filename is returned unchanged.
     """
+    filename = str(filename)  # ensure we work with strings
     exts = ("", ".gz", ".GZ", ".bz2", ".BZ2", ".z", ".Z")
     for ext in exts:
         filename = filename.removesuffix(ext)

tests/test_os.py

@@ -12,17 +12,51 @@
 
 
 class TestPath:
-    def test_zpath(self, tmp_path: Path):
+    def test_zpath_str(self, tmp_path: Path):
         tmp_gz = tmp_path / "tmp.gz"
         tmp_gz.touch()
         ret_path = zpath(str(tmp_gz))
+        assert isinstance(ret_path, str)
         assert ret_path == str(tmp_gz)
 
         tmp_not_bz2 = tmp_path / "tmp_not_bz2"
         tmp_not_bz2.touch()
 
         ret_path = zpath(f"{tmp_not_bz2}.bz2")
         assert ret_path == str(tmp_not_bz2)
+        assert isinstance(ret_path, str)
+
+    def test_zpath_path(self, tmp_path: Path):
+        # Test with Path input
+        tmp_gz = tmp_path / "tmp.gz"
+        tmp_gz.touch()
+        ret_path = zpath(tmp_gz)
+        assert ret_path == str(tmp_gz)
+        assert isinstance(ret_path, str)
+
+    def test_zpath_multiple_extensions(self, tmp_path: Path):
+        exts = ["", ".gz", ".GZ", ".bz2", ".BZ2", ".z", ".Z"]
+        for ext in exts:
+            tmp_file = tmp_path / f"tmp{ext}"
+            # create files with all supported compression extensions
+            tmp_file.touch()
+
+        # zpath should return the file without compression extension
+        ret_path = zpath(tmp_path / "tmp")
+        assert ret_path == str(tmp_path / "tmp")
+        assert isinstance(ret_path, str)
+
+        (tmp_path / "tmp").unlink()  # Remove the uncompressed file
+        ret_path = zpath(tmp_path / "tmp")
+        assert ret_path == str(tmp_path / "tmp.gz")  # should find .gz first now
+
+    def test_zpath_nonexistent_file(self, tmp_path: Path):
+        # should return path as is for non-existent file
+        nonexistent = tmp_path / "nonexistent.txt"
+        ret_path = zpath(nonexistent)
+        assert ret_path == str(nonexistent)
+        ret_path = zpath(f"{nonexistent}.bz2")
+        assert ret_path == str(nonexistent)
 
     def test_find_exts(self):
         assert len(find_exts(MODULE_DIR, "py")) >= 18