windows: compare Ghostscript versions properly

src/ocrmypdf/subprocess/_windows.py

@@ -6,12 +6,15 @@
 
 import logging
 import os
+import re
 import shutil
 import sys
 from itertools import chain
 from pathlib import Path
 from typing import Any, Callable, Iterable, Iterator, TypeVar
 
+from packaging.version import InvalidVersion, Version
+
 if sys.version_info >= (3, 10):
     from typing import TypeAlias
 else:
@@ -100,6 +103,31 @@ def registry_path_tesseract(env=None) -> Iterator[Path]:
         log.warning(e)
 
 
+def _program_version_in_path_key(path: Path) -> tuple[str, Version | None]:
+    """Key function for comparing Ghostscript and Tesseract paths.
+
+    Ghostscript installs on Windows:
+        %PROGRAMFILES%/gs/gs9.56.1 -> ('gs', Version('9.56.1'))
+        %PROGRAMFILES%/gs/gs9.24 -> ('gs', Version('9.24'))
+
+    Tesseract looks like:
+        %PROGRAMFILES%/Tesseract-OCR -> ('Tesseract-OCR', None)
+
+    Thus ensuring the resulting tuple will order the alternatives correctly,
+    e.g. gs10.0 > gs9.99.
+    """
+    match = re.match(r'([^0-9]+)(.*)', str(path.name))
+    if match:
+        try:
+            program = match.group(1)
+            version_str = match.group(2)
+            version = Version(version_str)
+            return program, version
+        except InvalidVersion:
+            pass
+    return path.name, None
+
+
 def program_files_paths(env=None) -> Iterator[Path]:
     if not env:
         env = os.environ
@@ -117,7 +145,7 @@ def path_walker() -> Iterator[Path]:
     return iter(
         sorted(
             (p for p in path_walker()),
-            key=lambda p: (p.name, p.parent.name),
+            key=_program_version_in_path_key,
             reverse=True,
         )
     )