Allow users to subclass FileLock with custom keyword arguments

src/filelock/_api.py

@@ -87,6 +87,7 @@ def __new__(  # noqa: PLR0913
         thread_local: bool = True,  # noqa: ARG003, FBT001, FBT002
         *,
         is_singleton: bool = False,
+        **kwargs: dict[str, Any],  # capture remaining kwargs for subclasses  # noqa: ARG003
     ) -> Self:
         """Create a new lock object or if specified return the singleton instance for the lock file."""
         if not is_singleton:

tests/test_filelock.py

@@ -613,6 +613,21 @@ def test_lock_can_be_non_thread_local(
     lock.release(force=True)
 
 
+@pytest.mark.parametrize("lock_type", [FileLock, SoftFileLock])
+def test_subclass_compatibility(lock_type: type[BaseFileLock], tmp_path: Path) -> None:
+    class MyFileLock(lock_type):
+        def __init__(
+            self,
+            *args,  # noqa: ANN002
+            my_param: int = 0,
+            **kwargs,  # noqa: ANN003
+        ) -> None:
+            pass
+
+    lock_path = tmp_path / "a"
+    MyFileLock(str(lock_path), my_param=1)
+
+
 @pytest.mark.parametrize("lock_type", [FileLock, SoftFileLock])
 def test_singleton_and_non_singleton_locks_are_distinct(lock_type: type[BaseFileLock], tmp_path: Path) -> None:
     lock_path = tmp_path / "a"