Allow users to subclass FileLock with custom keyword arguments

[hmaarrfk]

Without this patch:

=============================================== FAILURES ===============================================
______________________________ test_subclass_compatibility[UnixFileLock] _______________________________

lock_type = <class 'filelock._unix.UnixFileLock'>

    @pytest.mark.parametrize("lock_type", [FileLock, SoftFileLock])
    def test_subclass_compatibility(lock_type):
        class MyFileLock(lock_type):
            def __init__(self, *args, my_param=None, **kwargs):
                pass
    
>       MyFileLock(my_param=1)
E       TypeError: BaseFileLock.__new__() got an unexpected keyword argument 'my_param'

tests/test_filelock.py:622: TypeError
______________________________ test_subclass_compatibility[SoftFileLock] _______________________________

lock_type = <class 'filelock._soft.SoftFileLock'>

    @pytest.mark.parametrize("lock_type", [FileLock, SoftFileLock])
    def test_subclass_compatibility(lock_type):
        class MyFileLock(lock_type):
            def __init__(self, *args, my_param=None, **kwargs):
                pass
    
>       MyFileLock(my_param=1)
E       TypeError: BaseFileLock.__new__() got an unexpected keyword argument 'my_param'

tests/test_filelock.py:622: TypeError
======================================= short test summary info ========================================

Resolves the unstated issues in the comment: #282 (comment)

[hmaarrfk]

With the updated test:

______________________________ test_subclass_compatibility[UnixFileLock] _______________________________

lock_type = <class 'filelock._unix.UnixFileLock'>
tmp_path = PosixPath('/tmp/pytest-of-mark/pytest-1/test_subclass_compatibility_Un0')

    @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)
E       TypeError: BaseFileLock.__new__() got an unexpected keyword argument 'my_param'

tests/test_filelock.py:628: TypeError
______________________________ test_subclass_compatibility[SoftFileLock] _______________________________

lock_type = <class 'filelock._soft.SoftFileLock'>
tmp_path = PosixPath('/tmp/pytest-of-mark/pytest-1/test_subclass_compatibility_So0')

    @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)
E       TypeError: BaseFileLock.__new__() got an unexpected keyword argument 'my_param'

tests/test_filelock.py:628: TypeError
======================================= short test summary info ========================================
FAILED tests/test_filelock.py::test_subclass_compatibility[UnixFileLock] - TypeError: BaseFileLock.__new__() got an unexpected keyword argument 'my_param'
FAILED tests/test_filelock.py::test_subclass_compatibility[SoftFileLock] - TypeError: BaseFileLock.__new__() got an unexpected keyword argument 'my_param'
========================================== 2 failed in 0.12s ===========================================

[hmaarrfk]

Thank you for your consideration

[hmaarrfk]

hmm. the cis were running. now they are not.

strange. do they need to be approved one at a time for me???

[gaborbernat]

What's your use case for subclassing?

[hmaarrfk]

I guess I had an implementation of #192 a while back (this got merged in in 2022, but we have had our own class since 2020)
https://github.com/ramonaoptics/python-multiuserfilelock/

and at the time we decided to use subclasses. We have since learned that subclassing creates these kinds of potential issues and we have generally moved away from using new subclasses. However this code is still in use today.

[hmaarrfk]

your help resolving the mypy issues would be greatly appreciated.

[gaborbernat]

[hmaarrfk]

thank you for the fast review

[hmaarrfk]

and for the fast release

[tornaria]

Note the added test gives a PytestUnraisableExceptionWarning:

=============================== warnings summary ===============================
tests/test_filelock.py::test_subclass_compatibility
  /usr/lib/python3.12/site-packages/_pytest/unraisableexception.py:78: PytestUnraisableExceptionWarning: Exception ignored in: <function BaseFileLock.__del__ at 0x7fc8f0cda0c0>
  
  Traceback (most recent call last):
    File "/builddir/python3-filelock-3.13.1/.xbps-testdir/1705527530/usr/lib/python3.12/site-packages/filelock/_api.py", line 317, in __del__
      self.release(force=True)
    File "/builddir/python3-filelock-3.13.1/.xbps-testdir/1705527530/usr/lib/python3.12/site-packages/filelock/_api.py", line 280, in release
      if self.is_locked:
         ^^^^^^^^^^^^^^
    File "/builddir/python3-filelock-3.13.1/.xbps-testdir/1705527530/usr/lib/python3.12/site-packages/filelock/_api.py", line 190, in is_locked
      return self._context.lock_file_fd is not None
             ^^^^^^^^^^^^^
  AttributeError: 'MySoftFileLock' object has no attribute '_context'
  
    warnings.warn(pytest.PytestUnraisableExceptionWarning(msg))

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
================== 83 passed, 20 skipped, 1 warning in 14.57s ==================

You need to call the parent class __init__, for instance:

--- a/tests/test_filelock.py
+++ b/tests/test_filelock.py
@@ -624,7 +624,8 @@ def test_subclass_compatibility(tmp_path: Path) -> None:
             my_param: int = 0,
             **kwargs: dict[str, Any],
         ) -> None:
-            pass
+            FileLock.__init__(self, lock_file, timeout, mode,
+                              thread_local, **kwargs)
 
     lock_path = tmp_path / "a"
     MyFileLock(str(lock_path), my_param=1)
@@ -639,7 +640,8 @@ def test_subclass_compatibility(tmp_path: Path) -> None:
             my_param: int = 0,
             **kwargs: dict[str, Any],
         ) -> None:
-            pass
+            SoftFileLock.__init__(self, lock_file, timeout, mode,
+                                  thread_local, **kwargs)
 
     MySoftFileLock(str(lock_path), my_param=1)