threading: ExceptHookArgs funkiness

[bluetech]

The threading.excepthook variable (added in Python 3.8) accepts a threading.ExceptHookArgs argument (available at runtime). The typing around it in typeshed is not straightforward:

typeshed/stdlib/2and3/threading.pyi

Lines 157 to 164 in 8c20938

	if sys.version_info >= (3, 8):
	import _thread
	# don't ask...
	_ExceptHookArgs = _thread.ExceptHookArgs
	ExceptHookArgs = _thread._ExceptHookArgs
	excepthook: Callable[[_ExceptHookArgs], Any]

Sorry but I guess I have to ask 😀

The _thread part is:

typeshed/stdlib/3/_thread.pyi

Lines 30 to 38 in 8c20938

	if sys.version_info >= (3, 8):
	def get_native_id() -> int: ... # only available on some platforms
	class ExceptHookArgs(NamedTuple):
	exc_type: Type[BaseException]
	exc_value: Optional[BaseException]
	exc_traceback: Optional[TracebackType]
	thread: Optional[Thread]
	def _ExceptHookArgs(args: Any) -> ExceptHookArgs: ...
	_excepthook: Callable[[ExceptHookArgs], Any]

My practical issue is that this:

import threading

def my_hook(args: threading.ExceptHookArgs) -> None:
    ...

results in

Function "_thread._ExceptHookArgs" is not valid as a type  [valid-type]

[hauntsaninja]

I believe this goes back to #3358 , cc @srittau

[srittau]

What I a useful comment I left there. The stubs try to follow the implementation (starting here) and I guess I wanted to express my consternation about the weird renaming going on there. That said, I don't think the stubs are accurate. _threading contains the namedtuple _ExceptHookArgs (although the docstrings refer to it as ExceptHookArgs). This gets imported into typing.pyi as ExceptHookArgs` (making the docstrings correct).

(In case _thread is not available, threading does some weird things, but I think we should ignore that.)

What we should probably do:

• _thread.pyi:
  • Remove _ExceptHookArgs.
  • Rename ExceptHookArgs to _ExceptHookArgs.
  • Change the argument type of _excepthook to _ExceptHookArgs.
• threading.pyi:
  • Remove the import of _thread.ExceptHookArgs.
  • Change the argument type of excepthook to _ExceptHookArgs`.