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bluetech opened this issue Nov 13, 2020 · 2 comments · Fixed by #4768
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threading: ExceptHookArgs funkiness #4767

bluetech opened this issue Nov 13, 2020 · 2 comments · Fixed by #4768

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

@srittau
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srittau commented Nov 13, 2020

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`.

bluetech added a commit to bluetech/typeshed that referenced this issue Nov 14, 2020
@bluetech
threading: fix ExceptHookArgs being a function instead of a type
ff9e037 
The previous typing meant `threading.ExceptHookArgs` could not be used
to type a value.

The new typing follows what cpython does in the happy path (`_thread`
exists rather than the pure-python fallback being used).

Fixes python#4767.
@bluetech bluetech mentioned this issue Nov 14, 2020
Merged
bluetech added a commit to bluetech/typeshed that referenced this issue Nov 14, 2020
@bluetech
threading: fix ExceptHookArgs being a function instead of a type
0b94a3e 
The previous typing meant `threading.ExceptHookArgs` could not be used
to type a value.

The new typing follows what cpython does in the happy path (`_thread`
exists rather than the pure-python fallback being used).

Fixes python#4767.
srittau pushed a commit that referenced this issue Nov 14, 2020
@bluetech
threading: fix ExceptHookArgs being a function instead of a type (#4768)
27a45df 
The previous typing meant `threading.ExceptHookArgs` could not be used
to type a value.

The new typing follows what cpython does in the happy path (`_thread`
exists rather than the pure-python fallback being used).

Fixes #4767.
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threading: fix ExceptHookArgs being a function instead of a type bluetech/typeshed
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@srittau @bluetech @hauntsaninja