AFAIK Python never hides stdlib codelines in tracebacks.
Why we should start to do it in asyncio?
On Tue, Nov 14, 2017 at 4:54 PM Mark E. Haase <meha...@gmail.com> wrote:
> If an exception is thrown while the `asyncio` event loop is running, the
> stack trace is pretty complicated. Here's an example:
>
> Traceback (most recent call last):
> File "sample_client.py", line 616, in <module>
> loop.run_until_complete(main_task)
> File "/usr/lib/python3.6/asyncio/base_events.py", line 437, in
> run_until_complete
> self.run_forever()
> File "/usr/lib/python3.6/asyncio/base_events.py", line 405, in
> run_forever
> self._run_once()
> File "/usr/lib/python3.6/asyncio/base_events.py", line 1382, in
> _run_once
> handle._run()
> File "/usr/lib/python3.6/asyncio/events.py", line 126, in _run
> self._callback(*self._args)
> File "/usr/lib/python3.6/asyncio/tasks.py", line 315, in _wakeup
> self._step()
> File "/usr/lib/python3.6/asyncio/tasks.py", line 239, in _step
> result = coro.send(None)
> File "sample_client.py", line 319, in main
> await actions[args.action](args, socket)
> File "/usr/lib/python3.6/asyncio/coroutines.py", line 105, in
> __next__
> return self.gen.send(None)
> File "sample_client.py", line 558, in sync_job
> await asyncio.sleep(args.delay)
> File "/usr/lib/python3.6/asyncio/coroutines.py", line 105, in
> __next__
> return self.gen.send(None)
> File "/usr/lib/python3.6/asyncio/tasks.py", line 522, in sleep
> future, result)
> File "/usr/lib/python3.6/asyncio/base_events.py", line 525, in
> call_later
> timer = self.call_at(self.time() + delay, callback, *args)
> File "/usr/lib/python3.6/asyncio/base_events.py", line 541, in
> call_at
> timer = events.TimerHandle(when, callback, args, self)
> File "/usr/lib/python3.6/asyncio/events.py", line 148, in __init__
> super().__init__(callback, args, loop)
> File "/usr/lib/python3.6/asyncio/events.py", line 92, in __init__
> self._source_traceback = traceback.extract_stack(sys._getframe(1))
> File "/usr/lib/python3.6/traceback.py", line 207, in extract_stack
> stack = StackSummary.extract(walk_stack(f), limit=limit)
> File "/usr/lib/python3.6/traceback.py", line 352, in extract
> filename, lineno, name, lookup_line=False, locals=f_locals))
> KeyboardInterrupt
>
> Most of the stack frames are inside asyncio (_run, _wakeup, _step) and
> reveal the mechanics of the event loop. The stack trace would be a lot
> easier to read (and more similar to a stack trace of an equivalent
> synchronous program) if it looked like this:
>
> Traceback (most recent call last):
> File "sample_client.py", line 616, in <module>
> loop.run_until_complete(main_task)
> ...
> File "sample_client.py", line 319, in main
> await actions[args.action](args, socket)
> ...
> File "sample_client.py", line 558, in sync_job
> await asyncio.sleep(args.delay)
> KeyboardInterrupt
>
> I recognize that the event loop mechanics are probably useful in some
> circumstances, but in my experience working with asyncio for the last year,
> I've found the stack traces are generally too noisy. For a while, I was
> pasting stack traces into a text editor and cleaning them up by hand, but a
> few months ago I wrote a custom excepthook that generates stack traces
> similar to the one above.
>
> def async_excepthook(type_, exc, tb):
> cause_exc = None
> cause_str = None
>
> if exc.__cause__ is not None:
> cause_exc = exc.__cause__
> cause_str = 'The above exception was the direct cause ' \
> 'of the following exception:'
> elif exc.__context__ is not None and not exc.__suppress_context__:
> cause_exc = exc.__context__
> cause_str = 'During handling of the above exception, ' \
> 'another exception occurred:'
>
> if cause_exc:
> async_excepthook(type(cause_exc), cause_exc,
> cause_exc.__traceback__)
>
> if cause_str:
> print('\n{}\n'.format(cause_str))
>
> print('Async Traceback (most recent call last):')
> for frame in traceback.extract_tb(tb):
> head, tail = os.path.split(frame.filename)
> if (head.endswith('asyncio') or tail == 'traceback.py') and \
> frame.name.startswith('_'):
> print(' ...')
> continue
> print(' File "{}", line {}, in {}'
> .format(frame.filename, frame.lineno, frame.name))
> print(' {}'.format(frame.line))
> print('{}: {}'.format(type_.__name__, exc))
>
> The meat of it is towards the bottom, "if
> head.endswith('asyncio')..."There are a lot of debatable details and this
> implementation is pretty hacky and clumsy, but I have found it valuable in
> my own usage, and I haven't yet missed the omitted stack frames.
>
> I'm posting here to get constructive criticism on the concept and would
> also like to hear if Curio or Trio have done anything like this. (Based on
> a quick skim of the docs, I don't think they are.) I might publish a PyPI
> package if anybody is interested.
>
> Cheers,
> Mark
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>
--
Thanks,
Andrew Svetlov
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