CPython issue: https://bugs.python.org/issue26654

Gentle ping. I think the PR is ready.

@hayo can you review and merge this?

sorry, wrong hayo, you probably mean haypo :)

@Haypo

@iceboy-sjtu Could you please sign CPython's contributor agreement?

@1st1 Signed online. Thank you.

@iceboy-sjtu Looking at this PR again -- a quick question: a lot of callable formatting functionality is already implemented as part of inspect.signature API. Would it be possible to just reuse that and drop all formatting logic from asyncio?

@1st1 This is just a quick fix for the issue that the error message includes positional arguments but it does not include keyword arguments which may be misleading. I agree that the original code looks ugly, but let's leave it as is as it does not cause any problem.

btw There are two problems using inspect.signature. Firstly, it does not work on builtin functions such as print, len, repr. It also does not work on any composition that includes these "non-workable functions" by functools.partial.

>>> inspect.signature(print)
ValueError: no signature found for builtin <built-in function print>
>>> inspect.signature(functools.partial(print, 0))
ValueError: no signature found for builtin <built-in function print>

Secondly, it does not recognize functools.partial.

>>> str(inspect.signature(functools.partial(lambda x: x, 0)))
'()'

Firstly, it does not work on builtin functions such as print, len, repr

asyncio can't work with them either. Some builtin functions are just not introspectable yet.

Secondly, it does not recognize functools.partial.

It does. In your example it prints (), which means your callable that does not accept any arguments. But I see the point now -- inspect.signature formats callable objects to show what arguments they can accept, whereas we want to format the function with all its bound arguments. That means we can't use the signature API here...

Acknowledged for inspect.signature. Seems good to merge?

Ping.

Will merge this after beta1.

Merged in b100957. Thanks a lot for fixing this!