bpo-31938: Fix default-value signatures of several functions in the select module

[asottile]

this appears to have regressed in 6dc57e2

https://bugs.python.org/issue31938

[taleinat]

If this is the proper way to do it, this PR should also fix the default values for poll.register and devpoll.register similarly.

[vstinner]

Oops, I didn't notice that you proposed a PR and so I wrote PR #21067 which is the same fix :-) Copy of my comment there.

inspect.signature() doesn't see the event_mask. Is it a bug in signature which doesn't support a signature written on two lines?

cc @serhiy-storchaka @1st1 @ambv

11:47:01 vstinner@apu$ ./python 
Python 3.10.0a0 (heads/pydoc_select:486e11db95, Jun 23 2020, 11:45:39) 
>>> import select
>>> select.epoll.register.__text_signature__
'($self, /, fd,\n         eventmask=select.EPOLLIN | select.EPOLLPRI | select.EPOLLOUT)'

>>> import inspect
>>> inspect.signature(select.epoll.register)
<Signature (self, /, fd)>

So pydoc doesn't show the whole signature:

./python -m pydoc select
(...)
     |  register(self, /, fd)
     |      Registers a new fd or raises an OSError if the fd is already registered.
     |      
     |        fd
     |          the target file descriptor of the operation
     |        eventmask
     |          a bit set composed of the various EPOLL constants
     |      
     |      The epoll interface supports all file descriptors that support poll.

[vstinner]

If this is the proper way to do it, this PR should also fix the default values for poll.register and devpoll.register similarly.

IMO the fix is correct, so I concur thta the two other functions signature should also be fixed.

By the way, I suggest to rephase the NEWS entry to explain that the change fix the "signature" rather than fixing "pydoc".

[asottile]

I fixed a few others as well -- good catch

[miss-islington]

Thanks @asottile for the PR, and @vstinner for merging it 🌮🎉.. I'm working now to backport this PR to: 3.8, 3.9.
🐍🍒⛏🤖

[miss-islington]

Sorry, @asottile and @vstinner, I could not cleanly backport this to 3.9 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker d051801052211b533c46a593b1c1bccf649a171c 3.9

[miss-islington]

Sorry @asottile and @vstinner, I had trouble checking out the 3.8 backport branch.
Please backport using cherry_picker on command line.
cherry_picker d051801052211b533c46a593b1c1bccf649a171c 3.8

[vstinner]

@asottile: Automated backport failed. Can you try to backport it manually (use cherry_picker or git cherry-pick -x)?

[bedevere-bot]

GH-21097 is a backport of this pull request to the 3.9 branch.

[bedevere-bot]

GH-21098 is a backport of this pull request to the 3.8 branch.

[vstinner]

pydoc doesn't show the eventmask parameter whereas it is in select.epoll.register.text_signature. I created bpo-41095: "inspect.signature() doesn't parse text_signature containing a newline character".