bug#22493: 25.1.50; open-gnutls-stream doesn't respect :nowait, so the connections are synchronous

[Eli Zaretskii <eliz@gnu.org>]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Date: Sun, 31 Jan 2016 01:40:51 +0100
> 
> I have now implemented this, but in a slightly different way.  I
> introduced a new process slot to say that we shouldn't be writing yet.
> 
> However, the Lisp part of the implementation is not very satisfactory.
> This is basically it:
> 
>   (let ((process (open-network-stream name buffer host service
>                                       :nowait nowait)))
>     (if nowait
>         (progn
>           (gnutls-mark-process process t)
>           (set-process-sentinel process 'gnutls-async-sentinel)
>           process)
>       (gnutls-negotiate :process (open-network-stream name buffer host service)
>                         :type 'gnutls-x509pki
>                         :hostname host))))
> ...
> 
> (defun gnutls-async-sentinel (process change)
>   (when (string-match "open" change)
>     (gnutls-negotiate :process process
>                       :type 'gnutls-x509pki
>                       :hostname (car (process-contact process)))
>     (gnutls-mark-process process nil)))
> 
> 
> The problem here is that this library is now putting a sentinel on the
> process.  But any callers that want an asynchronous connection will also
> be setting sentinels on the same process, which means that the
> connection sentinel will be overwritten.
> 
> I've kludged this together in one of the callers (in url-http.el), but
> that's too ugly to live.  (It checks for a sentinel and daisy-chains the
> previous one.  Eek.)
> 
> So that has to be rewritten.  But I'm not sure how...  We, like, have
> several layers of possible sentinels here, and...  uhm...

Ahmm... maybe it would have been better to wait until the discussion
completes and reaches some solid conclusions?

> Ideas?

Like I wrote elsewhere, I don't understand what this gives us.  The
sentinel runs in the main thread, so you still wait for the GnuTLS
handshake to complete.  Right?