bug#63181: 28.2; Can't suppress server-already-running warning

bug#63181: 28.2; Can't suppress server-already-running warning

[Dave Abrahams]

with emacs -Q or emacs -q, you can run

(dlet ((warning-suppress-types '((server))))
  (server-mode))

from the *scratch* buffer, and if a server is already running, you just
get nil.  But: if I put that stanza at the beginning of my early-init.el
(or init.el) and have no other configuration, I get a warning if the
server is already running.

Warning (server): Unable to start the Emacs server.
There is an existing Emacs server, named "server".
To start the server in this Emacs process, stop the existing
server or call ‘M-x server-force-delete’ to forcibly disconnect it. Disable showing Disable logging

It should be possible to suppress this warning programmatically, but I
can't find a way.



In GNU Emacs 28.2 (build 1, x86_64-apple-darwin22.3.0, Carbon Version 169 AppKit 2299.4)
of 2023-03-13 built on DaveMBP16.luannocracy.com
Windowing system distributor 'Apple Inc.', version 13.3.1
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bug#63181: 28.2; Can't suppress server-already-running warning

[Eli Zaretskii]

> From: Dave Abrahams <dave@boostpro.com>
> Date: Sat, 29 Apr 2023 19:27:14 -0700
> 
> with emacs -Q or emacs -q, you can run
> 
> (dlet ((warning-suppress-types '((server))))
>   (server-mode))
> 
> from the *scratch* buffer, and if a server is already running, you just
> get nil.  But: if I put that stanza at the beginning of my early-init.el
> (or init.el) and have no other configuration, I get a warning if the
> server is already running.
> 
> Warning (server): Unable to start the Emacs server.
> There is an existing Emacs server, named "server".
> To start the server in this Emacs process, stop the existing
> server or call ‘M-x server-force-delete’ to forcibly disconnect it. Disable showing Disable logging
> 
> It should be possible to suppress this warning programmatically, but I
> can't find a way.

Why do you let-bind the variable, instead of assigning a value to it?
It's a defcustom, so it is meant to be bound with setq.  You seem to
assume that the warning produced by server-mode will be processed
inside the binding, but that is not true during startup: warnings
emitted during startup are delayed until after the init files are read
and processed, and by that time your let-binding is long gone.

If you, for some reason, insist on doing this with a let-binding, you
will need to move this to after-init-hook or emacs-startup-hook, which
are invoked after loading the init files, and warnings are no longer
delayed.

bug#63181: 28.2; Can't suppress server-already-running warning

[Dave Abrahams]

I let-bind because I don’t want to suppress all server warnings forever, which is what I presume adding ‘sever to the list means ; just this one. Thanks for the explanation 

Sent from my iPhone

> On Apr 29, 2023, at 10:55 PM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
> 
>> 
>> From: Dave Abrahams <dave@boostpro.com>
>> Date: Sat, 29 Apr 2023 19:27:14 -0700
>> 
>> with emacs -Q or emacs -q, you can run
>> 
>> (dlet ((warning-suppress-types '((server))))
>>  (server-mode))
>> 
>> from the *scratch* buffer, and if a server is already running, you just
>> get nil.  But: if I put that stanza at the beginning of my early-init.el
>> (or init.el) and have no other configuration, I get a warning if the
>> server is already running.
>> 
>> Warning (server): Unable to start the Emacs server.
>> There is an existing Emacs server, named "server".
>> To start the server in this Emacs process, stop the existing
>> server or call ‘M-x server-force-delete’ to forcibly disconnect it. Disable showing Disable logging
>> 
>> It should be possible to suppress this warning programmatically, but I
>> can't find a way.
> 
> Why do you let-bind the variable, instead of assigning a value to it?
> It's a defcustom, so it is meant to be bound with setq.  You seem to
> assume that the warning produced by server-mode will be processed
> inside the binding, but that is not true during startup: warnings
> emitted during startup are delayed until after the init files are read
> and processed, and by that time your let-binding is long gone.
> 
> If you, for some reason, insist on doing this with a let-binding, you
> will need to move this to after-init-hook or emacs-startup-hook, which
> are invoked after loading the init files, and warnings are no longer
> delayed.

bug#63181: 28.2; Can't suppress server-already-running warning

[Eli Zaretskii]

> From: Dave Abrahams <dave@boostpro.com>
> Date: Mon, 1 May 2023 08:27:46 -0700
> Cc: 63181@debbugs.gnu.org
> 
> I let-bind because I don’t want to suppress all server warnings forever, which is what I presume adding ‘sever to the list means ; just this one. Thanks for the explanation 

If you want to suppress these warnings only during startup, you can
restore the original value of warning-suppress-types in
emacs-startup-hook.

Did you try my other suggestions? did they work? can we close this bug
report?

bug#63181: 28.2; Can't suppress server-already-running warning

[Dave Abrahams]

> On May 1, 2023, at 8:54 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> From: Dave Abrahams <dave@boostpro.com>
>> Date: Mon, 1 May 2023 08:27:46 -0700
>> Cc: 63181@debbugs.gnu.org
>> 
>> I let-bind because I don’t want to suppress all server warnings forever, which is what I presume adding ‘sever to the list means ; just this one. Thanks for the explanation 
> 
> If you want to suppress these warnings only during startup, you can
> restore the original value of warning-suppress-types in
> emacs-startup-hook.

Saving and restoring this thing manually seems very inelegant compared with allowing `let' to do what it's designed for, and I don't want to globally override 

I should point out that I wasn't presuming that warnings would be issued immediately, only that the setting of warning-suppress-types would be examined in whichever function was responsible for queueing warnings, rather than (only) the code that reports them.

> 
> Did you try my other suggestions? did they work? can we close this bug
> report?

This works for me:

;;
;; Start the server, suppressing warnings
;;
;; I often run a 2nd emacs especially when working on configuration,
;; and I don't like startup to be noisy.  But the suppression doesn't
;; work unless I defer the work because warning processing is
;; deferred until after startup; see
;; https://debbugs.gnu.org/cgi/bugreport.cgi?bug=63181
(add-hook 'emacs-startup-hook
	  (lambda ()
	    (dlet ((warning-suppress-types '((server))))
	      (server-mode))))

Whether to close the bug is up to you of course, but IMO there's still a problem, at *least* in documentation.  Ideally the value of warning-suppress-types should be respected at the time warnings are queued, but if not, the documentation should be updated with a caveat about trying to use it during startup.  But really, who wants more caveats? ;-)

bug#63181: 28.2; Can't suppress server-already-running warning

[Eli Zaretskii]

> From: Dave Abrahams <dave@boostpro.com>
> Date: Mon, 1 May 2023 09:24:10 -0700
> Cc: 63181@debbugs.gnu.org
> 
> > Did you try my other suggestions? did they work? can we close this bug
> > report?
> 
> This works for me:
> 
> ;;
> ;; Start the server, suppressing warnings
> ;;
> ;; I often run a 2nd emacs especially when working on configuration,
> ;; and I don't like startup to be noisy.  But the suppression doesn't
> ;; work unless I defer the work because warning processing is
> ;; deferred until after startup; see
> ;; https://debbugs.gnu.org/cgi/bugreport.cgi?bug=63181
> (add-hook 'emacs-startup-hook
> 	  (lambda ()
> 	    (dlet ((warning-suppress-types '((server))))
> 	      (server-mode))))

That's a good solution, thanks.

> Whether to close the bug is up to you of course, but IMO there's still a problem, at *least* in documentation.  Ideally the value of warning-suppress-types should be respected at the time warnings are queued, but if not, the documentation should be updated with a caveat about trying to use it during startup.  But really, who wants more caveats? ;-)

The documentation was already fixed to mention this caveat and the
proposed solutions, as you will find if you look at the emacs-29
branch of the Emacs Git repository.

More generally, I think it's unreasonable to assume that every
let-binding takes effect for everything that is triggered inside the
body of the binding.  A prominent example where this is not true is
when the body triggers some display-related feature -- the binding
doesn't work in that case because redisplay happens later, after the
command performed its thing and returned to the Emacs main loop.  In
addition, problems during startup are notoriously hard to detect and
debug if their warnings are suppressed, so I think it's completely
okay if suppressing them is not really easy.

So I don't think we have anything else to do here aside of documenting
the fact that warnings are delayed during startup, and so I'm closing
this bug.