GNU bug report logs - #79979
timeout-throttle initial return value

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Juri Linkov <juri <at> linkov.net>
To: bug-gnu-emacs <at> gnu.org
Subject: timeout-throttle initial return value
Date: Wed, 10 Dec 2025 09:16:04 +0200

[Message part 1 (text/plain, inline)]

This recipe demonstrates that unexpectedly 'timeout-throttle'
returns nil on the first call, contrary to its specification:

  (require 'timeout)
  (setq func (timeout-throttled-func (lambda () 1) 10))
  (funcall func) => nil
  (funcall func) => 1

This is because 'prog1' in 'timeout-throttled-func' causes it
to return nil on the first call.  Here is the fix:

[timeout-throttle-result.patch (text/x-diff, inline)]

diff --git a/lisp/emacs-lisp/timeout.el b/lisp/emacs-lisp/timeout.el
index 2b90650f02a..cf8a81a4f44 100644
--- a/lisp/emacs-lisp/timeout.el
+++ b/lisp/emacs-lisp/timeout.el
@@ -82,7 +82,7 @@ timeout--throttle-advice
         (result))
     (lambda (orig-fn &rest args)
       "Throttle calls to this function."
-      (prog1 result
+      (progn
         (unless (and throttle-timer (timerp throttle-timer))
           (setq result (apply orig-fn args))
           (setq throttle-timer
@@ -90,7 +90,8 @@ timeout--throttle-advice
                  (timeout--eval-value timeout-value) nil
                  (lambda ()
                    (cancel-timer throttle-timer)
-                   (setq throttle-timer nil)))))))))
+                   (setq throttle-timer nil)))))
+        result))))
 
 (defun timeout--debounce-advice (&optional delay default)
   "Return a function that debounces its argument function.
@@ -182,7 +183,7 @@ timeout-throttled-func
             "\n\nThrottle calls to this function"))
           (interactive (advice-eval-interactive-spec
                         (cadr (interactive-form func))))
-          (prog1 result
+          (progn
             (unless (and throttle-timer (timerp throttle-timer))
               (setq result (apply func args))
               (setq throttle-timer
@@ -190,14 +191,15 @@ timeout-throttled-func
                      (timeout--eval-value throttle-value) nil
                      (lambda ()
                        (cancel-timer throttle-timer)
-                       (setq throttle-timer nil)))))))
+                       (setq throttle-timer nil)))))
+            result))
       ;; NON-INTERACTIVE version
       (lambda (&rest args)
         (:documentation
          (concat
           (documentation func)
           "\n\nThrottle calls to this function"))
-        (prog1 result
+        (progn
           (unless (and throttle-timer (timerp throttle-timer))
             (setq result (apply func args))
             (setq throttle-timer
@@ -205,7 +207,8 @@ timeout-throttled-func
                    (timeout--eval-value throttle-value) nil
                    (lambda ()
                      (cancel-timer throttle-timer)
-                     (setq throttle-timer nil))))))))))
+                     (setq throttle-timer nil)))))
+          result)))))
 
 (defun timeout-debounced-func (func &optional delay default)
   "Return a debounced version of function FUNC.

Message #8 received at 79979 <at> debbugs.gnu.org (full text, mbox):

From: Karthik Chikmagalur <karthikchikmagalur <at> gmail.com>
To: Juri Linkov <juri <at> linkov.net>, 79979 <at> debbugs.gnu.org
Subject: Re: bug#79979: timeout-throttle initial return value
Date: Wed, 10 Dec 2025 00:02:23 -0800

> This is because 'prog1' in 'timeout-throttled-func' causes it
> to return nil on the first call.  Here is the fix:

Thank you Juri.  I have tested and applied the fix upstream, at
https://github.com/karthink/timeout.

Karthik

Message #11 received at 79979 <at> debbugs.gnu.org (full text, mbox):

From: Juri Linkov <juri <at> linkov.net>
To: Karthik Chikmagalur <karthikchikmagalur <at> gmail.com>
Cc: 79979 <at> debbugs.gnu.org
Subject: Re: bug#79979: timeout-throttle initial return value
Date: Wed, 10 Dec 2025 19:38:19 +0200

close 79979 31.0.50
thanks

>> This is because 'prog1' in 'timeout-throttled-func' causes it
>> to return nil on the first call.  Here is the fix:
>
> Thank you Juri.  I have tested and applied the fix upstream, at
> https://github.com/karthink/timeout.

Thanks for confirming.  So now pushed to the Emacs repo as well.

BTW, I also added ###autoload to 4 entry points of the package.

Message #16 received at 79979 <at> debbugs.gnu.org (full text, mbox):

From: Karthik Chikmagalur <karthikchikmagalur <at> gmail.com>
To: Juri Linkov <juri <at> linkov.net>
Cc: 79979 <at> debbugs.gnu.org
Subject: Re: bug#79979: timeout-throttle initial return value
Date: Wed, 10 Dec 2025 12:23:13 -0800

> BTW, I also added ###autoload to 4 entry points of the package.

Not autoloading these functions was intentional.  One of the Elisp
linters included with Emacs, perhaps package-lint, complains that only
interactive commands should be autoloaded.  So I assumed that this was
the official practice.

Karthik

Message #19 received at 79979 <at> debbugs.gnu.org (full text, mbox):

From: Juri Linkov <juri <at> linkov.net>
To: Karthik Chikmagalur <karthikchikmagalur <at> gmail.com>
Cc: 79979 <at> debbugs.gnu.org
Subject: Re: bug#79979: timeout-throttle initial return value
Date: Thu, 11 Dec 2025 09:03:39 +0200

>> BTW, I also added ###autoload to 4 entry points of the package.
>
> Not autoloading these functions was intentional.  One of the Elisp
> linters included with Emacs, perhaps package-lint, complains that only
> interactive commands should be autoloaded.  So I assumed that this was
> the official practice.

'package-lint--check-autoloads-on-private-functions' warns only
about autoloaded internal functions with "--" in their names.
While even package-lint.el has many non-interactive functions autoloaded.

Message #22 received at 79979 <at> debbugs.gnu.org (full text, mbox):

From: Karthik Chikmagalur <karthikchikmagalur <at> gmail.com>
To: Juri Linkov <juri <at> linkov.net>
Cc: 79979 <at> debbugs.gnu.org
Subject: Re: bug#79979: timeout-throttle initial return value
Date: Wed, 10 Dec 2025 23:11:29 -0800

>> Not autoloading these functions was intentional.  One of the Elisp
>> linters included with Emacs, perhaps package-lint, complains that only
>> interactive commands should be autoloaded.  So I assumed that this was
>> the official practice.
>
> 'package-lint--check-autoloads-on-private-functions' warns only
> about autoloaded internal functions with "--" in their names.
> While even package-lint.el has many non-interactive functions autoloaded.

Ah, that makes sense, thanks.  I knew that Emacs autoloads a bunch of
noninteractive functions, like in the seq library.

Karthik

Message #25 received at 79979 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Karthik Chikmagalur <karthikchikmagalur <at> gmail.com>
Cc: 79979 <at> debbugs.gnu.org, juri <at> linkov.net
Subject: Re: bug#79979: timeout-throttle initial return value
Date: Thu, 11 Dec 2025 09:49:03 +0200

> Cc: 79979 <at> debbugs.gnu.org
> From: Karthik Chikmagalur <karthikchikmagalur <at> gmail.com>
> Date: Wed, 10 Dec 2025 12:23:13 -0800
> 
> > BTW, I also added ###autoload to 4 entry points of the package.
> 
> Not autoloading these functions was intentional.  One of the Elisp
> linters included with Emacs, perhaps package-lint, complains that only
> interactive commands should be autoloaded.  So I assumed that this was
> the official practice.

No, there's no official practice in place which says that only
interactive commands should be autoloaded.  If you look at our
sources, you will find that our practice is very far from that, and
for good reasons.

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