* Calling internal-default-process-sentinel from another sentinel?
@ 2020-11-18 13:28 Štěpán Němec
2020-11-18 14:19 ` Stefan Monnier
0 siblings, 1 reply; 5+ messages in thread
From: Štěpán Němec @ 2020-11-18 13:28 UTC (permalink / raw)
To: emacs-devel
For an asynchronous process I'd like to preserve the default sentinel
behaviour (insert a status message into the process's buffer, if there
is one), and only in one particular case (successful completion) add
some other functionality (follow up with a custom action).
Such a use case doesn't seem uncommon and simply calling
'internal-default-process-sentinel' from a custom sentinel would seem a
good solution, but the "internal-" prefix or the fact that such usage is
completely absent from Emacs core and very rare even in 3rd party
code[1] don't inspire confidence.
I'd appreciate advice or opinions on whether reusing
internal-default-process-sentinel is acceptable or if there are good
alternatives other than emulating its behaviour manually in the custom
sentinel.
Thank you,
Štěpán
[1] As indicated e.g. by https://github.com/search?q=internal-default-process-sentinel+language%3A%22Emacs+Lisp%22&type=Code
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Calling internal-default-process-sentinel from another sentinel?
2020-11-18 13:28 Calling internal-default-process-sentinel from another sentinel? Štěpán Němec
@ 2020-11-18 14:19 ` Stefan Monnier
2020-11-18 14:37 ` Štěpán Němec
0 siblings, 1 reply; 5+ messages in thread
From: Stefan Monnier @ 2020-11-18 14:19 UTC (permalink / raw)
To: Štěpán Němec; +Cc: emacs-devel
> Such a use case doesn't seem uncommon and simply calling
> 'internal-default-process-sentinel' from a custom sentinel would seem a
> good solution, but the "internal-" prefix or the fact that such usage is
> completely absent from Emacs core and very rare even in 3rd party
> code[1] don't inspire confidence.
`add-function` is your friend.
(add-function :around (process-sentinel proc)
(lambda (orig-fun proc state)
(if (one particular case)
(do the thing)
(funcall orig-fun proc state))))
-- Stefan
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Calling internal-default-process-sentinel from another sentinel?
2020-11-18 14:19 ` Stefan Monnier
@ 2020-11-18 14:37 ` Štěpán Němec
2020-11-18 14:44 ` Stefan Monnier
0 siblings, 1 reply; 5+ messages in thread
From: Štěpán Němec @ 2020-11-18 14:37 UTC (permalink / raw)
To: Stefan Monnier; +Cc: emacs-devel
On Wed, 18 Nov 2020 09:19:36 -0500
Stefan Monnier wrote:
>> Such a use case doesn't seem uncommon and simply calling
>> 'internal-default-process-sentinel' from a custom sentinel would seem a
>> good solution, but the "internal-" prefix or the fact that such usage is
>> completely absent from Emacs core and very rare even in 3rd party
>> code[1] don't inspire confidence.
>
> `add-function` is your friend.
>
> (add-function :around (process-sentinel proc)
> (lambda (orig-fun proc state)
> (if (one particular case)
> (do the thing)
> (funcall orig-fun proc state))))
Thanks, I've seen similar examples in the code base, but always advising
an Elisp sentinel, not 'internal-default-process-sentinel', which is a C
function, and IIUC also would/might be called from C (e.g. from
status_notify ?). Or is the actual default sentinel some kind of a
wrapper?
And even for Elisp sentinels, I figured I'd rather avoid advice, as even
when using a self-removing piece of advice, it still applies to all
(even unrelated) calls of the same sentinel function occurring until the
removal. Or am I missing something?
--
Štěpán
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Calling internal-default-process-sentinel from another sentinel?
2020-11-18 14:37 ` Štěpán Němec
@ 2020-11-18 14:44 ` Stefan Monnier
2020-11-18 15:12 ` Štěpán Němec
0 siblings, 1 reply; 5+ messages in thread
From: Stefan Monnier @ 2020-11-18 14:44 UTC (permalink / raw)
To: Štěpán Němec; +Cc: emacs-devel
>>> Such a use case doesn't seem uncommon and simply calling
>>> 'internal-default-process-sentinel' from a custom sentinel would seem a
>>> good solution, but the "internal-" prefix or the fact that such usage is
>>> completely absent from Emacs core and very rare even in 3rd party
>>> code[1] don't inspire confidence.
>>
>> `add-function` is your friend.
>>
>> (add-function :around (process-sentinel proc)
>> (lambda (orig-fun proc state)
>> (if (one particular case)
>> (do the thing)
>> (funcall orig-fun proc state))))
>
> Thanks, I've seen similar examples in the code base, but always advising
> an Elisp sentinel, not 'internal-default-process-sentinel', which is a C
> function, and IIUC also would/might be called from C (e.g. from
> status_notify ?). Or is the actual default sentinel some kind of a
> wrapper?
This is not advising 'internal-default-process-sentinel'. It just
replaces the sentinel by a new function which often delegates to the
previous function, whichever that previous function was and without
affecting that previous function's definition.
> And even for Elisp sentinels, I figured I'd rather avoid advice, as even
> when using a self-removing piece of advice, it still applies to all
> (even unrelated) calls of the same sentinel function occurring until the
> removal. Or am I missing something?
You're confused: this is not an "advice".
Stefan
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Calling internal-default-process-sentinel from another sentinel?
2020-11-18 14:44 ` Stefan Monnier
@ 2020-11-18 15:12 ` Štěpán Němec
0 siblings, 0 replies; 5+ messages in thread
From: Štěpán Němec @ 2020-11-18 15:12 UTC (permalink / raw)
To: Stefan Monnier; +Cc: emacs-devel
On Wed, 18 Nov 2020 09:44:18 -0500
Stefan Monnier wrote:
>>> `add-function` is your friend.
>>>
>>> (add-function :around (process-sentinel proc)
>>> (lambda (orig-fun proc state)
>>> (if (one particular case)
>>> (do the thing)
>>> (funcall orig-fun proc state))))
>>
>> Thanks, I've seen similar examples in the code base, but always advising
>> an Elisp sentinel, not 'internal-default-process-sentinel', which is a C
>> function, and IIUC also would/might be called from C (e.g. from
>> status_notify ?). Or is the actual default sentinel some kind of a
>> wrapper?
>
> This is not advising 'internal-default-process-sentinel'. It just
> replaces the sentinel by a new function which often delegates to the
> previous function, whichever that previous function was and without
> affecting that previous function's definition.
>
>> And even for Elisp sentinels, I figured I'd rather avoid advice, as even
>> when using a self-removing piece of advice, it still applies to all
>> (even unrelated) calls of the same sentinel function occurring until the
>> removal. Or am I missing something?
>
> You're confused: this is not an "advice".
Indeed, I hadn't realized that, even though "(process-sentinel proc)"
above would (before the add-function modification) evaluate to
'internal-default-process-sentinel', using `add-function' on that form
really works through `set-process-sentinel' (via a gv place reference)
and is thus different from advising 'internal-default-process-sentinel'
directly.
Thank you!
--
Štěpán
^ permalink raw reply [flat|nested] 5+ messages in thread
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2020-11-18 13:28 Calling internal-default-process-sentinel from another sentinel? Štěpán Němec
2020-11-18 14:19 ` Stefan Monnier
2020-11-18 14:37 ` Štěpán Němec
2020-11-18 14:44 ` Stefan Monnier
2020-11-18 15:12 ` Štěpán Němec
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