Re: Calling internal-default-process-sentinel from another sentinel?

[Stefan Monnier <monnier@iro.umontreal.ca>]

>>> 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