Re: [RFC] Option to kill `emacs --daemon' when closing the last client frame

[Jim Porter]

On 10/20/2021 5:13 AM, Eli Zaretskii wrote:
> Unlike "other programs", Emacs doesn't aim to support such use
> patterns with the ALTERNATE_EDITOR thing.  It is supposed to allow the
> user to invoke emacsclient without knowing whether a server already
> runs, by starting the server the first time.  That is why we don't
> kill the server when the last client exits: it is against the use case
> we want to support.

My expectation (which is really just personal preference informed by 
other programs I'm used to) is that since `emacs --daemon' is created on 
as-needed basis in this configuration, it would also be killed when it's 
no longer needed. If I wanted `emacs --daemon' to live forever, I'd 
probably just set it up to start when my system boots.

However, I don't know if I can make a particularly compelling argument 
as to why this *should* be how things work, aside from just saying that 
I find the symmetry of this behavior simpler/easier to remember. It's in 
the same vein as a refcounted object in a program (e.g. 
`std::shared_ptr' for C++ programmers): I can make new `emacsclient's, 
which increment the refcount, and once the refcount drops to 0, the 
underlying entity (i.e. the daemon) is automatically cleaned up.

In the end though, it's just what I like / what makes the most sense to 
me. If other people see things similarly, I'd be happy to write a patch, 
but if I'm the only one who wants this, then I can always customize my 
.emacs to my liking instead.

> We could add an optional command-line argument to do what you want,
> but I wonder why would that be useful, when we already have
> kill-emacs.

That's one option, although it might take a bit of work to support that 
(assuming I understand what you mean). As far as I understand how 
ALTERNATE_EDITOR works, there's not an easy way to automatically start 
the Emacs daemon *and* provide it with some extra options. That is, 
ALTERNATE_EDITOR="emacs --daemon --foo" would start the daemon, but 
wouldn't create a client to connect to it.

Another method might be to add an option like 
`daemon-kill-when-no-clients' that defaults to nil. Then after an 
`emacsclient' is killed, we can consult that variable, and if it's true, 
kill the daemon if there are no remaining clients.

- Jim