Re: async-shell-command and prefix argument

[Eli Zaretskii <eliz@gnu.org>]

> From: Marcin Borkowski <mbork@mbork.pl>
> Cc: Juri Linkov <juri@linkov.net>, emacs-devel@gnu.org
> Date: Sun, 20 Jan 2019 06:10:38 +0100
> 
> I'm astonished, however, that you consider this a `weird use-case'.

It is weird because you, in effect, give up any diagnostic output from
the command, such as warnings or errors, up front.  Since no one can
reliably predict such diagnostics, I wonder how do you even know that
those commands did what you intended them to do.  It's like flying
blind while also turning off all the instruments.

> OTOH, some external commands are there only for their side effects -
> think `rm' or `aunpack or `xdg-open'.  (Notice that the last two often
> /have/ output, only that you may be not interested in seeing it.)

Commands invoked "for side effects" will not produce any output, so
setting async-shell-command-display-buffer to nil will do exactly what
(I think) you want: display nothing if there's no output, and display
the diagnostics otherwise.

OTOH, if such a command does display something, it means the author of
the command thought it was important enough to show that, even though
the command is "for side effects".

> Does it make sense?

Not really, sorry.