bug#12972: [PATCH] Avoid regression in mailcap-view-file similar to Bug#44824

[Maxim Nikulin]

On 02/07/2021 01:38, Eli Zaretskii wrote:
> > From: Maxim Nikulin Date: Fri, 2 Jul 2021 00:01:59 +0700
> >
> > --- a/lisp/net/mailcap.el
> > +++ b/lisp/net/mailcap.el
> > -    (start-process-shell-command command nil command)))
...
> > +    (make-process
> > +     :name "mailcap-view-file" :connection-type 'pipe :noquery t
> > +     :buffer nil ; "*Messages*" may be suitable for debugging
> > +     :sentinel (lambda (proc event)
> > +                 (when (and (memq (process-status proc) '(exit signal))
> > +                            (/= (process-exit-status proc) 0))
> > +                   (message
> > +                    "Command %s: %s."
> > +                    (mapconcat #'identity (process-command proc) " ")
> > +                    (substring event 0 -1))))
> > +     :command (list shell-file-name shell-command-switch command))))
>
> First, you replace start-process-shell-command with make-process, and
> I'm not sure I understand why.  If all you want is to use pipes, why
> not simply bind process-connection-type around the call to
> start-process-shell-command?

> > +    ;; An alternative is `process-connection-type' let-bound to nil for
> > +    ;; `start-process-shell-command' call (with no chance to report failure).
-----------------------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

> > If main process of the handler fails then show a message with exit
> > reason.
---^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

> And with other handlers, this could be an
> incompatible behavior change if the handler behaves differently when
> its standard handles are connected to a pipe rather than a terminal
> device.

Example of such handler, please.