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

[Maxim Nikulin]

I am giving up with this issue.

My summary. New function `mailcap-view-file' has a problem similar to 
Bug#44824 (kde-open5 and "gio open" called directly or through xdg-open 
are unreliable in Emacs, I consider it as fixed in Org mode) that was 
reported by several users and refused by developers as not reproducible 
at first. I tried my best to draw attention to this problem and then to 
suggest a change that fixes the obscure problem and improves error 
handling. I am unaware of any real negative consequences of my patch. It 
is up to Emacs developers to leave the new bug as is or to fix it in a 
way they like

On 03/07/2021 00:28, Eli Zaretskii wrote:
> > From: Maxim Nikulin Date: Fri, 2 Jul 2021 23:24:23 +0700
> >
> > On 02/07/2021 19:37, Eli Zaretskii wrote:
> > > > From: Maxim Nikulin Date: Fri, 2 Jul 2021 19:21:55 +0700
> > > >
> > > > > 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.
> > >
> > > Why do you need one?
> >
> > Because of I can not imagine such case for mailcap handler in Emacs yet
> > and, accordingly to you, "this could be an incompatible behavior change".
>
> You don't need to imagine it, you just need to trust me that I know
> what I'm talking about: it would be an incompatible change.

Is it a kind of Church of Emacs that I have to just believe in you? 
Previous time you were trying to convince me that unconditional 'pipe is 
perfectly safe when I was unsure concerning behavior on Windows.

You prefer to keep reasons of your objections unveiled. I see no issue 
with the patch. It can be by a few lines shorter but the price is worse 
user experience. I have no idea how to move further.

Finally, the patch touches month-old unreleased code, so I see no point 
to discuss that it is "incompatible".

P.S. It was my fault to use `make-process' in Org since the function is 
not available in Emacs-24. I'm sorry for that incompatibility.