Re: [BUG] org-open-file immediately termininates when calling xdg-open that calls emacsclient

[Max Nikulin]

On 22/05/2022 11:37, Ihor Radchenko wrote:
> I have a problem with the following commits:
>
> 869b7a21b org-open-file: Avoid make-process for Emacs 24 compatibility
> 5db61eb0f org.el: Avoid xdg-open silent failure
>
> They both set process-connection-type to nil/'pipe. Somehow, this change
> breaks org-open-file for me when org-open-file calls xdg-open and xdg is
> confugured to open the file with emacsclient. I only see a flicker and
> the file does not open. Sometimes, Emacs even crashes.

I can not reproduce a problem, however I tried to factor-out xdg-open. 
Emacs-27.1, a minimal LXC container, so "&" to simulate kde-open5 
starting process in background. On the other hand I consider behavior 
when emacsclient is called from emacs as confusing due to requirement of 
C-x # to notify emacs about completion.

---- >8 ----
#+begin_src elisp
  (push '("\\.txt\\'" . "emacsclient %s &") org-file-apps)
#+end_src

[[file:some.txt]]
---- 8< ----

Nothing happens if emacs server is not started, but error handling was 
sacrificed for compatibility with old emacs versions.

Do you see the same problem for a function from mailcap.el in the 
development emacs version?

Eli Zaretskii suspected some compatibility issue, but he successfully 
resisted my attempts to pull some details from him. I know how to create 
a MIME handler that will cause 100% CPU consumption by Emacs for pipe 
processes, but he does not consider it as a real problem.

> If I change the process type back to default tty value, things work
> again as expected.

You might try `call-process' with 0 as DESTINATION (attention! not nil!).

See #+begin_comment snippet from the following patch (this part was not 
committed since Robert convinced me that it is confusing):
Max Nikulin to emacs-orgmode. [PATCH v3] Fix FAQ entry about mailto 
links. Mon, 14 Feb 2022 20:22:14 +0700. 
https://list.orgmode.org/9437ade2-af18-f97e-8790-a2df27c9017c@gmail.com

I do not know a way to reliably launch external MIME handler from Emacs. 
All means I am aware of have some caveats.