bug#48129: 28.0.50; Per file-handle (stdin, stdout and stderr) process-connection-type variable

[Thomas Hisch]

On 5/1/21 8:09 AM, Eli Zaretskii wrote:
> > From: Thomas Hisch <thomas.hisch@ims.co.at>
> > Date: Sat, 1 May 2021 01:10:10 +0200
> >
> >
> > I would like that the configuration options of the three file
> > handles (stdin, stdout and stderr), when a new process is created
> > in emacs, are improved.  What I'm specifically asking for is to
> > add support for individually specifying for each file-handle
> > whether it should be connected to a pty or not.  Currently the
> > value of the process-connection-type variable applies to all
> > three file handles at once, which leads to a problem with the
> > following use-case:
> >
> > Usually a program outputs ANSI escape sequences when its stdout
> > file-handle is connected to a pty. It is currently not possible to
> > communicate with a subprocess that is created by `start-file-process' by
> > writing to a pty (via stdin) and avoiding that this subprocess writes
> > ANSI escape sequences to stdout. This use-case is needed by magit, which
> > currently doesn't have support for displaying ANSI escape sequences but
> > it needs to communicate with it's started subprocesses via a PTY
> > (https://github.com/magit/magit/issues/3549).
>
> We have make-pipe-process; can't you solve your problem by connecting
> your process's stdout to such a pipe-process?  If not, why not?

Thx Eli for the fast reply! I had to study the docs of make-pipe-process
and make-process to understand what you mean. However, I'm not fully
sure if I fully get what you mean.

AFAICS the pipe process which is returned by make-pipe-process can be
passed to the :stderr keyword argument of make-process. Is that what you
head in mind?

According to the docs of make-process, process-connection-type is
ignored if :stderr is passed to make-process:

>  This parameter and the value of ‘process-connection-type’ are
ignored if a non-‘nil’ value is specified for the ‘:stderr’ parameter;
in that case, the type will always be ‘pipe’.

What I want is that stdout and stderr are connected to a pipe but stdin
is connected to a pty.

Here is the new test script that I used

(let* (
      (stderr-buffer (get-buffer-create "*stderr*"))
      (stderr-proc (make-pipe-process :name "stderr"
                      :buffer stderr-buffer))
      (process-buf (get-buffer-create "*temp*")))
    (make-process
     :name "isatty"
     :buffer process-buf ;; it is not possible to pass the output of
make-pipe-process to :buffer
     :connection-type 'pty ;; unfortunately ignored if :stderr is used
     :stderr stderr-proc
     :command (list "/tmp/output-isatty.py")))

Best regards
Thomas
Diese E-Mail enthält vertrauliche und/oder rechtlich geschützte Informationen. 
Wenn Sie nicht der richtige Adressat sind oder diese E-Mail irrtümlich erhalten 
haben, informieren Sie bitte sofort den Absender und vernichten Sie diese Mail. 
Das unerlaubte Kopieren sowie die unbefugte Weitergabe dieser Mail ist nicht 
gestattet.

This e-mail may contain confidential and/or privileged information. If you are 
not the intended recipient (or have received this e-mail in error) please 
notify the sender immediately and destroy this e-mail. Any unauthorized 
copying, disclosure or distribution of the material in this e-mail is strictly 
prohibited.

IMS Nanofabrication GmbH FN: 208021 p, FB-Gericht: Wien; Sitz: Schreygasse 3, 
1020, Vienna (Austria),Tel. +43 1 214 48 94; E-Mail: imsoffice@ims.co.at; 
DVR-Nr: 0374369; www.ims.co.at