Re: Can emacsclient send environment variables even if it doesn't create a frame?

[Yoichi Nakayama]

On Thu, Mar 30, 2023 at 12:46 AM Eli Zaretskii <eliz@gnu.org> wrote:
>
> > From: Yoichi Nakayama <yoichi.nakayama@gmail.com>
> > Date: Wed, 29 Mar 2023 22:45:09 +0900
> >
> > Currently, emacsclient sends environment variables to the server process 
> > only
> > if it is going to create a frame. So it is impossible to refer to 
> > environment
> > variables when calling EDITOR=emacsclient from other programs.
> > In contrast, if EDITOR="emacsclient -t" or EDITOR="emacsclient -c" (that is,
> > emacsclient creates new frames), you can refer emacsclient's environment
> > variables via server-buffer-clients.
> >
> > Is it possible to eliminate the following conditional branching by 
> > create_frame
> > in lib-src/emacsclient.c?
>
> That would mean a single frame could "inherit" environment variables
> from different shells, which will be at least confusing, if not
> contradictory.  For example, what about environment variables like
> PATH?

No, it will not update the frame-parameter of the existing frame.
I’ve confirmed
   (frame-parameter nil 'environment) => nil
on the window/buffer created by the modified emacsclient, while
   (process-get (car server-buffer-clients) 'env)
returns environment variables on it.

Also, in the following usage, git will perform exclusive control and
prevent committing to the same repository at the same time, so
multiple clients will not edit the same COMMIT_EDITMSG file.
So the single buffer does not "inherit" environment variables
from different shells.

> > Use case:
> > Refer GIT_INDEX_FILE to show correct diff even when emacsclient is invoked
> > by `git commit -a` or `git commit filename` (where GIT_INDEX_FILE points to
> > a temporary index file), along with the commit message edit buffer.
>
> Why cannot you call emacsclient in that case with -t or -c option?
> AFAIR, Git can use a Git-special variable GIT_EDITOR, so you could
> define that to create a new frame without affecting the more general
> EDITOR setting.

I can use emacsclient with -t or -c option, and I can also use emacsclient
without those option too. If we don't have magit installed, we can edit the
commit message in either case, without any restrictions.

If we have magit installed, in addition to the window for editing the commit
message, it also opens a window for the change diff. I'm trying to fix an
issue with magit that sometimes presents incorrect change diffs.
I found a fix that uses GIT_INDEX_FILE in the client's environment variables
    https://github.com/magit/magit/pull/4888
but it doesn't work if emacsclient doesn't open a new frame. Because
if emacsclient doesn't create a frame, emacsclient's environment variables
aren't passed to the server side and there is no way to use them.

-- 
Yoichi NAKAYAMA