bug#58073: 29.0.50; Uninstalled emacs sends startup messages to stderr

[Jonas Bernoulli <jonas@bernoul.li>]

>> Due to reasons that aren't important here, I recently had to replace the
>> symlink with a wrapper script, and that resulted in these messages being
>> send to stderr.

I was very wrong about that not being important here.

Installing emacs using guix sets EMACSLOADPATH in a file that is sourced
by the shells startup file.  To me it looks like they are abusing this
variable; it makes it impossible to use an emacs that wasn't installed
using guix, without something to counter their modification.  I did that
with a wrapper script.

The value that is set somewhere in the shell's init files is something
like "/home/jonas/.guix-home/profile/share/emacs/site-lisp".  It doesn't
contain an empty element, which would "stand for the default value of
`load-path'", according to (info "(emacs)General Variables").

The side startup file is located inside this directory and contains

  (when (require 'guix-emacs nil t)
    (guix-emacs-autoload-packages)
    (advice-add 'package-load-all-descriptors :after
                #'guix-emacs-load-package-descriptors))

The file "guix-emacs.el" is located in the same directory.  So the
purpose of setting EMACSLOADPATH seems to be to allow using `require' to
load that file.  This doesn't seem right to me, they could just as well
extend the load-path inside "site-lisp.el", or load their additional
init file using `load'.

To deal with the incomplete EMACSLOADPATH, as set in the shell
environment, they use a wrapper script named "emacs" and located on PATH:

  #!/gnu/store/4y5m9lb8k3qkb1y9m02sw9w9a6hacd16-bash-minimal-5.1.8/bin/bash
  export XDG_DATA_DIRS="/gnu/store/h6qdfd4sjdg28jq16600hcjky0cfw9gx-shared-mime-info-1.15/share:/gnu/store/bnsf9il448hl5xjavbhq3rcx355svz2v-glib-2.70.2/share:/gnu/store/7njbpmsgwmx59xn2r6q097iy2wwscb44-gtk+-3.24.30/share:/gnu/store/w0ssipd06il3kvyvqihpmw4lwbhwwfq3-emacs-28.1/share${XDG_DATA_DIRS:+:}$XDG_DATA_DIRS"
  export GTK_PATH="/gnu/store/7njbpmsgwmx59xn2r6q097iy2wwscb44-gtk+-3.24.30/lib/gtk-3.0${GTK_PATH:+:}$GTK_PATH"
  export PATH="$PATH${PATH:+:}/gnu/store/0c1yfbxyv877mlgychfgvmk5ha2jqh52-gzip-1.10/bin:/gnu/store/8fpk2cja3f07xls48jfnpgrzrljpqivr-coreutils-8.32/bin"
  export EMACSLOADPATH="$EMACSLOADPATH${EMACSLOADPATH:+:}/gnu/store/w0ssipd06il3kvyvqihpmw4lwbhwwfq3-emacs-28.1/share/emacs/28.1/lisp"
  exec -a "$0" "/gnu/store/w0ssipd06il3kvyvqihpmw4lwbhwwfq3-emacs-28.1/bin/.emacs-28.1-real" "$@"

I am under the impression that they should stop setting EMACSLOADPATH
and should either invent their own variable to replace that or load
"guix-emacs.el" using simpler means as I suggested above.

What do you think?  I intend to raise the issue with the guix folks but
would first like to hear your opinion.

If I unset EMACSLOADPATH, then everything works as expected.

> Emacs has special support for running from the build tree, but in your
> case it somehow doesn't realize that.

As a side-note, the wrapper script that I previously used looked like
this:

  #!/bin/sh
  export EMACSLOADPATH="\
  /home/jonas/.guix-home/profile/share/emacs/site-lisp:\
  /home/jonas/src/emacs/emacs/lisp"
  exec -a "$0" "/home/jonas/src/emacs/emacs/src/emacs" "$@"

The build tree is at "/home/jonas/src/emacs/emacs"; I think the value I
set above is correct (correct me if I am wrong), so it seems that when
running from the build tree EMACSLOADPATH has to be unset; explicitly
doubling down on the defaults doesn't work.  I also tried with an empty
element.