bug#61100: 29.0.60; `shell-command' displays all of *Shell Command Output* in the minibuffer

bug#61100: 29.0.60; `shell-command' displays all of *Shell Command Output* in the minibuffer

[Reza Shafiei]

Hello Emacs maintainers,

I apologize in advance for any mistakes since English is not my native
language and it is the first time that I report a bug.

How to reproduce:
1) emacs -Q
2) (setq shell-command-dont-erase-buffer t)
3) M-! with some command that generates short output, like
   M-! echo "foo".  Output is displayed in the minibuffer:
   ----------------
   foo
   ----------------
4) M-! with another command that also generates short output,
   like M-! echo "bar".  You will see that the output of previous
   commands is also displayed again in the minibuffer:
   ----------------
   foo
   bar
   ----------------

`shell-command-on-region' has the same behavior.

What I understand form the documentation of these two commands is
that only the output of the most recent command should be
displayed in the minibuffer (if it is short of course), not the
entire content of *Shell Command Output*.

Thanks

In GNU Emacs 29.0.60 (build 1, x86_64-pc-linux-gnu, GTK+ Version
 3.24.36, cairo version 1.17.6) of 2023-01-25 built on reza-manjaro
Repository revision: cfb180329b567d907c11fc9f2bd24728729ec689
Repository branch: makepkg
System Description: Manjaro Linux

Configured using:
 'configure --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib
 --localstatedir=/var --mandir=/usr/share/man --with-gameuser=:games
 --with-modules --without-libotf --without-m17n-flt --without-gconf
 --with-native-compilation --with-xinput2 --with-pgtk --without-xaw3d
 --with-sound=alsa --with-tree-sitter --without-gpm
 --without-compress-install --with-mailutils
 '--program-transform-name=s/\([ec]tags\)/\1.emacs/'
 'CFLAGS=-march=x86-64 -mtune=generic -O2 -pipe -fno-plt -fexceptions
 -Wp,-D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security
 -fstack-clash-protection -fcf-protection'
 LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro,-z,now'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG JSON
LCMS2 LIBSYSTEMD LIBXML2 MODULES NATIVE_COMP NOTIFY INOTIFY PDUMPER PGTK
PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS
TREE_SITTER WEBP XIM GTK3 ZLIB

Important settings:
  value of $LC_MONETARY: en_GB.UTF-8
  value of $LC_NUMERIC: en_GB.UTF-8
  value of $LC_TIME: en_GB.UTF-8
  value of $LANG: en_GB.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media puny dired
dired-loaddefs rfc822 mml mml-sec password-cache epa derived epg rfc6068
epg-config gnus-util text-property-search time-date mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader cl-loaddefs
comp comp-cstr warnings icons subr-x rx cl-seq cl-macs gv cl-extra
help-mode bytecomp byte-compile cl-lib sendmail rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mail-utils rmc iso-transl tooltip cconv
eldoc paren electric uniquify ediff-hook vc-hooks lisp-float-type
elisp-mode mwheel term/pgtk-win pgtk-win term/common-win pgtk-dnd
tool-bar dnd fontset image regexp-opt fringe tabulated-list replace
newcomment text-mode lisp-mode prog-mode register page tab-bar menu-bar
rfn-eshadow isearch easymenu timer select scroll-bar mouse jit-lock
font-lock syntax font-core term/tty-colors frame minibuffer nadvice seq
simple cl-generic indonesian philippine cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms
cp51932 hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese composite emoji-zwj charscript charprop case-table
epa-hook jka-cmpr-hook help abbrev obarray oclosure cl-preloaded button
loaddefs theme-loaddefs faces cus-face macroexp files window
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget keymap hashtable-print-readable backquote threads dbusbind
inotify dynamic-setting system-font-setting font-render-setting cairo
gtk pgtk lcms2 multi-tty make-network-process native-compile emacs)

Memory information:
((conses 16 76291 5234)
 (symbols 48 7101 0)
 (strings 32 19469 2200)
 (string-bytes 1 588970)
 (vectors 16 15606)
 (vector-slots 8 321294 14309)
 (floats 8 27 46)
 (intervals 56 252 0)
 (buffers 984 10))

bug#61100: 29.0.60; `shell-command' displays all of *Shell Command Output* in the minibuffer

[Eli Zaretskii]

> From: Reza Shafiei <joghd1988@outlook.com>
> Date: Fri, 27 Jan 2023 15:16:01 +0000
> msip_labels: 
> 
> I apologize in advance for any mistakes since English is not my native
> language and it is the first time that I report a bug.
> 
> How to reproduce:
> 1) emacs -Q
> 2) (setq shell-command-dont-erase-buffer t)
> 3) M-! with some command that generates short output, like
>    M-! echo "foo".  Output is displayed in the minibuffer:
>    ----------------
>    foo
>    ----------------
> 4) M-! with another command that also generates short output,
>    like M-! echo "bar".  You will see that the output of previous
>    commands is also displayed again in the minibuffer:
>    ----------------
>    foo
>    bar
>    ----------------
> 
> `shell-command-on-region' has the same behavior.
> 
> What I understand form the documentation of these two commands is
> that only the output of the most recent command should be
> displayed in the minibuffer (if it is short of course), not the
> entire content of *Shell Command Output*.

Thanks.

The documentation describes the default situation, where
shell-command-dont-erase-buffer is not customized.

I've now updated the documentation to describe this effect of
customizing that variable.  I think this fixes the discrepancy.

bug#61100: 29.0.60; `shell-command' displays all of *Shell Command Output* in the minibuffer

[Reza Shafiei]

> From: Eli Zaretskii <eliz@gnu.org>
>
> I've now updated the documentation to describe this effect of
> customizing that variable.  I think this fixes the discrepancy.

Yes, it does.  Thanks.

But is it really the intended/expected behavior?  I thought it is not;
that's why I reported it.  I customize shell-command-dont-erase-buffer
because I like to be able to see and compare the output of different
commands in *Shell Command Output*, and refer to them later.

If it is the intended behavior, then now the documentation clarifies it.
Thanks again.

bug#61100: 29.0.60; `shell-command' displays all of *Shell Command Output* in the minibuffer

[Eli Zaretskii]

> From: Reza Shafiei <joghd1988@outlook.com>
> CC: "61100@debbugs.gnu.org" <61100@debbugs.gnu.org>
> Date: Fri, 27 Jan 2023 19:15:24 +0000
> msip_labels:
> 
> 
> > From: Eli Zaretskii <eliz@gnu.org>
> >
> > I've now updated the documentation to describe this effect of
> > customizing that variable.  I think this fixes the discrepancy.
> 
> Yes, it does.  Thanks.
> 
> But is it really the intended/expected behavior?  I thought it is not;
> that's why I reported it.  I customize shell-command-dont-erase-buffer
> because I like to be able to see and compare the output of different
> commands in *Shell Command Output*, and refer to them later.
> 
> If it is the intended behavior, then now the documentation clarifies it.

I don't see how we can have the behavior you expected without a
complete redesign of how the output buffer and the text in it are
managed.  I won't object to such a redesign if someone wants to work
on that, but I also don't think it's very important to do that on
behalf of a minor feature such as shell-command-dont-erase-buffer.