bug#65702: 30.0.50; compile-command not honored in shell buffers

[Matthias Meulien]

I customize the default compile command using directory local
variables. For example, with a '.dir-locals' containing the following:

;;; Directory Local Variables            -*- no-byte-compile: t -*-
;;; For more information see (info "(emacs) Directory Variables")

((nil . ((compilation-search-path . (nil "builddir"))
         (compile-command . "meson setup builddir . --cross-file 
crossfile_arm.ini ; pushd builddir && meson compile ; popd")
         (compilation-environment . ("TERM=ansi"))
         (ispell-local-dictionary . "en")
         (project-vc-merge-submodules . nil)))
 (c++-mode . ((c-basic-offset . 2)
              (indent-tabs-mode . nil))))

When I enter the *vc-dir* buffer for the corresponding Git local
repository, and I press 'C-x p c' ('project-compile' command) then the
default compile command has the value specified in the previous
'.dir-locals.el'.

Same with 'meson.build', 'README.md', '*.cc', '*.h', etc. files.

But when 'project-compile' is called from a shell buffer after I pressed
'C-x p s' then the default compile command is 'make -k'.  This is
strange and looks like a bug to my eyes.

(I successfully reproduced from 'emacs -Q').



In GNU Emacs 30.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
 3.24.37, cairo version 1.16.0) of 2023-08-30 built on carbon
Repository revision: 297ccd967f24e37bc51c057da43c862291a55ddd
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12101007
System Description: Debian GNU/Linux 12 (bookworm)

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES NOTIFY
INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS TREE_SITTER WEBP X11 XDBE XIM XINPUT2 XPM GTK3 ZLIB

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

Major mode: Shell

Minor modes in effect:
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  goto-address-mode: t
  highlight-changes-visible-mode: t
  breadcrumb-mode: t
  minions-mode: t
  global-company-mode: t
  company-mode: t
  desktop-save-mode: t
  server-mode: t
  pixel-scroll-precision-mode: t
  save-place-mode: t
  shell-dirtrack-mode: t
  comint-fontify-input-mode: t
  electric-pair-mode: t
  icomplete-mode: t
  global-so-long-mode: t
  global-auto-revert-mode: t
  auto-insert-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-layout-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tab-bar-mode: t
  file-name-shadow-mode: t
  context-menu-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  window-divider-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:
/home/matthias/.config/emacs/elpa/dictionary-20201001.1727/dictionary hides 
/usr/local/share/emacs/30.0.50/lisp/net/dictionary

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Memory information:
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 (strings 32 213796 6304) (string-bytes 1 6773049) (vectors 16 108792)
 (vector-slots 8 2137202 94939) (floats 8 751 3676)
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