bug#61925: 30.0.50; normal-mode does not set up local variables in temporary buffers (scratch, with-temp-buffer)

[Wolfgang Scherer]

The command `normal-mode' does not set file local variables, if a
buffer does not have a `buffer-file-name'. This affects *scratch* and
buffers created using `with-temp-buffer'.

The behavior changed at some time between Emacs version 20.5.2.2 and 20.6.3.
See output from various Emacs versions further below.

If that was an intentional change, it should be prominently documented
to avoid the confusion when examples do not work in a *scratch* buffer.
I would even recommend a warning prompt in normal-mode, when called
interactively.

After executing the the test expression

(let ((expected-value (not (default-value 'truncate-lines)))
sep)
(princ "# |:sec:| local variables test\n")
(dolist (fn (list nil "fake-file-name"))
(with-temp-buffer
(insert (format (concat ";; -*-"
" mode: fundamental;"
" truncate-lines: %S;"
" -*-")
expected-value))
(let ((buffer-file-name fn))
(normal-mode)
(princ (format (concat sep
".. code-block:: elisp\n"
"\n"
" ;; emacs-version: %s\n"
" ;; buffer-file-name: %S\n"
" ;; truncate-lines: %S\n"
" ;; expected-value: %S\n")
emacs-version buffer-file-name
expected-value truncate-lines))))
(setq sep "\n"))
(princ "# |:sec:| local variables test\n"))

the following output is shown in the *Message* buffer:

# |:sec:| local variables test
.. code-block:: elisp

;; emacs-version: 30.0.50
;; buffer-file-name: nil
;; truncate-lines: t
;; expected-value: nil

.. code-block:: elisp

;; emacs-version: 30.0.50
;; buffer-file-name: "fake-file-name"
;; truncate-lines: t
;; expected-value: t
# |:sec:| local variables test

Here is the output from various Emacs versions, I have access to:

# |:sec:| local variables test
.. code-block:: elisp

;; emacs-version: 22.1.1
;; buffer-file-name: nil
;; truncate-lines: t
;; expected-value: t

.. code-block:: elisp

;; emacs-version: 22.1.1
;; buffer-file-name: "fake-file-name"
;; truncate-lines: t
;; expected-value: t
# |:sec:| local variables test

# |:sec:| local variables test
.. code-block:: elisp

;; emacs-version: 24.3.1
;; buffer-file-name: nil
;; truncate-lines: t
;; expected-value: t

.. code-block:: elisp

;; emacs-version: 24.3.1
;; buffer-file-name: "fake-file-name"
;; truncate-lines: t
;; expected-value: t
# |:sec:| local variables test

# |:sec:| local variables test
.. code-block:: elisp

;; emacs-version: 24.5.1
;; buffer-file-name: nil
;; truncate-lines: t
;; expected-value: t

.. code-block:: elisp

;; emacs-version: 24.5.1
;; buffer-file-name: "fake-file-name"
;; truncate-lines: t
;; expected-value: t
# |:sec:| local variables test

# |:sec:| local variables test
.. code-block:: elisp

;; emacs-version: 25.2.2
;; buffer-file-name: nil
;; truncate-lines: t
;; expected-value: t

.. code-block:: elisp

;; emacs-version: 25.2.2
;; buffer-file-name: "fake-file-name"
;; truncate-lines: t
;; expected-value: t
# |:sec:| local variables test

# |:sec:| local variables test
.. code-block:: elisp

;; emacs-version: 26.3
;; buffer-file-name: nil
;; truncate-lines: t
;; expected-value: nil

.. code-block:: elisp

;; emacs-version: 26.3
;; buffer-file-name: "fake-file-name"
;; truncate-lines: t
;; expected-value: t
# |:sec:| local variables test

# |:sec:| local variables test
.. code-block:: elisp

;; emacs-version: 27.1
;; buffer-file-name: nil
;; truncate-lines: t
;; expected-value: nil

.. code-block:: elisp

;; emacs-version: 27.1
;; buffer-file-name: "fake-file-name"
;; truncate-lines: t
;; expected-value: t
# |:sec:| local variables test

In GNU Emacs 30.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
3.24.33, cairo version 1.16.0) of 2023-03-02 built on franke
Repository revision: 828c49ae29fd318547d7bbe4e7fdc65da316e309
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12101003
System Description: Ubuntu 22.04.1 LTS

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 WEBP X11 XDBE XIM XINPUT2 XPM GTK3 ZLIB

Important settings:
value of $LANG: de_DE.UTF-8
locale-coding-system: utf-8-unix

Major mode: Messages

Minor modes in effect:
tooltip-mode: t
global-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
buffer-read-only: 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 mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils help-mode novice
display-line-numbers time-date subr-x cl-loaddefs cl-lib rmc iso-transl
tooltip cconv eldoc paren electric uniquify ediff-hook vc-hooks
lisp-float-type elisp-mode mwheel term/x-win x-win term/common-win x-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 lcms2 dynamic-setting system-font-setting font-render-setting
cairo move-toolbar gtk x-toolkit xinput2 x multi-tty
make-network-process emacs)

Memory information:
((conses 16 50622 7192)
(symbols 48 6822 0)
(strings 32 16418 2244)
(string-bytes 1 443040)
(vectors 16 9557)
(vector-slots 8 153161 11625)
(floats 8 39 119)
(intervals 56 747 136)
(buffers 976 13))