Subject: 30.0.50; normal-mode does not set up local variables in temporary buffers (scratch, with-temp-buffer)
From: Wolfgang Scherer <[email-masked]>
To: [email-masked]
Date: Fri, 3 Mar 2023 00:11:13 +0100
List-Id: <debbugs-submit.debbugs.gnu.org>

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:
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rfc2045 ietf-drums mm-util mail-prsvr mail-utils help-mode novice
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inotify lcms2 dynamic-setting system-font-setting font-render-setting
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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))