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bug#61925: 30.0.50; normal-mode does not set up local variables in tempo
From: |
Wolfgang Scherer |
Subject: |
bug#61925: 30.0.50; normal-mode does not set up local variables in temporary buffers (scratch, with-temp-buffer) |
Date: |
Sun, 5 Mar 2023 06:03:53 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.0 |
And AFAICT, it _is_ documented in the ELisp Reference manual:
-- Command: normal-mode &optional find-file
This function establishes the proper major mode and buffer-local
variable bindings for the current buffer. It calls ‘set-auto-mode’
(see below). As of Emacs 26.1, it no longer runs
‘hack-local-variables’, this now being done in ‘run-mode-hooks’ at
the initialization of major modes (*note Mode Hooks::).
And the documentation of run-mode-hooks says:
-- Function: run-mode-hooks &rest hookvars
Major modes should run their mode hook using this function. It is
similar to ‘run-hooks’ (*note Hooks::), but it also runs
‘change-major-mode-after-body-hook’, ‘hack-local-variables’ (when
the buffer is visiting a file) (*note File Local Variables::) ^^^^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Just for your information, the machinery in `normal-mode' and
`run-mode-hooks' is -- at least in some edge cases -- out of
sync.
Here is a case, where normal-mode in Emacs > 26.1 still calls
`hack-local-variables', which causes a discrepancy, depending on
`delay-mode-hooks', when `after-change-major-mode-hook' alters
the value of a local variable, which is also set in the local
variables list. The reason is, that in `normal-mode'
`after-change-major-mode-hook' is not called the same way as it
is in `run-mode-hooks'.
;; for all cases: `after-change-major-mode-hook' establishes local
;; variable and sets the value to "hello"
;; case 1: buffer with `buffer-file-name' == nil, `delay-mode-hooks' case 1.1:
nil, case 1.2: t
(check-normal-mode-in-temp-buffer nil nil nil t ) ::go:: ;; => hello
(check-normal-mode-in-temp-buffer t nil nil t ) ::go:: ;; => good-bye
;; case 2: buffer with `buffer-file-name' not nil, `delay-mode-hooks' case 2.1:
nil, case 2.2: t
(check-normal-mode-in-temp-buffer nil t nil t ) ::go:: ;; => hello
(check-normal-mode-in-temp-buffer t t nil t ) ::go:: ;; => good-bye
The following is the complete test setup that I used for testing:
(defun check-normal-mode (&optional set-delay-mode-hooks set-buffer-file-name
find-file)
(interactive)
(let ((buffer-file-name (or buffer-file-name (and set-buffer-file-name (or null-device
"/dev/null"))))
(delay-mode-hooks (if set-delay-mode-hooks t)))
(normal-mode find-file)))
(defun check-normal-mode-in-temp-buffer (set-delay-mode-hooks
set-buffer-file-name change-hook after-hook)
(let ((hook-function #'(lambda () (make-local-variable 'wsx-here-i-am) (setq
wsx-here-i-am "hello"))))
(if change-hook
(add-hook 'change-major-mode-after-body-hook hook-function)
(remove-hook 'change-major-mode-after-body-hook hook-function))
(if after-hook
(add-hook 'after-change-major-mode-hook hook-function)
(remove-hook 'after-change-major-mode-hook hook-function))
(put 'wsx-here-i-am 'safe-local-variable 'string-or-null-p)
(with-temp-buffer
(insert ";; -*- mode: lisp-interaction; truncate-lines: t; wsx-here-i-am: \"good
bye\"; -*-\n")
(normal-mode)
(check-normal-mode set-delay-mode-hooks set-buffer-file-name)
(describe-variable 'wsx-here-i-am)
)
(remove-hook 'change-major-mode-after-body-hook hook-function)
(remove-hook 'after-change-major-mode-hook hook-function)
(put 'wsx-here-i-am 'safe-local-variable nil)))
;; Emacs >= 26.1
(check-normal-mode-in-temp-buffer nil nil nil nil) ::go:: ;; => void
(check-normal-mode-in-temp-buffer t nil nil nil) ::go:: ;; => good-bye
(check-normal-mode-in-temp-buffer nil t nil nil) ::go:: ;; => good-bye
(check-normal-mode-in-temp-buffer t t nil nil) ::go:: ;; => good-bye
(check-normal-mode-in-temp-buffer nil nil t nil) ::go:: ;; => hello
(check-normal-mode-in-temp-buffer t nil t nil) ::go:: ;; => good-bye
(check-normal-mode-in-temp-buffer nil t t nil) ::go:: ;; => good-bye
(check-normal-mode-in-temp-buffer t t t nil) ::go:: ;; => good-bye
(check-normal-mode-in-temp-buffer nil nil nil t ) ::go:: ;; => hello
(check-normal-mode-in-temp-buffer t nil nil t ) ::go:: ;; => good-bye
(check-normal-mode-in-temp-buffer nil t nil t ) ::go:: ;; => hello
(check-normal-mode-in-temp-buffer t t nil t ) ::go:: ;; => good-bye
;; Emacs < 26.1
(check-normal-mode-in-temp-buffer nil nil nil nil) ::go:: ;; => good-bye
(check-normal-mode-in-temp-buffer t nil nil nil) ::go:: ;; => good-bye
(check-normal-mode-in-temp-buffer nil t nil nil) ::go:: ;; => good-bye
(check-normal-mode-in-temp-buffer t t nil nil) ::go:: ;; => good-bye
(check-normal-mode-in-temp-buffer nil nil t nil) ::go:: ;; => good-bye
(check-normal-mode-in-temp-buffer t nil t nil) ::go:: ;; => good-bye
(check-normal-mode-in-temp-buffer nil t t nil) ::go:: ;; => good-bye
(check-normal-mode-in-temp-buffer t t t nil) ::go:: ;; => good-bye
(check-normal-mode-in-temp-buffer nil nil nil t ) ::go:: ;; => good-bye
(check-normal-mode-in-temp-buffer t nil nil t ) ::go:: ;; => good-bye
(check-normal-mode-in-temp-buffer nil t nil t ) ::go:: ;; => good-bye
(check-normal-mode-in-temp-buffer t t nil t ) ::go:: ;; => good-bye