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Subject: |
[PATCH] define-derived-mode clobbers syntax tables |
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Date: |
Mon, 16 Dec 2013 03:12:43 -0800 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 |
Repro:
1) Visit shell script with comments. See comments fontified properly.
2) M-x find-library sh-script RET
3) M-x eval-buffer
4) Return to shell script buffer
5) C-x C-v RET
6) Observe that comments are no longer fontified as comments.
The define-derived-mode macro in sh-script.el emits code that clobbers
sh-mode-syntax-table because we don't have a :syntax-table argument. I
think the following patch changes the code to the expected behavior.
~/edev/trunk
$ bzr diff
=== modified file 'lisp/emacs-lisp/derived.el'
--- lisp/emacs-lisp/derived.el 2013-05-27 16:12:52 +0000
+++ lisp/emacs-lisp/derived.el 2013-12-16 11:09:41 +0000
@@ -206,11 +206,11 @@
,(if declare-syntax
`(progn
(unless (boundp ',syntax)
- (put ',syntax 'definition-name ',child))
- (defvar ,syntax (make-syntax-table))
- (unless (get ',syntax 'variable-documentation)
- (put ',syntax 'variable-documentation
- (purecopy ,(format "Syntax table for `%s'." child))))))
+ (put ',syntax 'definition-name ',child)
+ (defvar ,syntax (make-syntax-table))
+ (unless (get ',syntax 'variable-documentation)
+ (put ',syntax 'variable-documentation
+ (purecopy ,(format "Syntax table for `%s'."
child)))))))
,(if declare-abbrev
`(progn
(put ',abbrev 'definition-name ',child)
That is, we shouldn't touch the syntax table variable at all unless the
variable is unbound.
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--- Begin Message ---
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Subject: |
Re: bug#16160: [PATCH] define-derived-mode clobbers syntax tables |
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Date: |
Mon, 12 Dec 2016 20:04:52 -0500 |
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User-agent: |
Gnus (www.gnus.org), GNU Emacs (www.gnu.org/software/emacs/) |
Version: 26.1
>> The repro steps are incorrect. Try these:
>>
>> 1) emacs -Q
>> 2) visit a shell script
>> 3) M-x find-library sh-script RET
>> 4) C-s define-derived-mode RET
>> 5) C-M-x
>> 6) switch to your shell script buffer
>> 7) C-x C-v
>> 8) Observe that the shell script is fontified incorrectly; the syntax
>> table is now clobbered.
Fixed in 8db7b65 along the suggested lines.
So AIUI the issue is that define-derived-mode expands to
(defvar ,syntax (make-syntax-table))
Normally this has no effect if ,syntax is already bound.
But M-x eval-defun resets defvars to their default settings...
Hence if you selectively re-evaluate only the mode definition from
sh-script.el, you get the reported problem.
So I changed it to explicitly check if ,syntax is bound.
This will however now make things go wrong in the opposite way for
someone who has been playing around with customizing a syntax table that
was actually defined by define-derived-mode and wants to reset it by
re-evaluating the derived mode definition. But AFAICS there's no way to
fix both scenarios, and the second seems less likely (?) to me than the
one reported here.
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