GNU bug report logs - #23272
25.0.92; syntax-propertize-via-font-lock considered harmful

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Dmitry Gutov <dgutov <at> yandex.ru>
To: bug-gnu-emacs <at> gnu.org
Subject: 25.0.92; syntax-propertize-via-font-lock considered harmful
Date: Tue, 12 Apr 2016 01:54:01 +0300

It makes it impossible to call syntax-propertize without enabling
font-lock-mode first, e.g. when delay-mode-hooks is used.

Example:

(with-temp-buffer
  (insert "-- -*- mode: ada -*-")
  (delay-mode-hooks
    (set-auto-mode))
  (syntax-propertize (point)))

=> (error "Font-lock trying to use keywords before setting them up")

I've hit this when working on a patch in
http://debbugs.gnu.org/cgi/bugreport.cgi?bug=23223#38.

Message #8 received at 23272 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Dmitry Gutov <dgutov <at> yandex.ru>
Cc: 23272 <at> debbugs.gnu.org
Subject: Re: 25.0.92; syntax-propertize-via-font-lock considered harmful
Date: Wed, 30 Oct 2019 16:56:54 +0100

Dmitry Gutov <dgutov <at> yandex.ru> writes:

> It makes it impossible to call syntax-propertize without enabling
> font-lock-mode first, e.g. when delay-mode-hooks is used.
>
> Example:
>
> (with-temp-buffer
>   (insert "-- -*- mode: ada -*-")
>   (delay-mode-hooks
>     (set-auto-mode))
>   (syntax-propertize (point)))
>
> => (error "Font-lock trying to use keywords before setting them up")

I'm unable to reproduce this bug on the current trunk.  Has this been
fixed in the three years since it was reported?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #13 received at 23272 <at> debbugs.gnu.org (full text, mbox):

From: Dmitry Gutov <dgutov <at> yandex.ru>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 23272 <at> debbugs.gnu.org
Subject: Re: bug#23272: 25.0.92; syntax-propertize-via-font-lock considered
 harmful
Date: Thu, 21 Nov 2019 01:22:41 +0200

On 30.10.2019 17:56, Lars Ingebrigtsen wrote:
> I'm unable to reproduce this bug on the current trunk.  Has this been
> fixed in the three years since it was reported?

I think it's still there as a possibility, but the odds of triggering it 
are becoming more rare with each year.

Looking at the backtrace, it requires a major mode that uses 
font-lock-syntactic-keywords and calls syntax-propertize-via-font-lock 
to set its syntax-propertize-function.

Since Emacs 26 (where the bug still reproduces), ada-mode has both 
switched to a proper syntax-propertize-function instead of the one 
mentioned above and moved out of Emacs core, so "mode: ada" isn't doing 
anything in 'emacs -Q'.

So the repro scenario is like this now:

(define-derived-mode foo-mode fundamental-mode "Foo"
  (setq-local syntax-propertize-function
	      (syntax-propertize-via-font-lock nil)))

(with-temp-buffer
  (insert "-- -*- mode: foo -*-")
  (delay-mode-hooks
    (set-auto-mode))
  (syntax-propertize (point)))

The resulting backtrace:

Debugger entered--Lisp error: (error "Font-lock trying to use keywords 
before setting th...")
  signal(error ("Font-lock trying to use keywords before setting th..."))
  error("Font-lock trying to use keywords before setting th...")
  font-lock-compile-keywords(nil t)
  font-lock-fontify-syntactic-keywords-region(1 21)
  #f(compiled-function (start end) #<bytecode 0x15817a4f1981>)(1 21)
  syntax-propertize(21)

Considering font-lock-syntactic-keywords are obsolete since Emacs 24, 
this is not very important, and people should feel free to close this if 
a fix is not found soon.

Message #16 received at 23272 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Dmitry Gutov <dgutov <at> yandex.ru>
Cc: 23272 <at> debbugs.gnu.org
Subject: Re: bug#23272: 25.0.92; syntax-propertize-via-font-lock considered
 harmful
Date: Thu, 21 Nov 2019 13:34:14 +0100

Dmitry Gutov <dgutov <at> yandex.ru> writes:

> Since Emacs 26 (where the bug still reproduces), ada-mode has both
> switched to a proper syntax-propertize-function instead of the one 
> mentioned above and moved out of Emacs core, so "mode: ada" isn't
> doing anything in 'emacs -Q'.
>
> So the repro scenario is like this now:
>
> (define-derived-mode foo-mode fundamental-mode "Foo"
>   (setq-local syntax-propertize-function
> 	      (syntax-propertize-via-font-lock nil)))
>
> (with-temp-buffer
>   (insert "-- -*- mode: foo -*-")
>   (delay-mode-hooks
>     (set-auto-mode))
>   (syntax-propertize (point)))

Ah; thanks for the explanation.

> Considering font-lock-syntactic-keywords are obsolete since Emacs 24,
> this is not very important, and people should feel free to close this
> if a fix is not found soon.

OK; I'll leave it open for now, but probably closing this in a month or
so if nothing further happens.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #21 received at 23272-done <at> debbugs.gnu.org (full text, mbox):

From: Stefan Kangas <stefan <at> marxist.se>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 23272-done <at> debbugs.gnu.org, Dmitry Gutov <dgutov <at> yandex.ru>
Subject: Re: bug#23272: 25.0.92;
 syntax-propertize-via-font-lock considered harmful
Date: Sat, 29 Feb 2020 03:19:26 +0100

Lars Ingebrigtsen <larsi <at> gnus.org> writes:

>> Considering font-lock-syntactic-keywords are obsolete since Emacs 24,
>> this is not very important, and people should feel free to close this
>> if a fix is not found soon.
>
> OK; I'll leave it open for now, but probably closing this in a month or
> so if nothing further happens.

That was 14 weeks ago, and there have been no further comments.

I'm therefore closing this bug now.

Best regards,
Stefan Kangas

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