bug#73872: 30.0.91; emacs-lisp-mode-syntax-table active when calling `describe-variable' on variable with textually large value.

[Eli Zaretskii <eliz@gnu.org>]

Ping!  Sigurd, could you please answer Stefan's questions?

> Cc: Sigurd Dam Sonniks <sigurddam@hotmail.com>, 73872@debbugs.gnu.org
> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Date: Thu, 14 Nov 2024 09:40:48 -0500
> 
> >> When you call `describle-variable' on a variable with a value that's
> >> large enough that it's moved to the end of the help buffer, the syntax
> >> table is changed to `emacs-lisp-mode-syntax-table' but never changed
> >> back. There is a very easy fix where you just set it back to
> >> `help-mode-syntax-table' at the end of the enclosing
> >> `with-current-buffer', but I guess you could also switch to a
> >> temporary buffer instead. Below is the relevant code snippet with the
> >> first suggested fix applied.
> 
> I'm curious: in which context did you notice this?
> Does it lead to an undesirable behavior in a specific case?
> 
> > Shouldn't the syntax table be left at that value until the buffer is
> > reused for another variable/function?  Otherwise, why do we set the
> > syntax table to this value?  Stefan, do you know the reason?
> 
> FWIW, according to my reading of the Git history, this behavior dates
> back at least to 2001 when Miles split `help.el` into several files
> (I didn't bother to check the previous history of that code on
> `help.el`), so it's far from new.
> 
> AFAICT the syntax-table of the *Help* buffer shouldn't matter very much
> once the buffer is filled: it affects only navigation by the user, where
> the prose part would presumably prefer a syntax-table somewhat like that
> of `text-mode` whereas the var's value part would prefer something like
> that of `elisp-mode`.
> 
> But, AFAICT the `help-mode-syntax-table` happens to be a derivative of
> `emacs-lisp-mode-syntax-table` just with extra matching of ‘...’, so
> reverting to it would be safe enough in most cases.  This said, I think
> The Right Thing™ would be to add a `syntax-table` property on the
> printed value (regardless if it stays at the beginning or is moved to
> the end of the buffer) so it's not affected by the syntax-table used in
> the rest of the buffer.
> 
> 
>         Stefan
> 
> 
> 
> 
>