bug#15658: 24.1; (wishlist) Easy way to make a file-local variable also permanent-local

[yary]

I was working on this about 5 years ago, before 24.1, and the use case
I had for this doesn't apply to my current situation. So it might
already work as I wanted it, and my wants have changed! OK to close
this.

-y

On Tue, May 10, 2022 at 11:14 AM Lars Ingebrigtsen <larsi@gnus.org> wrote:
>
> yary <not.com@gmail.com> writes:
>
> > There are occasional needs to preserve buffer-local variables across
> > major-mode changes. In the specific case of directory-local variables,
> > an automated solution looks to be feasible, see "bug#15577: 24.3;
> > dir-local variables not applied when switching major-mode"
> >
> > File-local variables on the other hand are not as easy to categorize as
> > to their intent- for a particular mode, vs the file contents in general.
> >
> > I propose adding `permanent' as another special "variable name" (along
> > the lines of `mode', `eval', `coding', and `unibyte') to let people
> > mark the file variables they want to remain between mode changes. For
> > example:
> >
> > ; mode: Lisp
> > ; fill-column: 75
> > ; comment-column: 50
> > ; permanent: fill-column tab-width
> >
> > would set & keep fill-column at 75 between mode changes, and would
> > preserve between major-mode switches any changes to tab-width.
>
> (I'm going through old bug reports that unfortunately weren't resolved
> at the time.)
>
> With the following:
>
> ;; Local variables:
> ;; foo-var: t
> ;; end:
>
> foo-var is set whenever I change the major mode.  Has the behaviour
> changed here since Emacs 24.1?  (The earliest Emacs I have is Emacs
> 25.1.)
>
> --
> (domestic pets only, the antidote for overdose, milk.)
>    bloggy blog: http://lars.ingebrigtsen.no