Subject: Re: bug#57003: 28.1.90; Can local variables be loaded before loading major mode?

From: Ihor Radchenko <[email-masked]>
Date: Sun, 07 Aug 2022 21:52:33 +0800

Lars Ingebrigtsen <[email-masked]> writes:

> Ihor Radchenko <[email-masked]> writes:
>
>> Agree. However, the file-local variables specifically are not equivalent
>> to the mode hooks. File/directory-local variables can be set on
>> per-file/per-project basis, which is much more convenient compared to
>> explicitly defining a global hook.
>
> I think you can say something like
>
> (eval . (org-startup-folded-mode))
>
> to your .dir-locals (etc) to achieve this.  (And then you have to add
> that to `safe-local-eval-forms' to avoid getting prompted, but Org could
> do that in general.  And, of course, add this functionality as a minor
> mode instead of just a variable.)

I do not think that it is a good idea.

1. Having a need to do the eval is not expected by users.
2. Allowing eval is not safe compared to setting variables. Your
   suggestion about `safe-local-eval-forms' will not work well because
   even in your example it is not just about running
   (org-startup-folded-mode); org-startup-folded has 7 allowed values -
   marking each (org-startup-folded-mode value) form as safe sounds
   awkward.
3. org-startup-folded is just an example. We have numerous variables
   like this. I can recall at least several dozens without looking into
   source code. Creating a minor mode for each and every single possible
   variable like this is not maintainable. We will certainly forget
   creating dedicated modes when adding similar variables in future.
4. We have a somewhat similar approach in org-link settings - each link
   type is activated by evaluating a sexp. The result is slow Org
   startup time.

   If we implement per-file settings like you suggested, each setting
   will require partial re-evaluation of (org-mode). 
   A handful of settings like you suggested will easily degrade Org
   startup time by an order of magnitude.

Best,
Ihor