Re: Turning on/off tree-sitter modes

[Stephen Berman <stephen.berman@gmx.net>]

On Sat, 23 Nov 2024 20:50:30 +0200 Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Juri Linkov <juri@linkov.net>
>> Cc: Eli Zaretskii <eliz@gnu.org>,  johan.myreen@gmail.com,  emacs-devel@gnu.org
>> Recently Philip rightly noticed that 'major-mode-remap-alist'
>> would be sufficient.  And indeed, such a command could be implemented
>> just as
>> 
>>   (defun treesit-add-enabled-mode (non-ts-mode ts-mode)
>>     (setopt major-mode-remap-alist
>>             (cons (cons non-ts-mode ts-mode)
>>                   major-mode-remap-alist)))
>
> But is it okay to have a command modify a user option?  Do we have
> examples of this anywhere else?

One example (admittedly having a much narrower scope than the
tree-sitter case) is `todo-top-priorities-overrides' in todo-mode.el.
Here's its doc string:

  List of rules specifying number of top priority items to show.
  These rules override ‘todo-top-priorities’ on invocations of
  M-x todo-filter-top-priorities and
  M-x todo-filter-top-priorities-multifile.  Each rule is a list
  of the form (FILE NUM ALIST), where FILE is a member of
  ‘todo-files’, NUM is a number specifying the default number of
  top priority items for each category in that file, and ALIST,
  when non-nil, consists of conses of a category name in FILE and a
  number specifying the default number of top priority items in
  that category, which overrides NUM.
  
  This variable should be set interactively by
  M-x todo-set-top-priorities-in-file or
  M-x todo-set-top-priorities-in-category.

Steve Berman