Re: Turning on/off tree-sitter modes

[Dmitry Gutov]

On 03/12/2024 16:55, Stefan Monnier wrote:
> +;;;###autoload (add-to-list 'major-mode-remap-defaults
> +;;;###autoload              '(cmake-mode . cmake-ts-mode-maybe))
> +
> +;;;###autoload
> +(defun cmake-ts-mode-maybe ()
> +  "Enable `cmake-ts-mode' if available."
> +  (cond
> +   ((treesit-ready-p 'cmake) (cmake-ts-mode))
> +   ((fboundp 'cmake-mode) (cmake-mode))
> +   (t (fundamental-mode))))

Should we do this switch if the grammar is not available? We could stay 
with the tree-sitter mode if it doesn't anything bad.

Take for example rust-ts-mode, or dockerfile-ts-mode: the body of the 
major mode function is wrapped in

  (when (treesit-ready-p 'dockerfile)
     ...
    )

which checks for the grammar, emits the warning and does nothing 
otherwise. So dockerfile-ts-mode behaves like prog-mode in this case, 
even highlighting strings using the default syntax table.

If there are downsides, they would probably be limited to having the mm 
keymap enabled, or dockerfile-ts-mode-hook run, which could be good too 
- depending on what the user expects to happen.