Re: Average-user-facing interface for tree-sitter

[Stefan Monnier]

>> BTW, I see that `global-treesit-mode--turn-on` is currently a (non
>> official) alias of `treesit-mode`, but I think it should only call
>> `treesit-mode` in those buffers where there is some indication that the
>> major mode provides some treesit-mode support (e.g., currently that
>> could be if `major-mode-backend-function` is set).
>
> I’m changing it to what you described in another email. (So
> major-mode-backend-function is goner). I can use treesit-font-lock-settings
> as the minimum criterion.
>
>> 
>> And then maybe `treesit-mode` should signal an error (and turn itself
>> off) if it's enabled in a buffer whose major mode does not provide any
>> support for `treesit-mode`.
>
> So currently treesit-mode signals a warning if it can’t activate tree-sitter
> and (eq this-command ’treesit-mode), but if it is called in find-file-hook,
> etc set up by global-treesit-mode, it doesn’t signal a warning.

That's why define-globalized-minor-mode has a TURN-ON function
argument separately from the MODE argument: the TURN-ON function has
to determine whether to enable the minor mode or not.  It shouldn't
blindly call `treesit-mode` but first check whether `treesit-mode`
is applicable.

This way, `treesit-mode` can always signal an error when called in
a buffer where it's not applicable: it's always the responsibility of
the caller to check beforehand.


        Stefan