Detecting tree-sitter based major-modes for end-user customization and third party functions/packages

[Jostein Kjønigsen]

Hey everyone.

This may or may not have been answered in an earlier thread about the subject, but I couldn't really find it, so if this email and question represents a duplicate: sorry in advance.

With that said, I'll get straight down to business.

While as a major-mode author, I can decide to use tree-sitter to implement key functionality, we don't expect end-users to (need to) have the same level awareness about the technology used to implement the modes they are consuming.

However end-users often want to customize Emacs based on major-mode agnostic properties of the current major-mode none the less. Examples are adding hooks for prog-mode, c-mode-common-mode (from cc-mode), etc. This may also apply to other third-party packages, in how they interact with buffers (if prog-mode do this, if text-mode do that, etc).

I expect these kinda of needs to arise for tree-sitter based major-modes sooner rather than later, where one may be able to leverage tree-sitter node-manipulation functions rather than use text-based equivalents.

But to be able to leverage tree-sitter based functions, one would first need to know that one is interacting with a tree-sitter based major-mode. And to customize one, one would need a hook.

So how do we plan to expose this to end-users and other developers?

Looking at (treesit-major-mode-setup), I can't see it leaving any traces to be reliably detected later. Should we add some (documented) buffer-local variables to be able to detect this later? Should we create a mostly empty minor-mode for easy detection and ability to add hooks?

Or does anyone have any other suggestions for how we can solve this user-facing need of tree-sitter?

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Kind regards
Jostein Kjønigsen
jostein.kjønigsen.no
jostein@kjonigsen.net - jostein@gmail.com