Questions about tree-sitter

["Augustin Chéneau (BTuin)" <btuin@mailo.com>]

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Hello,

I have a few questions about tree-sitter.

I'm currently developing a grammar for GNU Bison alongside a tree-sitter
major mode, it's a work in progress.  The grammar is here:
<https://gitlab.com/btuin2/tree-sitter-bison>, still incomplete but so
far able to parse simple files, and the major mode prototype is
attached to this message.

So, the questions:

1. Is there a way to reload a grammar?

Emacs is pretty nice as a playground for testing grammars, but once a
grammar is loaded, it won't be loaded again until Emacs restarts (as far
as I know).
Is it possible to reload a grammar after modifying it?


2. How to mix multiple languages?

It would be very useful for Bison since its mixed with C or other languages.
According to the documentation I need to use the function
`treesit-range-rules` to set the variable `treesit-range-settings`, but
it seems to have no effect.  The language in the selected nodes doesn't
change (as attested by `(treesit-language-at (point))`).

I did it that way (extracted from the attachment):

(setq-local treesit-range-settings
       (treesit-range-rules
        :embed 'c
        :host 'bison
        '((undelimited_code_block) @capture)))

Am I missing something?


3. Is it possible to trigger a hook when a node is modified?

Since Bison supports multiple languages (C, C++, Java and D), I'd like
to watch the declaration "%language LANGUAGE" to change the embedded
language when needed.
Is there a way to do that?


Thanks!

[-- Attachment #2: bison-ts-mode.el --]
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;;; bison-ts-mode --- Tree-sitter mode for Bison

;;; Commentary:

;;; Code:

(require 'treesit)

(declare-function treesit-parser-create "treesit.c")
(declare-function treesit-induce-sparse-tree "treesit.c")
(declare-function treesit-node-child-by-field-name "treesit.c")
(declare-function treesit-search-subtree "treesit.c")
(declare-function treesit-node-parent "treesit.c")
(declare-function treesit-node-next-sibling "treesit.c")
(declare-function treesit-node-type "treesit.c")
(declare-function treesit-node-child "treesit.c")
(declare-function treesit-node-end "treesit.c")
(declare-function treesit-node-start "treesit.c")
(declare-function treesit-node-string "treesit.c")
(declare-function treesit-query-compile "treesit.c")
(declare-function treesit-query-capture "treesit.c")
(declare-function treesit-parser-add-notifier "treesit.c")
(declare-function treesit-parser-buffer "treesit.c")
(declare-function treesit-parser-list "treesit.c")

(defun bison-ts--font-lock-settings (language)
  (treesit-font-lock-rules
   :language language
   :feature 'comment
   '((comment) @font-lock-comment-face)

  :language language
  :feature 'declaration
  '((declaration (declaration_name) @font-lock-keyword-face))))

(define-derived-mode bison-ts-mode prog-mode "Bison"
  "A mode for Bison."
  (when (treesit-ready-p 'bison)
	(setq-local treesit-font-lock-settings (bison-ts--font-lock-settings 'bison))
	(setq-local treesit-font-lock-feature-list
                '((comment)
                  (declaration)))

	(setq-local treesit-range-settings
          (treesit-range-rules
           :embed 'c
           :host 'bison
           '((undelimited_code_block) @capture)))

    (treesit-major-mode-setup)))

(provide 'bison-ts-mode)
;;; bison-ts-mode.el ends here