Introduce support for TOML config-format

This commit introduces support for the semi-popular TOML
config-format[1] through a new major-mode: toml-ts-mode.

I've read through the full spec[2], and from what I can see this
major-mode should provide correct syntax-highligting for every sort of
config-declaration which adheres to the specification.

Besides that it also adds support for imenu and basic tree-sitter
based navigation.

[1] https://toml.io/en/
[2] https://toml.io/en/v1.0.0

admin/notes/tree-sitter/build-module/batch.sh

@@ -1,6 +1,7 @@
 #!/bin/bash
 
 languages=(
+    'bash'
     'c'
     'cmake'
     'cpp'
@@ -13,8 +14,9 @@ languages=(
     'json'
     'python'
     'rust'
-    'typescript'
+    'toml'
     'tsx'
+    'typescript'
 )
 
 for language in "${languages[@]}"

lisp/textmodes/toml-ts-mode.el

@@ -0,0 +1,187 @@
+;;; toml-ts-mode.el --- tree-sitter support for TOML  -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2022 Free Software Foundation, Inc.
+
+;; Author     : Jostein Kjønigsen <jostein@kjonigsen.net>
+;; Maintainer : Jostein Kjønigsen <jostein@kjonigsen.net>
+;; Created    : December 2022
+;; Keywords   : toml languages tree-sitter
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+;;
+
+;;; Code:
+
+(require 'treesit)
+
+(declare-function treesit-parser-create "treesit.c")
+(declare-function treesit-induce-sparse-tree "treesit.c")
+(declare-function treesit-node-start "treesit.c")
+(declare-function treesit-node-child-by-field-name "treesit.c")
+
+(defcustom toml-ts-mode-indent-offset 2
+  "Number of spaces for each indentation step in `toml-ts-mode'."
+  :version "29.1"
+  :type 'integer
+  :safe 'integerp
+  :group 'toml)
+
+(defvar toml-ts-mode--syntax-table
+  (let ((table (make-syntax-table)))
+    (modify-syntax-entry ?_  "_"     table)
+    (modify-syntax-entry ?\\ "\\"    table)
+    (modify-syntax-entry ?=  "."     table)
+    (modify-syntax-entry ?\' "\""    table)
+    (modify-syntax-entry ?#  "<"   table)
+    (modify-syntax-entry ?\n "> b"  table)
+    (modify-syntax-entry ?\^m "> b" table)
+    table)
+  "Syntax table for `toml-ts-mode'.")
+
+(defvar toml-ts-mode--indent-rules
+  `((toml
+     ((node-is "]") parent-bol 0)
+     ((parent-is "string") parent-bol toml-ts-mode-indent-offset)
+     ((parent-is "array") parent-bol toml-ts-mode-indent-offset))))
+
+(defvar toml-ts-mode--font-lock-settings
+  (treesit-font-lock-rules
+   :language 'toml
+   :feature 'comment
+   '((comment) @font-lock-comment-face)
+
+   :language 'toml
+   :feature 'constant
+   '((boolean) @font-lock-constant-face)
+
+   :language 'toml
+   :feature 'delimiter
+   '((["="]) @font-lock-delimiter-face)
+
+   :language 'toml
+   :feature 'number
+   '([(integer) (float) (local_date) (local_date_time) (local_time)]
+     @font-lock-number-face)
+
+   :language 'toml
+   :feature 'string
+   '((string) @font-lock-string-face)
+
+   :language 'toml
+   :feature 'escape-sequence
+   :override t
+   '((escape_sequence) @font-lock-escape-face)
+
+   :language 'toml
+   :feature 'pair
+   :override t            ; Needed for overriding string face on keys.
+   '((bare_key) @font-lock-property-face
+     (quoted_key) @font-lock-property-face
+     (table ("[" @font-lock-bracket-face
+             (_) @font-lock-type-face
+             "]" @font-lock-bracket-face))
+     (table_array_element ("[[" @font-lock-bracket-face
+                           (_) @font-lock-type-face
+                           "]]" @font-lock-bracket-face))
+     (table (quoted_key) @font-lock-type-face)
+     (table (dotted_key (quoted_key)) @font-lock-type-face))
+
+   :language 'toml
+   :feature 'error
+   :override t
+   '((ERROR) @font-lock-warning-face))
+  "Font-lock settings for TOML.")
+
+(defun toml-ts-mode--get-table-name (node)
+  "Obtains the header-name for the associated tree-sitter `NODE'."
+  (if node
+      (treesit-node-text
+       (car (cdr (treesit-node-children node))))
+    "Root table"))
+
+(defun toml-ts-mode--imenu-1 (node)
+  "Helper for `toml-ts-mode--imenu'.
+Find string representation for NODE and set marker, then recurse
+the subtrees."
+  (let* ((ts-node (car node))
+         (subtrees (mapcan #'toml-ts-mode--imenu-1 (cdr node)))
+         (name (toml-ts-mode--get-table-name ts-node))
+         (marker (when ts-node
+                   (set-marker (make-marker)
+                               (treesit-node-start ts-node)))))
+    (cond
+     ((null ts-node) subtrees)
+     (subtrees
+      `((,name ,(cons name marker) ,@subtrees)))
+     (t
+      `((,name . ,marker))))))
+
+(defun toml-ts-mode--imenu ()
+  "Return Imenu alist for the current buffer."
+  (let* ((node (treesit-buffer-root-node))
+         (table-tree (treesit-induce-sparse-tree
+                      node "^table$" nil 1000))
+         (table-array-tree (treesit-induce-sparse-tree
+                            node "^table_array_element$" nil 1000))
+         (table-index (toml-ts-mode--imenu-1 table-tree))
+         (table-array-index (toml-ts-mode--imenu-1 table-array-tree)))
+    (append
+     (when table-index `(("Headers" . ,table-index)))
+     (when table-array-index `(("Arrays" . ,table-array-index))))))
+
+
+;;;###autoload
+(add-to-list 'auto-mode-alist '("\\.toml\\'" . toml-ts-mode))
+
+;;;###autoload
+(define-derived-mode toml-ts-mode text-mode "TOML"
+  "Major mode for editing TOML, powered by tree-sitter."
+  :group 'toml-mode
+  :syntax-table toml-ts-mode--syntax-table
+
+  (when (treesit-ready-p 'toml)
+    (treesit-parser-create 'toml)
+
+    ;; Comments
+    (setq-local comment-start "# ")
+    (setq-local commend-end "")
+
+    ;; Indent.
+    (setq-local treesit-simple-indent-rules toml-ts-mode--indent-rules)
+
+    ;; Navigation.
+    (setq-local treesit-defun-type-regexp
+                (rx (or "table" "table_array_element")))
+
+    ;; Font-lock.
+    (setq-local treesit-font-lock-settings toml-ts-mode--font-lock-settings)
+    (setq-local treesit-font-lock-feature-list
+                '((comment)
+                  (constant number pair string)
+                  (escape-sequence)
+                  (delimiter error)))
+
+    ;; Imenu.
+    (setq-local imenu-create-index-function #'toml-ts-mode--imenu)
+    (setq-local which-func-functions nil) ;; Piggyback on imenu
+
+    (treesit-major-mode-setup)))
+
+(provide 'toml-ts-mode)
+
+;;; toml-ts-mode.el ends here