--- /dev/null
+;;; go-ts-mode.el --- tree-sitter support for Go -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2022 Free Software Foundation, Inc.
+
+;; Author : Randy Taylor <dev@rjt.dev>
+;; Maintainer : Randy Taylor <dev@rjt.dev>
+;; Created : December 2022
+;; Keywords : go 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)
+(eval-when-compile (require 'rx))
+
+(declare-function treesit-parser-create "treesit.c")
+(declare-function treesit-induce-sparse-tree "treesit.c")
+(declare-function treesit-node-child "treesit.c")
+(declare-function treesit-node-child-by-field-name "treesit.c")
+(declare-function treesit-node-start "treesit.c")
+(declare-function treesit-node-type "treesit.c")
+
+(defcustom go-ts-mode-indent-offset 4
+ "Number of spaces for each indentation step in `go-ts-mode'."
+ :version "29.1"
+ :type 'integer
+ :safe 'integerp
+ :group 'go)
+
+(defvar go-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 ?| "." table)
+ (modify-syntax-entry ?^ "." table)
+ (modify-syntax-entry ?! "." table)
+ (modify-syntax-entry ?< "." table)
+ (modify-syntax-entry ?> "." table)
+ (modify-syntax-entry ?\\ "\\" table)
+ (modify-syntax-entry ?/ ". 124b" table)
+ (modify-syntax-entry ?* ". 23" table)
+ (modify-syntax-entry ?\n "> b" table)
+ table)
+ "Syntax table for `go-ts-mode'.")
+
+(defvar go-ts-mode--indent-rules
+ `((go
+ ((node-is ")") parent-bol 0)
+ ((node-is "]") parent-bol 0)
+ ((node-is "}") parent-bol 0)
+ ((node-is "labeled_statement") no-indent)
+ ((parent-is "argument_list") parent-bol go-ts-mode-indent-offset)
+ ((parent-is "block") parent-bol go-ts-mode-indent-offset)
+ ((parent-is "const_declaration") parent-bol go-ts-mode-indent-offset)
+ ((parent-is "default_case") parent-bol go-ts-mode-indent-offset)
+ ((parent-is "expression_case") parent-bol go-ts-mode-indent-offset)
+ ((parent-is "expression_switch_statement") parent-bol 0)
+ ((parent-is "field_declaration_list") parent-bol go-ts-mode-indent-offset)
+ ((parent-is "import_spec_list") parent-bol go-ts-mode-indent-offset)
+ ((parent-is "labeled_statement") parent-bol go-ts-mode-indent-offset)
+ ((parent-is "literal_value") parent-bol go-ts-mode-indent-offset)
+ ((parent-is "type_spec") parent-bol go-ts-mode-indent-offset)
+ ((parent-is "var_declaration") parent-bol go-ts-mode-indent-offset)
+ (no-node parent-bol 0)))
+ "Tree-sitter indent rules for `go-ts-mode'.")
+
+(defvar go-ts-mode--keywords
+ '("break" "case" "chan" "const" "continue" "default" "defer" "else"
+ "fallthrough" "for" "func" "go" "goto" "if" "import" "interface" "map"
+ "package" "range" "return" "select" "struct" "switch" "type" "var")
+ "Go keywords for tree-sitter font-locking.")
+
+(defvar go-ts-mode--operators
+ '("+" "&" "+=" "&=" "&&" "==" "!=" "-" "|" "-=" "|=" "||" "<" "<="
+ "*" "^" "*=" "^=" "<-" ">" ">=" "/" "<<" "/=" "<<=" "++" "=" ":=" "%"
+ ">>" "%=" ">>=" "--" "!" "..." "&^" "&^=" "~")
+ "Go operators for tree-sitter font-locking.")
+
+(defvar go-ts-mode--font-lock-settings
+ (treesit-font-lock-rules
+ :language 'go
+ :feature 'bracket
+ '((["(" ")" "[" "]" "{" "}"]) @font-lock-bracket-face)
+
+ :language 'go
+ :feature 'comment
+ '((comment) @font-lock-comment-face)
+
+ :language 'go
+ :feature 'constant
+ '([(false) (iota) (nil) (true)] @font-lock-constant-face
+ (const_declaration
+ (const_spec name: (identifier) @font-lock-constant-face)))
+
+ :language 'go
+ :feature 'delimiter
+ '((["," "." ";" ":"]) @font-lock-delimiter-face)
+
+ :language 'go
+ :feature 'function
+ '((call_expression
+ function: (identifier) @font-lock-function-name-face)
+ (call_expression
+ function: (selector_expression
+ field: (field_identifier) @font-lock-function-name-face))
+ (function_declaration
+ name: (identifier) @font-lock-function-name-face)
+ (method_declaration
+ name: (field_identifier) @font-lock-function-name-face))
+
+ :language 'go
+ :feature 'keyword
+ `([,@go-ts-mode--keywords] @font-lock-keyword-face)
+
+ :language 'go
+ :feature 'label
+ '((label_name) @font-lock-constant-face)
+
+ :language 'go
+ :feature 'number
+ '([(float_literal)
+ (imaginary_literal)
+ (int_literal)] @font-lock-number-face)
+
+ :language 'go
+ :feature 'string
+ '([(interpreted_string_literal)
+ (raw_string_literal)
+ (rune_literal)] @font-lock-string-face)
+
+ :language 'go
+ :feature 'type
+ '([(package_identifier) (type_identifier)] @font-lock-type-face)
+
+ :language 'go
+ :feature 'variable
+ '((identifier) @font-lock-variable-name-face)
+
+ :language 'go
+ :feature 'escape-sequence
+ :override t
+ '((escape_sequence) @font-lock-escape-face)
+
+ :language 'go
+ :feature 'property
+ :override t
+ '((field_identifier) @font-lock-property-face
+ (keyed_element (_ (identifier) @font-lock-property-face)))
+
+ :language 'go
+ :feature 'error
+ :override t
+ '((ERROR) @font-lock-warning-face))
+ "Tree-sitter font-lock settings for `go-ts-mode'.")
+
+(defun go-ts-mode--imenu ()
+ "Return Imenu alist for the current buffer."
+ (let* ((node (treesit-buffer-root-node))
+ (func-tree (treesit-induce-sparse-tree
+ node "function_declaration" nil 1000))
+ (type-tree (treesit-induce-sparse-tree
+ node "type_spec" nil 1000))
+ (func-index (go-ts-mode--imenu-1 func-tree))
+ (type-index (go-ts-mode--imenu-1 type-tree)))
+ (append
+ (when func-index `(("Function" . ,func-index)))
+ (when type-index `(("Type" . ,type-index))))))
+
+(defun go-ts-mode--imenu-1 (node)
+ "Helper for `go-ts-mode--imenu'.
+Find string representation for NODE and set marker, then recurse
+the subtrees."
+ (let* ((ts-node (car node))
+ (children (cdr node))
+ (subtrees (mapcan #'go-ts-mode--imenu-1
+ children))
+ (name (when ts-node
+ (treesit-node-text
+ (pcase (treesit-node-type ts-node)
+ ("function_declaration"
+ (treesit-node-child-by-field-name ts-node "name"))
+ ("type_spec"
+ (treesit-node-child-by-field-name ts-node "name"))))))
+ (marker (when ts-node
+ (set-marker (make-marker)
+ (treesit-node-start ts-node)))))
+ (cond
+ ((or (null ts-node) (null name)) subtrees)
+ (subtrees
+ `((,name ,(cons name marker) ,@subtrees)))
+ (t
+ `((,name . ,marker))))))
+
+;;;###autoload
+(add-to-list 'auto-mode-alist '("\\.go\\'" . go-ts-mode))
+
+;;;###autoload
+(define-derived-mode go-ts-mode prog-mode "Go"
+ "Major mode for editing Go, powered by tree-sitter."
+ :group 'go
+ :syntax-table go-ts-mode--syntax-table
+
+ (when (treesit-ready-p 'go)
+ (treesit-parser-create 'go)
+
+ ;; Comments.
+ (setq-local comment-start "// ")
+ (setq-local comment-end "")
+ (setq-local comment-start-skip (rx "//" (* (syntax whitespace))))
+
+ ;; Imenu.
+ (setq-local imenu-create-index-function #'go-ts-mode--imenu)
+ (setq-local which-func-functions nil)
+
+ ;; Indent.
+ (setq-local indent-tabs-mode t
+ treesit-simple-indent-rules go-ts-mode--indent-rules)
+
+ ;; Font-lock.
+ (setq-local treesit-font-lock-settings go-ts-mode--font-lock-settings)
+ (setq-local treesit-font-lock-feature-list
+ '(( comment)
+ ( keyword string type)
+ ( constant escape-sequence function label number
+ property variable)
+ ( bracket delimiter error operator)))
+
+ (treesit-major-mode-setup)))
+
+;; go.mod support.
+
+(defvar go-mod-ts-mode--syntax-table
+ (let ((table (make-syntax-table)))
+ (modify-syntax-entry ?/ ". 124b" table)
+ (modify-syntax-entry ?\n "> b" table)
+ table)
+ "Syntax table for `go-mod-ts-mode'.")
+
+(defvar go-mod-ts-mode--indent-rules
+ `((gomod
+ ((node-is ")") parent-bol 0)
+ ((parent-is "exclude_directive") parent-bol go-ts-mode-indent-offset)
+ ((parent-is "module_directive") parent-bol go-ts-mode-indent-offset)
+ ((parent-is "replace_directive") parent-bol go-ts-mode-indent-offset)
+ ((parent-is "require_directive") parent-bol go-ts-mode-indent-offset)
+ ((parent-is "retract_directive") parent-bol go-ts-mode-indent-offset)
+ ((go-mod-ts-mode--in-directive-p) no-indent go-ts-mode-indent-offset)
+ (no-node no-indent 0)))
+ "Tree-sitter indent rules for `go-mod-ts-mode'.")
+
+(defun go-mod-ts-mode--in-directive-p ()
+ "Return non-nil if inside a directive.
+When entering an empty directive or adding a new entry to one, no node
+will be present meaning none of the indentation rules will match,
+because there is no parent to match against. This function determines
+what the parent of the node would be if it were a node."
+ (lambda (node _ _ &rest _)
+ (unless (treesit-node-type node)
+ (save-excursion
+ (backward-up-list)
+ (back-to-indentation)
+ (pcase (treesit-node-type (treesit-node-at (point)))
+ ("exclude" t)
+ ("module" t)
+ ("replace" t)
+ ("require" t)
+ ("retract" t))))))
+
+(defvar go-mod-ts-mode--keywords
+ '("exclude" "go" "module" "replace" "require" "retract")
+ "go.mod keywords for tree-sitter font-locking.")
+
+(defvar go-mod-ts-mode--font-lock-settings
+ (treesit-font-lock-rules
+ :language 'gomod
+ :feature 'bracket
+ '((["(" ")"]) @font-lock-bracket-face)
+
+ :language 'gomod
+ :feature 'comment
+ '((comment) @font-lock-comment-face)
+
+ :language 'gomod
+ :feature 'keyword
+ `([,@go-mod-ts-mode--keywords] @font-lock-keyword-face)
+
+ :language 'gomod
+ :feature 'number
+ '([(go_version) (version)] @font-lock-number-face)
+
+ :language 'gomod
+ :feature 'operator
+ '((["=>"]) @font-lock-operator-face)
+
+ :language 'gomod
+ :feature 'error
+ :override t
+ '((ERROR) @font-lock-warning-face))
+ "Tree-sitter font-lock settings for `go-mod-ts-mode'.")
+
+;;;###autoload
+(add-to-list 'auto-mode-alist '("/go\\.mod\\'" . go-mod-ts-mode))
+
+;;;###autoload
+(define-derived-mode go-mod-ts-mode prog-mode "Go Mod"
+ "Major mode for editing go.mod files, powered by tree-sitter."
+ :group 'go
+ :syntax-table go-mod-ts-mode--syntax-table
+
+ (when (treesit-ready-p 'gomod)
+ (treesit-parser-create 'gomod)
+
+ ;; Comments.
+ (setq-local comment-start "// ")
+ (setq-local comment-end "")
+ (setq-local comment-start-skip (rx "//" (* (syntax whitespace))))
+
+ ;; Indent.
+ (setq-local indent-tabs-mode t
+ treesit-simple-indent-rules go-mod-ts-mode--indent-rules)
+
+ ;; Font-lock.
+ (setq-local treesit-font-lock-settings go-mod-ts-mode--font-lock-settings)
+ (setq-local treesit-font-lock-feature-list
+ '((comment)
+ (keyword)
+ (number)
+ (bracket error operator)))
+
+ (treesit-major-mode-setup)))
+
+(provide 'go-ts-mode)
+
+;;; go-ts-mode.el ends here
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