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;;; gn-mode.el - A major mode for editing gn files.
;; Copyright 2015 The Chromium Authors. All rights reserved.
;; Use of this source code is governed by a BSD-style license that can be
;; found in the LICENSE file.
;; Author: Elliot Glaysher <>
;; Created: April 03, 2015
;; Keywords: tools, gn, ninja, chromium
;; This file is not part of GNU Emacs.
;; This is not the official copy. The official copy can be found at:
;;; Commentary:
;; A major mode for editing GN files. GN stands for Generate Ninja. GN is the
;; meta build system used in Chromium. For more information on GN, see the GN
;; manual: <>
;;; To Do:
;; - We syntax highlight builtin actions, but don't highlight instantiations of
;; templates. Should we?
(require 'smie)
(defgroup gn nil
"Major mode for editing Generate Ninja files."
:prefix "gn-"
:group 'languages)
(defcustom gn-indent-basic 2
"The number of spaces to indent a new scope."
:group 'gn
:type 'integer)
(defcustom gn-format-command "gn format --stdin"
"The command to run to format gn files in place."
:group 'gn
:type 'string)
(defgroup gn-faces nil
"Faces used in Generate Ninja mode."
:group 'gn
:group 'faces)
(defface gn-embedded-variable
'((t :inherit font-lock-variable-name-face))
"Font lock face used to highlight variable names in strings."
:group 'gn-faces)
(defface gn-embedded-variable-boundary
'((t :bold t
:inherit gn-embedded-variable))
"Font lock face used to highlight the '$' that starts a
variable name or the '{{' and '}}' which surround it."
:group 'gn-faces)
(defvar gn-font-lock-reserved-keywords
'("true" "false" "if" "else"))
(defvar gn-font-lock-target-declaration-keywords
'("action" "action_foreach" "bundle_data" "copy" "create_bundle" "executable"
"group" "loadable_module" "shared_library" "source_set" "static_library"
;; pool() is handled specially since it's also a variable name
(defvar gn-font-lock-buildfile-fun-keywords
'("assert" "config" "declare_args" "defined" "exec_script" "foreach"
"forward_variables_from" "get_label_info" "get_path_info"
"get_target_outputs" "getenv" "import" "not_needed" "print"
"process_file_template" "read_file" "rebase_path" "set_default_toolchain"
"set_defaults" "set_sources_assignment_filter" "split_list" "template"
"tool" "toolchain" "propagates_configs" "write_file"))
(defvar gn-font-lock-predefined-var-keywords
'("current_cpu" "current_os" "current_toolchain" "default_toolchain"
"host_cpu" "host_os" "invoker" "python_path" "root_build_dir" "root_gen_dir"
"root_out_dir" "target_cpu" "target_gen_dir" "target_name" "target_os"
(defvar gn-font-lock-var-keywords
'("all_dependent_configs" "allow_circular_includes_from" "arflags" "args"
"asmflags" "assert_no_deps" "bundle_deps_filter" "bundle_executable_dir"
"bundle_plugins_dir" "bundle_resources_dir" "bundle_root_dir" "cflags"
"cflags_c" "cflags_cc" "cflags_objc" "cflags_objcc" "check_includes"
"code_signing_args" "code_signing_outputs" "code_signing_script"
"code_signing_sources" "complete_static_lib" "configs" "data" "data_deps"
"defines" "depfile" "deps" "include_dirs" "inputs" "ldflags" "lib_dirs"
"libs" "output_dir" "output_extension" "output_name"
"output_prefix_override" "outputs" "pool" "precompiled_header"
"precompiled_header_type" "precompiled_source" "product_type" "public"
"public_configs" "public_deps" "response_file_contents" "script" "sources"
"testonly" "visibility" "write_runtime_deps" "bundle_contents_dir"))
(defconst gn-font-lock-keywords
`((,(regexp-opt gn-font-lock-reserved-keywords 'words) .
(,(regexp-opt gn-font-lock-target-declaration-keywords 'words) .
(,(regexp-opt gn-font-lock-buildfile-fun-keywords 'words) .
;; pool() as a function
(1 font-lock-function-name-face))
(,(regexp-opt gn-font-lock-predefined-var-keywords 'words) .
(,(regexp-opt gn-font-lock-var-keywords 'words) .
;; $variables_like_this
(1 'gn-embedded-variable-boundary t)
(2 'gn-embedded-variable t))
;; ${variables_like_this}
("\\(\\${\\)\\([^\n }]+\\)\\(}\\)"
(1 'gn-embedded-variable-boundary t)
(2 'gn-embedded-variable t)
(3 'gn-embedded-variable-boundary t))
;; {{placeholders}} (see substitute_type.h)
("\\({{\\)\\([^\n }]+\\)\\(}}\\)"
(1 'gn-embedded-variable-boundary t)
(2 'gn-embedded-variable t)
(3 'gn-embedded-variable-boundary t))))
(defun gn-smie-rules (kind token)
"These are slightly modified indentation rules from the SMIE
Indentation Example info page. This changes the :before rule
and adds a :list-intro to handle our x = [ ] syntax."
(pcase (cons kind token)
(`(:elem . basic) gn-indent-basic)
(`(,_ . ",") (smie-rule-separator kind))
(`(:list-intro . "") gn-indent-basic)
(`(:before . ,(or `"[" `"(" `"{"))
(if (smie-rule-hanging-p) (smie-rule-parent)))
(`(:before . "if")
(and (not (smie-rule-bolp)) (smie-rule-prev-p "else")
(defun gn-fill-paragraph (&optional justify)
"We only fill inside of comments in GN mode."
(interactive "P")
(or (fill-comment-paragraph justify)
;; Never return nil; `fill-paragraph' will perform its default behavior
;; if we do.
(defun gn-run-format ()
"Run 'gn format' on the buffer in place."
;; We can't `save-excursion' here; that will put us at the beginning of the
;; shell output, aka the beginning of the document.
(let ((my-start-line (line-number-at-pos)))
(shell-command-on-region (point-min) (point-max) gn-format-command nil t)
(goto-line my-start-line)))
(defvar gn-mode-map
(let ((map (make-sparse-keymap)))
(define-key map "\C-c\C-f" 'gn-run-format)
(define-derived-mode gn-mode prog-mode "GN"
"Major mode for editing gn (Generate Ninja)."
:group 'gn
(setq-local comment-use-syntax t)
(setq-local comment-start "#")
(setq-local comment-end "")
(setq-local indent-tabs-mode nil)
(setq-local fill-paragraph-function 'gn-fill-paragraph)
(setq-local font-lock-defaults '(gn-font-lock-keywords))
;; For every 'rule("name") {', adds "name" to the imenu for quick navigation.
(setq-local imenu-generic-expression
'((nil "^\s*[a-zA-Z0-9_]+(\"\\([a-zA-Z0-9_]+\\)\")\s*{" 1)))
(smie-setup nil #'gn-smie-rules)
(setq-local smie-indent-basic gn-indent-basic)
;; python style comment: “# …”
(modify-syntax-entry ?# "< b" gn-mode-syntax-table)
(modify-syntax-entry ?\n "> b" gn-mode-syntax-table)
(modify-syntax-entry ?_ "w" gn-mode-syntax-table))
(add-to-list 'auto-mode-alist '("\\.gni?\\'" . gn-mode))
(provide 'gn-mode)