emacs: Bundle an Emacs major mode, mgmtconfig-mode

This provides syntax highlighting, commenting, and rudimentary indentation of the mgmt language.

TODO.md

@@ -75,7 +75,7 @@ level and how many hours you'd like to spend on the patch.
 - [ ] automatic language formatter, ala `gofmt`
 - [ ] gedit/gnome-builder/gtksourceview syntax highlighting
 - [ ] vim syntax highlighting
-- [ ] emacs syntax highlighting
+- [x] emacs syntax highlighting: see `misc/emacs/`
 
 ## Other
 

misc/emacs/README.md

@@ -0,0 +1,12 @@
+[![MELPA](https://melpa.org/packages/mgmtconfig-mode-badge.svg)](https://melpa.org/#/mgmtconfig-mode)
+[![MELPA Stable](https://stable.melpa.org/packages/mgmtconfig-mode-badge.svg)](https://stable.melpa.org/#/mgmtconfig-mode)
+
+# `mgmtconfig-mode`
+
+[Mgmt](https://github.com/purpleidea/mgmt/) is a distributed, event-driven, parallel configuration management tool.
+
+`mgmtconfig-mode` is an Emacs major mode for editing the [mgmt language](https://purpleidea.com/blog/2018/02/05/mgmt-configuration-language/).
+
+## Installation
+
+See the MELPA Emacs Lisp package archive’s [getting started](https://melpa.org/#/getting-started) guide.  Then, select “Options → Manage Emacs Packages” from the menu in Emacs.

misc/emacs/mgmtconfig-mode.el

@@ -0,0 +1,131 @@
+;;; mgmtconfig-mode.el --- mgmt configuration management language
+
+;; Copyright (C) 2013-2018+ James Shubin and the project contributors
+;; Written by James Shubin <james@shubin.ca> and the project contributors
+;;
+;; This program 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.
+;;
+;; This program 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 this program.  If not, see <http:;;www.gnu.org/licenses/>.
+
+;; Author: Peter Oliver <mgmtconfig@mavit.org.uk>
+;; Maintainer: Mgmt contributors <https://github.com/purpleidea/mgmt>
+;; Keywords: languages
+;; URL: https://github.com/purpleidea/mgmt/misc/emacs
+;; Package-Requires: ((emacs "24.3"))
+
+;;; Commentary:
+;;
+;; Major mode for editing the mgmt config language.  Mgmt is a
+;; distributed, event-driven, parallel configuration management tool.
+;;
+;; https://github.com/purpleidea/mgmt
+
+;;; Code:
+
+(require 'smie)
+
+(defconst mgmtconfig-smie-grammar
+      (smie-prec2->grammar
+       (smie-bnf->prec2
+        '((map ("{" pairs "}"))
+          (pairs (pair) (pair "," pairs))
+          (pair (key "=>" value))
+          (key)
+          (value)))))
+
+(defun mgmtconfig-smie-rules (method token)
+  "Rules for indenting the mgmt language.
+METHOD and TOKEN are as for `smie-rules-function'."
+  (pcase (cons method token)
+    ;; Statements in mgmt end at the end of a line.  This causes SMIE
+    ;; not to indent every line as if it were a continuation of the
+    ;; statement on the previous line:
+    (`(:list-intro . ,_) t)))
+
+(defconst mgmtconfig-mode-syntax-table
+  (let ((st (make-syntax-table)))
+    (modify-syntax-entry ?# "<" st)
+    (modify-syntax-entry ?\n ">" st)
+    st))
+
+(defconst mgmtconfig-mode-highlights
+  ;; Keywords and types cribbed from
+  ;; https://github.com/purpleidea/mgmt/blob/master/lang/lexer.nex.
+  ;; Resources from
+  ;; https://github.com/purpleidea/mgmt/tree/master/resources.
+  `((,(regexp-opt (list "if"
+                        "else"
+                        "in"
+                        "true"
+                        "false")
+                  'words)
+     . font-lock-keyword-face)
+    (,(concat "^\\s-*" (regexp-opt (list "actions"
+                                         "augeas"
+                                         "autoedge"
+                                         "autogroup"
+                                         "aws_ec2"
+                                         "edge"
+                                         "exec"
+                                         "file"
+                                         "graph"
+                                         "group"
+                                         "hostname"
+                                         "interfaces"
+                                         "kv"
+                                         "metaparams"
+                                         "mgraph"
+                                         "msg"
+                                         "noop"
+                                         "nspawn"
+                                         "password"
+                                         "pkg"
+                                         "print"
+                                         "refresh"
+                                         "resources"
+                                         "semaphore"
+                                         "sendrecv"
+                                         "svc"
+                                         "timer"
+                                         "uid"
+                                         "user"
+                                         "util"
+                                         "virt")
+                                   'words))
+     . font-lock-builtin-face)
+    (,(regexp-opt (list "bool"
+                        "str"
+                        "int"
+                        "float"
+                        "struct"
+                        "variant")
+                  'words)
+     . font-lock-type-face)
+    ("\\$\\w+" . font-lock-variable-name-face)))
+
+;;;###autoload
+(define-derived-mode mgmtconfig-mode prog-mode "mgmt"
+  "Major mode for editing the mgmt config language."
+
+  (setq-local comment-start "# ")
+  (setq-local comment-start-skip "#+\\s-*")
+
+  (setq font-lock-defaults '(mgmtconfig-mode-highlights))
+
+  (smie-setup mgmtconfig-smie-grammar #'mgmtconfig-smie-rules))
+
+;;;###autoload
+(add-to-list 'auto-mode-alist '("\\.mcl\\'" . mgmtconfig-mode))
+
+(provide 'mgmtconfig-mode)
+
+;;; mgmtconfig-mode.el ends here