Fixes and tweaks for the new Less CSS mode

* etc/NEWS: Add an entry for the new mode.

* lisp/textmodes/less-css-mode.el (less-css): Tweak docstring.
(less-css-lessc-command): Tweak docstring. Don't mark it as
safe. Don't autoload.
(less-css-compile-at-save, less-css-lessc-options)
(less-css-output-directory): Tweak docstrings. Don't autoload.
(less-css-output-file-name): Tweak docstring. Don't mark it as safe.
(less-css-input-file-name): Tweak docstring. Don't autoload.
(less-css-compile-maybe): Use `when' for one-armed `if'.
(less-css--output-path): Tweak docstring.
(less-css--maybe-shell-quote-command): Remove function.
(less-css-compile): Don't autoload. Tweak docstring and message. Fix
compiler warning. Use `string-join' instead of `mapconcat'.
(less-css-font-lock-keywords): Use `font-lock-variable-name-face' for
variables.
(less-css-mode-syntax-table, less-css-mode-map): New variables.
(less-css-mode): Change status line mode name from "LESS" to
"Less". Tweak docstring. Move syntax table definitions to
`less-css-mode-syntax-table'.
(less-css-indent-line): Remove function.

2 files changed, 122 insertions, 145 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 3f38153048c..9e86af57757 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1106,6 +1106,9 @@ fontification, and commenting for embedded JavaScript and CSS.
 
 ** New minor mode 'pixel-scroll-mode' provides smooth pixel-level scrolling.
 
+** New major mode 'less-css-mode' (a minor variant of 'css-mode') for
+editing Less files.
+
 
 * Incompatible Lisp Changes in Emacs 26.1
 
diff --git a/lisp/textmodes/less-css-mode.el b/lisp/textmodes/less-css-mode.el
index 8a981d67b93..b38f2594291 100644
--- a/lisp/textmodes/less-css-mode.el
+++ b/lisp/textmodes/less-css-mode.el
@@ -1,36 +1,41 @@
-;;; less-css-mode.el --- Major mode for editing LESS CSS files (lesscss.org)
-;;
-;; Copyright (C) 2011-2014 Steve Purcell
-;;
+;;; less-css-mode.el --- Major mode for editing Less CSS files  -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2011-2017 Free Software Foundation, Inc.
+
 ;; Author: Steve Purcell <steve@sanityinc.com>
-;; URL: https://github.com/purcell/less-css-mode
-;; Keywords: less css mode
-;; Version: DEV
-;;
-;; 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 2 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.
-;;
+;; Maintainer: Simen Heggestøyl <simenheg@gmail.com>
+;; Keywords: hypermedia
+
+;; 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 <http://www.gnu.org/licenses/>.
+
 ;;; Commentary:
-;;
-;; This mode provides syntax highlighting for LESS CSS files, plus
-;; optional support for compilation of .less files to .css files at
-;; the time they are saved: use `less-css-compile-at-save' to enable
-;; this.
+
+;; This mode provides syntax highlighting for Less CSS files
+;; (http://lesscss.org/), plus optional support for compilation of
+;; .less files to .css files at the time they are saved: use
+;; `less-css-compile-at-save' to enable this.
 ;;
 ;; Command line utility "lessc" is required if setting
 ;; `less-css-compile-at-save' to t.  To install "lessc" using the
-;; Node.js package manager, run "npm install less"
+;; Node.js package manager, run "npm install less".
 ;;
 ;; Also make sure the "lessc" executable is in Emacs' PATH, example:
-;; (setq exec-path (cons (expand-file-name "~/.gem/ruby/1.8/bin") exec-path))
-;; or customize `less-css-lessc-command' to point to your "lessc" executable.
+;; (push (expand-file-name "~/.gem/ruby/1.8/bin") exec-path)
+;; or customize `less-css-lessc-command' to point to your "lessc"
+;; executable.
 ;;
 ;; We target lessc >= 1.4.0, and thus use the `--no-color' flag by
 ;; default.  You may want to adjust `less-css-lessc-options' for
@@ -56,148 +61,122 @@
 ;;
 ;; If you don't need CSS output but would like to be warned of any
 ;; syntax errors in your .less source, consider using `flymake-less':
-;; https://github.com/purcell/flymake-less
-;;
+;; https://github.com/purcell/flymake-less.
+
 ;;; Credits
-;;
+
 ;; The original code for this mode was, in large part, written using
 ;; Anton Johansson's scss-mode as a template -- thanks Anton!
 ;; https://github.com/antonj
-;;
+
 ;;; Code:
 
-(require 'derived)
 (require 'compile)
-
-;; There are at least three css-mode.el implementations, but we need
-;; the right one in order to work as expected, not the versions by
-;; Landström or Garshol
-
 (require 'css-mode)
-(unless (or (boundp 'css-navigation-syntax-table)
-            (functionp 'css-smie-rules))
-  (error "Wrong css-mode.el: please use the version by Stefan Monnier, bundled with Emacs >= 23"))
+(require 'derived)
+(eval-when-compile (require 'subr-x))
 
 (defgroup less-css nil
-  "Less-css mode"
+  "Less CSS mode."
   :prefix "less-css-"
   :group 'css)
 
-;;;###autoload
 (defcustom less-css-lessc-command "lessc"
-  "Command used to compile LESS files.
-Should be lessc or the complete path to your lessc executable,
-  e.g.: \"~/.gem/ruby/1.8/bin/lessc\""
-  :type 'file
-  :group 'less-css
-  :safe 'stringp)
+  "Command used to compile Less files.
+Should be \"lessc\" or the complete path to your lessc
+executable, e.g.: \"~/.gem/ruby/1.8/bin/lessc\"."
+  :type 'file)
 
-;;;###autoload
 (defcustom less-css-compile-at-save nil
-  "If non-nil, the LESS buffers will be compiled to CSS after each save."
-  :type 'boolean
-  :group 'less-css
-  :safe 'booleanp)
-
+  "If non-nil, Less buffers are compiled to CSS after each save."
+  :type 'boolean)
 ;;;###autoload
-(defcustom less-css-lessc-options '("--no-color")
-  "Command line options for less executable.
+(put 'less-css-compile-at-save 'safe-local-variable 'booleanp)
 
+(defcustom less-css-lessc-options '("--no-color")
+  "Command line options for Less executable.
 Use \"-x\" to minify output."
-  :type '(repeat string)
-  :group 'less-css
-  :safe t)
-
+  :type '(repeat string))
 ;;;###autoload
-(defcustom less-css-output-directory nil
-  "Directory in which to save CSS, or nil to use the LESS file's directory.
+(put 'less-css-lessc-options 'safe-local-variable t)
 
-This path is expanded relative to the directory of the LESS file
+(defcustom less-css-output-directory nil
+  "Directory in which to save CSS, or nil to use the Less file's directory.
+This path is expanded relative to the directory of the Less file
 using `expand-file-name', so both relative and absolute paths
 will work as expected."
-  :type 'directory
-  :group 'less-css
-  :safe 'stringp)
-
+  :type 'directory)
 ;;;###autoload
+(put 'less-css-output-directory 'safe-local-variable 'stringp)
+
 (defcustom less-css-output-file-name nil
   "File name in which to save CSS, or nil to use <name>.css for <name>.less.
-
 This can be also be set to a full path, or a relative path.  If
 the path is relative, it will be relative to the value of
 `less-css-output-dir', if set, or the current directory by
 default."
-  :type 'file
-  :group 'less-css
-  :safe 'stringp)
+  :type 'file)
 (make-variable-buffer-local 'less-css-output-file-name)
 
-;;;###autoload
 (defcustom less-css-input-file-name nil
   "File name which will be compiled to CSS.
-
 When the current buffer is saved `less-css-input-file-name' file
-will be compiled to css instead of the current file.
+will be compiled to CSS instead of the current file.
 
 Set this in order to trigger compilation of a \"master\" .less
 file which includes the current file.  The best way to set this
 variable in most cases is likely to be via directory local
 variables.
 
-This can be also be set to a full path, or a relative path. If
-the path is relative, it will be relative to the the current directory by
-default."
-  :type 'file
-  :group 'less-css
-  :safe 'stringp)
+This can be also be set to a full path, or a relative path.  If
+the path is relative, it will be relative to the the current
+directory by default."
+  :type 'file)
+;;;###autoload
+(put 'less-css-input-file-name 'safe-local-variable 'stringp)
 (make-variable-buffer-local 'less-css-input-file-name)
 
 (defconst less-css-default-error-regex
   "^\\(?:\e\\[31m\\)?\\([^\e\n]*\\|FileError:.*\n\\)\\(?:\e\\[39m\e\\[31m\\)? in \\(?:\e\\[39m\\)?\\([^ \r\n\t\e]+\\)\\(?:\e\\[90m\\)?\\(?::\\| on line \\)\\([0-9]+\\)\\(?::\\|, column \\)\\([0-9]+\\):?\\(?:\e\\[39m\\)?")
 
-
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-;; Compilation to CSS
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;; Compilation to CSS
 
 (add-to-list 'compilation-error-regexp-alist-alist
              (list 'less-css less-css-default-error-regex 2 3 4 nil 1))
 (add-to-list 'compilation-error-regexp-alist 'less-css)
 
-
 (defun less-css-compile-maybe ()
   "Run `less-css-compile' if `less-css-compile-at-save' is non-nil."
-  (if less-css-compile-at-save
-      (less-css-compile)))
+  (when less-css-compile-at-save
+    (less-css-compile)))
 
 (defun less-css--output-path ()
-  "Calculate the path for the compiled CSS file created by `less-css-compile'."
-  (expand-file-name (or less-css-output-file-name
-                        (concat (file-name-nondirectory (file-name-sans-extension buffer-file-name)) ".css"))
-                    (or less-css-output-directory default-directory)))
+  "Return the path to use for the compiled CSS file."
+  (expand-file-name
+   (or less-css-output-file-name
+       (concat
+        (file-name-nondirectory
+         (file-name-sans-extension buffer-file-name))
+        ".css"))
+   (or less-css-output-directory default-directory)))
 
-(defun less-css--maybe-shell-quote-command (command)
-  "Selectively shell-quote COMMAND appropriately for `system-type'."
-  (funcall (if (eq system-type 'windows-nt)
-               'identity
-             'shell-quote-argument) command))
-
-;;;###autoload
 (defun less-css-compile ()
-  "Compiles the current buffer to css using `less-css-lessc-command'."
+  "Compile the current buffer to CSS using `less-css-lessc-command'."
   (interactive)
-  (message "Compiling less to css")
-  (let ((compilation-buffer-name-function (lambda (mode-name) "*less-css-compilation*")))
+  (message "Compiling Less to CSS")
+  (let ((compilation-buffer-name-function
+         (lambda (_) "*less-css-compilation*")))
     (save-window-excursion
       (with-current-buffer
           (compile
-           (mapconcat 'identity
-                      (append (list (less-css--maybe-shell-quote-command less-css-lessc-command))
-                              (mapcar 'shell-quote-argument less-css-lessc-options)
-                              (list (shell-quote-argument
-                                     (or less-css-input-file-name buffer-file-name))
-                                    (shell-quote-argument (less-css--output-path))))
-                      " "))
+           (string-join
+            (append
+             (list less-css-lessc-command)
+             (mapcar #'shell-quote-argument less-css-lessc-options)
+             (list (shell-quote-argument
+                    (or less-css-input-file-name buffer-file-name))
+                   (shell-quote-argument (less-css--output-path))))
+            " "))
         (add-hook 'compilation-finish-functions
                   (lambda (buf msg)
                     (unless (string-match-p "^finished" msg)
@@ -205,54 +184,49 @@ default."
                   nil
                   t)))))
 
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-;; Minor mode
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;; Major mode
 
-;; TODO: interpolation ("@{val}"), escaped values (~"..."), JS eval (~`...`), custom faces
+;; TODO:
+;; - interpolation ("@{val}")
+;; - escaped values (~"...")
+;; - JS eval (~`...`)
+;; - custom faces.
 (defconst less-css-font-lock-keywords
   '(;; Variables
-    ("@[a-z_-][a-z-_0-9]*" . font-lock-constant-face)
+    ("@[a-z_-][a-z-_0-9]*" . font-lock-variable-name-face)
     ("&" . font-lock-preprocessor-face)
     ;; Mixins
-    ("\\(?:[ \t{;]\\|^\\)\\(\\.[a-z_-][a-z-_0-9]*\\)[ \t]*;" . (1 font-lock-keyword-face)))
-  )
-
+    ("\\(?:[ \t{;]\\|^\\)\\(\\.[a-z_-][a-z-_0-9]*\\)[ \t]*;" .
+     (1 font-lock-keyword-face))))
+
+(defvar less-css-mode-syntax-table
+  (let ((st (make-syntax-table css-mode-syntax-table)))
+    ;; C++-style comments.
+    (modify-syntax-entry ?/ ". 124b" st)
+    (modify-syntax-entry ?* ". 23" st)
+    (modify-syntax-entry ?\n "> b" st)
+    ;; Special chars that sometimes come at the beginning of words.
+    (modify-syntax-entry ?. "'" st)
+    st))
+
+(defvar less-css-mode-map
+  (let ((map (make-sparse-keymap)))
+    (define-key map "\C-c\C-c" 'less-css-compile)
+    map))
+
+;;;###autoload (add-to-list 'auto-mode-alist '("\\.less\\'" . less-css-mode))
 ;;;###autoload
-(define-derived-mode less-css-mode css-mode "LESS"
-  "Major mode for editing LESS files, http://lesscss.org/
+(define-derived-mode less-css-mode css-mode "Less"
+  "Major mode for editing Less files (http://lesscss.org/).
 Special commands:
 \\{less-css-mode-map}"
   (font-lock-add-keywords nil less-css-font-lock-keywords)
-  ;; cpp-style comments
-  (modify-syntax-entry ?/ ". 124b" less-css-mode-syntax-table)
-  (modify-syntax-entry ?* ". 23" less-css-mode-syntax-table)
-  (modify-syntax-entry ?\n "> b" less-css-mode-syntax-table)
-  ;; Special chars that sometimes come at the beginning of words.
-  (modify-syntax-entry ?. "'" less-css-mode-syntax-table)
-
-  (set (make-local-variable 'comment-start) "//")
-  (set (make-local-variable 'comment-end) "")
-  (set (make-local-variable 'indent-line-function) 'less-css-indent-line)
-  (when (functionp 'css-smie-rules)
-    (smie-setup css-smie-grammar #'css-smie-rules
-                :forward-token #'css-smie--forward-token
-                :backward-token #'css-smie--backward-token))
-
+  (setq-local comment-start "//")
+  (setq-local comment-end "")
+  (setq-local comment-continue " *")
+  (setq-local comment-start-skip "/[*/]+[ \t]*")
+  (setq-local comment-end-skip "[ \t]*\\(?:\n\\|\\*+/\\)")
   (add-hook 'after-save-hook 'less-css-compile-maybe nil t))
 
-(define-key less-css-mode-map "\C-c\C-c" 'less-css-compile)
-
-(defun less-css-indent-line ()
-  "Indent current line according to LESS CSS indentation rules."
-  (let ((css-navigation-syntax-table less-css-mode-syntax-table))
-    (if (fboundp 'css-indent-line)
-        (css-indent-line)
-      (smie-indent-line))))
-
-;;;###autoload
-(add-to-list 'auto-mode-alist '("\\.less\\'" . less-css-mode))
-
-
 (provide 'less-css-mode)
 ;;; less-css-mode.el ends here