less: Add a linter script to avoid compiling files.

Using lessc to check a less file results in a NameError if the file references a
variable defined in a file that inherits it. This commit adds a new linter that
just calls the less parser instead. The variable g:syntastic_less_use_less_lint
should be set to use the linter over lessc.

syntax_checkers/less-lint.coffee

@@ -0,0 +1,41 @@
+#!/usr/bin/env node
+
+fs = require 'fs'
+less = require 'less'
+args = process.argv.slice(1)
+options = {}
+
+args = args.filter (arg) ->
+    match = arg.match(/^-I(.+)$/)
+    if match
+        options.paths.push(match[1]);
+        return false
+
+    match = arg.match(/^--?([a-z][\-0-9a-z]*)(?:=([^\s]+))?$/i)
+    if match
+        arg = match[1]
+    else
+        return arg
+
+    switch arg
+        when 'strict-imports' then options.strictImports = true
+        when 'include-path'
+            options.paths = match[2].split(if os.type().match(/Windows/) then ';' else ':')
+                .map (p) ->
+                    if p
+                        return path.resolve(process.cwd(), p)
+        when 'O0' then options.optimization = 0
+        when 'O1' then options.optimization = 1
+        when 'O2' then options.optimization = 2
+
+options.filename = args[1]
+
+parser = new(less.Parser) options
+
+fs.readFile(options.filename, 'utf-8', (err,data) ->
+    parser.parse(data, (err, tree) ->
+        if err
+            less.writeError err
+            process.exit(1)
+    )
+)

syntax_checkers/less-lint.js

@@ -0,0 +1,57 @@
+// Generated by CoffeeScript 1.3.3
+(function() {
+  var args, fs, less, options, parser;
+
+  fs = require('fs');
+
+  less = require('less');
+
+  args = process.argv.slice(1);
+
+  options = {};
+
+  args = args.filter(function(arg) {
+    var match;
+    match = arg.match(/^-I(.+)$/);
+    if (match) {
+      options.paths.push(match[1]);
+      return false;
+    }
+    match = arg.match(/^--?([a-z][\-0-9a-z]*)(?:=([^\s]+))?$/i);
+    if (match) {
+      arg = match[1];
+    } else {
+      return arg;
+    }
+    switch (arg) {
+      case 'strict-imports':
+        return options.strictImports = true;
+      case 'include-path':
+        return options.paths = match[2].split(os.type().match(/Windows/) ? ';' : ':').map(function(p) {
+          if (p) {
+            return path.resolve(process.cwd(), p);
+          }
+        });
+      case 'O0':
+        return options.optimization = 0;
+      case 'O1':
+        return options.optimization = 1;
+      case 'O2':
+        return options.optimization = 2;
+    }
+  });
+
+  options.filename = args[1];
+
+  parser = new less.Parser(options);
+
+  fs.readFile(options.filename, 'utf-8', function(err, data) {
+    return parser.parse(data, function(err, tree) {
+      if (err) {
+        less.writeError(err);
+        return process.exit(1);
+      }
+    });
+  });
+
+}).call(this);

syntax_checkers/less.vim

@@ -9,6 +9,14 @@
 "             See http://sam.zoy.org/wtfpl/COPYING for more details.
 "
 "============================================================================
+
+" To send additional options to less use the variable g:syntastic_less_options.
+" The default is
+"   let g:syntastic_less_options = "--no-color"
+"
+" To use less-lint instead of less set the variable
+" g:syntastic_less_use_less_lint.
+
 if exists("loaded_less_syntax_checker")
     finish
 endif
@@ -23,8 +31,15 @@ if !exists("g:syntastic_less_options")
     let g:syntastic_less_options = "--no-color"
 endif
 
+if !exists("g:syntastic_less_use_less_lint") || g:syntastic_less_use_less_lint == 0
+    let s:check_file = 'lessc'
+else
+    let s:check_file = 'node ' . expand('<sfile>:p:h') . '/less-lint.js'
+end
+
 function! SyntaxCheckers_less_GetLocList()
-    let makeprg = 'lessc '. g:syntastic_less_options .' '.  shellescape(expand('%')) . ' /dev/null'
+    let makeprg = s:check_file . ' ' . g:syntastic_less_options . ' ' .
+                \ shellescape(expand('%')) . ' /dev/null'
 
     "lessc >= 1.2
     let errorformat = '%m in %f:%l:%c'