Fix #861 and introduce tests for errors

lib/less/parser.js

@@ -780,6 +780,8 @@ less.Parser = function Parser(env) {
                     var elements = [], e, c, args = [], arg, index = i, s = input.charAt(i), name, value, important = false;
 
                     if (s !== '.' && s !== '#') { return }
+                    
+                    save(); // stop us absorbing part of an invalid selector
 
                     while (e = $(/^[#.](?:[\w-]|\\(?:[A-Fa-f0-9]{1,6} ?|[^A-Fa-f0-9]))+/)) {
                         elements.push(new(tree.Element)(c, e, i));
@@ -818,6 +820,8 @@ less.Parser = function Parser(env) {
                     if (elements.length > 0 && ($(';') || peek('}'))) {
                         return new(tree.mixin.Call)(elements, args, index, env.filename, important);
                     }
+                    
+                    restore();
                 },
 
                 //

test/less-test.js

@@ -44,6 +44,33 @@ fs.readdirSync('test/less').forEach(function (file) {
     });
 });
 
+fs.readdirSync('test/less/errors').forEach(function (file) {
+    if (! /\.less/.test(file)) { return }
+
+    toCSS('test/less/errors/' + file, function (err, less) {
+        var name = path.basename(file, '.less');
+
+        fs.readFile(path.join('test/less/errors', name) + '.txt', 'utf-8', function (e, expectedErr) {
+            sys.print("- error/" + name + ": ")
+            if (err.message === expectedErr) { sys.print(stylize('OK', 'green')) }
+            else if (!err) {
+                sys.print(stylize("No Error", 'red'));
+            } else {
+                sys.print(stylize("FAIL", 'yellow') + '\n');
+                
+                require('diff').diffLines(expectedErr, err.message).forEach(function(item) {
+                  if(item.added || item.removed) {
+                    sys.print(stylize(item.value, item.added ? 'green' : 'red'));
+                  } else {
+                    sys.print(item.value);
+                  }
+                })
+            }
+            sys.puts("");
+        });
+    });
+});
+
 function toCSS(path, callback) {
     var tree, css;
     fs.readFile(path, 'utf-8', function (e, str) {

test/less/errors/comment-in-selector.less

@@ -0,0 +1 @@
+#gaga /* Comment */ span { color: red }

test/less/errors/comment-in-selector.txt

@@ -0,0 +1 @@
+Syntax Error on line 1