move selector joining into visitor

lib/less/join-selector-visitor.js

@@ -1,6 +1,6 @@
 (function (tree) {
     tree.joinSelectorVisitor = function() {
-        this.context = [];
+        this.contexts = [[]];
         this._visitor = new tree.visitor(this);
     };
 
@@ -18,16 +18,23 @@
         },
 
         visitRuleset: function (rulesetNode, visitArgs) {
+            var context = this.contexts[this.contexts.length - 1];
+            var paths = [];
+            this.contexts.push(paths);
 
+            if (! rulesetNode.root) {
+                rulesetNode.joinSelectors(paths, context, rulesetNode.selectors);
+                rulesetNode.paths = paths;
+            }
             return rulesetNode;
         },
-        visitMedia: function (rulesetNode, visitArgs) {
-
-            return rulesetNode;
+        visitRulesetOut: function (rulesetNode) {
+            this.contexts.length = this.contexts.length - 1;
         },
-        visitDirective: function (rulesetNode, visitArgs) {
-
-            return rulesetNode;
+        visitMedia: function (mediaNode, visitArgs) {
+            var context = this.contexts[this.contexts.length - 1];
+            mediaNode.ruleset.root = (context.length === 0 || context[0].multiMedia);
+            return mediaNode;
         }
     };
 

lib/less/tree/media.js

@@ -16,7 +16,6 @@ tree.Media.prototype = {
     toCSS: function (ctx, env) {
         var features = this.features.toCSS(env);
 
-        this.ruleset.root = (ctx.length === 0 || ctx[0].multiMedia);
         return '@media ' + features + (env.compress ? '{' : ' {\n  ') +
                this.ruleset.toCSS(ctx, env).trim().replace(/\n/g, '\n  ') +
                            (env.compress ? '}': '\n}\n');

lib/less/tree/ruleset.js

@@ -186,10 +186,6 @@ tree.Ruleset.prototype = {
             debugInfo,     // Line number debugging
             rule;
 
-        if (! this.root) {
-            this.joinSelectors(paths, context, this.selectors);
-        }
-
         // Compile rules and rulesets
         for (var i = 0; i < this.rules.length; i++) {
             rule = this.rules[i];
@@ -249,7 +245,7 @@ tree.Ruleset.prototype = {
         } else {
             if (rules.length > 0) {
                 debugInfo = tree.debugInfo(env, this);
-                selector = paths.map(function (p) {
+                selector = this.paths.map(function (p) {
                     return p.map(function (s) {
                         return s.toCSS(env);
                     }).join('').trim();