preliminary support for evaluating JavaScript code inside LESS

lib/less/tree/javascript.js

@@ -0,0 +1,32 @@
+(function (tree) {
+
+tree.JavaScript = function (string, index) {
+    this.expression = string;
+    this.index = index;
+};
+tree.JavaScript.prototype = {
+    toCSS: function () {
+        return this.evaluated;
+    },
+    eval: function (env) {
+        var result,
+            expression = new(Function)('return (' + this.expression + ')'),
+            context = {};
+
+        for (var k in env.frames[0].variables()) {
+            context[k.slice(1)] = env.frames[0].variables()[k].value.eval(env).toCSS();
+        }
+
+        try {
+            result = expression.call(context);
+            this.evaluated = JSON.stringify(result);
+        } catch (e) {
+            throw { message: "JavaScript evaluation error: '" + e.name + ': ' + e.message + "'" ,
+                    index: this.index };
+        }
+        return this;
+    }
+};
+
+})(require('less/tree'));
+

lib/less/tree/mixin.js

@@ -55,10 +55,11 @@ tree.mixin.Definition = function (name, params, rules) {
     this.frames = [];
 };
 tree.mixin.Definition.prototype = {
-    toCSS: function () { return "" },
-    variable: function (name) { return this.parent.variable.call(this, name) },
-    find:     function ()     { return this.parent.find.apply(this, arguments) },
-    rulesets: function ()     { return this.parent.rulesets.apply(this) },
+    toCSS:     function () { return "" },
+    variable:  function (name) { return this.parent.variable.call(this, name) },
+    variables: function ()     { return this.parent.variables.call(this) },
+    find:      function ()     { return this.parent.find.apply(this, arguments) },
+    rulesets:  function ()     { return this.parent.rulesets.apply(this) },
 
     eval: function (env, args) {
         var frame = new(tree.Ruleset)(null, []), context;

lib/less/tree/ruleset.js

@@ -56,17 +56,20 @@ tree.Ruleset.prototype = {
     match: function (args) {
         return !args || args.length === 0;
     },
-    variable: function (name) {
-        if (this._variables) { return this._variables[name] }
+    variables: function () {
+        if (this._variables) { return this._variables }
         else {
-            return (this._variables = this.rules.reduce(function (hash, r) {
+            return this._variables = this.rules.reduce(function (hash, r) {
                 if (r instanceof tree.Rule && r.variable === true) {
                     hash[r.name] = r;
                 }
                 return hash;
-            }, {}))[name];
+            }, {});
         }
     },
+    variable: function (name) {
+        return this.variables()[name];
+    },
     rulesets: function () {
         if (this._rulesets) { return this._rulesets }
         else {