Support || operator for variables

lib/less/parser.js

@@ -1049,6 +1049,16 @@ less.Parser = function Parser(env) {
                     return operation || m;
                 }
             },
+            bor: function() {
+
+            	var m, a, op, operation;
+            	if (m = $(this.addition)) {
+            		while ((op = $(/^\|\|\s+/)) && (a = $(this.addition))) {
+            			operation = new(tree.Operation)(op, [operation || m, a]);
+            		}
+            		return operation || m;
+            	}
+            },
 
             //
             // An operand is anything that can be part of an operation,
@@ -1075,7 +1085,7 @@ less.Parser = function Parser(env) {
             expression: function () {
                 var e, delim, entities = [], d;
 
-                while (e = $(this.addition) || $(this.entity)) {
+                while (e = $(this.bor) || $(this.entity)) {
                     entities.push(e);
                 }
                 if (entities.length > 0) {

lib/less/tree/color.js

@@ -58,11 +58,12 @@ tree.Color.prototype = {
     //
     operate: function (op, other) {
         var result = [];
-
+        if (op == '||') {
+        	return this||other;
+        }
         if (! (other instanceof tree.Color)) {
             other = other.toColor();
         }
-
         for (var c = 0; c < 3; c++) {
             result[c] = tree.operate(op, this.rgb[c], other.rgb[c]);
         }

lib/less/tree/import.js

@@ -23,7 +23,7 @@ tree.Import = function (path, imports) {
         this.path = path.value.value || path.value;
     }
 
-    this.css = /css$/.test(this.path);
+    this.css = /css$/.test(this.path) && !/less\.css$/.test(this.path);//precompile less.css and .less files!
 
     // Only pre-compile .less files
     if (! this.css) {

lib/less/tree/operation.js

@@ -26,6 +26,7 @@ tree.operate = function (op, a, b) {
         case '-': return a - b;
         case '*': return a * b;
         case '/': return a / b;
+        case '||': return a || b;
     }
 };
 

lib/less/tree/ruleset.js

@@ -62,6 +62,7 @@ tree.Ruleset.prototype = {
         else {
             return this._variables = this.rules.reduce(function (hash, r) {
                 if (r instanceof tree.Rule && r.variable === true) {
+                	r.prevValue = hash[r.name];
                     hash[r.name] = r;
                 }
                 return hash;

lib/less/tree/value.js

@@ -3,7 +3,11 @@
 tree.Value = function (value) {
     this.value = value;
     this.is = 'value';
+    if (value ===undefined) {
+    	this.operate = function(op,other){return op=='||'?other:undefined;};
+    }
 };
+
 tree.Value.prototype = {
     eval: function (env) {
         if (this.value.length === 1) {

lib/less/tree/variable.js

@@ -11,14 +11,26 @@ tree.Variable.prototype = {
 
         if (variable = tree.find(env.frames, function (frame) {
             if (v = frame.variable(name)) {
-                return v.value.eval(env);
+            	if (!v.isEvaluating) { //stop recursive evaluation by returning a special value
+	            		v.isEvaluating = true;
+	            	try {
+	            		return v.value.eval(env);
+	            	} finally {
+	            		v.isEvaluating = undefined;
+	            	}
+            	} else if (v.prevValue) {
+            		return v.prevValue.value.eval(env);
+            	} else {
+            		return new tree.Value(undefined);
+            	}
             }
-        })) { return variable }
+        })) { return variable; }
         else {
             throw { message: "variable " + name + " is undefined",
                     index: this.index };
         }
     }
 };
 
+
 })(require('less/tree'));