From aeba089de19610b0b6590ca786dcc0cabeb25e51 Mon Sep 17 00:00:00 2001
From: Philip Guerrant <pguerrant@gmail.com>
Date: Mon, 2 Dec 2013 15:23:16 -0700
Subject: [PATCH] Add support for default variables using "?"

---
 lib/less/parser.js       | 28 +++++++++++++++++++++++-----
 lib/less/tree/rule.js    |  5 +++--
 lib/less/tree/ruleset.js |  4 +++-
 3 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/lib/less/parser.js b/lib/less/parser.js
index 32197d668..c1619d560 100644
--- a/lib/less/parser.js
+++ b/lib/less/parser.js
@@ -886,6 +886,19 @@ less.Parser = function Parser(env) {
                 if (input.charAt(i) === '@' && (name = $(/^(@[\w-]+)\s*:/))) { return name[1]; }
             },
 
+            //
+            // The name portion of a default variable definition. Used in the `rule` parser
+            //
+            //     ?fink:
+            //
+            defaultVariable: function () {
+                var name;
+
+                if (input.charAt(i) === '?' && (name = $(/^(\?[\w-]+)\s*:/))) {
+                    return name[1].replace('?', '@');
+                }
+            },
+
             //
             // extend syntax - used to extend selectors
             //
@@ -1319,19 +1332,24 @@ less.Parser = function Parser(env) {
                 }
             },
             rule: function (tryAnonymous) {
-                var name, value, c = input.charAt(i), important, merge = false;
+                var name, value, c = input.charAt(i), important, isDefault, isVar, merge = false;
                 save();
 
                 if (c === '.' || c === '#' || c === '&') { return; }
 
-                if (name = $(this.variable) || $(this.ruleProperty)) {
+                name = $(this.defaultVariable);
+                isDefault = !!name;
+                name = name || $(this.variable);
+                isVar = !!name;
+                name = name || $(this.ruleProperty);
+
+                if (name) {
                     // prefer to try to parse first if its a variable or we are compressing
                     // but always fallback on the other one
-                    value = !tryAnonymous && (env.compress || (name.charAt(0) === '@')) ?
+                    value = !tryAnonymous && (env.compress || isVar) ?
                         ($(this.value) || $(this.anonymousValue)) :
                         ($(this.anonymousValue) || $(this.value));
 
-
                     important = $(this.important);
                     if (name[name.length-1] === "+") {
                         merge = true;
@@ -1339,7 +1357,7 @@ less.Parser = function Parser(env) {
                     }
 
                     if (value && $(this.end)) {
-                        return new (tree.Rule)(name, value, important, merge, memo, env.currentFileInfo);
+                        return new (tree.Rule)(name, value, important, merge, memo, env.currentFileInfo, null, isDefault);
                     } else {
                         furthest = i;
                         restore();
diff --git a/lib/less/tree/rule.js b/lib/less/tree/rule.js
index 20562094d..1a6404041 100644
--- a/lib/less/tree/rule.js
+++ b/lib/less/tree/rule.js
@@ -1,6 +1,6 @@
 (function (tree) {
 
-tree.Rule = function (name, value, important, merge, index, currentFileInfo, inline) {
+tree.Rule = function (name, value, important, merge, index, currentFileInfo, inline, isDefault) {
     this.name = name;
     this.value = (value instanceof tree.Value) ? value : new(tree.Value)([value]);
     this.important = important ? ' ' + important.trim() : '';
@@ -9,6 +9,7 @@ tree.Rule = function (name, value, important, merge, index, currentFileInfo, inl
     this.currentFileInfo = currentFileInfo;
     this.inline = inline || false;
     this.variable = (name.charAt(0) === '@');
+    this.isDefault = isDefault;
 };
 
 tree.Rule.prototype = {
@@ -40,7 +41,7 @@ tree.Rule.prototype = {
                               this.value.eval(env),
                               this.important,
                               this.merge,
-                              this.index, this.currentFileInfo, this.inline);
+                              this.index, this.currentFileInfo, this.inline, this.isDefault);
         }
         finally {
             if (strictMathBypass) {
diff --git a/lib/less/tree/ruleset.js b/lib/less/tree/ruleset.js
index a89dfb001..69fd42dac 100644
--- a/lib/less/tree/ruleset.js
+++ b/lib/less/tree/ruleset.js
@@ -145,7 +145,9 @@ tree.Ruleset.prototype = {
         else {
             return this._variables = this.rules.reduce(function (hash, r) {
                 if (r instanceof tree.Rule && r.variable === true) {
-                    hash[r.name] = r;
+                    if (!r.isDefault || !hash[r.name]) {
+                        hash[r.name] = r;
+                    }
                 }
                 return hash;
             }, {});