implements function isDefined. see #84

Author: Horcrux7

src/com/inet/lib/less/FunctionExpression.java

@@ -137,6 +137,7 @@ public String unit( CssFormatter formatter ) {
             case "cos":
             case "tan":
             case "length":
+            case "isdefined":
                 return "";
             case "acos":
             case "asin":
@@ -288,6 +289,10 @@ public void appendTo( CssFormatter formatter ) {
                 case "if":
                     get( get( 0 ).booleanValue( formatter ) ? 1 : 2 ).appendTo( formatter ); 
                     return;
+                case "isdefined":
+                    Expression param = get( 0 );
+                    formatter.append( Boolean.toString( param instanceof VariableExpression ? formatter.getVariable( param.toString() ) != null : true ) );
+                    return;
                 default:
                     CustomLessFunction customLessFunction = Less.CUSTOM_FUNKTIONS.get( super.toString() );
                     if( customLessFunction != null ) {
@@ -690,6 +695,11 @@ private void eval( CssFormatter formatter ) {
                         booleanValue = false;
                     }
                     return;
+                case "isdefined":
+                    type = BOOLEAN;
+                    param = get( 0 );
+                    booleanValue = param instanceof VariableExpression ? formatter.getVariable( param.toString() ) != null : true;
+                    return;
                 case "ispixel":
                     type = BOOLEAN;
                     param = get( 0 );

test/com/inet/lib/less/samples/less_org_tests/less/functions.css

@@ -137,6 +137,12 @@
   percent: true;
   em: true;
   cat: true;
+  a: true;
+  b: false;
+  c: red;
+  d: blue;
+  f: true;
+  g: red;
 }
 #alpha {
   alpha: rgba(153, 94, 51, 0.6);

test/com/inet/lib/less/samples/less_org_tests/less/functions.less

@@ -147,6 +147,14 @@
     percent: ispercentage(32%);
     em: isem(32em);
     cat: isunit(32cat, cat);
+
+    @foo: 1;
+    a:isdefined(@foo);
+    b:isdefined(@bar);
+    c:if(isdefined(@foo), red, blue);
+    d:if(isdefined(@bar), red, blue);
+    f:isdefined("hello");
+    g:if(isdefined("hello"), red, blue);
   }
 }