percentage function should throw error if result would be NaN

lib/less/functions/math-helper.js

@@ -0,0 +1,16 @@
+var Dimension = require("../tree/dimension");
+
+var MathHelper = function() {
+};
+MathHelper._math = function (fn, unit, n) {
+    if (!(n instanceof Dimension)) {
+        throw { type: "Argument", message: "argument must be a number" };
+    }
+    if (unit == null) {
+        unit = n.unit;
+    } else {
+        n = n.unify();
+    }
+    return new Dimension(fn(parseFloat(n.value)), unit);
+};
+module.exports = MathHelper;

lib/less/functions/math.js

@@ -1,5 +1,5 @@
-var Dimension = require("../tree/dimension"),
-    functionRegistry = require("./function-registry");
+var functionRegistry = require("./function-registry"),
+    mathHelper = require("./math-helper.js");
 
 var mathFunctions = {
     // name,  unit
@@ -15,27 +15,15 @@ var mathFunctions = {
     acos:  "rad"
 };
 
-function _math(fn, unit, n) {
-    if (!(n instanceof Dimension)) {
-        throw { type: "Argument", message: "argument must be a number" };
-    }
-    if (unit == null) {
-        unit = n.unit;
-    } else {
-        n = n.unify();
-    }
-    return new Dimension(fn(parseFloat(n.value)), unit);
-}
-
 for (var f in mathFunctions) {
     if (mathFunctions.hasOwnProperty(f)) {
-        mathFunctions[f] = _math.bind(null, Math[f], mathFunctions[f]);
+        mathFunctions[f] = mathHelper._math.bind(null, Math[f], mathFunctions[f]);
     }
 }
 
 mathFunctions.round = function (n, f) {
     var fraction = typeof f === "undefined" ? 0 : f.value;
-    return _math(function(num) { return num.toFixed(fraction); }, null, n);
+    return mathHelper._math(function(num) { return num.toFixed(fraction); }, null, n);
 };
 
 functionRegistry.addMultiple(mathFunctions);

lib/less/functions/number.js

@@ -1,6 +1,7 @@
 var Dimension = require("../tree/dimension"),
     Anonymous = require("../tree/anonymous"),
-    functionRegistry = require("./function-registry");
+    functionRegistry = require("./function-registry"),
+    mathHelper = require("./math-helper.js");
 
 var minMax = function (isMin, args) {
     args = Array.prototype.slice.call(args);
@@ -71,6 +72,10 @@ functionRegistry.addMultiple({
         return new Dimension(Math.pow(x.value, y.value), x.unit);
     },
     percentage: function (n) {
-        return new Dimension(n.value * 100, '%');
+        var result = mathHelper._math(function(num) {
+            return num * 100;
+        }, '%', n);
+
+        return result;
     }
 });

test/less/errors/percentage-non-number-argument.less

@@ -0,0 +1,3 @@
+div {
+  percentage: percentage(16/17);
+}

test/less/errors/percentage-non-number-argument.txt

@@ -0,0 +1,4 @@
+ArgumentError: error evaluating function `percentage`: argument must be a number in {path}percentage-non-number-argument.less on line 2, column 15:
+1 div {
+2   percentage: percentage(16/17);
+3 }