Allow nfbind bound function to handle missing args

CHANGES.md

@@ -1,5 +1,6 @@
  - Q.any gives an error message from the last rejected promise
  - Throw if callback supplied to "finally" is invalid (@grahamrhay)
+ - Allow the function created with nfbind to handle missing arguments
 
 ## 1.4.1
 

q.js

@@ -268,6 +268,7 @@ function uncurryThis(f) {
 // http://jsperf.com/uncurrythis
 
 var array_slice = uncurryThis(Array.prototype.slice);
+var array_concat = uncurryThis(Array.prototype.concat);
 
 var array_reduce = uncurryThis(
     Array.prototype.reduce || function (callback, basis) {
@@ -345,6 +346,14 @@ function isObject(value) {
     return value === Object(value);
 }
 
+// Pad an array value with nulls to the specified length.  Longer arrays are left alone.
+function padArrayTo(array, length) {
+    if (array.length < length) {
+        array.length = length;
+    }
+    return array;
+}
+
 // generator related shims
 
 // FIXME: Remove this function once ES6 generators are in SpiderMonkey.
@@ -1921,8 +1930,9 @@ Q.denodeify = function (callback /*...args*/) {
         throw new Error("Q can't wrap an undefined function");
     }
     var baseArgs = array_slice(arguments, 1);
+    var expectLength = callback.length - baseArgs.length - 1;
     return function () {
-        var nodeArgs = baseArgs.concat(array_slice(arguments));
+        var nodeArgs = baseArgs.concat(padArrayTo(array_slice(arguments), expectLength));
         var deferred = defer();
         nodeArgs.push(deferred.makeNodeResolver());
         Q(callback).fapply(nodeArgs).fail(deferred.reject);

spec/q-spec.js

@@ -2343,6 +2343,15 @@ describe("node support", function () {
             });
         });
 
+        it("allows bound function to support missing arguments", function () {
+            return Q.nfbind(function (a, b, c, d, callback) {
+                callback(null, !d);
+            }).call({}, 1, 2, 3)
+            .then(function (nod) {
+                expect(nod).toBe(true);
+            });
+        });
+
     });
 
     describe("nbind", function () {