Allow execution of helpers on the context

Fixes #285

dist/handlebars.js

@@ -1743,8 +1743,9 @@ JavaScriptCompiler.prototype = {
     this.context.aliases.helperMissing = 'helpers.helperMissing';
 
     var helper = this.lastHelper = this.setupHelper(paramSize, name, true);
+    var nonHelper = this.nameLookup('depth' + this.lastContext, name, 'context');
 
-    this.push(helper.name);
+    this.push(helper.name + ' || ' + nonHelper);
     this.replaceStack(function(name) {
       return name + ' ? ' + name + '.call(' +
           helper.callParams + ") " + ": helperMissing.call(" +

lib/handlebars/compiler/compiler.js

@@ -866,8 +866,9 @@ JavaScriptCompiler.prototype = {
     this.context.aliases.helperMissing = 'helpers.helperMissing';
 
     var helper = this.lastHelper = this.setupHelper(paramSize, name, true);
+    var nonHelper = this.nameLookup('depth' + this.lastContext, name, 'context');
 
-    this.push(helper.name);
+    this.push(helper.name + ' || ' + nonHelper);
     this.replaceStack(function(name) {
       return name + ' ? ' + name + '.call(' +
           helper.callParams + ") " + ": helperMissing.call(" +

spec/qunit_spec.js

@@ -165,6 +165,14 @@ test("functions", function() {
                   "functions are bound to the context");
 });
 
+test("functions with context argument", function() {
+  shouldCompileTo("{{awesome frank}}",
+      {awesome: function(context) { return context; },
+        frank: "Frank"},
+      "Frank", "functions are called with context arguments");
+});
+
+
 test("paths with hyphens", function() {
   shouldCompileTo("{{foo-bar}}", {"foo-bar": "baz"}, "baz", "Paths can contain hyphens (-)");
   shouldCompileTo("{{foo.foo-bar}}", {foo: {"foo-bar": "baz"}}, "baz", "Paths can contain hyphens (-)");