Make the function passed to a block helper have an identical signature to top-level template methods

lib/handlebars/vm.js

@@ -627,13 +627,16 @@ Handlebars.JavaScriptCompiler = function() {};
 Handlebars.VM = {
   programWithDepth: function(fn) {
     var args = Array.prototype.slice.call(arguments, 1);
-    return function(context) {
+    return function(context, helpers, partials, data) {
+      args[0] = helpers || args[0];
+      args[1] = partials || args[1];
+      args[2] = data || args[2];
       return fn.apply(this, [context].concat(args));
     };
   },
   program: function(fn, helpers, partials, data) {
-    return function(context) {
-      return fn(context, helpers, partials, data);
+    return function(context, h2, p2, d2) {
+      return fn(context, h2 || helpers, p2 || partials, d2 || data);
     };
   },
   noop: function() { return ""; },

spec/qunit_spec.js

@@ -599,5 +599,36 @@ test("passing in data to a compiled function that expects data - works with bloc
   equals("#win happy world?", result);
 });
 
+test("you can override inherited data when invoking a helper", function() {
+  var template = Handlebars.compile("{{#hello}}{{world zomg}}{{/hello}}", true);
+
+  var helpers = {
+    hello: function(fn) {
+      return fn({exclaim: "?", zomg: "world"}, null, null, {adjective: "sad"});
+    },
+    world: function(thing, data) {
+      return data.adjective + " " + thing + (this.exclaim || "");
+    }
+  };
+
+  var result = template({exclaim: true, zomg: "planet"}, helpers, null, {adjective: "happy"});
+  equals("sad world?", result);
+});
 
 
+test("you can override inherited data when invoking a helper with depth", function() {
+  var template = Handlebars.compile("{{#hello}}{{world ../zomg}}{{/hello}}", true);
+
+  var helpers = {
+    hello: function(fn) {
+      return fn({exclaim: "?"}, null, null, {adjective: "sad"});
+    },
+    world: function(thing, data) {
+      return data.adjective + " " + thing + (this.exclaim || "");
+    }
+  };
+
+  var result = template({exclaim: true, zomg: "world"}, helpers, null, {adjective: "happy"});
+  equals("sad world?", result);
+});
+