Make it possible for helpers to let downstream helpers know what the path to the current object is

lib/handlebars.js

@@ -183,7 +183,7 @@ var Handlebars = {
     }
   },
 
-  handleBlock: function(lookup, context, arg, fn, notFn) {
+  handleBlock: function(lookup, context, arg, fn, notFn, name) {
     var out = "", args;
     originalArgs = arg.length ? arg : [null]
 
@@ -199,11 +199,11 @@ var Handlebars = {
     else {
       if (!Handlebars.isEmpty(lookup)) {
         // TODO: which case is this, and what does it mean for multiple args
-        out = out + Handlebars.helperMissing.call(arg[0], lookup, fn);
+        out = out + Handlebars.helperMissing.call(arg[0], lookup, fn, name);
       }
 
       if (notFn != null) {
-        out = out + Handlebars.helperMissing.not.call(arg[0], lookup, notFn);
+        out = out + Handlebars.helperMissing.not.call(arg[0], lookup, notFn, name);
       }
     }
 
@@ -260,7 +260,7 @@ Handlebars.SafeString.prototype.toString = function() {
   return this.string.toString();
 }
 
-Handlebars.helperMissing = function(object, fn) {
+Handlebars.helperMissing = function(object, fn, name) {
   var ret = "";
 
   if(object === true) {
@@ -273,10 +273,17 @@ Handlebars.helperMissing = function(object, fn) {
     }
     return ret;
   } else {
-		return fn(object);
+    var ContextWrapper = function(parent) {
+      this.__path__ = parent.__path__ ? parent.__path__.concat(name) : [name];
+    };
+
+    ContextWrapper.prototype = object;
+    var proxy = new ContextWrapper(this);
+
+		return fn(proxy);
 	}
 };
-Handlebars.helperMissing.not = function(context, fn) {
+Handlebars.helperMissing.not = function(context, fn, name) {
   return fn(context);
 }
 
@@ -404,7 +411,7 @@ Handlebars.Compiler.prototype = {
     this.fn += "var " + fnId + " = function(context) {" + result + "}; ";
     this.fn += "lookup = " + this.lookupFor(mustache) + "; ";
 		this.fn += "arg = [" + params.join(", ") + "] ;";
-    this.fn += "stack.push(context);";
+    this.fn += "stack.push(context); ";
 
     if (compiler.continueInverted) {
       var invertedCompiler = this.compileToEndOfBlock(mustache);
@@ -413,7 +420,7 @@ Handlebars.Compiler.prototype = {
     else {
       this.fn += " var " + fnId + "Not = null;";
     }
-    this.fn += "out = out + Handlebars.handleBlock(lookup, wrappedContext, arg, " + fnId + ", " + fnId + "Not);"
+    this.fn += "out = out + Handlebars.handleBlock(lookup, wrappedContext, arg, " + fnId + ", " + fnId + "Not, '" + mustache + "');"
 
     this.fn += "stack.pop();";
     this.openBlock = false;

test/handlebars.js

@@ -89,6 +89,32 @@ test("functions with context argument", function() {
       "Frank", "functions are called with context arguments");
 });
 
+test("functions receive the current path as part of the 'this'", function() {
+  template = "Hello {{#person}}{{show name}}{{/person}}"
+  object   = { person: { name: "Alan" } };
+  fallback = {
+    show: function(context) {
+      return context + " (from " + this.__path__.join("/") + ")";
+    }
+  }
+  shouldCompileTo(template, [object, fallback], "Hello Alan (from person)")
+});
+
+test("block helpers don't mess with the path receive the current path as part of the 'this'", function() {
+  template = "Hello {{#block}}{{#person}}{{#info}}{{show name}}{{/info}}{{/person}}{{/block}}. {{show other/name}}"
+  object   = { person: { info: { name: "Alan" } }, other: { name: "Yehuda" } };
+  fallback = { 
+    show: function(context) { 
+      var ret = context;
+      if(this.__path__) ret += " (from " + this.__path__.join("/") + ")";
+      return ret;
+    }, block: function(context, fn) {
+      return fn(this);
+    }
+  }
+  shouldCompileTo(template, [object, fallback], "Hello Alan (from person/info). Yehuda")
+});
+
 test("nested paths", function() {
   shouldCompileTo("Goodbye {{alan/expression}} world!", {alan: {expression: "beautiful"}},
                   "Goodbye beautiful world!", "Nested paths access nested objects");
@@ -432,7 +458,7 @@ test("block multi-params work", function() {
     return fn({greeting: "Goodbye", adj: "cruel", noun: "world"});
   }}
   shouldCompileTo(string, [hash, fallback], "Message: Goodbye cruel world", "block helpers with multiple params");
-})
+});
 
 module("safestring");