A few more lingering bugs:

* add helperMissing.not to the specs
* add Handlebars.Utils.isEmpty
* add runtime handling for inverse sections
* fix __get__ to pass an IdNode to evaluate
* handle case in wrapProgram where context is undefined

lib/handlebars/runtime.js

@@ -140,6 +140,38 @@ Handlebars.Runtime.prototype = {
     this.buffer = this.buffer + data.apply(this.wrapContext(), params);
   },
 
+  // TODO: Block and Inverse can share code
+  inverse: function(block) {
+    var mustache  = block.mustache,
+        id        = mustache.id;
+
+    var idObj     = this.accept(id),
+        data      = idObj.data,
+        isInverse = Handlebars.Utils.isEmpty(data);
+
+    if(toString.call(data) !== "[object Function]") {
+      params = [data];
+      data   = this.context.evaluate({depth: 0, parts: ["helperMissing"]}, this.stack).data;
+      id     = "helperMissing";
+    } else {
+      params = this.evaluateParams(mustache.params);
+      id     = id.parts.join("/");
+    }
+
+    if(isInverse) {
+      var not = data.not;
+
+      if(not) {
+        var context = this.wrapContext();
+        params.push(this.wrapProgram(block.program));
+
+        this.buffer = this.buffer + not.apply(this.wrapContext(), params);
+      } else {
+        throw new Handlebars.Exception("Not .not property found on " + id);
+      }
+    }
+  },
+
   content: function(content) {
     this.buffer += content.string;
   },
@@ -150,6 +182,8 @@ Handlebars.Runtime.prototype = {
     for(var i=0, l=params.length; i<l; i++) {
       params[i] = this.accept(params[i]).data;
     }
+
+    if(params.length === 0) { params = [undefined]; }
     return params;
   },
 
@@ -160,6 +194,7 @@ Handlebars.Runtime.prototype = {
     var stack     = proxy.__stack__   = this.stack.slice(0);
 
     proxy.__get__ = function(path) {
+      path = new Handlebars.AST.IdNode(path.split("/"));
       return context.evaluate(path, stack).data
     };
 
@@ -175,7 +210,7 @@ Handlebars.Runtime.prototype = {
     var fallback = this.context.fallback;
 
     return function(context) {
-      if(context.isWrappedContext) { context = context.__data__; }
+      if(context && context.isWrappedContext) { context = context.__data__; }
       var runtime = new Handlebars.Runtime(context, fallback, stack);
       runtime.accept(program);
       return runtime.buffer;

lib/handlebars/utils.js

@@ -44,6 +44,19 @@ Handlebars.Utils = {
           return str;
       }
     });
+  },
+  isEmpty: function(value) {
+    if (typeof value === "undefined") {
+      return true;
+    } else if (value === null) {
+      return true;
+		} else if (value === false) {
+			return true;
+    } else if(Object.prototype.toString.call(value) === "[object Array]" && value.length == 0) {
+      return true;
+    } else {
+      return false;
+    }
   }
 }
 

spec/qunit_spec.js

@@ -15,6 +15,10 @@ var helperMissing = function(context, fn) {
   } else {
 		return fn(context);
 	}
+};
+
+helperMissing.not = function(context, fn) {
+  return fn(context);
 }
 
 var shouldCompileTo = function(string, hash, expected, message) {