Allow helperMissing to apply to simple mustaches (paves the way to support things like link_to in a Rails context)

lib/handlebars.js

@@ -54,7 +54,7 @@ Handlebars.registerPartial = function(name, str) {
   this.partials[name] = str;
 };
 
-Handlebars.registerHelper('helperMissing', function(context, fn) {
+Handlebars.registerHelper('blockHelperMissing', function(context, fn) {
   var ret = "";
 
   if(context === true) {

lib/handlebars/runtime.js

@@ -113,11 +113,22 @@ Handlebars.Runtime.prototype = {
       params[i] = this[param.type](param).data;
     }
 
-    if(toString.call(idObj.data) === "[object Function]") {
-      buf = idObj.data.apply(this.wrapContext(), params);
+    var data = idObj.data;
+
+    var type = toString.call(data);
+    var functionType = (type === "[object Function]");
+
+    if(!functionType && params.length) {
+      params = params.slice(0);
+      params.unshift(data || mustache.id.original);
+      data = this.context.helpers.helperMissing;
+      functionType = true;
+    }
+
+    if(functionType) {
+      buf = data.apply(this.wrapContext(), params);
     } else {
-      if(params.length) { throw new Error(mustache.id.parts.join("/") + " is not a Function, so you cannot have Function parameters"); }
-      buf = idObj.data;
+      buf = data;
     }
 
     if(buf && mustache.escaped) { buf = Handlebars.Utils.escapeExpression(buf); }
@@ -136,7 +147,7 @@ Handlebars.Runtime.prototype = {
 
     if(toString.call(data) !== "[object Function]") {
       params = [data];
-      data   = this.context.helpers.helperMissing;
+      data   = this.context.helpers.blockHelperMissing;
     } else {
       params = this.evaluateParams(mustache.params);
     }

spec/qunit_spec.js

@@ -1,5 +1,11 @@
 module("basic context");
 
+Handlebars.registerHelper('helperMissing', function(helper, context) {
+  if(helper === "link_to") {
+    return new Handlebars.SafeString("<a>" + context + "</a>");
+  }
+});
+
 var shouldCompileTo = function(string, hash, expected, message) {
   var template = Handlebars.compile(string);
   if(Object.prototype.toString.call(hash) === "[object Array]") {
@@ -459,3 +465,11 @@ test("constructing a safestring from a string and checking its type", function()
   equal(safe, "testing 1, 2, 3", "SafeString is equivalent to its underlying string");
 });
 
+module("helperMissing");
+
+test("if a context is not found, helperMissing is used", function() {
+  var string = "{{hello}} {{link_to world}}"
+  var context = { hello: "Hello", world: "world" };
+
+  shouldCompileTo(string, context, "Hello <a>world</a>")
+})