fix(error message): improve error on ngModule redefinition

- when a user reuses an angular module, i.e. by specifying the same
module
  name in multiple ngDefine calls, redefinition (i.e. adding more
 `module:some.angular.module` dependencies) is not allowed, as angular
  does not allow to re-define module definitions
- added detailed error message to better reflect that issue

Closes #1

Author: nikku

README.md

@@ -40,7 +40,7 @@ We will check out how to employ `ngDefine` to [define AngularJS modules](#Angula
 
 ### AngularJS Module Definition
 
-AngularJS modules may be declared using `#ngDefine(name, dependencies, callback)`. 
+AngularJS modules may be declared using `#ngDefine(name[, dependencies], callback)`. 
 The function accepts the name of the module to be defined or looked up and a callback function that may define or configure the module.
 A (optional) list of arbitrary RequireJS dependencies can be passed that are resolved before the callback function is executed.
 

src/ngDefine.js

@@ -4,7 +4,7 @@
  * @version 1.0.0
  * @author Nico Rehwaldt <http://github.com/Nikku>
  *
- * @license MIT
+ * @license (c) 2013 Nico Rehwaldt, MIT
  */
 (function(window) {
 
@@ -70,7 +70,9 @@
     }
 
     if (modules.length && exists) {
-      throw new Error("Failed to define module " + name + ". Already exists");
+      throw new Error(
+        "Cannot re-define angular module " + name + " with new dependencies [" + modules + "]. " +
+        "Make sure the module is not defined else where or define a sub-module with additional angular module dependencies instead.");
     }
 
     if (modules.length || !exists) {
@@ -102,7 +104,7 @@
   var angularDefine = function(angular) {
     return function(name, dependencies, body) {
       if (!dependencies) {
-        throw new Error("wrong number of arguments, expected name, [dependencies, ]body");
+        throw new Error("wrong number of arguments, expected name[, dependencies], body");
       }
       internalModule(angular, name, dependencies, body);
     };

test/errorSpec.js

@@ -0,0 +1,24 @@
+define([ 'ngDefine' ], function() {
+
+  return describe('ngDefine()', function() {
+
+    describe('should throw error', function() {
+
+      it("when redefining angular module with additional dependencies", function() {
+
+        var foo, bar;
+
+        ngDefine('myerror.module', ['module:ng'], function() {
+          this.foo = true;
+        });
+
+        expect(function() {
+          ngDefine('myerror.module', ['module:ng'], function() {
+            this.bar = true;
+          });
+        }).toThrow();
+
+      });
+    });
+  });
+});

test/runner.html

@@ -10,6 +10,7 @@
     <script src="lib/jasmine/jasmine-html.js"></script>
 
     <script src="../lib/require/require.js"></script>
+    <script src="main.js"></script>
 
     <script>
       (function() {
@@ -25,16 +26,16 @@
           },
           shim: {
             'angular' : { deps: [ 'jquery' ], exports: 'angular' },
-            'angular-resource': { deps: [ 'angular' ] }, 
-            'angular-mocks': { deps: [ 'angular' ] }, 
+            'angular-resource': { deps: [ 'angular' ] },
+            'angular-mocks': { deps: [ 'angular' ] },
           },
           packages: [
             { name: 'test', location: 'test' },
             { name: 'my-module', location: 'test/my-module' },
             { name: 'my-other-module', location: 'test/my-other-module' }
           ]
         });
-
+        
         var jasmineEnv = jasmine.getEnv();
         jasmineEnv.updateInterval = 1000;
 
@@ -47,7 +48,8 @@
         };
 
         var specs = [
-          'test/appSpec'
+          'test/appSpec',
+          'test/errorSpec'
         ];
 
         var testOnly = window.location.hash.substring(1);