Modules and namespace / name collision in AngularJS

Question

Consider the following jfiddle http://jsfiddle.net/bchapman26/9uUBU/29/

//angular.js example for factory vs service
var app = angular.module('myApp', ['module1', 'module2']);

var service1module = angular.module('module1', []);

service1module.factory('myService', function() {
    return {
        sayHello: function(text) {
            return "Service1 says \"Hello " + text + "\"";
        },
        sayGoodbye: function(text) {
            return "Service1 says \"Goodbye " + text + "\"";
        }
    };
});

var service2module = angular.module('module2', []);

service2module.factory('myService', function() {
    return {
        sayHello: function(text) {
            return "Service2 says \"Hello " + text + "\"";
        },
        sayGoodbye: function(text) {
            return "Service2 says \"Goodbye " + text + "\"";
        }
    };
});

function HelloCtrl($scope, myService) {
    $scope.fromService1 = myService.sayHello("World");
}

function GoodbyeCtrl($scope, myService) {
    $scope.fromService2 = myService.sayGoodbye("World");
}​

I have 2 modules (module1 and module2). Both module1 and module2 define a service called myService. This appears to create a name clash on myService within Angular when both modules are imported into myApp. It appears AngularJs just uses the second service definition without warning you of the possible issue.

Very large projects (or just reusing modules in general) would have a risk of names clashing, which could be difficult to debug.

Is there a way to prefix names with the module name so that name clashes don't happen?

Answer 1

As of today, AngularJS modules do not provide any sort of namespacing that would prevent collisions between objects in different modules. The reason is that an AngularJS app has a single injector that holds names for all objects without respect to module names.

The AngularJS Developer Guide says:

To manage the responsibility of dependency creation, each Angular application has an injector. The injector is a service locator that is responsible for construction and lookup of dependencies.

As you've mentioned, nasty bugs can result when injecting modules into your main/app module. When collisions happen they are silent and the winner is determined by whichever was the last module injected.

So no, there's not a built in way of avoiding these collisions. Maybe this will happen in the future. For large apps where this problem becomes more likely, you're right that naming conventions are your best tool. Consider whether objects belonging to a module or function area might use a short prefix.