Optional dependencies in AngularJS

Apparently not using automatic injection. However, you can inject the injector and check for the service:

myApp.controller('MyController', [
    '$scope', '$injector', 'firstRequiredService', 'secondRequiredService', 
    function ($scope, $injector, firstRequiredService, secondRequiredService) {
        if ($injector.has('firstOptionalService')) {
            var firstOptionalService = $injector.get('firstOptionalService');
        }
    }
]);