feat(missingFallbackDefaultText): enables a feature to return a defau…

…lt text for displaying in case of missing translations including fallback stack

In case you have defined a missingTranslationHandlerFactory, you now have the possibility to define a return value which is set instead of the translationId.
This gives a lot of flexibility for certain use cases.
Example factory:
        $provide.factory('customTranslationHandler', function () {
          return function (translationID, uses) {

          };
        });

src/service/translate.js

@@ -1039,7 +1039,19 @@ angular.module('pascalprecht.translate').provider('$translate', ['$STORAGE_KEY',
           );
         } else {
           // No translation found in any fallback language
-          deferred.resolve(translationId);
+
+          // If we have a handler factory - we might also call it here to determine if it provides
+          // a default text for a translationid that can't be found anywhere in our tables
+          if ($missingTranslationHandlerFactory) {
+            var resultString = $injector.get($missingTranslationHandlerFactory)(translationId, $uses);
+            if (resultString !== undefined) {
+              deferred.resolve(resultString);
+            } else {
+              deferred.resolve(translationId);
+            }
+          } else {
+            deferred.resolve(translationId);
+          }
         }
         return deferred.promise;
       };

test/unit/service/translate.spec.js

@@ -472,14 +472,23 @@ describe('pascalprecht.translate', function () {
 
     describe('multi fallback language', function () {
 
-      beforeEach(module('pascalprecht.translate', function ($translateProvider) {
+      beforeEach(module('pascalprecht.translate', function ($translateProvider, $provide) {
         $translateProvider
           .translations('de_DE', translationMock)
           .translations('en_EN', { 'TRANSLATION__ID': 'bazinga' })
           .translations('fr_FR', { 'SUPERTEST': 'it works!' })
           .translations('en_UK', { 'YAY': 'it really does!' })
           .fallbackLanguage(['en_EN', 'fr_FR', 'en_UK'])
           .preferredLanguage('de_DE');
+
+        // factory provides a default fallback text being defined in the factory
+        // gives a maximum of flexibility
+        $provide.factory('customTranslationHandler', function () {
+          return function (translationID, uses) {
+              return 'NO KEY FOUND';
+          };
+        });
+        $translateProvider.useMissingTranslationHandler('customTranslationHandler');
       }));
 
       var $translate, $rootScope, $q;
@@ -518,8 +527,39 @@ describe('pascalprecht.translate', function () {
         expect(value[2]).toEqual('it works!');
         expect(value[3]).toEqual('it really does!');
       });
+
+
+      it('should use fallback languages and miss one of the translation keys', function () {
+        var deferred = $q.defer(),
+          promise = deferred.promise,
+          value;
+
+        promise.then(function (translations) {
+          value = translations;
+        });
+
+        $q.all([
+          $translate('EXISTING_TRANSLATION_ID'),
+          $translate('TRANSLATION__ID'),
+          $translate('SUPERTEST'),
+          $translate('YAY'),
+          $translate('NOT_EXISTING')
+        ]).then(function (translations) {
+          deferred.resolve(translations);
+        });
+
+        $rootScope.$digest();
+
+        expect(value[0]).toEqual('foo');
+        expect(value[1]).toEqual('bazinga');
+        expect(value[2]).toEqual('it works!');
+        expect(value[3]).toEqual('it really does!');
+        expect(value[4]).toEqual('NO KEY FOUND');
+      });
     });
 
+
+
     describe('registered loader', function () {
 
       beforeEach(module('pascalprecht.translate', function ($translateProvider, $provide) {