Merge pull request aws-amplify#1396 from powerful23/cognito-hostedUI-doc

fix(@aws-amplify/auth): dispatching failure event when hosted UI and documentation enhancement for hosted UI

docs/media/authentication_guide.md

@@ -675,6 +675,10 @@ class MyApp extends React.Component {
 
 export default withOAuth(MyApp);
 ``` 
+
+#### Handling Authentication Events
+
+When using the hosted UI, you can handle authentication events by creating event listeners with the [Hub module]({%if jekyll.environment == 'production'%}{{site.amplify.baseurl}}{%endif%}/media/hub_guide#listening-authentication-events).
 
 ### Enabling MFA
 

docs/media/hub_guide.md

@@ -9,6 +9,9 @@ AWS Amplify has a local event bus system called Hub. It is a lightweight impleme
 Import:
 ```js
 import { Hub } from 'aws-amplify';
+
+// or
+import { Hub } from '@aws-amplify/core';
 ```
 
 ## Working with the API

docs/media/i18n_guide.md

@@ -8,6 +8,9 @@ AWS Amplify I18n module is a lightweight internationalization solution.
 
 ```js
 import { I18n } from 'aws-amplify';
+
+// or 
+import { I18n } from '@aws-amplify/core';
 ```
 
 ## Working with the API

packages/auth/src/Auth.ts

@@ -166,6 +166,7 @@ export default class AuthClass {
                 },
                 onFailure: (err) => {
                     logger.debug("Error in cognito hosted auth response", err);
+                    dispatchAuthEvent('signIn_failure', err);
                 }
             };
             // if not logged in, try to parse the url.
@@ -320,7 +321,7 @@ export default class AuthClass {
                     resolve(user);
                 }
             },
-        onFailure: (err) => {
+            onFailure: (err) => {
                 logger.debug('signIn failure', err);
                 dispatchAuthEvent('signIn_failure', err);
                 reject(err);