Wrap exception handling around all of loadSession

The user might (probably does) have a session even if we haven't actually tried
to load it yet, so wrap the whole loadSession code in the error handler we were
using for restoring sessions so we gracefully handle exceptions that happen
before trying to restore sessions too.

Remove the catch in MatrixChat that sent you to the login screen.  This is
never the right way to handle an error condition: we should only display the
login screen if we successfully determined that the user has no session, or
they explicitly chose to blow their sessions away.

src/Lifecycle.js

@@ -1,6 +1,7 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
 Copyright 2017 Vector Creations Ltd
+Copyright 2018 New Vector Ltd
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -65,6 +66,7 @@ import sdk from './index';
  *     failed.
  */
 export function loadSession(opts) {
+    return new Promise.resolve().then(() => {
         const fragmentQueryParams = opts.fragmentQueryParams || {};
         let enableGuest = opts.enableGuest || false;
         const guestHsUrl = opts.guestHsUrl;
@@ -89,8 +91,8 @@ export function loadSession(opts) {
                 guest: true,
             }, true).then(() => true);
         }
-
-    return _restoreFromLocalStorage().then((success) => {
+        return _restoreFromLocalStorage();
+    }).then((success) => {
         if (success) {
             return true;
         }
@@ -101,6 +103,8 @@ export function loadSession(opts) {
 
         // fall back to login screen
         return false;
+    }).catch((e) => {
+        return _handleLoadSessionFailure(e);
     });
 }
 
@@ -196,6 +200,7 @@ function _registerAsGuest(hsUrl, isUrl, defaultDeviceDisplayName) {
 //      SessionStore to avoid bugs where the view becomes out-of-sync with
 //      localStorage (e.g. teamToken, isGuest etc.)
 function _restoreFromLocalStorage() {
+    return Promise.resolve().then(() => {
         if (!localStorage) {
             return Promise.resolve(false);
         }
@@ -222,17 +227,16 @@ function _restoreFromLocalStorage() {
                 homeserverUrl: hsUrl,
                 identityServerUrl: isUrl,
                 guest: isGuest,
-        }, false).catch((e) => {
-            return _handleRestoreFailure(e);
-        }).then(() => true);
+            }, false).then(() => true);
         } else {
             console.log("No previous session found.");
             return Promise.resolve(false);
         }
+    });
 }
 
-function _handleRestoreFailure(e) {
-    console.log("Unable to restore session", e);
+function _handleLoadSessionFailure(e) {
+    console.log("Unable to load session", e);
 
     const def = Promise.defer();
     const SessionRestoreErrorDialog =
@@ -253,7 +257,7 @@ function _handleRestoreFailure(e) {
         }
 
         // try, try again
-        return _restoreFromLocalStorage();
+        return loadSession();
     });
 }
 

src/components/structures/MatrixChat.js

@@ -1,7 +1,7 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
 Copyright 2017 Vector Creations Ltd
-Copyright 2017 New Vector Ltd
+Copyright 2017, 2018 New Vector Ltd
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -351,15 +351,15 @@ export default React.createClass({
                     guestIsUrl: this.getCurrentIsUrl(),
                     defaultDeviceDisplayName: this.props.defaultDeviceDisplayName,
                 });
-            }).catch((e) => {
-                console.error('Error attempting to load session', e);
-                return false;
             }).then((loadedSession) => {
                 if (!loadedSession) {
                     // fall back to showing the login screen
                     dis.dispatch({action: "start_login"});
                 }
             });
+            // Note we don't catch errors from this: we catch everything within
+            // loadSession as there's logic there to ask the user if they want
+            // to try logging out.
         }).done();
     },
 

src/components/views/dialogs/SessionRestoreErrorDialog.js

@@ -1,5 +1,6 @@
 /*
 Copyright 2017 Vector Creations Ltd
+Copyright 2018 New Vector Ltd
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.