Defending from failing APIs

chrome/browser/resources/google_now/background.js

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // 'use strict'; TODO(vadimt): Uncomment once crbug.com/237617 is fixed.
 
 /**
  * @fileoverview The event page for Google Now for Chrome implementation.
  * The Google Now event page gets Google Now cards from the server and shows
  * them as Chrome notifications.
  * The service performs periodic updating of Google Now cards.
  * Each updating of the cards includes 4 steps:
  * 1. Obtaining the location of the machine;
  * 2. Processing requests for cards dismissals that are not yet sent to the
  *    server;
  * 3. Making a server request based on that location;
  * 4. Showing the received cards as notifications.
  */
 
 // TODO(vadimt): Use background permission to show notifications even when all
 // browser windows are closed.
 // TODO(vadimt): Decide what to do in incognito mode.
 // TODO(vadimt): Honor the flag the enables Google Now integration.
 // TODO(vadimt): Figure out the final values of the constants.
 // TODO(vadimt): Remove 'console' calls.
-// TODO(vadimt): Consider sending JS stacks for unexpected exceptions (including
-// ones from verify()), unfinished and infinite tasks, chrome.* API errors and
+// TODO(vadimt): Consider sending JS stacks for chrome.* API errors and
 // malformed server responses.
 
 /**
  * Standard response code for successful HTTP requests. This is the only success
  * code the server will send.
  */
 var HTTP_OK = 200;
 
 /**
  * Initial period for polling for Google Now Notifications cards to use when the
@@ skipping 199 matching lines @@
     callback();
     return;
   }
 
   if (typeof parsedResponse.expiration_timestamp_seconds != 'number') {
     callback();
     return;
   }
 
   tasks.debugSetStepName('parseAndShowNotificationCards-storage-get');
   storage.get(['activeNotifications', 'recentDismissals'], function(items) {

[not at google - send to devlin, 2013/05/24 00:01:12]

instead you could call

storage.get({
  'activeNotifications': {},
  'recentDismissals': {}
}, function(items) {
  ...
});

which does the default value handling for you.

     console.log('parseAndShowNotificationCards-get ' + JSON.stringify(items));
+    items.activeNotifications = items.activeNotifications || {};
+    items.recentDismissals = items.recentDismissals || {};
 
     // Build a set of non-expired recent dismissals. It will be used for
     // client-side filtering of cards.
     var updatedRecentDismissals = {};
     var currentTimeMs = Date.now();
     for (var notificationId in items.recentDismissals) {
       if (currentTimeMs - items.recentDismissals[notificationId] <
           DISMISS_RETENTION_TIME_MS) {
         updatedRecentDismissals[notificationId] =
             items.recentDismissals[notificationId];
@@ skipping 150 matching lines @@
 /**
  * Tries to send dismiss requests for all pending dismissals.
  * @param {function(boolean)} callbackBoolean Completion callback with 'success'
  *     parameter. Success means that no pending dismissals are left.
  */
 function processPendingDismissals(callbackBoolean) {
   tasks.debugSetStepName('processPendingDismissals-storage-get');
   storage.get(['pendingDismissals', 'recentDismissals'], function(items) {
     console.log('processPendingDismissals-storage-get ' +
                 JSON.stringify(items));
+    items.pendingDismissals = items.pendingDismissals || [];
+    items.recentDismissals = items.recentDismissals || {};
+
     var dismissalsChanged = false;
 
     function onFinish(success) {
       if (dismissalsChanged) {
         storage.set({
           pendingDismissals: items.pendingDismissals,
           recentDismissals: items.recentDismissals
         });
       }
       callbackBoolean(success);
@@ skipping 40 matching lines @@
 /**
  * Opens URL corresponding to the clicked part of the notification.
  * @param {string} notificationId Unique identifier of the notification.
  * @param {function(Object): string} selector Function that extracts the url for
  *     the clicked area from the button action URLs info.
  */
 function onNotificationClicked(notificationId, selector) {
   tasks.add(CARD_CLICKED_TASK_NAME, function(callback) {
     tasks.debugSetStepName('onNotificationClicked-get-activeNotifications');
     storage.get('activeNotifications', function(items) {
+      items.activeNotifications = items.activeNotifications || {};
+
       var actionUrls = items.activeNotifications[notificationId].actionUrls;
       if (typeof actionUrls != 'object') {
         callback();
         return;
       }
 
       var url = selector(actionUrls);
 
       if (typeof url != 'string') {
         callback();
@@ skipping 24 matching lines @@
     dismissalAttempts.start();
 
     // Deleting the notification in case it was re-added while this task was
     // scheduled, waiting for execution.
     chrome.notifications.clear(
         notificationId,
         function() {});
 
     tasks.debugSetStepName('onNotificationClosed-get-pendingDismissals');
     storage.get('pendingDismissals', function(items) {
+      items.pendingDismissals = items.pendingDismissals || [];
+
       var dismissal = {
         notificationId: notificationId,
         time: Date.now()
       };
       items.pendingDismissals.push(dismissal);
       storage.set({pendingDismissals: items.pendingDismissals});
       processPendingDismissals(function(success) { callback(); });
     });
   });
 }
 
 /**
  * Initializes the event page on install or on browser startup.
  */
 function initialize() {
   // Create an update timer for a case when for some reason location request
   // gets stuck.
   updateCardsAttempts.start(MAXIMUM_POLLING_PERIOD_SECONDS);
 
   var initialStorage = {
-    activeNotifications: {},
-    recentDismissals: {}
+    activeNotifications: {}
   };
   storage.set(initialStorage);
 
   requestLocation();
 }
 
 chrome.runtime.onInstalled.addListener(function(details) {
   console.log('onInstalled ' + JSON.stringify(details));
   if (details.reason != 'chrome_update') {
-    storage.set({pendingDismissals: []});
     initialize();
   }
 });
 
 chrome.runtime.onStartup.addListener(function() {
   console.log('onStartup');
   initialize();
 });
 
 chrome.notifications.onClicked.addListener(
@@ skipping 12 matching lines @@
         if (!Array.isArray(actionUrls.buttonUrls))
           return undefined;
 
         return actionUrls.buttonUrls[buttonIndex];
       });
     });
 
 chrome.notifications.onClosed.addListener(onNotificationClosed);
 
 chrome.location.onLocationUpdate.addListener(updateNotificationsCards);