Fix Core Data concurrency issues in AccountService

RELEASE-NOTES.txt

@@ -1,8 +1,8 @@
 22.1
 -----
+* [**] [internal] Refactor updating account related Core Data operations, which ususally happens during log in and out of the app. [#20394]
 * [***] [internal] Refactor uploading photos (from the device photo, the Free Photo library, and other sources) to the WordPress Media Library. Affected areas are where you can choose a photo and upload, including the "Media" screen, adding images to a post, updating site icon, etc. [#20322]
 
-
 22.0
 -----
 * [*] Remove large title in Reader and Notifications tabs. [#20271]

WordPress/Classes/Services/AccountService.h

@@ -94,7 +94,7 @@ extern NSNotificationName const WPAccountEmailAndDefaultBlogUpdatedNotification;
  Updates the default blog for the specified account.  The default blog will be the one whose siteID matches
  the accounts primaryBlogID.
  */
-- (void)updateDefaultBlogIfNeeded:(WPAccount *)account;
+- (void)updateDefaultBlogIfNeeded:(WPAccount *)account inContext:(NSManagedObjectContext *)context;
 
 /**
  Syncs the details for the account associated with the provided auth token, then

WordPress/Classes/Services/AccountService.m

@@ -351,12 +351,14 @@ - (void)updateAccountWithID:(NSManagedObjectID *)objectID withUserDetails:(Remot
     // Make sure the account is saved before updating its default blog.
     [self.coreDataStack performAndSaveUsingBlock:^(NSManagedObjectContext *context) {
         WPAccount *account = [context existingObjectWithID:objectID error:nil];
-        [self updateDefaultBlogIfNeeded:account];
+        [self updateDefaultBlogIfNeeded:account inContext:context];
     }];
 }
 
-- (void)updateDefaultBlogIfNeeded:(WPAccount *)account
+- (void)updateDefaultBlogIfNeeded:(WPAccount *)account inContext:(NSManagedObjectContext *)context
 {
+    NSParameterAssert(account.managedObjectContext == context);
+
     if (!account.primaryBlogID || [account.primaryBlogID intValue] == 0) {
         return;
     }
@@ -375,17 +377,27 @@ - (void)updateDefaultBlogIfNeeded:(WPAccount *)account
 
     // Update app extensions if needed.
     if ([account isDefaultWordPressComAccount]) {
-        [self setupAppExtensionsWithDefaultAccount];
+        [self setupAppExtensionsWithDefaultAccount:account inContext:context];
     }
 }
 
 - (void)setupAppExtensionsWithDefaultAccount
 {
-    WPAccount * __block defaultAccount = nil;
-    [self.coreDataStack.mainContext performBlockAndWait:^{
-        defaultAccount = [WPAccount lookupDefaultWordPressComAccountInContext:self.coreDataStack.mainContext];
+    NSManagedObjectContext *context = self.coreDataStack.mainContext;
+    [context performBlockAndWait:^{
+        WPAccount *account = [WPAccount lookupDefaultWordPressComAccountInContext:context];
+        if (account == nil) {
+            return;
+        }
+        [self setupAppExtensionsWithDefaultAccount:account inContext:context];
     }];
+}
+
+- (void)setupAppExtensionsWithDefaultAccount:(WPAccount *)defaultAccount inContext:(NSManagedObjectContext *)context
+{
+    NSParameterAssert(defaultAccount.managedObjectContext == context);
 
+    NSManagedObjectID *defaultAccountObjectID = defaultAccount.objectID;
     Blog *defaultBlog = [defaultAccount defaultBlog];
     NSNumber *siteId    = defaultBlog.dotComID;
     NSString *blogName  = defaultBlog.settings.name;
@@ -412,7 +424,7 @@ - (void)setupAppExtensionsWithDefaultAccount
         NSString *todayExtensionBlogName = [sharedDefaults objectForKey:AppConfigurationWidgetStatsToday.userDefaultsSiteNameKey];
         NSString *todayExtensionBlogUrl = [sharedDefaults objectForKey:AppConfigurationWidgetStatsToday.userDefaultsSiteUrlKey];
 
-        Blog *todayExtensionBlog = [Blog lookupWithID:todayExtensionSiteID in:self.coreDataStack.mainContext];
+        Blog *todayExtensionBlog = [Blog lookupWithID:todayExtensionSiteID in:context];
         NSTimeZone *timeZone = [todayExtensionBlog timeZone];
 
         if (todayExtensionSiteID == NULL || todayExtensionBlog == nil) {
@@ -423,6 +435,7 @@ - (void)setupAppExtensionsWithDefaultAccount
         }
 
         dispatch_async(dispatch_get_main_queue(), ^{
+            WPAccount *defaultAccount = [self.coreDataStack.mainContext existingObjectWithID:defaultAccountObjectID error:nil];
 
             TodayExtensionService *service = [TodayExtensionService new];
             [service configureTodayWidgetWithSiteID:todayExtensionSiteID

WordPress/Classes/Services/BlogService.m

@@ -447,7 +447,7 @@ - (void)mergeBlogs:(NSArray<RemoteBlog *> *)blogs withAccountID:(NSManagedObject
 
     // Ensure that the account has a default blog defined (if there is one).
     AccountService *service = [[AccountService alloc] initWithCoreDataStack:self.coreDataStack];
-    [service updateDefaultBlogIfNeeded:account];
+    [service updateDefaultBlogIfNeeded:account inContext:context];
 }
 
 - (void)updateBlogWithRemoteBlog:(RemoteBlog *)remoteBlog account:(WPAccount *)account inContext:(NSManagedObjectContext *)context