Error E020 during sync

Describe the bug

I am using floccus firefox addon to sync bookmarks to Nextcloud. Since some days I get following error:

E020: Antwort des Servers konnte nicht gelesen werden. Ist die Bookmarks App auf Ihrem Server installiert? JSON.parse: unexpected character at line 1 column 1 of the JSON data

To Reproduce Steps to reproduce the behavior:

1. Go to floccus addon
2. Click on ‘Jetzt synchronisieren’ (sync now)
3. See error

Expected behavior Floccus should sync the bookmarks.

Screenshots If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: Ubuntu 20.04
• Browser firefox
• Browser Version 80.0.1 (64-Bit)
• Floccus version: 4.3.0
• Floccus sync method: nextcloud bookmarks

Server (please complete the following information):

• OS: Ubuntu 18.04
• Nextcloud version: 19.0.3
• Bookmarks app version: 3.4.1

Debug log With each sync following appears in debug log:

2020-10-03T21:46:57.684Z Starting sync process for account [e-mail]
2020-10-03T21:46:57.743Z Using normal strategy
2020-10-03T21:46:58.656Z Fetching bookmarks
2020-10-03T21:46:59.630Z Syncing failed with E020: Antwort des Servers konnte nicht gelesen werden. Ist die Bookmarks App auf Ihrem Server installiert?
JSON.parse: unexpected character at line 1 column 1 of the JSON data

• Debug log provided

floccus-4.3.0-2020-10-04.log

Additional context

I sync server folder /privat to bookmark folder Nextcloud ([e-mail]).

In Nextcloud log I see following error:

[index] Error: Exception: Call to undefined function OCA\Bookmarks\Db\array_first() at <<closure>>

0. /var/www/html/nextcloud/lib/private/AppFramework/App.php line 137
   OC\AppFramework\Http\Dispatcher->dispatch(OCA\Bookmarks\Co ... {}, "getBookmarks")
1. /var/www/html/nextcloud/lib/private/AppFramework/Routing/RouteActionHandler.php line 47
   OC\AppFramework\App::main("OCA\\Bookmarks\ ... r", "getBookmarks", OC\AppFramework\ ... {}, {_route: "bookma ... "})
2. <<closure>>
   OC\AppFramework\Routing\RouteActionHandler->__invoke({_route: "bookma ... "})
3. /var/www/html/nextcloud/lib/private/Route/Router.php line 297
   call_user_func(OC\AppFramework\ ... {}, {_route: "bookma ... "})
4. /var/www/html/nextcloud/lib/base.php line 1012
   OC\Route\Router->match("/apps/bookmarks/public/rest/v2/bookmark")
5. /var/www/html/nextcloud/index.php line 37
   OC::handleRequest()

GET /index.php/apps/bookmarks/public/rest/v2/bookmark?page=0&limit=300
from 192.168.135.54 by fermat at 2020-10-04T05:42:03+00:00

and

[index] Error: Exception: Call to undefined function OCA\Bookmarks\Db\array_first() at <<closure>>

0. /var/www/html/nextcloud/lib/private/AppFramework/App.php line 137
   OC\AppFramework\Http\Dispatcher->dispatch(OCA\Bookmarks\Co ... {}, "hashFolder")
1. /var/www/html/nextcloud/lib/private/AppFramework/Routing/RouteActionHandler.php line 47
   OC\AppFramework\App::main("OCA\\Bookmarks\ ... r", "hashFolder", OC\AppFramework\ ... {}, {folderId: "-1", ... "})
2. <<closure>>
   OC\AppFramework\Routing\RouteActionHandler->__invoke({folderId: "-1", ... "})
3. /var/www/html/nextcloud/lib/private/Route/Router.php line 297
   call_user_func(OC\AppFramework\ ... {}, {folderId: "-1", ... "})
4. /var/www/html/nextcloud/lib/base.php line 1012
   OC\Route\Router->match("/apps/bookmarks ... h")
5. /var/www/html/nextcloud/index.php line 37
   OC::handleRequest()

GET /index.php/apps/bookmarks/public/rest/v2/folder/-1/hash
from 192.168.135.54 by fermat at 2020-10-04T05:42:02+00:00

every minute, so every time floccus tries to sync.

[marcelklehr]

@gerroon Sorry for the late response, I somehow missed your comment. In this case the culprit is likely the emoji in the bookmark title. Make sure your nextcloud database uses utf8_mb4 encoding.

[gerroon]

Hi

I installed 3.4.3 unstable for NC 19 (manually replaced the bookmarks app) from the releases and I still seem to have this issue.

I am using Floccus 4.3.0 on Linux Firefox 81

E020: Could not parse server response. Is the bookmarks app installed on your server? JSON.parse: unexpected character at line 1 column 1 of the JSON data 

End of the debug log

2020-10-17T04:22:07.825Z (nextcloud-folders)CREATE     - #undefined[GitHub - daviddao/awful-ai: 😈Awful AI is a curated list to track current scary usages of AI - hoping to raise awareness](https://github.com/daviddao/awful-ai) parentId: 5
2020-10-17T04:22:10.859Z [Error: E020: Could not parse server response. Is the bookmarks app installed on your server?
JSON.parse: unexpected character at line 1 column 1 of the JSON data]
2020-10-17T04:22:10.863Z Syncing failed with E020: Could not parse server response. Is the bookmarks app installed on your server?
JSON.parse: unexpected character at line 1 column 1 of the JSON data