[Bug] TypeError: Argument Of Type NoneType Is Not Iterable

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Bug: TypeError: argument of type "NoneType" is not iterable in KOReader Sync plugin

KOReader is a popular e-reader application for Android devices, allowing users to sync their e-books with Calibre, a powerful e-book management software. However, some users have reported encountering a frustrating error when attempting to sync their e-books using the KOReader Sync plugin. In this article, we will delve into the details of this bug, explore the possible causes, and provide a step-by-step guide to reproduce and resolve the issue.

The error in question is a TypeError: argument of type 'NoneType' is not iterable, which occurs when the KOReader Sync plugin attempts to sync e-books with Calibre. The error message is as follows:

calibre, version 7.23.0
ERROR: Unhandled exception: <b>TypeError</b>:argument of type 'NoneType' is not iterable

calibre 7.23  embedded-python: False
Linux-6.12.17_1-x86_64-with-glibc2.39 Linux ('64bit', 'ELF')
('Linux', '6.12.17_1', '#1 SMP PREEMPT_DYNAMIC Tue Mar  4 23:20:38 UTC 2025')
Python 3.13.2
Interface language: None
EXE path: /usr/bin/python3
Successfully initialized third party plugins: Gather KFX-ZIP (from KFX Input) (1, 49, 0) && Package KFX (from KFX Input) (1, 49, 0) && Apple Books covers (0, 1, 0) && Count Pages (1, 13, 6) && Goodreads (1, 8, 2) && KFX metadata reader (from KFX Input) (1, 49, 0) && KFX Input (1, 49, 0) && KOReader Sync (0, 6, 8) && Kindle hi-res covers (0, 5, 1) && Kobo Books (1, 9, 2) && Kobo Metadata (1, 5, 0) && Kobo Utilities (2, 16, 13) && KoboTouchExtended (3, 6, 7) && Obok DeDRM (10, 0, 3)
Traceback (most recent call last):
  File "calibre_plugins.koreader.action", line 793, in sync_to_calibre
    sidecar_contents = self.get_sidecar(device, sidecar_path)
  File "calibre_plugins.koreader.action", line 376, in get_sidecar
    parsed_contents = parse_sidecar_lua(decoded_contents)
  File "calibre_plugins.koreader.action", line 126, in parse_sidecar_lua
    if 'bookmarks' in decoded_lua:
       ^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: argument of type 'NoneType' is not iterable

To reproduce this bug, follow these steps:

  1. Install KOReader on your Android device and connect it to your computer via USB.
  2. Mount your microSD card as an MTP device and access it via Calibre's "Connect/Share" feature.
  3. Refresh the "On Device" list in Calibre to ensure that the e-book folder is properly connected.
  4. Press the "KOReader Sync" button to initiate the sync process.
  5. Wait for a while until the application halts and displays the error popup.

The expected behavior is that the KOReader Sync plugin should successfully sync the e-books with Calibre, updating the stats and ensuring that the e-book collection is up-to-date.

This bug does not occur when using the KOReader instance on Calibre/Kobo pairing. The problem is specific to the Android device and the MTP connection.

The TypeError: argument of type 'NoneType' is not iterable error in the KOReader Sync plugin is a frustrating issue that can prevent users from syncing their e-books with Calibre. By following the reproduction steps outlined in this article, users can identify the problem and potentially resolve it by updating the KOReader Sync plugin or exploring alternative solutions. We hope that this article has provided valuable insights and assistance in resolving this bug.

If you are experiencing this issue, try the following troubleshooting tips:

  • Update the KOReader Sync plugin to the latest version.
  • Check the Calibre version and ensure that it is up-to-date.
  • Verify the MTP connection and ensure that the microSD card is properly mounted.
  • Try syncing the e-books using a different method, such as Wi-Fi or Bluetooth.

By following these tips and exploring the possible causes of the bug, users can potentially resolve the issue and enjoy seamless e-book syncing with Calibre.
Q&A: Bug - TypeError: argument of type "NoneType" is not iterable in KOReader Sync plugin

In our previous article, we explored the details of the TypeError: argument of type 'NoneType' is not iterable error in the KOReader Sync plugin. This error can prevent users from syncing their e-books with Calibre, a powerful e-book management software. In this Q&A article, we will address some of the most frequently asked questions related to this bug, providing valuable insights and assistance to users who are experiencing this issue.

A: The error is caused by a NoneType value being passed to a function that expects an iterable (such as a list or a dictionary). In the case of the KOReader Sync plugin, the error occurs when the plugin attempts to parse the sidecar data, which is not properly formatted.

A: To reproduce the error, follow these steps:

  1. Install KOReader on your Android device and connect it to your computer via USB.
  2. Mount your microSD card as an MTP device and access it via Calibre's "Connect/Share" feature.
  3. Refresh the "On Device" list in Calibre to ensure that the e-book folder is properly connected.
  4. Press the "KOReader Sync" button to initiate the sync process.
  5. Wait for a while until the application halts and displays the error popup.

A: The expected behavior is that the KOReader Sync plugin should successfully sync the e-books with Calibre, updating the stats and ensuring that the e-book collection is up-to-date.

A: The error occurs only when using the KOReader instance on Android device because the MTP connection is not properly handled by the plugin. This issue is specific to the Android device and the MTP connection.

A: To troubleshoot the error, try the following steps:

  1. Update the KOReader Sync plugin to the latest version.
  2. Check the Calibre version and ensure that it is up-to-date.
  3. Verify the MTP connection and ensure that the microSD card is properly mounted.
  4. Try syncing the e-books using a different method, such as Wi-Fi or Bluetooth.

A: Yes, you can potentially resolve the error by updating the KOReader Sync plugin or exploring alternative solutions. However, the best course of action will depend on the specific circumstances of your setup.

The TypeError: argument of type 'NoneType' is not iterable error in the KOReader Sync plugin is a frustrating issue that can prevent users from syncing their e-books with Calibre. By following the troubleshooting tips and exploring the possible causes of the bug, users can potentially resolve the issue and enjoy seamless e-book syncing with Calibre. We hope that this Q&A article has provided valuable insights and assistance to users who are experiencing this issue.