TypeError: 'NoneType' object is not iterable

[anonymous]

2015-06-22 09:16:17,772 Trac[main] ERROR: Internal Server Error: 
Traceback (most recent call last):
  File "build\bdist.win32\egg\trac\web\main.py", line 551, in _dispatch_request
    dispatcher.dispatch(req)
  File "build\bdist.win32\egg\trac\web\main.py", line 225, in dispatch
    resp = chosen_handler.process_request(req)
  File "build\bdist.win32\egg\cards\core.py", line 63, in process_request
    Card.delete_by_id(self.env, card_id)
  File "build\bdist.win32\egg\cards\model.py", line 102, in delete_by_id
    stack, rank = cursor.fetchone()
TypeError: 'NoneType' object is not iterable

[Ryan J Ollos]

I can reproduce by attempting to delete a card that has already been deleted. There could be protection implemented, but the limitation is already documented in CardsPlugin#KnownLimitations.

[Peter Suter]

Right. I'd really like to do something about that limitation at some point. While double-deletes could usually easily be detected and ignored, I assume to solve the problem in general a combination of auto-refresh and conflict detection based on some kind of version number checks would be required. Suggestions welcome.

[Peter Suter]

In 14811:

CardsPlugin: Support for collaborative editing.

• Conflict detection mechanism.
• DB upgrade.
• Refresh button.
• Auto-refresh every 10 seconds when the cards are visible.
• Bump version to 1.2

(fix #12428)