[Kolab-devel] [issue4871] Changes to kolab tasks are sometimes not synced to kmail (RT#10242)

When you modify a task the modification is sometimes not synced to the imap server.

To Reproduce:
1. Create a new Task
2. Click the checkbox in the tasklist to mark it as completed
3. Mark it as uncompleted the same way
4. Mark it as completed again
5. Rename the task

Changes 2 and 3 are synced the rest not. If you restart Kontact and it rereads
the kolab objects the task is shown under the old summary and is uncompleted.

Analysis shows that the conflictpreventer class is involved here. For some
reason it does not remove the payload of the created task in step 1 and when it
sees the same task in step 3 it detects a false positive conflict. It then sees
two incidences with the same serial number: (You get a WARNING: Two incidences
with the same SerialNumber. Ignoring: 24533) And ignores the second one.
Afterwards the transaction is not finished and the task is still a part of the
list of updates. So further changes to this todo lead to "kontact:
incidenceUpdatedSilent(): skipping and updating mPendingUpdates with incidence"

So further changes even with a different payload are ignored. 

Currently I do not understand why this behavior can't be reproduced with events
or tasks if you do not use the checkboxes but set the completion status in the
incidenceeditor.

The following test case does _not_ trigger this
1. Create a task
2. Open the task editor and set it as completed
3. Set it to uncompleted (0%)
4. Set it to completed (100%)
5. Rename the task

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assignedto: aheinecke
keyword: enterprise35, kde client
messages: 28841
nosy: aheinecke, allen, emanuel, laurent, ludwig, sergio, till, vkrause
priority: urgent
status: in-progress
title: Changes to kolab tasks are sometimes not synced to kmail (RT#10242)

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Kolab issue tracker <[email protected]>
<https://roundup.kolab.org/issue4871>
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