Details and discussion in thread including:

  https://sourceforge.net/p/roundup/mailman/message/37247607/

short form:

sorted method uses:

  value.sort(key=lambda a:a[property], reverse=reverse)

but a[property] is always a string so you get 1, 12, 2, 21, 22 etc.

Need to covert a[property] into it's actual declared type.
Hyperdb has a sort_repr(cls, a[property], property) method
for just this purpose. However there is no method defined for
Integer or Number. Define one for Integer and Number returning
int(val) or float(val) respectively. Also need to handle case
where value (a[property] is None) (see issue2551120) as this
causes a crash.

Extensive discussion on how to handle None state and set it to some
value that will allow the sort to work is inconclusive so far.
I suggest using int(sys.maxint || sys.maxsize) (python2/3)
and float('inf'). This should sort unknown to the end.

Once sort_repr is done for Integer and Float something like:

   cls = self._db.getclass(self._prop.classname)
   sort_repr = cls.property.sort_repr # (or maybe cls[property])
   value.sort(key=lambda a:sort_repr(cls, a[property], property),
              reverse=reverse)

but I am not sure what self is passed to sort_repr.

Problem found by ngaba.

Hi Nagy:

I have struck out on trying to reproduce this in my tracker.  So I am
starting from scratch (simpler tracker) to reproduce the problem.

My plan is to start with the classic tracker. Change the schema for
the status class removing the order property and adding:

   ord = Integer()

so this is the integer property I will use for ordering. Use
setorderprop('ord') for the status class to get that field to be used
for ordering.

The 8 statuses in the classic tracker will have the same value for ord
as they used to have for order. Except item 5 in-progress will have an
ord value of 15.

If I sort a list of issues in a multilink by the status using
sorted(), I should see in-progress(ord=15) between items with ord
values of 1 and 2.

Then I will change the issue.item template to display items in the
superseder multilink using:

        <a tal:repeat="sup context.superseder.sorted('ord')"
        tal:content="python:sup['id'] + '-' + sup['status'] +
               ','*(not repeat['sup'].end)"
        tal:attributes="href string:issue${sup/id}"></a>

Then I will create an issue with 8 superseder issues, one in each
state.  I should see the superseder issues mis-sorted with
in-progress(ord=15) after unread(ord=1) and before deferred(ord=2)
with the mis-sorted item.

Does this sound like it will reproduce the problem you are describing?

Hi John:

Yes, I think your steps will reproduce the issue.

Hi Nagy:

I think this patch fixes it. Can you apply it over the previous patch
for None value causing traceback and let me know if it fixes it.

Untar classic_overlay.tgz to get the changes (schema.py,
issue.item.html, initial_data.py) from classic template I
used to reproduce this.

Dear John,

Thank you for the patch.
It seems it fixed the bug described in msg7235 here (using my own different schema.py, ofc).

Committed on:

changeset:   6421:9c57f2814597

Marked needs testing. Same issue with testing as issue2551120.
The testing framework for the templating functions does not
have a complete db. The mock that exists to test templating isn't 
sufficient to test this code.