#33724: Changing from list to set in `exclude` raises errors, and is not
documented.
-------------------------------------+-------------------------------------
     Reporter:  אורי                 |                    Owner:  nobody
         Type:  Bug                  |                   Status:  new
    Component:  Database layer       |                  Version:  4.1
  (models, ORM)                      |
     Severity:  Release blocker      |               Resolution:
     Keywords:                       |             Triage Stage:  Accepted
    Has patch:  0                    |      Needs documentation:  0
  Needs tests:  0                    |  Patch needs improvement:  0
Easy pickings:  0                    |                    UI/UX:  0
-------------------------------------+-------------------------------------

Comment (by אורי):

 Replying to [comment:6 Claude Paroz]:
 > Still I wonder if the performance gain is worth the loss of consistency.
 I wouldn't mind if exclude was defined to always be a set, but having to
 code defensively by expecting list or set is a loss in my point of view.

 I think logically it should be a set, because we don't need the same value
 twice and the order doesn't matter. But we should decide how to handle old
 code where it was a list. Maybe define it a set from now on, and write in
 the documentation that it must be a set. But I don't see any problem with
 including the following 4 lines every time we use `exclude`:

 {{{
     if exclude is None:
         exclude = set()
     else:
         exclude = set(exclude)
 }}}

 By the way, since these 4 lines are repeated, maybe we can define a util
 function that takes `exclude` as an argument, and return a set. Either
 `set()` (if `exclude is None`) or `set(exclude)` otherwise.

-- 
Ticket URL: <https://code.djangoproject.com/ticket/33724#comment:7>
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