[Django] #12517: Mistake in example for django.db.models.get_prep_lookup()

[Django]

#12517: Mistake in example for django.db.models.get_prep_lookup()
------------------------------------+---------------------------------------
 Reporter:  dja...@pressure.net.nz  |       Owner:  nobody    
   Status:  new                     |   Milestone:            
Component:  Documentation           |     Version:  SVN       
 Keywords:                          |       Stage:  Unreviewed
Has_patch:  0                       |  
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 http://docs.djangoproject.com/en/dev/howto/custom-model-
 fields/#django.db.models.get_prep_lookup

 In the example, the return value for an exact lookup is wrapped in a list:

 {{{
 #!python
     def get_prep_lookup(self, lookup_type, value):
         # We only handle 'exact' and 'in'. All others are errors.
         if lookup_type == 'exact':
             return [self.get_prep_value(value)]
 }}}

 This then gets passed to the DB connection's compiler in
 get_db_prep_lookup, and seeing a list, does a typecast to ARRAY (in the
 case of Postgres).

 I think the example should in fact return just the value, not wrapped in a
 list (also as per the default implementation of get_prep_lookup in the
 source):

 {{{
 #!python
     def get_prep_lookup(self, lookup_type, value):
         # We only handle 'exact' and 'in'. All others are errors.
         if lookup_type == 'exact':
             return self.get_prep_value(value)
 }}}

 By making this change to a custom field I have, the undesired typecast
 behaviour described above is avoided.

-- 
Ticket URL: <http://code.djangoproject.com/ticket/12517>
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