add_filter in django/db/models/ sql/query.py causes exception when model have 'evaluate' attribute

[LukaszKorzybski]

I was migrating some django project recently from django 1.0.4 to 1.2.
In Django 1.2/1.1 I found that if model have 'evaluate' attribute then
one will get exception in admin edit page for that model if the page
contains inline forms with related models:

Exception Value:  'Shipper' object has no attribute 'prepare'
Exception Location:     .../django/db/models/sql/expressions.py in
__init__, line 12

It is caused by the fact that add_filter function in django/db/models/sql/query.py does such a check:

...
1005.  elif hasattr(value, 'evaluate'):
1006.      # If value is a query expression, evaluate it
1007.      value = SQLEvaluator(value, self) ...
1008.      having_clause = value.contains_aggregate
...

The problem is that "value" in this case is Shipper model which in
have "evaluate" method so it is recognized as query expression here.

Greetings,

[LukaszKorzybski]

Ups I forgot to do some formatting of the text, sorry for that :/

[Alex Gaynor]

Updated the syntax.