#6191: Admin delete view doesn't show all items in some circumstances
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          Reporter:  nicklane              |         Owner:  carljm    
            Status:  new                   |     Milestone:            
         Component:  django.contrib.admin  |       Version:  SVN        
        Resolution:                        |      Keywords:  nfa-someday
             Stage:  Accepted              |     Has_patch:  1          
        Needs_docs:  0                     |   Needs_tests:  0          
Needs_better_patch:  1                     |  
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Comment (by carljm):

 The attached patch is based on nicklane's 6191.patch, updated to apply to
 trunk, and with a number of new tests. Just uploading for the tests; I
 don't think the fix is ready for trunk.

 Notably (among other things), the new tests test that:

 1. If a model has two foreign keys to it from a single related model, both
 are followed (the original issue here, passes after the patch).

 2. A given object is only displayed once in the list, even if it can be
 found through two different paths (passes before the patch, fails after
 it).

 3. A cyclic dependency still only lists each object once, not repeatedly
 until an arbitrary max recursion is hit (this is #11296, currently fails
 both before and after).

 IMO, kmtracey is right: the real fix here is to re-use the same code that
 is actually used to collect the objects for deletion (that's
 Model._collect_sub_objects). Otherwise we're likely to continue to see
 recurring problems with mismatches between the two duplicate algorithms.
 It's tricky, because get_deleted_objects generates a nested data structure
 for display, where Model._collect_sub_objects generates a flat one. I
 think it's possible by adding a callback hook to
 Model._collect_sub_objects, so get_deleted_objects can be notified each
 time _collect_sub_objects recurses. This is the route I'm planning to
 pursue, and I think I should be able to get all three of the above cases
 to pass (fixing both this and #11296), and eliminate the duplicate logic.
 Comments welcome.

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Ticket URL: <http://code.djangoproject.com/ticket/6191#comment:15>
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