Added tests for corner case with deleting where objects are deleted in the wrong order.

These tests currently fail, by design, fix will be committed shortly.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@7721 bcc190cf-cafb-0310-a4f2-bffc1f526a37

3 files changed, 110 insertions, 5 deletions

diff --git a/django/db/models/loading.py b/django/db/models/loading.py
index e62188adf7..6837e070ac 100644
--- a/django/db/models/loading.py
+++ b/django/db/models/loading.py
@@ -2,6 +2,8 @@
 
 from django.conf import settings
 from django.core.exceptions import ImproperlyConfigured
+from django.utils.datastructures import SortedDict
+
 import sys
 import os
 import threading
@@ -18,10 +20,10 @@ class AppCache(object):
     # http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/66531.
     __shared_state = dict(
         # Keys of app_store are the model modules for each application.
-        app_store = {},
+        app_store = SortedDict(),
 
         # Mapping of app_labels to a dictionary of model names to model code.
-        app_models = {},
+        app_models = SortedDict(),
 
         # Mapping of app_labels to errors raised when trying to import the app.
         app_errors = {},
@@ -133,7 +135,7 @@ class AppCache(object):
         """
         self._populate()
         if app_mod:
-            return self.app_models.get(app_mod.__name__.split('.')[-2], {}).values()
+            return self.app_models.get(app_mod.__name__.split('.')[-2], SortedDict()).values()
         else:
             model_list = []
             for app_entry in self.app_models.itervalues():
@@ -149,7 +151,7 @@ class AppCache(object):
         """
         if seed_cache:
             self._populate()
-        return self.app_models.get(app_label, {}).get(model_name.lower())
+        return self.app_models.get(app_label, SortedDict()).get(model_name.lower())
 
     def register_models(self, app_label, *models):
         """
@@ -159,7 +161,7 @@ class AppCache(object):
             # Store as 'name: model' pair in a dictionary
             # in the app_models dictionary
             model_name = model._meta.object_name.lower()
-            model_dict = self.app_models.setdefault(app_label, {})
+            model_dict = self.app_models.setdefault(app_label, SortedDict())
             if model_name in model_dict:
                 # The same model may be imported via different paths (e.g.
                 # appname.models and project.appname.models). We use the source
diff --git a/tests/modeltests/delete/__init__.py b/tests/modeltests/delete/__init__.py
new file mode 100644
index 0000000000..8b13789179
--- /dev/null
+++ b/tests/modeltests/delete/__init__.py
@@ -0,0 +1 @@
+
diff --git a/tests/modeltests/delete/models.py b/tests/modeltests/delete/models.py
new file mode 100644
index 0000000000..d4f7dd1d1f
--- /dev/null
+++ b/tests/modeltests/delete/models.py
@@ -0,0 +1,102 @@
+# coding: utf-8
+"""
+Tests for some corner cases with deleting.
+"""
+
+from django.db import models
+
+class DefaultRepr(object):
+    def __repr__(self):
+        return u"<%s: %s>" % (self.__class__.__name__, self.__dict__)
+
+class A(DefaultRepr, models.Model):
+    pass
+
+class B(DefaultRepr, models.Model):
+    a = models.ForeignKey(A)
+
+class C(DefaultRepr, models.Model):
+    b = models.ForeignKey(B)
+
+class D(DefaultRepr, models.Model):
+    c = models.ForeignKey(C)
+    a = models.ForeignKey(A)
+
+# Simplified, we have:
+# A
+# B -> A
+# C -> B
+# D -> C
+# D -> A
+
+# So, we must delete Ds first of all, then Cs then Bs then As.
+# However, if we start at As, we might find Bs first (in which 
+# case things will be nice), or find Ds first.
+
+
+__test__ = {'API_TESTS': """
+# Due to the way that transactions work in the test harness,
+# doing m.delete() here can work but fail in a real situation,
+# since it may delete all objects, but not in the right order.
+# So we manually check that the order of deletion is correct.
+
+# Also, it is possible that the order is correct 'accidentally', due
+# solely to order of imports etc.  To check this, we set the order
+# that 'get_models()' will retrieve to a known 'tricky' order, and
+# then try again with the reverse and try again.  Slightly naughty
+# access to internals here.
+
+>>> from django.utils.datastructures import SortedDict
+>>> from django.db.models.loading import cache
+
+# Nice order
+>>> cache.app_models['delete'].keyOrder = ['a', 'b', 'c', 'd']
+>>> del A._meta._related_objects_cache
+>>> del B._meta._related_objects_cache
+>>> del C._meta._related_objects_cache
+>>> del D._meta._related_objects_cache
+
+
+
+>>> a1 = A()
+>>> a1.save()
+>>> b1 = B(a=a1)
+>>> b1.save()
+>>> c1 = C(b=b1)
+>>> c1.save()
+>>> d1 = D(c=c1, a=a1)
+>>> d1.save()
+
+>>> sd = SortedDict()
+>>> a1._collect_sub_objects(sd)
+>>> list(reversed(sd.keys()))
+[<class 'modeltests.delete.models.D'>, <class 'modeltests.delete.models.C'>, <class 'modeltests.delete.models.B'>, <class 'modeltests.delete.models.A'>]
+>>> a1.delete()
+
+# Same again with a known bad order
+>>> cache.app_models['delete'].keyOrder = ['d', 'c', 'b', 'a']
+>>> del A._meta._related_objects_cache
+>>> del B._meta._related_objects_cache
+>>> del C._meta._related_objects_cache
+>>> del D._meta._related_objects_cache
+
+
+>>> a2 = A()
+>>> a2.save()
+>>> b2 = B(a=a2)
+>>> b2.save()
+>>> c2 = C(b=b2)
+>>> c2.save()
+>>> d2 = D(c=c2, a=a2)
+>>> d2.save()
+
+>>> sd2 = SortedDict()
+>>> a2._collect_sub_objects(sd2)
+>>> list(reversed(sd2.keys()))
+[<class 'modeltests.delete.models.D'>, <class 'modeltests.delete.models.C'>, <class 'modeltests.delete.models.B'>, <class 'modeltests.delete.models.A'>]
+>>> a2.delete()
+
+
+
+"""
+}