Ticket #11957: 11957-r12936.diff

django/contrib/admin/__init__.py

@@ -4 +4 @@
 from django.contrib.admin.sites import AdminSite, site
 from django.utils.importlib import import_module
 
-# A flag to tell us if autodiscover is running.  autodiscover will set this to
-# True while running, and False when it finishes.
-LOADING = False
-
 def autodiscover():
     """
     Auto-discover INSTALLED_APPS admin.py modules and fail silently when
     not present. This forces an import on them to register any admin bits they
     may want.
     """
-    # Bail out if autodiscover didn't finish loading from a previous call so
-    # that we avoid running autodiscover again when the URLconf is loaded by
-    # the exception handler to resolve the handler500 view.  This prevents an
-    # admin.py module with errors from re-registering models and raising a
-    # spurious AlreadyRegistered exception (see #8245).
-    global LOADING
-    if LOADING:
-        return
-    LOADING = True
-
     import imp
+    import copy
     from django.conf import settings
 
     for app in settings.INSTALLED_APPS:
@@ -54 +41 @@
 
         # Step 3: import the app's admin file. If this has errors we want them
         # to bubble up.
-        import_module("%s.admin" % app)
-    # autodiscover was successful, reset loading flag.
-    LOADING = False
+        try:
+            model_registry_before_import = copy.copy(site._registry)
+            import_module("%s.admin" % app)
+        except:
+            # Reset the model registry to the state before the last import as this import will have to reoccur
+            # on the next request and this could raise NotRegistered and AlreadyRegistered exceptions (see #8245).
+            site._registry = model_registry_before_import
+            raise

tests/regressiontests/bug8245/tests.py

@@ -18 +18 @@
         else:
             self.fail(
                 'autodiscover should have raised a "Bad admin module" error.')
-        # Calling autodiscover again should bail out early and not raise an
-        # AlreadyRegistered error.
-        admin.autodiscover()
+        # Calling autodiscover again should raise the very same error it did the first time, not an AlreadyRegistered error.
+        try:
+            admin.autodiscover()
+        except Exception, e:
+            self.failUnlessEqual(str(e), "Bad admin module")
+        else:
+            self.fail(
+                'autodiscover should have raised a "Bad admin module" error.')