Ticket #8245: 8245.diff

django/contrib/admin/__init__.py

@@ -2 +2 @@
 from django.contrib.admin.options import StackedInline, TabularInline
 from django.contrib.admin.sites import AdminSite, site
 
+LOADING_FLAG = '_admin_autodiscover_loading'
+
 def autodiscover():
     """
-    Auto-discover INSTALLED_APPS admin.py modules and fail silently when 
+    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.
     """
@@ -21 +23 @@
         # should) bubble up, but a missing __path__ (which is legal, but weird)
         # fails silently -- apps that do weird things with __path__ might
         # need to roll their own admin registration.
+        app_mod = __import__(app, {}, {}, [app.split('.')[-1]])
+        # Bail out if this app didn't finish loading from a previous call so
+        # that we avoid masking the real exception with an AlreadyRegistered
+        # exception.
+        if getattr(app_mod, LOADING_FLAG, False):
+            continue
+        # Set a flag to designate that this app is loading.
+        setattr(app_mod, LOADING_FLAG, True)
         try:
-            app_path = __import__(app, {}, {}, [app.split('.')[-1]]).__path__
+            app_path = app_mod.__path__
         except AttributeError:
             continue
 
@@ -38 +48 @@
         # Step 3: import the app's admin file. If this has errors we want them
         # to bubble up.
         __import__("%s.admin" % app)
+        # Import was successful, remove loading flag.
+        delattr(app_mod, LOADING_FLAG)