Fixed #21711 -- Enforced unicity of model names.

django/apps/registry.py

@@ -185,7 +185,6 @@ class Apps(object):
         # call get_app_config().
         model_name = model._meta.model_name
         app_models = self.all_models[app_label]
-        # Defensive check for extra safety.
         if model_name in app_models:
             raise RuntimeError(
                 "Conflicting '%s' models in application '%s': %s and %s." %

django/db/models/base.py

@@ -162,12 +162,6 @@ class ModelBase(type):
                 new_class._default_manager = new_class._default_manager._copy_to_model(new_class)
                 new_class._base_manager = new_class._base_manager._copy_to_model(new_class)
 
-        # Bail out early if we have already created this class.
-        try:
-            return new_class._meta.apps.get_registered_model(new_class._meta.app_label, name)
-        except LookupError:
-            pass
-
         # Add all attributes to the class.
         for obj_name, obj in attrs.items():
             new_class.add_to_class(obj_name, obj)
@@ -285,13 +279,8 @@ class ModelBase(type):
             return new_class
 
         new_class._prepare()
-
         new_class._meta.apps.register_model(new_class._meta.app_label, new_class)
-        # Because of the way imports happen (recursively), we may or may not be
-        # the first time this model tries to register with the framework. There
-        # should only be one class for each model, so we always return the
-        # registered version.
-        return new_class._meta.apps.get_registered_model(new_class._meta.app_label, name)
+        return new_class
 
     def copy_managers(cls, base_managers):
         # This is in-place sorting of an Options attribute, but that's fine.

django/db/models/query_utils.py

@@ -7,6 +7,7 @@ circular import difficulties.
 """
 from __future__ import unicode_literals
 
+from django.apps import apps
 from django.db.backends import utils
 from django.utils import six
 from django.utils import tree
@@ -185,22 +186,28 @@ def deferred_class_factory(model, attrs):
     being replaced with DeferredAttribute objects. The "pk_value" ties the
     deferred attributes to a particular instance of the model.
     """
-    class Meta:
-        proxy = True
-        app_label = model._meta.app_label
-
     # The app registry wants a unique name for each model, otherwise the new
-    # class won't be created (we get an old one back). Therefore, we generate
+    # class won't be created (we get an exception). Therefore, we generate
     # the name using the passed in attrs. It's OK to reuse an existing class
     # object if the attrs are identical.
     name = "%s_Deferred_%s" % (model.__name__, '_'.join(sorted(list(attrs))))
     name = utils.truncate_name(name, 80, 32)
 
-    overrides = dict((attr, DeferredAttribute(attr, model)) for attr in attrs)
-    overrides["Meta"] = Meta
-    overrides["__module__"] = model.__module__
-    overrides["_deferred"] = True
-    return type(str(name), (model,), overrides)
+    try:
+        return apps.get_model(model._meta.app_label, name)
+
+    except LookupError:
+
+        class Meta:
+            proxy = True
+            app_label = model._meta.app_label
+
+        overrides = dict((attr, DeferredAttribute(attr, model)) for attr in attrs)
+        overrides["Meta"] = Meta
+        overrides["__module__"] = model.__module__
+        overrides["_deferred"] = True
+        return type(str(name), (model,), overrides)
+
 
 # The above function is also used to unpickle model instances with deferred
 # fields.