Added SQLite backend which passes all current tests

1 files changed, 21 insertions, 0 deletions

diff --git a/django/db/models/loading.py b/django/db/models/loading.py
index 0ed6caffa4..e0d943853b 100644
--- a/django/db/models/loading.py
+++ b/django/db/models/loading.py
@@ -265,6 +265,10 @@ class AppCache(object):
         self.app_models = state['app_models']
         self.app_errors = state['app_errors']
 
+    def temporary_state(self):
+        "Returns a context manager that restores the state on exit"
+        return StateContextManager(self)
+
     def unregister_all(self):
         """
         Wipes the AppCache clean of all registered models.
@@ -275,6 +279,23 @@ class AppCache(object):
         self.app_models = SortedDict()
         self.app_errors = {}
 
+
+class StateContextManager(object):
+    """
+    Context manager for locking cache state.
+    Useful for making temporary models you don't want to stay in the cache.
+    """
+
+    def __init__(self, cache):
+        self.cache = cache
+
+    def __enter__(self):
+        self.state = self.cache.save_state()
+
+    def __exit__(self, type, value, traceback):
+        self.cache.restore_state(self.state)
+
+
 cache = AppCache()
 
 # These methods were always module level, so are kept that way for backwards