Fixed #14270 - related manager classes should be cached

Thanks to Alex Gaynor for the report and initial patch, and mrmachine for
more work on it.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16916 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/utils/functional.py

@@ -28,6 +28,18 @@ def memoize(func, cache, num_args):
         return result
     return wrapper
 
+class cached_property(object):
+    """
+    Decorator that creates converts a method with a single
+    self argument into a property cached on the instance.
+    """
+    def __init__(self, func):
+        self.func = func
+
+    def __get__(self, instance, type):
+        res = instance.__dict__[self.func.__name__] = self.func(instance)
+        return res
+
 class Promise(object):
     """
     This is just a base class for the proxy class created in
@@ -288,4 +300,4 @@ def partition(predicate, values):
     results = ([], [])
     for item in values:
         results[predicate(item)].append(item)
-    return results
+    return results