Merged Unicode branch into trunk (r4952:5608). This should be fully

backwards compatible for all practical purposes.

Fixed #2391, #2489, #2996, #3322, #3344, #3370, #3406, #3432, #3454, #3492, #3582, #3690, #3878, #3891, #3937, #4039, #4141, #4227, #4286, #4291, #4300, #4452, #4702


git-svn-id: http://code.djangoproject.com/svn/django/trunk@5609 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/utils/functional.py

@@ -18,7 +18,7 @@ def memoize(func, cache):
         return result
     return wrapper
 
-class Promise:
+class Promise(object):
     """
     This is just a base class for the proxy class created in
     the closure of the lazy function. It can be used to recognize
@@ -47,6 +47,11 @@ def lazy(func, *resultclasses):
                 self.__dispatch[resultclass] = {}
                 for (k, v) in resultclass.__dict__.items():
                     setattr(self, k, self.__promise__(resultclass, k, v))
+            self._delegate_str = str in resultclasses
+            self._delegate_unicode = unicode in resultclasses
+            assert not (self._delegate_str and self._delegate_unicode), "Cannot call lazy() with both str and unicode return types."
+            if self._delegate_unicode:
+                self.__unicode__ = self.__unicode_cast
 
         def __promise__(self, klass, funcname, func):
             # Builds a wrapper around some magic method and registers that magic
@@ -62,8 +67,56 @@ def lazy(func, *resultclasses):
             self.__dispatch[klass][funcname] = func
             return __wrapper__
 
+        def __unicode_cast(self):
+            return self.__func(*self.__args, **self.__kw)
+
+        def __str__(self):
+            # As __str__ is always a method on the type (class), it is looked
+            # up (and found) there first. So we can't just assign to it on a
+            # per-instance basis in __init__.
+            if self._delegate_str:
+                return str(self.__func(*self.__args, **self.__kw))
+            else:
+                return Promise.__str__(self)
+
+        def __cmp__(self, rhs):
+            if self._delegate_str:
+                s = str(self.__func(*self.__args, **self.__kw))
+            elif self._delegate_unicode:
+                s = unicode(self.__func(*self.__args, **self.__kw))
+            else:
+                s = self.__func(*self.__args, **self.__kw)
+            if isinstance(rhs, Promise):
+                return -cmp(rhs, s)
+            else:
+                return cmp(s, rhs)
+
+        def __mod__(self, rhs):
+            if self._delegate_str:
+                return str(self) % rhs
+            elif self._delegate_unicode:
+                return unicode(self) % rhs
+            else:
+                raise AssertionError('__mod__ not supported for non-string types')
+
     def __wrapper__(*args, **kw):
         # Creates the proxy object, instead of the actual value.
         return __proxy__(args, kw)
 
     return __wrapper__
+
+def allow_lazy(func, *resultclasses):
+    """
+    A decorator that allows a function to be called with one or more lazy
+    arguments. If none of the args are lazy, the function is evaluated
+    immediately, otherwise a __proxy__ is returned that will evaluate the
+    function when needed.
+    """
+    def wrapper(*args, **kwargs):
+        for arg in list(args) + kwargs.values():
+            if isinstance(arg, Promise):
+                break
+        else:
+            return func(*args, **kwargs)
+        return lazy(func, *resultclasses)(*args, **kwargs)
+    return wrapper