Improved order of methods in proxy class in lazy().

This order reads more naturally and puts methods into three groups:

1. The methods required to support the implementation of __proxy__, e.g.
   __deepcopy__ doesn't come from `object` and __reduce__ is
   overridden to support behavior required explicitly for pickling of
   lazy objects.

2. Methods that are specifically overridden from `object` which we
   don't want to inherit from the provided resultclasses. These will be
   skipped later when we add methods from the resultclasses.

3. Additional methods - that is _add__, __radd__, and __mod__ - don't
   come from `object`, but typically from `str` and `int` which are the
   most common use cases.

Co-authored-by: Nick Pope <nick@nickpope.me.uk>

1 files changed, 16 insertions, 10 deletions

diff --git a/django/utils/functional.py b/django/utils/functional.py
index 6ee630c021..e3be672282 100644
--- a/django/utils/functional.py
+++ b/django/utils/functional.py
@@ -104,8 +104,12 @@ def lazy(func, *resultclasses):
                 (func, self.__args, self.__kw) + resultclasses,
             )
 
-        def __repr__(self):
-            return repr(self.__cast())
+        def __deepcopy__(self, memo):
+            # Instances of this class are effectively immutable. It's just a
+            # collection of functions. So we don't need to do anything
+            # complicated for copying.
+            memo[id(self)] = self
+            return self
 
         @classmethod
         def __prepare_class__(cls):
@@ -133,6 +137,12 @@ def lazy(func, *resultclasses):
         def __cast(self):
             return func(*self.__args, **self.__kw)
 
+        # Explicitly wrap methods which are defined on object and hence would
+        # not have been overloaded by the loop over resultclasses below.
+
+        def __repr__(self):
+            return repr(self.__cast())
+
         def __str__(self):
             # object defines __str__(), so __prepare_class__() won't overload
             # a __str__() method from the proxied class.
@@ -171,8 +181,8 @@ def lazy(func, *resultclasses):
         def __hash__(self):
             return hash(self.__cast())
 
-        def __mod__(self, rhs):
-            return self.__cast() % rhs
+        # Explicitly wrap methods which are required for certain operations on
+        # int/str objects to function correctly.
 
         def __add__(self, other):
             return self.__cast() + other
@@ -180,12 +190,8 @@ def lazy(func, *resultclasses):
         def __radd__(self, other):
             return other + self.__cast()
 
-        def __deepcopy__(self, memo):
-            # Instances of this class are effectively immutable. It's just a
-            # collection of functions. So we don't need to do anything
-            # complicated for copying.
-            memo[id(self)] = self
-            return self
+        def __mod__(self, other):
+            return self.__cast() % other
 
     @wraps(func)
     def __wrapper__(*args, **kw):