Fixed #19543 -- implemented SimpleLazyObject.__repr__

Thanks to Florian Hahn for the patch

django/utils/functional.py

@@ -305,6 +305,15 @@ class SimpleLazyObject(LazyObject):
     def __reduce__(self):
         return (self.__newobj__, (self.__class__,), self.__getstate__())
 
+    # Return a meaningful representation of the lazy object for debugging
+    # without evaluating the wrapped object.
+    def __repr__(self):
+        if self._wrapped is empty:
+            repr_attr = self._setupfunc
+        else:
+            repr_attr = self._wrapped
+        return '<SimpleLazyObject: %r>' % repr_attr
+
     # Need to pretend to be the wrapped class, for the sake of objects that care
     # about this (especially in equality tests)
     __class__ = property(new_method_proxy(operator.attrgetter("__class__")))

docs/releases/1.6.txt

@@ -131,6 +131,9 @@ Minor features
   :setting:`TEMPLATE_STRING_IF_INVALID` for variables not present in the
   context, just like other template constructs.
 
+* SimpleLazyObjects will now present more helpful representations in shell
+  debugging situations.
+
 Backwards incompatible changes in 1.6
 =====================================
 

tests/utils_tests/simplelazyobject.py

@@ -59,10 +59,18 @@ class TestUtilsSimpleLazyObject(TestCase):
                          hash(SimpleLazyObject(complex_object)))
 
     def test_repr(self):
-        # For debugging, it will really confuse things if there is no clue that
+        # First, for an unevaluated SimpleLazyObject
-        # SimpleLazyObject is actually a proxy object. So we don't
+        x = SimpleLazyObject(complex_object)
-        # proxy __repr__
+        # __repr__ contains __repr__ of setup function and does not evaluate
-        self.assertTrue("SimpleLazyObject" in repr(SimpleLazyObject(complex_object)))
+        # the SimpleLazyObject
+        self.assertEqual("<SimpleLazyObject: %r>" % complex_object, repr(x))
+        self.assertEqual(empty, x._wrapped)
+
+        # Second, for an evaluated SimpleLazyObject
+        name = x.name # evaluate
+        self.assertTrue(isinstance(x._wrapped, _ComplexObject))
+        # __repr__ contains __repr__ of wrapped object
+        self.assertEqual("<SimpleLazyObject: %r>" % x._wrapped, repr(x))
 
     def test_bytes(self):
         self.assertEqual(b"I am _ComplexObject('joe')",