Fix min/max functions not allowing 'None' as default

Author: gazpachoking

src/future/builtins/new_min_max.py

@@ -6,6 +6,8 @@
 else:
     from builtins import max as _builtin_max, min as _builtin_min
 
+_SENTINEL = object()
+
 
 def newmin(*args, **kwargs):
     return new_min_max(_builtin_min, *args, **kwargs)
@@ -31,15 +33,15 @@ def new_min_max(_builtin_func, *args, **kwargs):
     if len(args) == 0:
         raise TypeError
 
-    if len(args) != 1 and kwargs.get('default') is not None:
+    if len(args) != 1 and kwargs.get('default', _SENTINEL) is not _SENTINEL:
         raise TypeError
 
     if len(args) == 1:
         iterator = iter(args[0])
         try:
             first = next(iterator)
         except StopIteration:
-            if kwargs.get('default') is not None:
+            if kwargs.get('default', _SENTINEL) is not _SENTINEL:
                 return kwargs.get('default')
             else:
                 raise ValueError('iterable is an empty sequence')

tests/test_future/test_builtins.py

@@ -1105,6 +1105,7 @@ def test_max(self):
         with self.assertRaises(TypeError):
             max(1, 2, default=0)
         self.assertEqual(max([], default=0), 0)
+        self.assertIs(max([], default=None), None)
 
     def test_min(self):
         self.assertEqual(min('123123'), '1')
@@ -1150,6 +1151,7 @@ def __getitem__(self, index):
                          sorted(data, key=f)[0])
         self.assertEqual(min([], default=5), 5)
         self.assertEqual(min([], default=0), 0)
+        self.assertIs(min([], default=None), None)
         with self.assertRaises(TypeError):
             max(None, default=5)
         with self.assertRaises(TypeError):