Merge pull request #186 from posita/posita/185-fix-ensure_new_type

Fix #185. Return argument unmolested from ensure_new_type if conversion to new type does not exist.

Author: edschofield

src/future/utils/__init__.py

@@ -28,7 +28,7 @@
     * tobytes(s)
         Take a text string, a byte string, or a sequence of characters taken
         from a byte string, and make a byte string.
-    
+
     * raise_from()
     * raise_with_traceback()
 
@@ -66,32 +66,32 @@ def python_2_unicode_compatible(cls):
     """
     A decorator that defines __unicode__ and __str__ methods under Python
     2. Under Python 3, this decorator is a no-op.
-    
+
     To support Python 2 and 3 with a single code base, define a __str__
     method returning unicode text and apply this decorator to the class, like
     this::
 
     >>> from future.utils import python_2_unicode_compatible
-    
+
     >>> @python_2_unicode_compatible
     ... class MyClass(object):
     ...     def __str__(self):
     ...         return u'Unicode string: \u5b54\u5b50'
-    
+
     >>> a = MyClass()
 
     Then, after this import:
 
     >>> from future.builtins import str
-    
+
     the following is ``True`` on both Python 3 and 2::
-    
+
     >>> str(a) == a.encode('utf-8').decode('utf-8')
     True
 
     and, on a Unicode-enabled terminal with the right fonts, these both print the
     Chinese characters for Confucius::
-    
+
     >>> print(a)
     >>> print(str(a))
 
@@ -108,13 +108,13 @@ def with_metaclass(meta, *bases):
     Function from jinja2/_compat.py. License: BSD.
 
     Use it like this::
-        
+
         class BaseForm(object):
             pass
-        
+
         class FormType(type):
             pass
-        
+
         class Form(with_metaclass(FormType, BaseForm)):
             pass
 
@@ -124,7 +124,7 @@ class Form(with_metaclass(FormType, BaseForm)):
     we also need to make sure that we downgrade the custom metaclass
     for one level to something closer to type (that's why __call__ and
     __init__ comes back from type etc.).
-    
+
     This has the advantage over six.with_metaclass of not introducing
     dummy classes into the final MRO.
     """
@@ -480,7 +480,7 @@ def implements_iterator(cls):
     From jinja2/_compat.py. License: BSD.
 
     Use as a decorator like this::
-        
+
         @implements_iterator
         class UppercasingIterator(object):
             def __init__(self, iterable):
@@ -489,7 +489,7 @@ def __iter__(self):
                 return self
             def __next__(self):
                 return next(self._iter).upper()
-    
+
     '''
     if PY3:
         return cls
@@ -520,7 +520,7 @@ def is_new_style(cls):
     function to test for whether a class is new-style. (Python 3 only has
     new-style classes.)
     """
-    return hasattr(cls, '__class__') and ('__dict__' in dir(cls) 
+    return hasattr(cls, '__class__') and ('__dict__' in dir(cls)
                                           or hasattr(cls, '__slots__'))
 
 # The native platform string and bytes types. Useful because ``str`` and
@@ -587,7 +587,7 @@ def native(obj):
 
     On Py2, returns the corresponding native Py2 types that are
     superclasses for backported objects from Py3:
-    
+
     >>> from builtins import str, bytes, int
 
     >>> native(str(u'ABC'))
@@ -656,7 +656,7 @@ def as_native_str(encoding='utf-8'):
     unicode, into one that returns a native platform str.
 
     Use it as a decorator like this::
-        
+
         from __future__ import unicode_literals
 
         class MyClass(object):
@@ -717,7 +717,7 @@ def ensure_new_type(obj):
             elif native_type == dict:
                 return newdict(obj)
             else:
-                return NotImplementedError('type %s not supported' % type(obj))
+                return obj
         else:
             # Already a new type
             assert type(obj) in [newbytes, newstr]
@@ -738,4 +738,3 @@ def ensure_new_type(obj):
            'tobytes', 'viewitems', 'viewkeys', 'viewvalues',
            'with_metaclass'
           ]
-

tests/test_future/test_utils.py

@@ -62,24 +62,24 @@ def test_native_str(self):
         for s in inputs:
             self.assertEqual(native_str(s), builtin_str(s))
             self.assertTrue(isinstance(native_str(s), builtin_str))
-        
-    def test_native(self):   
+
+    def test_native(self):
         a = int(10**20)     # long int
         b = native(a)
         self.assertEqual(a, b)
         if PY2:
             self.assertEqual(type(b), long)
         else:
             self.assertEqual(type(b), int)
-    
+
         c = bytes(b'ABC')
         d = native(c)
         self.assertEqual(c, d)
         if PY2:
             self.assertEqual(type(d), type(b'Py2 byte-string'))
         else:
             self.assertEqual(type(d), bytes)
-    
+
         s = str(u'ABC')
         t = native(s)
         self.assertEqual(s, t)
@@ -151,7 +151,7 @@ def test_raise_from_None(self):
         except ValueError as e:
             self.assertTrue(isinstance(e.__context__, TypeError))
             self.assertIsNone(e.__cause__)
-    
+
     @skip26
     def test_as_native_str(self):
         """
@@ -161,9 +161,9 @@ class MyClass(object):
             @as_native_str()
             def __repr__(self):
                 return u'abc'
-            
+
         obj = MyClass()
-       
+
         self.assertEqual(repr(obj), 'abc')
         if PY2:
             self.assertEqual(repr(obj), b'abc')
@@ -186,6 +186,9 @@ def test_ensure_new_type(self):
         self.assertEqual(ensure_new_type(i), i2)
         self.assertEqual(type(ensure_new_type(i)), int)
 
+        l = []
+        self.assertIs(ensure_new_type(l), l)
+
     def test_bytes_to_native_str(self):
         """
         Test for issue #47
@@ -215,7 +218,7 @@ class DatabaseError(Exception):
 
         # Python 2 and 3:
         from future.utils import raise_from
-        
+
         class FileDatabase:
             def __init__(self, filename):
                 try:
@@ -228,7 +231,7 @@ def __init__(self, filename):
             fd = FileDatabase('non_existent_file.txt')
         except Exception as e:
             assert isinstance(e.__cause__, IOError)   # FileNotFoundError on
-                                                      # Py3.3+ inherits from IOError        
+                                                      # Py3.3+ inherits from IOError
 
     def testCauseSyntax(self):
         try: