Fixed #9522 -- Modified handling of values in base serializer so that field subclasses can define their own value_to_string() method for serialization. Thanks to Alex Koshelev for the report and initial patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@10554 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/utils/encoding.py

@@ -41,6 +41,19 @@ def smart_unicode(s, encoding='utf-8', strings_only=False, errors='strict'):
         return s
     return force_unicode(s, encoding, strings_only, errors)
 
+def is_protected_type(obj):
+    """Determine if the object instance is of a protected type.
+
+    Objects of protected types are preserved as-is when passed to
+    force_unicode(strings_only=True).
+    """
+    return isinstance(obj, (
+        types.NoneType,
+        int, long,
+        datetime.datetime, datetime.date, datetime.time,
+        float, Decimal)
+    )
+
 def force_unicode(s, encoding='utf-8', strings_only=False, errors='strict'):
     """
     Similar to smart_unicode, except that lazy instances are resolved to
@@ -48,7 +61,7 @@ def force_unicode(s, encoding='utf-8', strings_only=False, errors='strict'):
 
     If strings_only is True, don't convert (some) non-string-like objects.
     """
-    if strings_only and isinstance(s, (types.NoneType, int, long, datetime.datetime, datetime.date, datetime.time, float, Decimal)):
+    if strings_only and is_protected_type(s):
         return s
     try:
         if not isinstance(s, basestring,):