Refactored ValidationError to allow persisting error params and error codes as the exception bubbles up

1 files changed, 46 insertions, 22 deletions

diff --git a/django/core/exceptions.py b/django/core/exceptions.py
index 2c79736e33..5975164d07 100644
--- a/django/core/exceptions.py
+++ b/django/core/exceptions.py
@@ -3,6 +3,9 @@ Global Django exception and warning classes.
 """
 import logging
 from functools import reduce
+import operator
+
+from django.utils.encoding import force_text
 
 
 class DjangoRuntimeWarning(RuntimeWarning):
@@ -74,46 +77,67 @@ NON_FIELD_ERRORS = '__all__'
 class ValidationError(Exception):
     """An error while validating data."""
     def __init__(self, message, code=None, params=None):
-        import operator
-        from django.utils.encoding import force_text
         """
         ValidationError can be passed any object that can be printed (usually
         a string), a list of objects or a dictionary.
         """
         if isinstance(message, dict):
-            self.message_dict = message
-            # Reduce each list of messages into a single list.
-            message = reduce(operator.add, message.values())
-
-        if isinstance(message, list):
-            self.messages = [force_text(msg) for msg in message]
+            self.error_dict = message
+        elif isinstance(message, list):
+            self.error_list = message
         else:
             self.code = code
             self.params = params
-            message = force_text(message)
-            self.messages = [message]
+            self.message = message
+            self.error_list = [self]
+
+    @property
+    def message_dict(self):
+        message_dict = {}
+        for field, messages in self.error_dict.items():
+            message_dict[field] = []
+            for message in messages:
+                if isinstance(message, ValidationError):
+                    message_dict[field].extend(message.messages)
+                else:
+                    message_dict[field].append(force_text(message))
+        return message_dict
+
+    @property
+    def messages(self):
+        if hasattr(self, 'error_dict'):
+            message_list = reduce(operator.add, self.error_dict.values())
+        else:
+            message_list = self.error_list
+
+        messages = []
+        for message in message_list:
+            if isinstance(message, ValidationError):
+                params = message.params
+                message = message.message
+                if params:
+                    message %= params
+                message = force_text(message)
+            else:
+                message = force_text(message)
+            messages.append(message)
+        return messages
 
     def __str__(self):
-        # This is needed because, without a __str__(), printing an exception
-        # instance would result in this:
-        # AttributeError: ValidationError instance has no attribute 'args'
-        # See http://www.python.org/doc/current/tut/node10.html#handling
-        if hasattr(self, 'message_dict'):
+        if hasattr(self, 'error_dict'):
             return repr(self.message_dict)
         return repr(self.messages)
 
     def __repr__(self):
-        if hasattr(self, 'message_dict'):
-            return 'ValidationError(%s)' % repr(self.message_dict)
-        return 'ValidationError(%s)' % repr(self.messages)
+        return 'ValidationError(%s)' % self
 
     def update_error_dict(self, error_dict):
-        if hasattr(self, 'message_dict'):
+        if hasattr(self, 'error_dict'):
             if error_dict:
-                for k, v in self.message_dict.items():
+                for k, v in self.error_dict.items():
                     error_dict.setdefault(k, []).extend(v)
             else:
-                error_dict = self.message_dict
+                error_dict = self.error_dict
         else:
-            error_dict[NON_FIELD_ERRORS] = self.messages
+            error_dict[NON_FIELD_ERRORS] = self.error_list
         return error_dict