Review step 1 - simplify to clarify

rest_framework/exceptions.py

@@ -58,45 +58,22 @@ class APIException(Exception):
         return self.detail
 
 
-def build_error_from_django_validation_error(exc_info):
-    code = getattr(exc_info, 'code', None) or 'invalid'
-    return [
-        ValidationErrorMessage(msg, code=code)
-        for msg in exc_info.messages
-    ]
-
-
 # The recommended style for using `ValidationError` is to keep it namespaced
 # under `serializers`, in order to minimize potential confusion with Django's
 # built in `ValidationError`. For example:
 #
 # from rest_framework import serializers
 # raise serializers.ValidationError('Value was invalid')
-
-class ValidationErrorMessage(six.text_type):
-    code = None
-
-    def __new__(cls, string, code=None, *args, **kwargs):
-        self = super(ValidationErrorMessage, cls).__new__(
-            cls, string, *args, **kwargs)
-
-        self.code = code
-        return self
-
-
 class ValidationError(APIException):
     status_code = status.HTTP_400_BAD_REQUEST
 
     def __init__(self, detail, code=None):
-        # If code is there, this means we are dealing with a message.
-        if code and not isinstance(detail, ValidationErrorMessage):
-            detail = ValidationErrorMessage(detail, code=code)
-
         # For validation errors the 'detail' key is always required.
         # The details should always be coerced to a list if not already.
         if not isinstance(detail, dict) and not isinstance(detail, list):
             detail = [detail]
         self.detail = _force_text_recursive(detail)
+        self.code = code
 
     def __str__(self):
         return six.text_type(self.detail)

rest_framework/fields.py

@@ -32,7 +32,7 @@ from rest_framework.compat import (
     unicode_to_repr
 )
 from rest_framework.exceptions import (
-    ValidationError, build_error_from_django_validation_error
+    ValidationError
 )
 from rest_framework.settings import api_settings
 from rest_framework.utils import html, humanize_datetime, representation
@@ -505,9 +505,7 @@ class Field(object):
                     raise
                 errors.extend(exc.detail)
             except DjangoValidationError as exc:
-                errors.extend(
-                    build_error_from_django_validation_error(exc)
-                )
+                errors.extend(exc.messages)
         if errors:
             raise ValidationError(errors)
 

rest_framework/serializers.py

@@ -20,11 +20,9 @@ from django.db.models.fields import FieldDoesNotExist
 from django.utils.functional import cached_property
 from django.utils.translation import ugettext_lazy as _
 
-from rest_framework import exceptions
 from rest_framework.compat import DurationField as ModelDurationField
 from rest_framework.compat import JSONField as ModelJSONField
 from rest_framework.compat import postgres_fields, unicode_to_repr
-from rest_framework.exceptions import ValidationErrorMessage
 from rest_framework.utils import model_meta
 from rest_framework.utils.field_mapping import (
     ClassLookupDict, get_field_kwargs, get_nested_relation_kwargs,
@@ -221,6 +219,7 @@ class BaseSerializer(Field):
 
         if self._errors and raise_exception:
             raise ValidationError(self.errors)
+
         return not bool(self._errors)
 
     @property
@@ -301,8 +300,7 @@ def get_validation_error_detail(exc):
         # exception class as well for simpler compat.
         # Eg. Calling Model.clean() explicitly inside Serializer.validate()
         return {
-            api_settings.NON_FIELD_ERRORS_KEY:
-                exceptions.build_error_from_django_validation_error(exc)
+            api_settings.NON_FIELD_ERRORS_KEY: list(exc.messages)
         }
     elif isinstance(exc.detail, dict):
         # If errors may be a dict we use the standard {key: list of values}.
@@ -424,9 +422,8 @@ class Serializer(BaseSerializer):
             message = self.error_messages['invalid'].format(
                 datatype=type(data).__name__
             )
-            error = ValidationErrorMessage(message, code='invalid')
             raise ValidationError({
-                api_settings.NON_FIELD_ERRORS_KEY: [error]
+                api_settings.NON_FIELD_ERRORS_KEY: [message]
             })
 
         ret = OrderedDict()
@@ -443,9 +440,7 @@ class Serializer(BaseSerializer):
             except ValidationError as exc:
                 errors[field.field_name] = exc.detail
             except DjangoValidationError as exc:
-                errors[field.field_name] = (
-                    exceptions.build_error_from_django_validation_error(exc)
-                )
+                errors[field.field_name] = list(exc.messages)
             except SkipField:
                 pass
             else:
@@ -580,18 +575,12 @@ class ListSerializer(BaseSerializer):
             message = self.error_messages['not_a_list'].format(
                 input_type=type(data).__name__
             )
-            error = ValidationErrorMessage(
-                message,
-                code='not_a_list'
-            )
             raise ValidationError({
-                api_settings.NON_FIELD_ERRORS_KEY: [error]
+                api_settings.NON_FIELD_ERRORS_KEY: [message]
             })
 
         if not self.allow_empty and len(data) == 0:
-            message = ValidationErrorMessage(
-                self.error_messages['empty'],
-                code='empty_not_allowed')
+            message = self.error_messages['empty']
             raise ValidationError({
                 api_settings.NON_FIELD_ERRORS_KEY: [message]
             })

rest_framework/validators.py

@@ -11,7 +11,7 @@ from __future__ import unicode_literals
 from django.utils.translation import ugettext_lazy as _
 
 from rest_framework.compat import unicode_to_repr
-from rest_framework.exceptions import ValidationError, ValidationErrorMessage
+from rest_framework.exceptions import ValidationError
 from rest_framework.utils.representation import smart_repr
 
 
@@ -101,10 +101,7 @@ class UniqueTogetherValidator(object):
             return
 
         missing = {
-            field_name: ValidationErrorMessage(
-                self.missing_message,
-                code='required')
-
+            field_name: self.missing_message
             for field_name in self.fields
             if field_name not in attrs
         }
@@ -190,9 +187,7 @@ class BaseUniqueForValidator(object):
         'required' state on the fields they are applied to.
         """
         missing = {
-            field_name: ValidationErrorMessage(
-                self.missing_message,
-                code='required')
+            field_name: self.missing_message
             for field_name in [self.field, self.date_field]
             if field_name not in attrs
         }
@@ -219,7 +214,7 @@ class BaseUniqueForValidator(object):
         if queryset.exists():
             message = self.message.format(date_field=self.date_field)
             raise ValidationError({
-                self.field: ValidationErrorMessage(message, code='unique'),
+                self.field: message,
             })
 
     def __repr__(self):